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8.10.1   IEEE-488 Interface Connector       

191

 

                                                        

   

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www.lakeshore.com

8.10.1 IEEE-488 
Interface Connector

Connect to the IEEE-488 Interface connector on the Model 372 rear panel with cables 
specified in the IEEE-488 standard. The cable has 24 conductors with an outer shield. 
The connectors are 24-way Amphenol 57 Series (or equivalent) with piggyback recep-
tacles to allow daisy chaining in multiple device systems. The connectors are secured 
in the receptacles by 2 captive locking screws with metric threads.

The total length of cable allowed in a system is 2 m (6.6 ft) for each device on the bus, 
or 20 m maximum. The Model 372 can drive a bus of up to 10 devices. A connector 
extender is required to use the IEEE-488 interface and relay terminal block at the 
same time. FIGURE 8-9 shows the IEEE-488 interface connector pin location and sig-
nal names as viewed from the Model 372 rear panel.

Pin

Symbol

Description

1

TXD+

Transmit data+

2

TXD-

Transmit data-

3

RXD+

Receive data+

4

EPWR+

Power from  (not used)

5

EPWR+

Power from  (not used)

6

RXD-

Receive data-

7

EPWR-

Power from switch- (not used)

8

EPWR-

Power from switch- (not used)

TABLE 8-8   

Ethernet pin and connector details

FIGURE 8-9   

IEEE-488 interface

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

Содержание 372

Страница 1: ... or applied for Lake Shore Cryotronics Inc reserves the right to add improve modify or withdraw functions design modifications or products at any time without notice Lake Shore shall not be liable for errors contained herein or for incidental or consequential damages in connection with furnishing performance or use of this material Rev 1 9 P N 119 372 12 March 2019 User s Manual Model 372 AC Resis...

Страница 2: ...ovided herein Lake Shore undertakes no responsibility that the products will be fit for any particular purpose for which you may be buying the Products Any implied warranty is limited in duration to the warranty period No oral or written information or advice given by the Company its Agents or Employees shall create a warranty or in any way increase the scope of this limited warranty Some countrie...

Страница 3: ... changes made to the firmware FIRMWARE LICENSE AGREEMENT continued Under the terms of this agreement you may only use the Model 372 firmwareasphysically installedinthe instrument Archivalcopiesare strictly forbidden You may not decompile disassemble or reverse engineer the firmware If you suspect there are problems with the firmware return the instrument to Lake Shore for repair under the terms of...

Страница 4: ...and Temperature Controller The object of the declaration described above is in conformity with the relevant Union harmonization legislation 2014 35 EU Low Voltage Directive 2014 30 EU EMC Directive 2011 65 EU RoHS References to the relevant harmonized standards used to the specification in relation to which conformity is declared EN 61010 1 2010 Overvoltage Category II Pollution Degree 2 EN 61326 ...

Страница 5: ...ctor of Quality Compliance EU DECLARATION OF CONFORMITY This declaration of conformity is issued under the sole responsibility of the manufacturer Manufacturer Lake Shore Cryotronics Inc 575 McCorkle Boulevard Westerville OH 43082 USA Object of the declaration Model s 372U 372U 6 372U 10 3708 3708 6 3708 10 Description AC Resistance Bridge and Temperature Controller The object of the declaration d...

Страница 6: ...th sensor and interface cables attached If the installation and operating instructions in the User s Manual are followed there should be no degradation in EMC performance This instrument is not intended for use in close proximity to RF Transmitters such as two way radios and cell phones Exposure to RF interference greater than that found in a typical laboratory environment may disturb the sensitiv...

Страница 7: ...ity Communication Options 10 1 6 1 Physical connectivity 10 1 6 2 Available Functions 10 1 6 3 Backwards Compatibility 10 1 7 Sensor Performance 11 1 7 1 Measurement Resolution 11 1 7 2 Electronic Accuracy 11 1 7 3 Self heating errors 11 1 7 4 Calibration accuracies 11 1 7 5 Interpolation errors 11 1 7 6 Overall accuracy 11 1 7 7 Lake Shore Rox 102B CB with 0 02 to 40 K Calibration 12 1 7 8 Lake S...

Страница 8: ...r 36 2 7 1 Warm Up and Temperature Drift 36 2 7 2 Resistor Installation 36 2 7 3 Resistor Self Heating and Thermal Resistance 36 2 7 4 Lead Resistance 37 2 7 5 Current Leakage 37 2 7 6 Cable Capacitance 37 2 7 7 Instrument Operation 39 2 8 Operating Tradeoffs 39 2 8 1 Resistor Self heating vs Excitation 39 2 8 2 Excitation vs Signal to Noise 40 2 8 3 Signal to Noise vs Measurement Bandwidth 40 2 9...

Страница 9: ...nnection 71 3 8 2 Calculating Still Heater Power 71 3 8 3 Calculating Still Heater Current 72 3 9 Monitor and Reference Outputs 72 3 10 Diagnostic Monitor Voltage Output 72 3 11 Reference Voltage Output 72 Chapter 4 Operation 4 1 General 73 4 1 1 Understanding Menu Navigation 73 4 2 Front Panel Description 74 4 2 1 Keypad Definitions 74 4 2 2 Annunciators 75 4 2 3 General Keypad Operation 76 4 3 D...

Страница 10: ...8 5 8 1 Unsupported Commands 118 5 8 2 Command Interpretation 118 5 8 3 Curve Location Numbering 118 5 8 4 Controlling While Scanning Differences 119 5 8 5 Hardware Differences 119 Chapter 6 Computer InterfaceOperation 6 1 General 121 6 2 IEEE 488 Interface 121 6 2 1 Changing IEEE 488 Interface Parameters 122 6 2 2 Remote Local Operation 122 6 2 3 IEEE 488 2 Command Structure 122 6 2 4 Status Syst...

Страница 11: ...ittent Lockups 184 8 4 Fuse Drawer 184 8 5 Line Voltage Selection 184 8 6 Fuse Replacement 185 8 7 Factory Reset Menu 185 8 7 1 Default Values 185 8 7 2 Product Information 187 8 8 Error Messages 187 8 9 Calibration Procedure 187 8 10 Rear Panel Connector Definition 188 8 10 1 IEEE 488 Interface Connector 191 8 10 2 Scan Control 192 8 11 Firmware Updates 193 8 11 1 Updating the Firmware 193 8 11 2...

Страница 12: ...Model 372 AC Resistance Bridge and Temperature Controller ...

Страница 13: ...asure ments D Multiple PID controllable outputs with up to 10 W of heater power available D Latest generation front panel for ease of use D 3 year standard warranty 1 Scanner control input DA 15 2 Sensor voltage current input 6 pin DIN 3 Secondary control input 6 pin DIN 4 Monitor output BNC 5 Reference output BNC 6 Sample heater output warm up heater output and still heater output terminal block ...

Страница 14: ...ct a scanner to the Model 372 This helps to further balance the measurement network and bolster the integrity of the noise rejec tion circuitry D All measurement circuitry is isolated from other instrument components limit ing the impact of any small electrical disturbances D The AC frequency options used for the measurement signal are selected to be naturally resilient to line voltage frequencies...

Страница 15: ...ility in the type of resistive sensors that are used A maxi mum of 39 calibration curves can be stored on the instrument and when used with a 3726 scanner up to 17 sensors can be connected simultaneously each with their own curve 1 3 6 Measure a Wide Range of Resistive Devices With up to 21 different current I excitation levels available the Model 372 is able to perform accurate impedance measurem...

Страница 16: ... a pre amp circuit in the 3726 scanner preserving the signal to noise ratio between the sensor and measurement circuitry of the Model 372 This allows connection cables of up to 10 m to be used between the Model 372 and the 3726 In cases where measurements are required at multiple locations simultaneously within an experiment space additional Model 372 units may be used together Five different AC e...

Страница 17: ...tures deserves uninterrupted attention from measurement devices The Model 372 uses a dedicated temperature control input that is designed specifically for connection to a negative temperature coeffi cient resistive sensor This input is designed to continuously monitor the temperature of the dilution refrigerator sample holder while the measurement input scans through the multiple other temperature...

Страница 18: ...e ment several protection mechanisms to reduce or eliminate this potential D The circuitry for the sample and still heaters are electrically isolated from other instrument sections D Multiple power range settings allow extremely fine or coarse power transitions depending on the need D Heater outputs are shunted during power up and power range changes eliminating the potential for unwanted power su...

Страница 19: ...s D Temperature thresholds can be set for all heater outputs meaning the heaters will automatically shut down if it is detected that the system is being overheated D An easy to access ALL OFF button is provided that shuts all heaters down instantly This eliminates the terrible experience of having to hurriedly search through menu options while your experiment continues to heat FIGURE 1 9 ALL OFF b...

Страница 20: ...e sensors but begin to lose resolution and accuracy when extremely low impedances are encountered such as in Hall effect or superconducting material mea surements However by adding a 3708 preamp and scanner to the Model 372 these materials can be characterized with the same accuracy and stability as when mea suring higher impedance devices To accomplish this the 3708 produces higher levels of DC b...

Страница 21: ...ections to be made with the scanner feature enabling measurement to be switched between those connections Unlike the 3726 scanner all connections that are not actively being measured are left open allowing the 3708 to be connected to Hall bar devices 1 5 2OvercomingCable Length With such small resultant voltages needing to be measured it can be very helpful to have these signals amplified slightly...

Страница 22: ...D Live graphical viewing of data using the Lake Shore Cryotronics Chart Recorder software D Load new calibration curves for use with new temperature sensors D Upload new firmware if required 1 6 3 Backwards Compatibility The Model 372 is designed for trouble free integration with existing equipment and software that has been built around the previous generation Model 370 D Emulation mode on the Mo...

Страница 23: ...voltage range 1 7 3 Self heating errors Self heating errors are measurement errors due to power dissipation in the sensor causing unwanted temperature rises Self heating error is given by Self heating error thermal resistance power Thermal resistances specified are typical values resulting from minimal heat sinking Improved values can be achieved with permanent installation 1 7 4 Calibration accur...

Страница 24: ...lue is different for the control input it is shown in blue 1 7 8 Lake Shore GR 50 AA with 0 05 to 6 K Calibration Values given are for measurement input If the value is different for the control input it is shown in blue FIGURE 1 13 Sensor performance for Lake Shore Rox 102B CB with 0 02 to 40 K calibration FIGURE 1 14 Sensor performance for Lake Shore GR 50 AA with 0 05 to 6 K calibration ...

Страница 25: ...shore com 1 7 9 Lake Shore CX 1010 SD with 0 01 to 325 K Calibration Values given are for measurement input If the value is different for the control input it is shown in blue FIGURE 1 15 Sensor performance for Lake Shore CX 1010 SD with 0 01 to 325 K calibration ...

Страница 26: ...nce Specification Table The values below apply to the measurement input The control input operates over a reduced range indicated by the black bordered cells These cells contain bracketed numbers to indicate the resolution that applies to the control input FIGURE 1 16 372 3726 performance specification table ...

Страница 27: ...1 7 11 372 3708PerformanceSpecificationTable 15 www lakeshore com 1 7 11 372 3708 Performance Specification Table FIGURE 1 17 372 3708 performance specification table ...

Страница 28: ...atched impedance voltage input and current output active CMR Excitation Sinusoidal AC current source Excitation frequency 9 8 Hz 11 6 Hz 13 7 Hz default 16 2 Hz or 18 2 Hz Excitation currents 22 ranges from 1 pA to 31 6 mA RMS Excitation accuracy 2 of nominal Minimum excitation power 10 18 W into a 100 k see Measurement Input Specifications table for other ranges Typical DC bias current 2 pA 1 of ...

Страница 29: ...racy 8 of nominal for 316 pA and 1 nA ranges 2 of nominal for the other ranges Power up current protection Current output shunted on power up Voltage input range 200 µV Voltage input over range 20 Maximum input voltage noise 20 nV xHz Range selection modes Manual standard autorange and Rox RX 102B CB optimized autorange Filter 1 s to 200 s settling time 1 to 80 filter window Additional software fe...

Страница 30: ...assis ground reference when on Shunted and isolated when off Heater connector Detachable terminal block Safety limits Curve temperature power up heater off shunted with a relay on power up short circuit protection compliance voltage limit relay disconnects output when off input temperature limit 1 8 6 Analog Still Output Type Variable DC voltage source Control modes Open loop still heater monitor ...

Страница 31: ...tation voltage excitation current excitation power control setpoint PID heater range heater output and quadrature reading Setpoint setting resolution Same as display resolution sensor dependent Heater output display Numeric display in percent of full scale for power or current Display annunciators Control input and alarm LED annunciators Autorange excitation mode autoscan control outputs remote Et...

Страница 32: ...ects one of several analog voltage diagnostic points must remain isolated Available signals 1 AC voltage driving positive negative side of current source programming resistor 2 AC voltage present on the positive negative side of the differential input amplifier 3 AC voltage present on the output of the differential input amplifier 4 AC voltage into the measurement channel or control input AD conve...

Страница 33: ...the power outlet The power jack and mating plug of the power cable meet Underwriters Laboratories UL and International Electrotechnical Commission IEC safety standards Ventilation The instrument has ventilation holes in its top and side covers Do not block these holes when the instrument is operating Do Not Operate in an Explosive Atmosphere Do not operate the instrument in the presence of flammab...

Страница 34: ... II of IEC 536 see Annex H CAUTION High voltages danger of electric shock background color yellow symbol and outline black CAUTION or WARNING See instrument documentation background color yellow symbol and outline black Off supply On supply Frame or chassis terminal Protective conductor terminal Earth ground terminal 3 Three phase alternating current power line Alternating or direct current power ...

Страница 35: ...d surface at lower and lower temperatures only exaggerate the problem In gen eral resistance bridge measurements are considered routine down to 100 mK in a capable cryogenic cooling system With careful installation of a high quality bridge like the Model 372 it is not difficult to achieve 50 mK Below that each detail of the overall system has to be optimized to a low end of between 5 and 20 mK 2 3...

Страница 36: ...ium Dewar a vacuum insulated Dewar that is large enough to contain the following components The Dewar sometimes includes a nitrogen outer jacket to improve efficiency or a superconducting magnet coil when needed D 4He reservoir a reservoir of liquid 4He at atmospheric pressure that provides bulk cooling down to 4 2 K The reservoir precools gas entering the vacuum space and it acts as a radiation s...

Страница 37: ...hamber where experiments can take place It may either be part of or attached to the mixing chamber and it is often designed for a unique purpose This will require a sepa rate temperature sensor if its temperature is different from the mixing chamber 2 4 2 3He Cryostat 3He cryostats are the least complex systems capable of reaching temperatures down to 300 mK Even at such relatively warm temperatur...

Страница 38: ...the end of the 3He evaporator where experiments can take place It may either be part of or attached to the evaporator and it is often designed for a unique purpose This will require a separate tem perature sensor if its temperature is different from the 3He evaporator 2 4 3 Adiabatic Demagnetization Refrigerator ADR The principals of ADR have been known for some time and many very capable systems ...

Страница 39: ...trol temperature by trimming current in the magnet with its heater output current source Resistive heating is not desirable D Superconducting magnet the superconducting magnet magnetizes the salt pill while in thermal contact with the precooling stage then demagnetizes it when thermally isolated The magnet power supply can be programmed by the Model 372 analog output and controlled via computer in...

Страница 40: ...ments use a four lead method to eliminate the effect of nominal lead resistance Excitation current is driven on one pair of leads while the resulting signal voltage is measured on the second pair Measurement errors from lead resistance are proportional to current flowing in the voltage leads Instrument voltage inputs are expected to have high impedance to prevent the unwanted current from flowing ...

Страница 41: ...presented as Z R jX where R is resistance in ohms j is the imaginary component and X is reactance also in ohms This is represented slightly differently in the Model 372 and is shown below in FIGURE 2 4 Keep in mind the Model 372 impedance measurement assumes the load is modeled as a series RLC circuit There are many applications such as determining parasitic cable capacitance where it is desired t...

Страница 42: ...uch high resistances These ranges should be used for relative measurements only The selected resistance range and excitation are always shown on the instrument dis play Refer to FIGURE 1 13 through FIGURE 1 15 for resistance and excitation ranges As shown in the figures not every combination of excitation and resistance range is possible Unusable combinations of range and excitation are automatica...

Страница 43: ...his manual often have to be tried in different combination to get the best results Specific recommendations on installation and lead wiring are given in Chapter 3 2 5 6 1 Shielding and Grounding Theory Begin any installation by separating noise sources from their targets Sources of E field and H field noise can be just about anything but the targets are most often sig nal leads and other wires and...

Страница 44: ...ital circuitry and chassis of the instrument by opto couplers This can improve measure ments in two ways First isolation makes it more difficult for digital noise from con trol circuits and computer interfaces to affect the measurement leads Second isolation breaks ground loops It is often desirable to extend shielding from the mea surement leads to the experimental Dewar If the instrument shield ...

Страница 45: ...differential input especially when mea suring large resistors Second common mode noise sources have the same effect on both sides of the resistor being measured ensuring that common mode voltages are not turned into normal mode voltages voltages are present between measurement leads Common mode voltage is rejected by the differential input but normal mode error voltage is measured along with the d...

Страница 46: ...a message if noise overloads the measurement electronics Refer to Chapter 7 for more information on diagnosing noise problems 2 6 1 Induced Electrical Noise Noise from the environment is typically classified as either electric field E field or magnetic field H field E field noise capacitively couples into measurement leads or the resistor being measured Voltage is induced on the leads as if the no...

Страница 47: ...n the instrument itself is digital computers used for data acquisition Computers with their high clock seeds generate a wide spectrum of noise and transmit it through line cords and interface cables Isolation in the Model 372 separates the measurement circuits from interface circuits but computers must still be treated carefully during installation of a system 2 6 5 Resistor Thermal Noise Thermal ...

Страница 48: ...arm up for at least 30 min before use to allow its internal temperature to stabilize Warm up is an exagger ated form of temperature drift because the temperature change inside the enclosure is larger and faster than would be experienced in a laboratory setting Temperature drift change in reading with change in ambient temperature is small in the Model 372 and seldom a significant factor in absolut...

Страница 49: ...e highest current excitations At the higher cur rents lead resistance of 100 can create drops of several volts in each lead These large voltage swings will measurably affect the millvolt and microvolt resistor mea surements If lead resistance exceeds the specified values the instrument will mea sure with reduced accuracy until the compliance voltage of approximately 7 V RMS is reached Keep the res...

Страница 50: ...idered if inductive noise reduction filters are placed in series with leads 2 7 6 2 Parasitic Capacitance Temperature Compensation When making temperature measurements with a resistive sensor the effects of para sitic capacitance that create an offset in measured resistance will result in a corre sponding offset in measured temperature This temperature reading can also be corrected using the measu...

Страница 51: ...cy response of the hardware filters This calibration eliminates instrument errors only and will not account for attenuation caused by lead capacitance that is different at each frequency The autorange algorithm includes a hysteresis band to prevent instability when the measured resistor is at a range boundary It is possible for the instrument to choose a different excitation current when approachi...

Страница 52: ...s with measurements noise effects worsen when signal size decreases when resistance increases and when bandwidth increases Excitation is limited by self heating and cannot always be increased to create larger signals Resistance can seldom be changed because it is the quantity being measured That leaves bandwidth to overcome signal to noise and improve resolution If noise cannot be reduced at its s...

Страница 53: ...ignals going back to the Model 372 and necessary control circuits The scanner is housed in a separate shielded enclosure so that it can be placed near the test Dewar Power for the scanner is taken directly from the regulated DC power supplies of the Model 372 Mounting bracket and 3m 10 ft cables to join the Model 372 are included with the scanner Mating connec tors are supplied for the scanner inp...

Страница 54: ... time of the 3726 and 3708 scanners are virtu ally the same as the range change settling time of the Model 372 Additional time may be required for the instrument to autorange if that feature is enabled and the resistance on the new channel changes significantly between scans 2 10 Temperature Measurement Temperature measurement is a popular use of resistance bridges because most of the temperature ...

Страница 55: ...n is not as severe as the drop in sensitivity is that excitation current is increased approximately 1 000 times by the Model 372 to maintain practical measurement parameters Sensi tivity and therefore resolution of most sensors changes with temperature so it is important to choose a sensor with high sensitivity in the most critical temperature range Two or more sensors may be necessary to cover a ...

Страница 56: ...at low temperatures The instrument can use curve options called CalCurves available with Lake Shore calibrated sensors or curves generated by the user The Lake Shore Temperature Measurement and Con trol catalog gives complete specifications for calibrated sensors and gives the calibra tion range available for each sensor The Model 372 uses either linear or cubic spline interpolation to convert sen...

Страница 57: ...second version ofCurve Handler is writtenin the Java programming language and is available through the Ethernet web interface on the Model 372 This version allows you to copy curves from files to the Model 372 and vice versa but it does not allow manipulation of curve data does not support the newer CURVE format needed to read write cubic spline curves and only works using the Ethernet interface R...

Страница 58: ... conductivity while G 10 epoxy impregnated fiberglass does not Sensor leads should have poor thermal con ductivity Sensor packages cooling loads and sample holders should have good ther mal conductivity to reduce temperature gradients Surprisingly the connections between thermally conductive mounting surfaces often have very poor thermal con ductivity 2 10 3 4 Contact Area Thermal contact area gre...

Страница 59: ...ting a significant length of lead wire in thermal con tact with every cooled surface between room temperature and the sensor Lead wires can be adhered to cold surfaces with varnish over a thin electrical insulator like ciga rette paper They can also be wound onto a bobbin that is firmly attached to the cold surface Some sensor packages include a heat sink bobbin and wrapped lead wires to simplify ...

Страница 60: ...system slow information to the sensor slows the response time For example if the temperature at the load drops slightly below the setpoint the controller gradually increases heating power If the feedback information is slow the controller puts too much heat into the system before it is told to reduce heat The excess heat causes a temperature overshoot which degrades control stability The best way ...

Страница 61: ...d Loop PID Control Closed loop PID control often called feedback control is the control mode most often associated with temperature controllers In this mode the controller attempts to keep the load at exactly the user entered setpoint that can be entered in resistance or temperature To do this it uses feedback from the control sensor to calculate and actively adjust the control heater output The M...

Страница 62: ...e setpoint changes quickly reducing the time it takes for temperature to reach the setpoint It can also see the error decreasing rapidly when the temperature nears the setpoint and reduce the output for less overshoot The derivative term can be useful in fast changing systems but it is often turned off during steady state con trol because it reacts too strongly to small disturbances or noise The d...

Страница 63: ...as a stable temperature reading from the control sensor It is also a good idea to begin at the center of the temperature range of the cooling sys tem not close to its highest or lowest temperature 2 11 3 1 Setting Heater Range Setting an appropriate heater output range is an important first part of the tuning process The heater range should allow enough heater power to comfortably over come the co...

Страница 64: ...r dis play should show a value greater than zero and less than 100 when temperature stabilizes The load temperature should stabilize at a temperature below the set point If the load temperature and heater display swing rapidly the heater range or proportional value may be set too high and should be reduced Very slow changes in load temperature that could be described as drifting are an indication ...

Страница 65: ...l 2 to 5 degree changes in setpoint and watch the load temperature react Trial and error can help improve the integral set ting by optimizing for experimental needs Faster integrals for example get to the setpoint more quickly at the expense of greater overshoot In most systems setpoint changes that raise the temperature act differently than changes that lower the tem perature If it was not possib...

Страница 66: ...54 cHAPTER 2 Cooling System Design and Temperature Control Model 372 AC Resistance Bridge and Temperature Controller ...

Страница 67: ...pping materials and contents until instructed to either return or discard them Open the shipping container and keep the container and shipping materials until all contents have been accounted for Check off each item on the packing list as it is unpacked Instruments themselves may be shipped as several parts The items included with the Model 372 are listed below Contact Lake Shore immediately if th...

Страница 68: ...nector pin out details Always turn off the instrument before making any rear panel connections This is espe cially critical when making sensor to instrument connections 3 4 Line Input Assembly This section describes how to properly connect the Model 372 to line power Please follow these instructions carefully to ensure proper operation of the instrument and the safety of operators 3 4 1 Line Volta...

Страница 69: ... when ordered Always plug the power cord into a properly grounded receptacle to ensure safe instru ment operation Position the Model 372 in such a way to enable easy access to the disconnecting device Failure to comply could result in death or injury to personnel If the power supply cord is damaged or lost it must be replaced Contact Lake Shore for a replacement to ensure proper voltage current an...

Страница 70: ...6 233 The control input sensor connector pins are defined in FIGURE 3 4 and TABLE 3 3 Refer to section 4 4 to configure the control input FIGURE 3 3 Measurement input connectors Input V Input I Pin Symbol Description Symbol Description 1 V Measurement voltage lead V I Measurement current lead I 2 VG Guard or shield for voltage lead V IG Guard or shield for current lead I 3 Shield Shield tied to me...

Страница 71: ...especially when measuring resistance above 100 k it is recom mended to use the driven guard configuration as described in section 3 5 4 FIGURE 3 5 shows the recommended measurement input cable configuration 3 5 4 Driven Guards A configuration of guarded and shielded cables is shown below and is recommended for long cables or when measuring large resistances Variations may be necessary depending on...

Страница 72: ...ds outside the Dewar should be shielded and in general protected from contact with earth ground Inside care must be taken to prevent electrical shorts between leads and conductive parts of the cooling system During installation it is important to check for these shorts as well as shorts between the leads themselves Measurement input guards should be terminated at the instru ment end of cables only...

Страница 73: ...fluorescent lights and vac uum pump motors D Cables should be supported to minimize stress on connectors and terminations Cable support should also limit movement and vibration of the cables during measurements because cable motion can generate electrical noise D Shielded cables should be used with the shields connected at both the scanner and Dewar connectors Resistor leads from non selected chan...

Страница 74: ...d voltage leads Follow all manufacturer recommenda tions on installation including lead arrangement or errors in temperature measure ment will result FIGURE 3 7 Example of instrument grounding Model 372 Model 372 case to earth ground through the power cord Shield tied to scanner connector no gap in shielding Short cables shielded only Long cables shielded and guarded Dewar is connected to earth gr...

Страница 75: ...ther be left open or all four measurement pins can be shorted together Pin connections for channels 1 through 4 are shown in FIGURE 3 9 channels 5 through 8 9 through 12 and 13 through 16 are wired the same way 3 6 3 Scanner Resistor Input Cabling The cable between scanner and Dewar should be kept as short as possible without causing strain on the cable or connections FIGURE 3 7 Short cables can i...

Страница 76: ... Shore P N G 106 233 3 6 5 Scanner Output Cabling A scanner to instrument cable Lake Shore P N G 112 374 is included with the 3726 and 3708 scanners The figure below illustrates the cable wiring This configuration is recommended when making cables for the scanner Shielded twisted pair cables as described in section 3 5 3 can be used instead of dual triaxial cables for less demand ing applications ...

Страница 77: ...tputCabling 65 www lakeshore com FIGURE 3 11 Scanner to instrument measurement cable To scanner Female DB15 Male DB15 To Model 372 Scan control Output V Output I Scan control Input V Input I Pin 1 Shield not attached ...

Страница 78: ... mate with the instrument and one connector receptacle end to mate with the scanner FIGURE 3 12 Scan control Pin Name Description 1 Scan present Signal to Model 370 that a scanner is installed 2 Digital common Common or ground for digital control signals 3 Digital common 4 Unused 5 Analog common Common or ground for analog signals 6 Analog common 7 Analog common 8 15 V 15 V referenced to scanner a...

Страница 79: ...ontrolled by the computer interface command DOUT The power supplies can also be used but external circuits must guarantee that current is limited or performance of the instru ment may be degraded FIGURE 3 13 Scan control connector Pin Name Description 2 Digital common Common or ground 5 V 3 Digital common 5 Analog common Common or ground for 15 V 6 Analog common 7 Analog common 8 15 V 15 V at 25 m...

Страница 80: ...ut the bracket is made of soft aluminum and additional holes can be added easily No mounting screws are included FIGURE 3 14 Scanner mounting bracket with a sample hole pattern 128 8 mm 5 07 in 141 5 mm 5 57 in 155 7 mm 6 13 in MATERIAL 2 286 MM 0 090 IN THICK ALUMINUM ALLOY 3003 H14 6 35 mm 0 25 in 50 8 mm 2 00 in 50 8 mm 2 00 in 50 8 mm 2 00 in 50 8 mm 2 00 in 30 2 mm 1 19 in 20 mm 0 79 in 6 35 ...

Страница 81: ...res an accurate heater resistance be entered into the instrument Some examples of heater resistance and output range are given in TABLE 3 7 Maxi mum power for a range is the lower of the two P I2R and P V2 R where P is heater power in watts I is the maximum current for the range and V is the compliance volt age of 10 V Heater output resolution is lost any time the compliance voltage limits the pow...

Страница 82: ...e sample heater can be limited with range set tings while the warm up heater can be limited by maximum current settings When setting up a temperature control system the lead wire for the heater must be capable of carrying a continuous current that is greater than the maximum current Wire manufacturers recommend 30 AWG or larger wire to carry 0 63 A of current but there is little advantage in using...

Страница 83: ...are being made nearby Heater output noise can be most detrimental when con trolling at very low temperatures The sample heater uses a fully linear power supply to minimize heater noise The switching power supply used for the warm up heater is turned completely off when the warm up heater is off For best results use the sample heater for control and ensure the warm up heater is off when controlling...

Страница 84: ...roblems that they are being used to diagnose 3 10 Diagnostic Monitor Voltage Output A BNC receptacle provides the connection for the diagnostic monitor voltage output Signal is carried on the center conductor and isolated measurement common is on the outer conductor The signal can be switched internally toone ofseveral diagnostic voltage test points It has a maximum voltage range of 15 V and shoul...

Страница 85: ...l FIGURE 4 2 Menu navigation example Item Convention Explanation A Bold Typically the first word in the menu navigation is in bold type which indicates the first key you will need to press B Q The arrow indicates that the screen is advancing to the next screen In the menu navi gation the item that follows the arrow is the next item you would see on the screen or the next action that you will need ...

Страница 86: ... decrement scanner channel 4 4 4 1 Sample Heater Displays the control loop information for Sample Heater 4 3 1 2 Warm up Heater Displays the control loop information for Warm up Heater 4 6 1 2 Setpoint Press this key to enter the control setpoint for the currently displayed loop if applicable 4 6 1 5 6 PID Man Out Displays menu allowing for manual adjustment of P I D and manual output values 4 6 1...

Страница 87: ...1 Current Mode On when Current Excitation mode is enabled 4 4 1 2 Autoscan On Off On when autoscanning the scanner channels 4 4 4 2 Remote On steady when the instrument is in the Remote mode may be controlled via the IEEE 488 inter face If the LED is not illuminated the instrument is in Local mode 4 7 3 1 Ethernet On steady when the Ethernet is connected and properly configured Blinks at a slow pa...

Страница 88: ... decimal point The proportional control parameter is an example of a parameter that requires num ber entry During a number entry sequence use the number entry keys to enter the number value press Enter to accept the new data Press Escape once to clear the entry and twice to return to the menu navigation mode D Alpha numeric entry allows you to enter character data using the number pad keys and the...

Страница 89: ...e exci tation and the resistance measurement after each update Power from stray noise sources is not included in the calculation 4 3 1 2 Control Loop and Scan Information The lower left quadrant of the display shows relevant control loop information for either the sample heater or warm up heater independent of display mode In addition it can be configured to display the active measurement input sc...

Страница 90: ... are frozen so they are not affected by transitional data Interface command RDGSTL 4 3 2 Display Modes The Model 372 provides several display modes designed to accommodate different instrument configurations and user preferences The measurement input display mode provides detailed information about the active measurement input channel sensor The control input display mode provides detailed informa...

Страница 91: ...g is displayed in large character format using the units assigned to the respec tive input s preferred units parameter The top half of the display also shows the max imum and the minimum sensor reading since the last Max Min reset The lower right quadrant describes the range excitation and power for the given channel as described in section 4 3 1 1 Menu navigation Display SetupQDisplay ModeQContro...

Страница 92: ...8 Small D Input and units each available display location has an associated Input and Units setting The input parameter determines which sensor will be used as the input of the displayed data The input can be the control input measurement input and corresponding channels if a scanner is attached or none If none is selected then the display location will be blank The units parameter determines whic...

Страница 93: ... keys are pressed independent of display mode or what information is currently displayed in the lower left quadrant the respective heater control loop information will be displayed for approximately 10 s before returning to the configured control scan info display This provides quick access to each heater output and associated control loop information for gathering information or changing control ...

Страница 94: ...ssible without exceeding the selected excitation voltage Current is changed to accommodate resistance range or voltage excitation parameter changes To use voltage excitation mode press Voltage Mode The LED annunciator above that key will light to indicate the excitation mode The excitation display line in the lower right corner of the display will also change to indicate the maximum excitation in ...

Страница 95: ...NTYPE 4 4 2 Resistance Range Selection Resistance ranges have approximately 20 over range but the range should be increased when the reading is at full scale so that the range guarantees enough over head to account for noise voltages When the reading is below 20 of full scale bet ter measurement resolution can be achieved by decreasing the resistance range To change the resistance range press the ...

Страница 96: ...e connected resistive temperature device The instrument will increase the resistance range if the measurement reaches full scale Normally over range errors are not created because of the approximate 20 over range capability of each of the inputs Over range errors are possible when resistance changes very quickly or when resis tance increases beyond the limit of the current excitation selection The...

Страница 97: ...ings on the active channel before moving on to the next channel The scan dwell time takes place after the hardware settling time and change pause time If a mea surement channel is used to control temperature and while autoscanning is enabled the firmware will use the pause and dwell times as specified More information about controlling while scanning can be found in section 4 6 1 6 To turn on the ...

Страница 98: ...enuation Filter settling time begins after the pause time finishes on range or channel change Because the Model 372 uses a linear average the measurement bandwidth is not a simple function of frequency The settle time can be set between 0 s and 200 s When the filter is on and the settle time is zero the instrument continues to calculate the filtered reading despite the unfiltered readings being di...

Страница 99: ...ease usability and reduce confusion the Model 372 provides a means of assigning a name to each of the inputs as well as each scanner channel if a scanner is attached The designated input name is used on the front panel display whenever possible to indicate which sensor reading is being displayed Refer to section 4 2 3 for alpha numeric entry Menu navigation Input SetupQ Input A 1 16 Q Input Name 1...

Страница 100: ...d curves All Model 370 curves were consid ered user curves and were allocated to locations 1 to 20 In order for existing 370 con trol software to read and write curves from locations 1 to 20 the Model 372 must be placed into emulation mode section 5 8 When in emulation mode the firmware will translate the 370 curve locations received over the remote interface to adhere to the new curve location nu...

Страница 101: ...te nominal frequencies of 9 8 Hz 11 6Hz 16 2 Hz and 18 2 Hz with the control input by default being assigned 16 2 Hz Frequency can be changed through firmware without turning the instrument off however the hardware must be allowed to settle before new readings are valid While running the measurement input and control input in parallel we recommend using different excitation frequencies for each in...

Страница 102: ...t be able to perform the most simple control functions A good starting point is deciding which control loop to use whether to operate in open or closed control mode and which tuning mode is best for the application Other parameters fall into place once these have been chosen Section 2 11 2 of this manual describes the principles of closed loop proportional integral and derivative PID control 4 6 1...

Страница 103: ...nce set the Heater Resistance setting to 25 for any resistance less than 50 or to 50 for any higher heater resistance The user max current setting is useful when using a non standard heater resistance value Refer to section 4 6 1 2 1 for more information on Max User Current TABLE 4 10 pro vides examples of different heater resistances and max current settings and the resulting maximum heater power...

Страница 104: ...current However unlike the warm up heater the sample heater can also be configured to display the output range by its full scale power and the output as power in watts This configuration is better for pre dicting the power entering the load but it relies on an accurate heater resistance being entered into the instrument section 4 6 1 1 With both heaters the heater output display on the front panel...

Страница 105: ...p control mode for tightly controlling temperature using the heater outputs of the Model 372 In this mode the controller attempts to keep the load at exactly the user entered setpoint temperature To do this it uses feedback from the control input sensor to calculate and actively adjust the control output setting The Model 372 uses a control algorithm called PID that refers to the three terms used ...

Страница 106: ...o section 4 3 2 for details on configuring display modes Since there is no sensor feedback in Open Loop mode there is nothing to prevent the sys tem from being overheated We recommend using the temperature limit feature to help protect the system from overheating section 4 4 10 Menu navigation Output Setup Q Sample Heater or Warm Up Heater Q Output Mode Q Zone 4 6 1 4 4 Warm Up Mode Warm up Heater...

Страница 107: ...Up Heater Off Analog Still Off Interface command OUTMODE 4 6 1 5 2 Proportional P The proportional parameter also called gain is the P part of the PID control equation It has a range of 0 001 to 1000 with a resolution of 0 001 The default value is 10 To set P first configure the output mode of the desired heater to Closed Loop PID mode section 4 6 1 4 Then press Sample Heater or Warm Up Heater to ...

Страница 108: ...section 4 6 1 3 to set the Heater Out display units When heater display units are configured as current the manual output parameter is set in percent of full scale cur rent for the selected heater range for both the warm up heater and the sample heater The Manual Output setting range is 0 to 100 with a resolution of 0 01 When the heater output display is configured for power the warm up heater man...

Страница 109: ... reading above the specified temperature is observed section 4 4 10 There are some instances when temperature control in ohms may be desired for example when a temperature curve is not available For these applications the Model 372 can control temperature in ohms To control in ohms set the preferred units parameter to ohms When controlling in ohms the setpoint resolution matches the display resolu...

Страница 110: ... rate that keeps the control output from reaching the extremes of 100 or 0 while ramping for optimal results The ramping feature is useful by itself but it is even more powerful when used with other features Setpoint ramps are often used with zone control mode As tempera ture is ramped through different temperature zones control parameters are auto matically selected for best control Ramps can be ...

Страница 111: ...lable to the connected heater The 100 mA range provides the maximum power and each successive lower range pro vides 10 times less power than the last Lower sample heater ranges are provided to allow good control resolution at lower temperatures where cooling power dimin ishes Heater range is an integral part of the closed loop control system so re tuning may be required when heater range is change...

Страница 112: ... the PID control algorithm uses the unfiltered input read ings from the control channel as its feedback This method offers the best control sta bility and some noise immunity because of the natural averaging that takes place in the integral I part of the control equation The control algorithm can be configured to use filtered readings instead of unfiltered readings This configuration can improve n...

Страница 113: ... change pause times as configured for the enabled measure ment channels In the case where two measurement input channels are used for con trol for example one channel tied to the sample heater and one channel tied to the warm up heater the firmware will scan to the sample heater control channel then to the warm up heater control channel before scanning back to non control chan nels TABLE 4 11 and ...

Страница 114: ...l scale This output can be configured to Open Loop section 4 6 1 4 3 Monitor Output or Still Output mode The Open Loop mode can be used to set the output to a specific constant value The Monitor Out mode uses the output to provide a voltage proportional to an input sensor reading to be used by an external device such as a data logger The Still Output mode is described in section 4 6 2 2 The voltag...

Страница 115: ...s restored The power up enable feature allows you to choose whether or not the heater range or analog output is turned off each time the instrument power is cycled Set the power up enable parameter to off to ensure that the heater range or analog output is turned off on power up Set it to on to return the heater range or ana log output to its previous setting when power is restored Menu navigation...

Страница 116: ...hen in local mode the Remote LED will not be illuminated Menu navigation Remote Local LED On Remote mode LED Off Local mode 4 8 Locking and Unlocking the Keypad The keypad lock feature prevents accidental changes to parameter values When the keypad is locked some parameter values may be viewed but most cannot be changed from the front panel ALL OFF is the only keypad function that remains active w...

Страница 117: ...me zone and will update to the programmed zone table settings when the setpoint crosses into a new zone To illustrate how the control parameters are updated in Zone mode consider the zone settings in TABLE 5 1 Starting from room temperature about 300 K and setting a setpoint of 2 K with Setpoint Ramping turned on the setpoint will begin ramping at the current setpoint ramp rate then once the setpo...

Страница 118: ...ge Relay 2 A On A Off Relay 1 A On A Off Proportional 0 0 1 000 Integral 0 10 000 Derivative 0 2 500 0 100 Ramp Rate Manual output Heater Range Relay 2 A On A Off Relay 1 A On A Off Proportional 0 0 1 000 Integral 0 10 000 Derivative 0 2 500 0 100 Ramp Rate Manual output Heater Range Relay 2 A On A Off Relay 1 A On A Off Proportional 0 0 1 000 Integral 0 10 000 Derivative 0 2 500 0 100 Ramp Rate M...

Страница 119: ...the warm up heater the maxi mum current provided to the heater will be 0 63 A Therefore if the Warm Up Per centage is set to 50 the current supplied to the heater will be 50 of 0 63 A or 0 32 A when the output is on For more information regarding the warm up heater resistance and current settings see section 4 6 1 2 Menu navigation Output SetupQWarm Up Heater Q Warm Up PercentageQ 0 to 100 Default...

Страница 120: ... Still Q Output Mode Q Monitor Out Output Setup Q Analog Still Q Control Input Q None A 1 16 Default Control Input Q None Interface command OUTMODE 5 4 1 Monitor Units The Monitor Units parameter determines the units of the Control Input sensor to use for creating the proportional voltage output The Monitor Out scaling parameter set tings are entered using the units chosen for this parameter Menu ...

Страница 121: ...le Menu navigation Output Setup Q Analog Still Q Polarity Q Unipolar or Bipolar Output Setup Q Analog Still Q Monitor Out 10 V Q See note below Output Setup Q Analog Still Q Monitor Out 0 V Q See note below Output Setup Q Analog Still Q Monitor Out 10 V Q See note below Monitor Out 10 V 0 V and 10 V settings depend on the Monitor Units selected and are limited to the acceptable values of the selec...

Страница 122: ... to On for an enabled alarm then the beeper inside the instrument will sound when the alarm activates The two relays on the Model 372 can also be tied to alarm functions as described in section 5 5 2 You may want to set the Visible parameter to Off if there is no need for showing the alarm state on the front panel for instance if you are using the alarm function to trig ger a relay The Audible par...

Страница 123: ...m has been activated you will be prompted with a Reset Alarm message Select No to enter the Alarm Setup menu Menu navigation Relays Alarms Q Alarm Setup Q Input A 1 16 QLatchingQ Off On Relays Alarms Q Alarm Setup Q Input A 1 16 QDeadbandQ see note below Low and High Setpoint limits are determined by the Preferred Units of the associated sensor input Default Latching Q Off Deadband Q 1 0000 K Inte...

Страница 124: ...o Follow parameter is set to Low the relay will energize if the con figured Alarm Input sensor goes into a low alarm state If it is set to High the relay will energize if the configured Alarm Input sensor goes into a high alarm state If the Alarm to Follow parameter is set to Both the relay will energize if the configured Alarm Input sensor goes into either a low alarm or a high alarm state In the...

Страница 125: ...el or from the com puter interface Refer to section 4 2 3 for alpha numeric entry D Serial number a sensor serial number of up to ten characters letters or numbers can be entered from either the front panel or from the computer interface Refer to section 4 2 3 for alpha numeric entry The default is blank D Format the format parameter tells the instrument what breakpoint data format to expect Diffe...

Страница 126: ...s 0 K to 9999 99 K Setting resolution is also six digits in sensor units The curve format parameter defines the range and resolution in sensor units as shown in TABLE 5 2 The sensor type determines the practical setting resolution TABLE 5 3 lists recommended sen sor units resolutions Enter the breakpoints with the sensor units value increasing as point number increases There should not be any brea...

Страница 127: ...ve and press Enter 3 Scroll to the desired curve and press Enter again 4 Edit the curve header parameters using the standard keypad operation methods described in section 4 2 3 The curve breakpoints are entered in a slightly differ ent way than other menu parameters 5 To access the breakpoint data highlight Curve Points in the Curve Edit menu screen and press Enter to enter the Curve Point entry s...

Страница 128: ... in the list To add a new breakpoint pair to a curve that has less than 200 pairs scroll to the end of the list and edit the 0 value pair by following the procedure for editing a breakpoint pair in section 5 7 1 1 If the curve still contains less than 200 pairs a new 0 value breakpoint will be added to the end of the list for entering another new breakpoint pair Menu navigation Curve Entry QEdit C...

Страница 129: ...hen press Enter 2 Scroll to the desired curve and press Enter 3 Choose Yes at the confirmation message to finalize the operation 4 To cancel the operation either choose No to the confirmation message or press Escape Menu navigation Curve EntryQErase Curve Q 21 59 Interface command CRVDEL 5 7 4 Copy Curve Temperature curves can be copied from one location in the Model 372 to another This is a good ...

Страница 130: ...odel 370 commands Each command will either be inter preted directly or it will be translated to the most appropriate Model 372 setting for full compatibility with the Model 370 5 8 2 Command Interpretation As areference the following commands are interpreted differently if Emulation mode is on D ANALOG D DISPLAY D ZONE D CRVPT D CRVHDR D CRVDEL D BAUD D INSET D INCRV The Model 372 must be in Emula...

Страница 131: ... non controlling channels to main tain stable PID control When autoscanning is disabled the Model 372 will not automatically switch back to the channel used for controlling if a non control channel is manually selected How ever if this behavior is desired autoscan can be enabled with a dwell time of 5 s being assigned to the channel used for control and 1 s for the non reading channel 5 8 5 Hardwa...

Страница 132: ...ss occur as a result of this decreasing the reso lution from 0 003 of range to 0 02 of range To accommodate scenarios where your load resistance is small on the order of 100 the current to voltage conversion resistor must be adjusted to maintain 10 V across it For example if the load resistor is 100 an added parallel resistor must be sized appropriately to maintain an equivalent resistance of 15 8...

Страница 133: ... devices through the bus The Bus Control ler designates to the devices on the bus which function to perform The Model 372 performs the functions of Talker and Listener but it cannot be a Bus Controller The Bus Controller is the digital computer that tells the Model 372 which functions to perform TABLE 6 1 defines the IEEE 488 capabilities and subsets for the Model 372 Instruments are connected to ...

Страница 134: ...ommands A uniline command message asserts only a single signal line The Model 372 recognizes two of these messages from the Bus Controller Remote REN and Interface Clear IFC The Model 372 sends one uniline command Service Request SRQ D REN Remote puts the Model 372 into remote mode D IFC Interface Clear stops current operation on the bus D SRQ Service Request tells the bus controller that the Mode...

Страница 135: ...ser programs and the instru ment issues responses Two or more command strings or queries can be chained together in one communication but they must be separated by a semi colon The total communication string must not exceed 255 characters in length A command string is issued by the computer and instructs the instrument to perform a function or change a parameter setting When a command is issued th...

Страница 136: ... register will set the summary bit for the register set in the status byte You may write to or read from an enable reg ister Each event register bit is logically ANDed to the corresponding enable bit of the enable register When you set an enable register bit and the corresponding bit is set in the event register the output summary of the register will be set which in turn sets the summary bit of t...

Страница 137: ...quest enable register When you set a service request enable register bit and the corresponding summary bit is set in the status byte the RQS MSS bit of the status byte will be set which in turn sets the service request hardware line on the bus 6 2 4 5 Reading Registers You can read any register in the status system using the appropriate query command Some registers clear when read others do not se...

Страница 138: ...unrecognized termina tors or an unsupported command D Execution Error EXE Bit 4 this bit is set if an execution error has been detected This occurs when the instrument is instructed to do something not within its capabilities D Query Error QYE Bit 2 this bit indicates a query error It occurs rarely and involves loss of data because the output queue is full D Operation Complete OPC Bit 0 when OPC i...

Страница 139: ...d with the STB query which returns the binary weighted sum of all bits in the status byte this is the MSS function of the bit Performing a serial poll will automatically clear the RQS function but it will not clear the MSS function A STB will read the status of the MSS bit along with all of the summary bits but also will not clear it To clear the MSS bit either clear the event register that set th...

Страница 140: ...he bus controller The user program may then direct the bus controller to serial poll the instruments on the bus to identify which one requested service the one with bit 6 set in its status byte Serial polling will automatically clear RQS of the status byte register This allows sub sequent serial polls to monitor bit 6 for an SRQ occurrence generated by other event types After a serial poll the sam...

Страница 141: ...nt The bus controller could then be instructed to look for an SRQ allowing additional communication with the instru ment while the initial process executes The OPC query has no interaction with bit 0 OPC of the standard event status reg ister If the OPC query is sent at the end of a command sequence the bus will be held until the instrument completes the operation that was initiated by the com man...

Страница 142: ...rogramming interface requires a certain configura tion to communicate properly with the Model 372 The proper configuration parame ters are listed in TABLE 6 5 The USB hardware connection uses the full speed 12 000 000 bits s profile of the USB 2 0 standard however since the interface uses a virtual serial com port at a fixed data rate the data throughput is still limited to a baud rate of 57 600 b...

Страница 143: ... message stating the wizard has finished installing the software for Lake Shore Model 372 AC Resistance Bridge and Temperature Controller will appear Click Finish to complete the installation 6 3 3 3 Installing the Driver From the Web The Model 372 USB driver is available on the Lake Shore website To install the driver it must be downloaded from the website and extracted Use the procedure in secti...

Страница 144: ...nces this will be between Network adapters and Ports COM LPT If the Other Devices item is not already expanded click the icon Lake Shore Model 372 should appear indented underneath Other Devices If it is not displayed as Lake Shore Model 372 it might be displayed as USB Device If neither are displayed click Action and then Scan for hardware changes which may open the Found New Hardware wizard auto...

Страница 145: ... face Each character is ten bits long and contains data bits bits for character timing and an error detection bit The instrument uses seven bits for data in the American Standard Code for Information Interchange ASCII format One start bit and one stop bit are necessary to synchronize consecutive characters Parity is a method of error detection One parity bit configured for odd parity is included i...

Страница 146: ...initiate communication more than 20 times per second When issuing queries or queries and commands together the user program should D Properly format and transmit the query including the terminator as 1 string D Prepare to receive a response immediately D Receive the entire response from the instrument including the terminator D Guarantee that no other communication is started during the response o...

Страница 147: ...to binary shows that the first 24 bits are ones and the last 8 bits are zeros This means that the first 24 bits of the Static IP Address 192 168 0 represent the subnet and the last 8 bits 12 represent the device D Gateway Address a gateway is a network traffic routing device that is used to route communication between networks If a gateway is not used then devices on a network can only communicate...

Страница 148: ...f Auto IP is the limitation of only working with a link local network which cannot connect to other networks including the internet Another disadvantage lies in the fact that an Auto IP assigned address will not be preserved through a device reconfiguration such as a power cycle To use Auto IP to automatically configure a link local IP address and subnet mask set the DHCP parameter to Off then set...

Страница 149: ... Multiple DNS servers are sometimes used for redundancy but multiple servers are not required and not all networks provide a DNS server DNS addresses can be configured automatically using the DHCP method if the network DHCP server is con figured to do so Your DHCP server must be configured appropriately to provide DNS server addresses Not all DHCP servers provide this functionality on your network...

Страница 150: ...referred Domain Name parameters and the assigned IP address The Preferred Domain Name parameter can only be accessed using the NET interface command section 6 6 1 or by using the Ethernet configuration page section 6 4 2 of the embedded website on the Model 372 If DNS reverse lookup is enabled on the network DNS server and the DNS address parameters are correctly configured the Model 372 will perf...

Страница 151: ... Model 372 has lost contact with the Ethernet module this may indicate a damaged Ethernet module D Acquiring Address the Model 372 is attempting to configure the IP address param eters using the enabled methods 6 4 2 2 MAC Address The Media Access Controller MAC Address is a physical hardware address assigned to all Ethernet devices MAC addresses are 48 bits and are generally written as six groups...

Страница 152: ...ocket while two socket connections are already open on a Model 372 will fail 6 4 4 Embedded Web Interface The Model 372 provides a web interface via an embedded web server that runs on the instrument Once the Model 372 is properly connected and the IP parameters prop erly configured the web interface can be opened using a web browser The web inter face should be accessible using any modern web bro...

Страница 153: ...72 Ethernet Configuration Page provides a means of reconfiguring the Ethernet config uration parameters of the Model 372 Ethernet Status Page provides status and statistics related to the current Ethernet connection FIGURE 6 4 Model 372 home page FIGURE 6 5 Ethernet configuration page FIGURE 6 6 Ethernet status page ...

Страница 154: ...6 5 Utilities The utilities embedded on the Model 372 are written using the Java programming language This theoretically allows the applications to run properly on many different platforms Windows Mac Linux etc although the applications are only sup ported on Microsoft Windows XP or Windows 7 and Vista and have been designed to work with the Java Runtime Environment JRE version 1 6 To download Jav...

Страница 155: ...o store the curve to a user curve location in the Model 372 click Write to Instrument The Write Curve to Instrument dialog box appears Select a user curve location to write the loaded temperature curve to and click OK To write the currently loaded curve to a file click Write to File A Save Browser dialog box appears First use the Files of Type drop down box to select the file format in which to sa...

Страница 156: ...Download the latest Model 372 Ethernet Firmware file from www lakeshore com 2 Once the firmware files have been downloaded connect to the embedded web site section 6 4 4 and navigate to the Utilities page 3 Click Launch Ethernet Firmware Updater 4 Accept any security warning messages that are presented refer to section 6 5 for an explanation of these security warnings The Ethernet Firmware Updater...

Страница 157: ...tentionally turning on and to prevent interrupting communication with the instrument To export the current configuration of the Model 372 to a file 1 On the Utilities page in the Model 372 embedded website click Export config FIGURE 6 7 2 In the Save File dialog box select the location and file name to which you want to export the current instrument configuration Click Save The utility will export...

Страница 158: ...ms 12 through 17 in the screenshot above It is used to configure the charting and logging functionality for the next data acquisition task When Start is pressed the parame ters in the configuration panel are used to determine D Sample period 13 the rate at which to acquire readings from the instrument in milli seconds D Number of data points to log 14 the number of data points to log if logging to...

Страница 159: ...lding the Ctrl key then clicking and dragging the chart After manually zooming or panning autoscaling in both axes is turned off and Reset Zoom Pan becomes active To return to autoscale mode click Reset Zoom Pan A screenshot of the currently displayed chart can be copied to the clipboard saved in the PNG image format or printed directly to a printer using the context menu that appears when right c...

Страница 160: ...Collapse Utilities Panel 10 When collapsed the same button becomes an Expand Utilities Panel button that can be used to restore the utilities panel on the form 6 5 4 5 Menu The standard dropdown menu includes the following sections File 1 D Interface Configuration can be used to configure the remote interface connec tion to the instrument D Exit closes the Chart Recorder application Log Chart 2 D ...

Страница 161: ...ommand Command name Form of the command input Syntax of user parameter input see key below Definition of first parameter Definition of second parameter Input Format a nn input Specify input A D curve number Input Curve Number Command Specify input curve 0 none 1 20 std curves 21 59 user curves INCRV input term INCRV Brief description of query Query name Form of the query input Syntax of user param...

Страница 162: ...150 cHAPTER 6 Computer Interface Operation Model 372 AC Resistance Bridge and Temperature Controller ...

Страница 163: ... 172 CMR Common Mode Reduction Cmd 158 QRDG Quadrature Reading Query 172 CMR Common Mode Reduction Query 158 RAMP Setpoint Ramp Parameter Cmd 173 CRVDEL Curve Delete Cmd 158 RAMP Setpoint Ramp Parameter Query 173 CRVHDR Curve Header Cmd 158 RAMPST Setpoint Ramp Status Query 173 CRVHDR Curve Header Query 159 RANGE Heater Range Cmd 173 CRVPT Curve Data Point Cmd 159 RANGE Heater Range Query 173 CRVP...

Страница 164: ...r to section 6 2 5 for a list of event flags Example To enable event flags 0 4 and 7 send the command ESE 145 term 145 is the sum of the bit weighting for each bit Begins common interface command Required to identify queries s n String of alphanumeric characters with length n Send these strings using surrounding quotes Quotes enable characters such as commas and spaces to be used without the instr...

Страница 165: ...acturer Manufacturer ID Format model Instrument model number instrument serial Instrument serial number firmware version Instrument firmware version Example LSCI MODEL372 1234567 1234567 1 0 OPC Operation Complete Command Input OPC term Remarks Generates an Operation Complete event in the Event Status Register upon comple tion of all pending selected device operations Send it as the last command i...

Страница 166: ... 2 6 for a list of status flags STB Status Byte Query Input STB term Returned bit weighting term Format nnn Remarks Acts like a serial poll but does not reset the register to all zeros The integer returned represents the sum of the bit weighting of the status flag bits that are set in the status byte register Refer to section 6 2 6 for a list of status flags TST Self Test Query Input TST term Retu...

Страница 167: ...hen an alarm condition occurs Valid entries 0 off 1 on Remarks Configures the alarm parameters for a channel On a Model 370 the alarm had an independent units setting The 372 uses preferred units therefore the data source units field is ignored but maintained for backwards compatibility Therefore pass a zero into this field when sending the command The audible and visible parameters are optional a...

Страница 168: ... out this parameter represents the data at which the analog output reaches 100 output low value If mode is monitor out this parameter represents the data at which the analog output reaches 100 output if bipolar or 0 output if positive only manual value If mode is Open Loop Manual Closed Loop PID Still or Warm up this parameter is the value of the analog output as it applies to the set mode Example...

Страница 169: ...S 232 Baud Rate Command Input BAUD bps term Format n bps Specifies Baud rate 0 300 Baud 1 1 200 Baud 2 9 600 Baud 3 57 600 default BAUD RS 232 Baud Rate Query Input BAUD term Returned bps term Format n refer to command for description BEEP Audible Alarm Beeper Command Input BEEP state term Format n state 0 off audible alarm beeper remains off 1 on audible alarm beeper is on when any alarm is activ...

Страница 170: ...ber Limited to 10 characters format Specifies the curve data format Valid entries 3 K lin ear 4 log K linear 7 K cubic spline limit value Specifies the curve temperature limit in kelvin coefficient Specifies the curves temperature coefficient Valid entries 1 negative 2 positive Example CRVHDR 21 RX 102B 00011134 4 1 5 1 term configures user curve 21 with a name of RX 102B serial no 00011134 data f...

Страница 171: ... 370 emulation mode the user curves are defined as 1 to 20 for backwards compatibility The curvature value field is only required if the curve point being loaded is used for a cubic spline interpolation curve and can be omitted when sending linear interpolation curves Example CRVPT 21 2 0 10191 470 000 N term sets User Curve 21 second data point to 0 10191 sensor units and 470 000 K CRVPT Curve Da...

Страница 172: ...ield display location to query 1 to 8 Returned input units term Format n n n refer to command for description DISPLAY Display Setup Command Input DISPLAY mode num fields displayed info term Format n n n mode Specifies display mode 0 measurement input 1 control input 2 Custom num fields When mode is set to Custom specifies number of fields display locations to display 0 2 large 1 4 large 2 8 small ...

Страница 173: ...ic high and D2 and D4 to logic low DOUT Digital Output Query Input DOUT term Returned bit weighting term Format nn refer to command for description EMUL 370 Emulation Mode Input EMUL state term Format n state 0 off 1 on Remarks The 370 emulation mode provide a means of using the Model 372 in place of a Model 370 in a software controlled system without updating the software The emulation mode setti...

Страница 174: ...uickly toggle between 0 s and the desired settle time to observe the filtering effects on the reading See section 4 4 7 for more information FILTER Filter Parameter Query Input FILTER input channel term Format nn input channel Specifies input or channel to query A CONTROL INPUT 1 to 16 measurement input Returned off on settle time window term Format n nnn nn refer to command for description FREQ E...

Страница 175: ... maximum heater output current if max current is set to User Specified warm up heater only current power Specifies whether the heater output displays in current or in power Valid entries 1 current 2 power Remarks Power displays in watts for output 0 sample heater and full scale for output 1 warm up heater When configuring the sample heater a zero should be passed in for the max current and max use...

Страница 176: ...ulation mode is enabled IEEE Returns terminator EOI enable address where terminator 2 LF and EOI enable 0 enabled INCRV Input Curve Number Command INCRV input curve number term Format a nn input Specifies which input or channel to configure A control input 1 to 16 measurement input channel 0 all mea surement input channels curve number Specifies which curve the input uses If specified curve type d...

Страница 177: ... enabled dwell pause curve number tempco term Format nn n nnn nnn nn n input channel Specifies which input or channel to configure A control input 1 to 16 measurement input 0 all channels mea surement input disabled enabled Specifies whether the input channel is disabled or enabled 0 disabled 1 enabled dwell Specifies a value for the autoscanning dwell time 1 to 200 s Not applicable for input chan...

Страница 178: ...INTYPE input channel mode excitation autor ange range cs shunt units term Format nn n nn nn n n n input channel Specifies which input or channel to configure A control input 1 to 16 measurement input channel 0 all measurement input channels mode Sensor excitation mode measurement input 0 Voltage Exci tation Mode 1 Current Excitation Mode control input 1 Current Excitation excitation Measurement in...

Страница 179: ... kelvin 2 ohms Remarks When configuring the control input A all parameters must be included but non applicable parameters will be ignored Example INTYPE 2 1 10 0 15 0 1 term sets measurement input channel 2 to current exci tation mode 20 k resistance range with a 31 6 nA excitation current autorange off excitation on with preferred units of kelvin Range Current Resistance 1 316 pA 632 k 2 1 nA 200...

Страница 180: ... Command Input LEDS off on term Format n off on 0 LEDs off 1 LEDs on Remarks If set to 0 front panel LEDs will not be functional Function can be used when display brightness is a problem Example LED 0 term turns all front panel LED functionality off LEDS Front Panel LEDs Query Input LEDS term Returned off on term Format n refer to command for description LOCK Keypad Lock Command Input LOCK state c...

Страница 181: ...de term Format n mode 0 local 1 remote 2 remote with local lockout Example MODE 2 term places the Model 372 into remote mode with local lockout MODE IEEE Interface Mode Query Input MODE term Returned mode term Format n refer to command for description MONITOR Monitor Reference Output Selection Command Input MONITOR source term Format n source 0 off 1 CS NEG 2 CS POS 3 VCM NEG 4 VCM POS 5 VDIF 6 VA...

Страница 182: ... DNS Sec DNS Pref Host Pref Domain Description term Format n n dd dd dd dd dd s 15 s 64 s 32 DHCP 0 DHCP off 1 DHCP on AUTO IP 0 Dynamically configured link local addressing Auto IP off 1 on IP IP address for static configuration Sub Mask Subnet mask for static configuration Gateway Gateway address for static configuration Pri DNS Primary DNS address for static configuration Sec DNS Secondary DNS ...

Страница 183: ...ed Ethernet parameters If the Ethernet interface is not configured then IP subnet mask gateway primary DNS and secondary DNS parameters will be 0 0 0 0 OUTMODE Output Mode Command Input OUTMODE output mode input channel powerup enable polarity filter delay term Format n n nn n n n nnn output Specifies which output to configure 0 sample heater 1 output 1 warm up heater 2 output 2 analog still mode ...

Страница 184: ...t 0 sample heater 1 output 1 warm up heater P value The value for control loop Proportional gain 0 0 to 1000 I value The value for control loop Integral reset 0 to 10000 D value The value for control loop Derivative rate 0 to 2500 Remarks Setting resolution is less than 6 digits indicated If output is not specified 0 sample heater is assumed for backwards compatibility Example PID 10 100 20 0 term...

Страница 185: ...ut is not specified 0 sample heater is assumed for backwards compatibility RAMPST Setpoint Ramp Status Query Input RAMPST output term Format n output 0 sample heater 1 output 1 warm up heater Returned ramp status term Format n ramp status 0 Not ramping 1 Setpoint is ramping Remarks If output is not specified 0 sample heater is assumed for backwards compatibility RANGE Heater Range Command Input RA...

Страница 186: ...for the specified channel RDGR Resistance Reading Query Input RDGR input channel term Format nn input channel Specifies which input or channel to query A control input 1 to 16 measurement input Returned ohm value term Format nnn nnnE nn Remarks Also see the RDGST command RDGST Input Reading Status Query Input RDGST input channel term Format nn input channel Specifies which input or channel to quer...

Страница 187: ...2 2 0 term relay 1 is setup in Alarms mode and activates when channel 2 low alarm activates RELAY Relay Parameter Query Input RELAY relay number term Format n relay number Specifies which relay to query 1 or 2 Returned mode channel alarm alarm type term Format n nn n refer to command for description RELAYST Relay Status Query Input RELAYST relay number term Format n relay number Specifies which re...

Страница 188: ... Reading Query Input SRDG input term Format n input channel Specifies which input or channel to query A control input 1 to 16 measurement input Returned sensor units value term Format nnn nnnE nn Remarks Value returned is always in ohms Also see the RDGST command STILL Still Output Command Input STILL value term Format nnnnnn value Specifies value for the Still output in percent E x a m p l e STIL...

Страница 189: ...gured using the OUTMODE command WARMUP Warmup Mode Parameter Query Input WARMUP output term Returned control percentage term Format n nnn refer to command for description WEBLOG Website Login Parameters Command Input WEBLOG username password term Format s 15 s 15 username 15 character string representing the website username password 15 character string representing the website password Example WE...

Страница 190: ...matches this output relay 2 Specifies the high relay state 0 off 1 on Only applicable when relay is configured in Zone mode and the relays control output matches this output Remarks Configures the control loop limit band parameters used in conjunction with the sta tus byte register Refer to section 6 2 6 When in Emulation mode the rate parame ter is omitted and additional analog 1 and analog 2 par...

Страница 191: ...Kits Description of kits 372S ACResistanceBridgewithScanner IncludesaLakeShoreModel372ACResistanceBridgewith a Lake Shore Model 3726 16 channel scanner and 3 m 10 ft cable Power is configured as shown inTABLE 7 3 372S 6 ACResistanceBridgewithScanner IncludesaLakeShoreModel372ACResistanceBridgewith a Lake Shore Model 3726 16 channel scanner and 6 m 20 ft cable Power is configured as shown inTABLE 7...

Страница 192: ...s ID 10 31 indium disks are 7 92 mm diameter 0 13 mm 0 312 in diameter 0 005 in ID 10 56 indium disks are 14 27 mm diameter 0 127 mm 0 562 diameter 0 005 in IF 5 Indium foil sheets quantity 5 When used as a washer between DT 470 CU silicon diode or other temperature sensors and refrigerator cold stages indium foil increases the thermal con tact area and prevents the sensor from detaching due to vi...

Страница 193: ...hore com FIGURE 7 1 Cable assembly to connect Model 372 to optional scanner FIGURE 7 2 Scan control To scanner Female DB15 Male DB15 To Model 372 Scan control Output V Output I Scan control Input V Input I Pin 1 Shield not attached ...

Страница 194: ...r of the instrument and to relieve strain on heavy cables The mounting ears are painted and do not guar antee good electrical contact between the instrument and cabinet They should not be used for ground strapping unless paint is removed from under all screws Ensure that there is a 25 mm 1 in clearance on both sides of the instrument after rack mounting FIGURE 7 3 Model RM 1 rack mount kit Item De...

Страница 195: ...h 6 Send the message terminator 7 Send the entire message string at one time including the terminator Many ter minal emulation programs do not 8 Send only one simple command at a time until communication is established 9 Be sure to spell commands correctly and use proper syntax 8 2 2 Existing Installation No Longer Working 1 Power the instrument off then on again to see if it is a soft failure 2 P...

Страница 196: ...crease the delay between all commands to 50 ms to make sure the instrument is not being overloaded 8 4 Fuse Drawer The fuse drawer supplied with the Model 372 holds the instrument line fuses and line voltage selection module The drawer holds two 5 mm 20 mm 0 2 in 0 79 in time delay fuses It requires two good fuses of the same rating to operate safely Refer to Section 8 6 for details 8 5 Line Volta...

Страница 197: ...sting fuse s Replace with proper slow blow time delay fuse ratings as follows 6 Re assemble the line input assembly in reverse order 7 Verify voltage indicator in the line input assembly window 8 Connect the instrument power cord 9 Turn the power switch ON l 8 7 Factory Reset Menu It is sometimes necessary to reset instrument parameter values or clear the contents of curve memory Both are stored i...

Страница 198: ... input Input A PID manual heater power MHO ouptu Default Control Filter Off Proportional P 10 0 Heater resistance 100 Integral I 20 0 Polarity Unipolar Derivative D 0 0 Power up enable Off Manual output 0 000 Heater output display Current Heater Default Setpoint ramping Off Heater range Off Setpoint change pause time 25 s Setpoint Default Warm up heater output setup Default Setpoint value 0 000 K ...

Страница 199: ...is disabled Refer to section 4 4 NOCURV Input has no curve Refer to section 4 4 12 Cannot Communicate with Input DSP The main microprocessor has lost communication with the sensor input DSP A temperature limit has been exceeded The temperature reading on a sensor input has exceeded the Temperature Limit set ting A detailed message will follow which includes a reference to which sensor inputs tempe...

Страница 200: ...hrough FIGURE 8 9 FIGURE 8 3 Measurement input Pin Voltage connector Current connector 1 V Voltage I Current 2 VG Voltage guard IG Current guard 3 SHIELD Shield SHIELD Shield 4 VG Voltage guard IG Current guard 5 V Voltage I Current 6 None Not used None Not used TABLE 8 3 Measurement input connector details FIGURE 8 4 Control input Pin Symbol Description 1 I Current 2 V Voltage 3 None Shield 4 V V...

Страница 201: ...lays and Output 3 and 4 Pin Description 1 Sample heater 2 Sample heater 3 Analog out still heater 4 Analog out still heater 5 Not used floating 6 Warm up heater 7 Warm up heater TABLE 8 5 Heater terminal block pin and connector details FIGURE 8 6 Relay terminal block for relays and Output 3 and 4 ...

Страница 202: ...4 Relay 2 normally open 5 Relay 2 normally closed 6 Relay 2 normally closed TABLE 8 6 Relay terminal block pin and connector details FIGURE 8 7 USB pin and connector details Pin Name Description 1 VCC 5 VDC 2 D Data 3 D Data 4 GND Ground TABLE8 7 USB pinand connector details FIGURE 8 8 Ethernet pin and connector details 2 1 3 4 EPWR EPWR RXD EPWR EPWR RXD TXD TXD ...

Страница 203: ...wed in a system is 2 m 6 6 ft for each device on the bus or 20 m maximum The Model 372 can drive a bus of up to 10 devices A connector extender is required to use the IEEE 488 interface and relay terminal block at the same time FIGURE 8 9 shows the IEEE 488 interface connector pin location and sig nal names as viewed from the Model 372 rear panel Pin Symbol Description 1 TXD Transmit data 2 TXD Tr...

Страница 204: ...D 7 Ground wire twisted pair with NRFD 20 GND 8 Ground wire twisted pair with NDAC 21 GND 9 Ground wire twisted pair with IFC 22 GND 10 Ground wire twisted pair with SRQ 23 GND 11 Ground wire twisted pair with ATN 24 GND Logic ground TABLE 8 9 IEEE 488 rear panel connector details FIGURE 8 10 Scan control Pin Name Description 1 Scan present Signal to Model 372 that a scanner is installed 2 Digital...

Страница 205: ... its limit a descriptive overload message is displayed An explanation of the error messages and likely causes follows 8 12 1 1 CSOVL Current Source Overload Measurement Input Only This message is displayed in the measurement input display field anytime the current source drive signal s into the current sample resistor s exceeds a 10 V peak limit The overload can occur at either CSPOS or CSNEG poin...

Страница 206: ... the differential overload error VDIF OVL is displayed The overload occurs at the VDIF point in the instrumentation amplifier circuit Refer to FIGURE 8 3 for the location of the VDIF monitoring point The signal voltage can be viewed on an oscilloscope by using the monitor output described in section 4 5 3 Usual causes of this error include D An attempt to measure a resistance that is much greater ...

Страница 207: ...hat the voltage pair of leads is twisted and shielded Likewise the current pair of leads should be twisted and shielded Twisted pair wiring reduces the differential signals potentially created by environmental noise However there is no advantage gained by twisting the current pair of leads together with the voltage pair of leads When twisted leads are not an option inside a Dewar the shielding mus...

Страница 208: ...ut to the oscilloscope should be used A battery operated oscilloscope is another option 8 12 2 1 Nominal Signal Levels For the measurement input measuring a 100 k balanced or floating resistor at a voltage excitation of 632 mV and a resistance range of 200 k with CMR on the fol lowing AC sine wave signals will be observed at the appropriate signal points For the control input when measuring a 10 k...

Страница 209: ...nd filter attenuated These frequencies might be computer generated power harmonic related or even radio frequencies 1 MHz Signals observed at this point are differential in nature and impressed across the measured resistor possibly heating it A level exceeding 10 V peak at this point triggers a VDIF OVL message Common mode voltage can be observed at the CMPOS and CMNEG monitoring points The normal...

Страница 210: ...ly to have difficulty with the phase relationship of the two signals As resistance and or cable length increases so should concern for this relationship Cable capacitance is the single biggest cause of this error refer to section 2 6 6 To complement the generated quadrature reactive reading the Model 372 has a means to observe the phase shift caused by cable capacitance by observing the VAD monito...

Страница 211: ...emory can be reset to default values from the front panel using the Factory Reset menu accessible by pressing and holding the Escape key 8 The Digi DC ME4 01T C is a module used to add Ethernet network capability Included on the module is 4 MB of flash memory used to store the firmware image that runs on the module as well as the utility applications and supporting files provided on the embedded w...

Страница 212: ...all sides of the instrument in a sturdy corrugated cardboard box After receiving your Model 372 AC resistance bridge and temperature controller please use reasonable care when removing the temperature controller from its protective packaging and inspect it carefully for damage If it shows any sign of damage please file a claim with the carrier immediately Do not destroy the shipping container it w...

Страница 213: ...to be made prepaid by the customer Equipment serviced under warranty will be returned prepaid by Lake Shore Equipment serviced out of warranty will be returned FOB Lake Shore 8 14 5 Restocking Fee Lake Shore reserves the right to charge a restocking fee for items returned for exchange or reimbursement ...

Страница 214: ...202 cHAPTER 8 Service Model 372 AC Resistance Bridge and Temperature Controller ...

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