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Lake Shore 370, User Manual

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Lake Shore Model 370 AC Resistance Bridge User’s Manual 

 

Model 370 Resistance Input Calibration Work Sheet for Paragraph 8.12.2.6 (Continued) 

 

Step Range/Setting  Coefficient 

# Resistor  Voltage  Filter 

Actual 

RDGR? 

Coefficient 

6 a 

316 nA Gain 

CALG 1,12 

200 k

Ω

 

63.2 

mV 10s  

 

 

6 b  100 nA Gain 

CALG 1,11 

200 k

Ω

 

20 

mV 10s  

 

 

6 c 

31.6 nA Gain 

CALG 1,10 

200 k

Ω

 

6.32 

mV 10s  

 

 

6 d  10 nA Gain 

CALG 1,9 

200 k

Ω

  

2 

mV 10s  

 

 

6 e 

3.16 nA Gain 

CALG 1,8 

200 k

Ω

  

632 

μ

V 

10s 

   

6 f 

1 nA Gain 

CALG 1,7 

200 k

Ω

  

200 

μ

V 

10s 

   

6 g  316 pA Gain 

CALG 1,6 

200 k

Ω

  

63.2 

μ

V 

50s 

   

6 h  100 pA Gain 

CALG 1,5 

200 k

Ω

  

20 

μ

V 

50s 

   

6 i 

31.6 pA Gain 

CALG 1,4 

200 k

Ω

 6.32 

μ

V  100s 

   

6 j 

10 pA Gain 

CALG 1,3 

200 k

Ω

  

2 

μ

V  200s 

   

 

Current Gain Coefficient = Actual Resistance /RDGR 
 
Step Range/Setting  Coefficient 

# Resistor  Voltage Filter 

Actual 

RDGR? 

Coefficient 

7a 

3.16 pA Gain 

CALG 1,2 

600 k

Ω

 2 

μ

V  200s  

 

 

7b 

1 pA Gain 

CALG 1,1 

2 M

Ω

  

2 

μ

V  200s  

 

 

 

Voltage Gain Coefficient = Actual Resistance/RDGR 

 

8.12.3 

Analog Voltage Output Calibration 

The Model 370 has 2 analog voltage outputs with a range of 

±

10V. These outputs can be calibrated independently of 

each other and their calibration is independent of the measurement input. A DC voltmeter with accuracy of 1 mV on a 
10 V range and cable to connect to the analog output are required. A zero offset and gain coefficient must be calculated 
for each output. The method used for calculating these coefficients provides the most accurate calibration of the DAC 
used in the instrument. 

 

To calibrate the analog voltage outputs perform the following sequence of operations. 

 

1.  Configure the analog voltage output for manual operation (Paragraph 4.16). Set the manual output value to +100%. 

Attach the voltmeter and allow the instrument to warm up for 1 hour. 

2.  Set the zero offset and gain calibration coefficients to their defaults: 

Analog Output 1: 

CALZ 4,1,0

 

 

CALG 4,1,1 

Analog Output 2: 

CALZ 4,2,0

 

 

CALG 4,2,1 

 

3.  Measure and record the +100% output voltage. 
4.  Set the manual output value to –100%. 
5.  Measure and record the –100% voltage. 
6.  Calculate the gain coefficient as: Coefficient = 20 V/(Voltage (+100%) – Voltage (–100%)). 

The gain should be 0.995 ±1%. 

7.  Send the gain coefficient for the appropriate output to the instrument: 

Analog Output 1: 

CALG 4,1,Coefficient 

Analog Output 2: 

CALG 4,2,Coefficient 

 

8.  Set the manual output value to 0%. 
9.  Measure and record the output voltage. 

 

8-22 

Service 

Summary of Contents for 370

Page 1: ...solely on company funds of Lake Shore Cryotronics Inc No government or other contractual support or relationship whatsoever has existed which in any way affects or mitigates proprietary rights of Lake Shore Cryotronics Inc in these developments Methods and apparatus disclosed herein may be subject to U S Patents existing or applied for Lake Shore Cryotronics Inc reserves the right to add improve m...

Page 2: ...o not allow the exclusion of liability for incidental or consequential damages so the above limitation may not apply to you LIMITED WARRANTY STATEMENT Continued 9 EXCEPT TO THE EXTENT ALLOWED BY APPLICABLE LAW THE TERMS OF THIS LIMITED WARRANTY STATEMENT DO NOT EXCLUDE RESTRICT OR MODIFY AND ARE IN ADDITION TO THE MANDATORY STATUTORY RIGHTS APPLICABLE TO THE SALE OF THE PRODUCT TO YOU CERTIFICATIO...

Page 3: ...USA hereby declare that the equipment specified conforms to the following Directives and Standards Application of Council Directives 73 23 EEC 89 336 EEC Standards to which Conformity is declared EN61010 1 2001 Overvoltage II Pollution Degree 2 EN61326 A2 2001 Class A Annex B Model Number 370 Ed Maloof Printed Name Vice President of Engineering Position B ...

Page 4: ... 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 sensitive measure...

Page 5: ...rds 2 7 2 4 5 5 Active Common Mode Reduction 2 8 2 4 5 6 Matched Impedance Current Source 2 8 2 4 6 Measurement Speed and Filtering 2 8 2 5 NOISE SOURCES 2 9 2 5 1 Induced Electrical Noise 2 9 2 5 2 Ground Loop Noise 2 9 2 5 3 Analog Circuit Noise 2 9 2 5 4 Digital Circuit Noise 2 9 2 5 5 Resistor Thermal Noise 2 10 2 5 6 Interference Between Two Model 370s 2 10 2 5 7 Vibration Noise 2 10 2 6 MEAS...

Page 6: ...5 System Nonlinearity 2 18 2 10 2 Closed Loop PID Control 2 19 2 10 2 1 Proportional P 2 19 2 10 2 2 Integral I 2 19 2 10 2 3 Derivative D 2 19 2 10 2 4 Manual Output 2 19 2 10 3 Tuning a Closed Loop PID Controller 2 21 2 10 3 1 Setting Heater Range 2 21 2 10 3 2 Tuning Proportional 2 21 2 10 3 3 Tuning Integral 2 22 2 10 3 4 Tuning Derivative 2 22 3 INSTALLATION 3 1 3 0 GENERAL 3 1 3 1 INSPECTION...

Page 7: ...Current 3 14 3 9 RELAY CONNECTION 3 15 3 10 RACK MOUNTING 3 15 4 OPERATION 4 1 4 0 GENERAL 4 1 4 1 TURNING POWER ON 4 1 4 2 DISPLAY DEFINITION 4 1 4 2 1 Reading Display 4 2 4 2 2 Display Update Indicator 4 2 4 2 3 Range Excitation and Power 4 2 4 2 4 Display and LED Annunciators 4 2 4 2 5 Temperature Control Display 4 3 4 3 KEPAD DEFINITION 4 3 4 3 1 Key Descriptions 4 3 4 3 2 General Keypad Opera...

Page 8: ...Limit 4 18 4 11 2 9 Heater Polarity 4 19 4 11 3 Changing Setpoint 4 19 4 11 4 Manually Setting PID Values 4 20 4 11 4 1 Manually Setting Proportional P 4 20 4 11 4 2 Manually Setting Integral I 4 20 4 11 4 3 Manually Setting Derivative D 4 20 4 11 5 Manual Heater Output 4 21 4 11 6 Heater Output Range and Heater Output Off 4 21 4 11 7 Setpoint Ramp 4 22 4 11 8 Controlling and Scanning 4 23 4 11 8 ...

Page 9: ... Hardware Support 6 12 6 2 4 Character Format 6 12 6 2 5 Message Strings 6 12 6 2 6 Message Flow Control 6 13 6 2 7 Serial Interface Example Programs 6 13 6 2 7 1 Visual Basic Serial Interface Program Setup 6 14 6 2 7 2 Program Operation 6 17 6 2 8 Troubleshooting 6 17 6 3 COMMAND SUMMARY 6 18 6 3 1 Interface Commands 6 20 7 OPTIONS AND ACCESSORIES 7 1 7 0 GENERAL 7 1 7 1 MODELS 7 1 7 2 OPTIONS 7 ...

Page 10: ... 6 1 GPIB Setting Configuration 6 6 6 2 DEV 12 Device Template Configuration 6 6 7 1 Model 112 374 Cable Assembly 7 4 8 1 Fuse Drawer 8 2 8 2 Power Fuse Access 8 2 8 3 Signal Flow Block Diagram 8 8 8 4 Location Of Important Internal Components 8 10 8 5 SCAN CONTROL Connector Details 8 11 8 6 Resistor Sensor INPUT Connectors 8 12 8 7 REFERENCE and MONITOR Connector Details 8 12 8 8 HEATER OUTPUT Co...

Page 11: ...or 16 with scanner PID temperature control IEEE 488 and RS 232C interfaces alarms relays and analog outputs Unique noise reduction elements o Patented current source preserves common mode noise rejection o Optically isolated measurement electronics eliminates the potential for ground loops Two 16 channel scanners Model 3716 scanner is optimized for low DC bias current Model 3716L scanner is optimi...

Page 12: ...s The Model 370 provides a unique patented matched impedance current source as its first defense against common mode noise Just as voltage input terminals for a differential input have the same input impedance the two current source output terminals of the Model 370 have the same source impedance This matched impedance ensures that common mode voltages do not become normal mode voltages With this ...

Page 13: ...nsors users can also generate their own curves as desired Temperature Control The Model 370 provides all of the circuitry and software for digital proportional integral derivative PID control Heater output is a variable DC current source with multiple power ranges from 0 1 µW to 1 W to drive a resistive heater nominal 100 Ω Heater output is designed for low noise with circuits to eliminate power s...

Page 14: ...he Model 370 that is optimized for low residual DC bias current Low bias provides the lowest available resistor self heating when excitation currents are in the range of 1 pA to 30 pA It also provides the best available accuracy when resistances are above 200 kΩ The tradeoff for these performance features is a slightly greater noise figure 33 nV Hz than the Models 3716L and 3708 Unused leads are c...

Page 15: ... nA 31 6 nA 7 fW 193 fW 5 6 fW 2 3 pW Instrument Performance Overall Performance Temperature K Measurement Resolution Electronic Accuracy Calibration Accuracy Self Heating Errors Interpolation Error Overall Accuracy 0 05 0 1 0 3 1 40 Ω 8 µK 1 Ω 3 8 µK 0 1 Ω 6 µK 0 1 Ω 83 µK 35 Ω 7 µK 9 7 Ω 36 µK 2 8 Ω 170 µK 0 7 Ω 580 µK 5 mK 5 mK 5 mK 5 mK 49 µK 155 µK 280 µK 18 µK 0 2 mK 0 2 mK 0 2 mK 0 2 mK 5 2...

Page 16: ...0 Ω 1 mΩ 10 pW 632 mΩ 1 mΩ 3 2 pW 1 0 µA 632 kΩ 600 mΩ 320 nW 200 kΩ 200 mΩ 100 nW 63 2 kΩ 60 mΩ 32 nW 20 kΩ 40 mΩ 10 nW 6 32 kΩ 13 mΩ 3 2 nW 2 0 kΩ 4 mΩ 1 nW 632 Ω 3 mΩ 320 pW 200 Ω 3 mΩ 100 pW 63 2 Ω 3 mΩ 32 pW 20 Ω 3 mΩ 10 pW 6 32 Ω 3 mΩ 3 2 pW 2 0 Ω 3 mΩ 1 0 pW 316 nA 2 0 MΩ 2 0 Ω 100 nW 632 kΩ 600 mΩ 32 nW 200 kΩ 200 mΩ 10 nW 63 2 kΩ 130 mΩ 3 2 nW 20 kΩ 40 mΩ 1 nW 6 32 kΩ 13 mΩ 320 pW 2 0 kΩ ...

Page 17: ... 60 µΩ 100 pW 632 mΩ 60 µΩ 32 pW 200 mΩ 60 µΩ 10 pW 3 16 µA 200 kΩ 200 mΩ 1 0 µW 63 2 kΩ 60 mΩ 320 nW 20 kΩ 20 mΩ 100 nW 6 32 kΩ 13 mΩ 32 nW 2 0 kΩ 4 0 mΩ 10 nW 632 Ω 1 3 mΩ 3 2 nW 200 Ω 400 µΩ 1 0 nW 63 2 Ω 200 µΩ 320 pW 20 Ω 200 µΩ 100 pW 6 32 Ω 200 µΩ 32 pW 2 0 Ω 200 µΩ 10 pW 632 mΩ 200 µΩ 3 2 pW 1 0 µA 632 kΩ 600 mΩ 320 nW 200 kΩ 200 mΩ 100 nW 63 2 kΩ 60 mΩ 32 nW 20 kΩ 40 mΩ 10 nW 6 32 kΩ 13 m...

Page 18: ...µΩ 100 pW 6 32 Ω 100 µΩ 32 pW 2 0 Ω 100 µΩ 10 pW 632 mΩ 100 µΩ 3 2 pW 1 0 µA 6 32 kΩ 6 3 mΩ 3 2 nW 2 0 kΩ 2 0 mΩ 1 0 nW 632 Ω 1 3 mΩ 320 pW 200 Ω 400 µΩ 100 pW 63 2 Ω 320 µΩ 32 pW 20 Ω 320 µΩ 10 pW 6 32 Ω 320 µΩ 3 2 pW 2 0 Ω 320 µΩ 1 0 pW 316 nA 20 kΩ 20 mΩ 1 0 nW 6 32 kΩ 6 3 mΩ 320 pW 2 0 kΩ 4 0 mΩ 100 pW 632 Ω 1 3 mΩ 32 pW 200 Ω 1 0 mΩ 10 pW 63 2 Ω 1 0 mΩ 3 2 pW 20 Ω 1 0 mΩ 1 0 pW 6 32 Ω 1 0 mΩ ...

Page 19: ...Temperature Resolution Sensor and temperature dependent Refer to Paragraph 1 2 Curve Memory Space for twenty 200 point curves Curve Entry Entered via front panel computer interface or CalCurve option Curve Format Ohm K Log Ohm K Temperature Control Control Type High resolution digital PID Control Modes Closed Loop PID Open Loop Tuning Modes Manual PID Zones Setpoint Units Ohms or Kelvin with tempe...

Page 20: ...370N AC resistance bridge only 3716 16 channel scanner for Model 370 3716L Low resistance 16 channel scanner for Model 370 3708 Ultra low resistance 8 channel preamp scanner for Model 370 3708 ARW Ultra low resistance 8 channel preamp scanner for Model 370 includes 370 upgrade for instruments with main version 9 27 2005 and input version 1 3 or earlier firmware Select a power configuration VAC 100...

Page 21: ...electrical outlet or use a three contact adapter with the grounding wire green firmly connected to an electrical ground safety ground at 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 side covers Do not block these holes wh...

Page 22: ...Lake Shore Model 370 AC Resistance Bridge User s Manual 1 12 Introduction This Page Intentionally Left Blank ...

Page 23: ...between 10 and 20 mK 2 2 TEMPERATURE SCALES Temperature conversions at such low temperatures can raise even more questions than resistance measurements One reason is the delay in getting a recognized temperature standard for very low temperatures As of the writing of this manual the International Temperature Scale of 1990 ITS 90 is the most current effort to define an internationally accepted temp...

Page 24: ...leads Good location for a temperature sensor for cool down monitoring and troubleshooting Still Heat Exchanger Chamber used to evaporate 3 He out of a dilute 3 He mix liquid 4 He containing some 3 He sometimes called mash It is the first stage below 1 K and is also used to liquefy returning 3 He The still requires a few milliwatts of heat from a resistive heater to sustain evaporation The Still Ou...

Page 25: ... Space Insulates refrigeration components and provides a clear workspace 1 K Pot 4 He Evaporator Pumped reservoir of 4 He maintained at 1 K Used in the process of condensing 3 He gas returning from pumping system Also used as a heat sink for measurement leads Good location for a temperature sensor for cool down monitoring and troubleshooting Heat Exchangers One or more heat exchangers serve to coo...

Page 26: ...wn monitoring and troubleshooting Heat Switch Allows thermal contact between the pre cooling stage and salt pill during magnetization then provides thermal isolation during demagnetization cooling The construction of the switch varies depending on temperature but could be superconducting exchange gas gas gap or mechanical Several types of heat switches can be controlled by the still heater or anal...

Page 27: ... have low noise and almost no DC component to self heat the measured resistor Two excitation modes are available to best utilize the features of the current source in different applications One lower current setting 1 pA is available but not specified because leakage and bias currents in the measurement circuits can be a large percentage of the excitation current The 1 pA current setting should be...

Page 28: ...wn on the instrument display Refer to Table 1 1 for resistance and excitation ranges As shown in Table 1 1 not every combination of excitation and resistance range is possible Unusable combinations of range and excitation are automatically locked out The Model 370 also continuously calculates and displays the excitation power being dissipated in the resistor as additional feedback to the operator ...

Page 29: ... coupling H field noise Conductive shields do not reduce the effects of H fields Two ways to minimize H field coupling are to reduce the loop area or break the loop as described with ground loops Loop area can be minimized by tightly twisting lead pairs both voltage and current within the shielded cables This not only reduces loop area but also guarantees that both leads are exposed to the same co...

Page 30: ...are low pass filter with a time constant of 200 milliseconds That filter is necessary to convert the changing output of the phase sensitive detector operating at 13 7 Hz to a stable DC signal The minimum filtering is sufficient to measure small resistance values with large excitation but that is not the true purpose of the AC Bridge As resistance increases and excitation decreases additional filte...

Page 31: ... any conductive circuit or loop when that loop contains changing current or magnetic field In measurements this problem is commonly referred to as a ground loop and generally results when improperly grounded instruments are exposed to AC line current Isolation reduces ground loop noise by breaking the loop or circuit The Model 370 has a well designed power supply and uses optical isolation between...

Page 32: ...ise sources would be the same frequency as the instrument One source of noise that can be very close to the measurement frequency of a Model 370 is another Model 370 When two or more instruments are operated with leads closely coupled in the same Dewar it is possible for them to beat against each other and cause small oscillations If this happens the measurement frequency of one instrument can be ...

Page 33: ...ad resistance without measurement error A lead resistance specification of 100 Ω plus 10 of resistance range for each of the four leads is given for most excitation currents This lead resistance will give a measurement error that is small compared to the specified accuracy on the resistance range and in most cases the error is not measurable The lead resistance specification is reduced to 10 Ω plu...

Page 34: ... for the frequency 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 curren...

Page 35: ...two filters making the widest bandwidth possible on the Model 370 200 ms Once the DC voltage is digitized the user can choose additional digital averaging to reduce bandwidth further and increase resolution Unfortunately reducing bandwidth increases time constant and settling time slows the instrument response to real changes in resistance because those changes are averaged along with the noise Pr...

Page 36: ...rol heater output when the control channel is not active Even with these features scanning during closed loop temperature control will never be as stable as a dedicated control instrument The biggest causes of control instability are the subtle changes in cooling power that are present in low temperature cooling systems These changes are offset by changes in heater output during closed loop contro...

Page 37: ...olution 2 9 1 4 Accuracy Resistive thermometers serve well as secondary standards and are much easier to use than most primary thermometers Accuracy of a resistive temperature sensor depends on how closely it is compared to a primary standard how the temperature scale is interpreted how much the sensor drifts over time and how well the conditions used in calibration are duplicated when the sensor ...

Page 38: ...poil the vacuum insulation Metals and ceramics do not have this problem but greases and varnishes must be checked Another source of problems is the wide extremes in temperature most sensors are exposed to The linear expansion coefficient of a materials becomes important when temperature changes are so large Never try to permanently bond materials with linear expansion coefficients that differ by m...

Page 39: ...be taken not to overheat the sensor A heat sink such as a metal wire clamp or alligator clip will heat sink the leads and protect the sensor Lead wires should be tinned before bonding to reduce the time that heat is applied to the sensor lead Solder flux should be cleaned after soldering to prevent corrosion 2 9 3 8 Heat Sinking Leads Sensor leads can be a significant source of error if they are n...

Page 40: ...lag If both control stability and measurement accuracy are critical it may be necessary to use two sensors one for each function Another reason to use a separate control sensor is that a dedicated control sensor can be run with higher excitation power The additional power will reduce the accuracy of the feedback sensor but create a larger signal for better control stability Accuracy of the control...

Page 41: ...to the output dt e I P I Output 1 By adding the integral to proportional contributions the error that is necessary in a proportional only system can be eliminated When the error is at zero controlling at the setpoint the output is held constant by the integral contribution The integral setting I is more predictable than the proportional setting It is related to the dominant time constant of the lo...

Page 42: ...Lake Shore Model 370 AC Resistance Bridge User s Manual PID Control bmp Figure 2 4 Examples of PID Control 2 20 Theory of Operation ...

Page 43: ...rature Lower heater ranges are normally needed for lower temperature The Model 370 is of no use controlling at or below the temperature reached when the heater was off 2 10 3 2 Tuning Proportional The proportional setting is so closely tied to heater range that they can be thought of as fine and course adjustments of the same setting An appropriate heater range must be known before moving on to th...

Page 44: ...oint If the temperature does not stabilize and begins to oscillate around the setpoint the integral setting is too low and should be doubled If the temperature is stable but never reaches the setpoint the integral setting is too high and should be decreased by half To verify the integral setting make a few small 2 to 5 degree changes in setpoint and watch the load temperature react Trial and error...

Page 45: ...iately if there is a shortage of parts or accessories Lake Shore is not responsible for any missing items if not notified within 60 days of shipment Inspect all items for both visible and hidden damage that occurred during shipment If damage is found contact Lake Shore immediately for instructions on how to file a proper insurance claim Lake Shore products are insured against damage during shipmen...

Page 46: ...asurement input Refer to Paragraph 3 4 for use with one resistor or Paragraph 3 5 for use with the Model 3716 Scanner SCAN CONTROL 15 pin D subminiature receptacle provides power supply output and digital control connections for the Model 3716 Scanner Refer to Paragraph 3 5 6 REFERENCE BNC receptacle provides connections for Frequency Reference Output Refer to Paragraph 3 6 MONITOR BNC receptacle ...

Page 47: ...etter T on the fuse rating indicates that the instrument requires a time delay or slow blow fuse Fuse values should be verified any time line voltage configuration is changed Instructions for changing and verifying a line fuse are given in Paragraph 8 5 3 3 3 Power Cord The Model 370 includes a 3 conductor power cord that mates with the IEC 320 C14 line cord receptacle Line voltage is present on t...

Page 48: ... VG Shield VG V Measurement voltage lead V Guard or shield for voltage lead V Shield tied to measurement common Guard or shield for voltage lead V Measurement voltage lead V Shield tied to measurement common Tied to measurement common I IG Shield IG I Measurement current lead I Guard or shield for current lead I Shield tied to measurement common Guard or shield for current lead I Measurement curre...

Page 49: ...milar low impedance to the same ground Good grounding of all chassis in a group of instruments prevents voltage differences between their chassis usually at line frequency from inducing noise on the measurement If good quality Earth ground is not available the chassis of line powered instruments should be strapped together with heavy gauge copper wire or ground strap Signal leads in communication ...

Page 50: ...tal Dewar Cables with signals sharing the same ground or common should be routed together to reduce ground loop area Cables with signals that differ in ground or signal size should be routed separately to reduce induced noise Cables should be kept away from noise generators like fluorescent lights and vacuum pump motors Cables should be supported to minimize stress on connectors and terminations C...

Page 51: ...tacles hold connections for up to sixteen 4 lead resistor inputs in four sets of four With the 3708 two 25 pin DIN receptacles hold connections for up to eight 4 lead resistor inputs They mate with 25 pin D subminiature plugs included with the scanner Lake Shore P N 106 253 Unused inputs can either be left open or all four measurement pins can be shorted together Pin connections for Channels 1 4 a...

Page 52: ...ical to the connectors used on the resistance input of the Model 370 The cables included with the scanner are adequate for most installations Connector pin definition on the scanner is identical to the input connector definition given in Paragraph 3 4 1 in case a cable must be made for a special application Guard pins are not connected inside the scanner but guards can be carried through the cable...

Page 53: ...Lake Shore Model 370 AC Resistance Bridge User s Manual 112 374a bmp Cable Wiring bmp Figure 3 9 Scanner to Instrument Measurement Cable Installation 3 9 ...

Page 54: ...e tied to isolated measurement circuits inside the instrument and must remain isolated from the instrument chassis and Earth ground 2 The connector body should not be used for shielding the scan control cable because the chassis of the instrument is at Earth ground and the chassis of the scanner is at isolated measurement common Figure 3 10 Scanner SCAN CONTROL Connector 3 5 7 Scanner Control Cabl...

Page 55: ...al Output 5 5 V 50 mA 15 V 25 mA Figure 3 11 SCAN CONTROL Signals Without A Scanner 3 5 9 Scanner Mounting Bracket A scanner mounting bracket is included with the Model 3716 L and 3708 Scanners so that it can be mounted on or very near the test Dewar Rigidly mounting the scanner will prevent unnecessary cable movement and help maintain a uniform shield connection over time The hole pattern for the...

Page 56: ... on the center conductor and isolated measurement common is on the outer conductor The signal is a TTL level digital voltage synchronized to the measurement frequency that can be used for synchronous lock in detection of AC measurement signals The output maintains TTL logic voltage levels when driving no more than 2 TTL loads Mating connector is not included 3 7 CONTROL HEATER OUTPUT The temperatu...

Page 57: ...n accurate heater resistance be entered into the instrument Some examples of heater resistance and output range are given in Table 3 1 Maximum power for a range is the lower of the two P I2 R and P V2 R where P is heater power in watts I is the maximum current for the range and V is the compliance voltage of 10 V Heater output resolution is lost any time the compliance voltage limits power If a pe...

Page 58: ... Connections Two BNC receptacles provides connections for Analog Voltage Output 1 and 2 with 10 V range 100 mA maximum current into a 100 Ω resistor Signal is carried on the center conductor and common is on the outer conductor The outputs are short circuit protected to prevent them from being damaged but operation into a resistance of less than 100 Ω is not recommended Mating connector not includ...

Page 59: ...driver to lock or unlock wires Insert wire into slot 1 2 3 4 5 6 Alarm Relays bmp Temrinal Block eps Figure 3 16 Alarm Relays Terminal Block 3 10 RACK MOUNTING The Model 370 can be installed into a 19 inch rack mount cabinet using the optional Lake Shore Model RM 1 Rack Mount Kit The kit contains mounting ears handles and screws that adapt the front of the instrument to fit into a 3 5 inch tall fu...

Page 60: ...Lake Shore Model 370 AC Resistance Bridge User s Manual 3 16 Installation This Page Intentionally Left Blank ...

Page 61: ...play if the measurement input has not been fully configured Messages listed in Paragraph 8 6 Instrument Hardware are related to the instrument hardware and may require help from Lake Shore service The messages listed in Paragraph 8 6 Measurement of Compliance Limit do not indicate a problem with the instrument and will disappear when input setup is complete The messages listed in Paragraph 8 6 Ill...

Page 62: ...ce of the display update indicator If the active scan channel is chosen for one of the display locations the channel number blinks while the channel is being read The blink pattern indicates both range and channel changes 4 2 3 Range Excitation and Power The lower right corner of the display provides feedback from the active resistance measurement and is continually updated for both autorange and ...

Page 63: ...if a scanner is installed Scanner Channel VW Manually increment or decrement scanner channel Zone Setup Setup temperature control zones for closed loop control Manual Output Change open loop control parameter Manual Output PID Change closed loop control parameters P I and D Setpoint Change the temperature control setpoint Control Setup Setup temperature control and setpoint ramp feature Still Outp...

Page 64: ...e key To skip over a parameter without changing its value press Enter before pressing an arrow or number key To return to the normal display in the middle of a setting sequence press Escape before pressing an arrow or number key Changes entered before Escape is pressed are kept 4 4 DISPLAY SETUP The display setup sequence for the Model 370 may seem complicated at first but the steps are necessary ...

Page 65: ... display If a scanner is attached the channel selection screen will appear to prompt for the input channel that is to appear in the chosen location If no scanner is attached the instrument will skip to source selection Display Setup Display Location 1 Select With Channel 1 Use the s or t key to select an input channel between 1 and 16 Select Scan for the display to follow the active scan channel P...

Page 66: ... 100 brightness will reduce the operating life of the display None of the brightness settings will turn the display off completely The instrument will operate with the display unplugged for applications that require absolute darkness but both the digital control and power supply cables must be unplugged with the instrument power turned off or damage to the display will result To change display bri...

Page 67: ...Available ranges are listed in Table 1 1 The following messages are displayed to indicate range limits Maximum Maximum resistance range has already been chosen Minimum Minimum resistance range has already been chosen Increase Excitation Voltage excitation must be increased before changing resistance range Decrease Excitation Voltage excitation must be decreased before changing resistance range The...

Page 68: ...ncrease input gain if the measurement drops below 20 of full scale Autorange is not recommended when resistance changes are very fast measurements are very noisy or when data acquisition cannot tolerate a range change delay in the middle of a data set To turn autorange on or off press the Autorange key The LED annunciator above the key lights to indicate autorange is on 4 5 3 Turning Excitation Of...

Page 69: ...ctive at the same time The next input setup screen appears as a prompt for the scanner dwell time Input Setup Channel 1 Enter A Value For Scan Dwell Time 10 s Use the data entry keys to enter a dwell time between 1 and 200 seconds Press Enter to accept the new selection and continue to the next setting screen Press Escape to restart the setting sequence and enter a new value Press Escape again to ...

Page 70: ...ature response curve the user must indicate the temperature coefficient of the device so that the control equation can be calculated correctly This setting sequence will be skipped if a curve is selected for a channel Platinum and Rhodium Iron RTDs are positive temperature coefficient and most thermistors and semiconductor RTDs like Cernox and Germanium are negative temperature coefficient The nex...

Page 71: ...nter to accept the new selection and continue to the next setting screen Press Escape to cancel the new selection and return to the normal display 4 7 2 Active Common Mode Reduction Active common mode reduction is a special feature of the Model 370 that can reduce noise on measurement leads It is most useful when excitation current is 1 μA or greater but should be left on unless one resistor lead ...

Page 72: ...ached the range and excitation keys are normally used to change parameters for the active scanner channel If all of the resistors connected to the scanner are the same it is convenient for these changes to affect all channels at the same time The Model 370 allows the user to configure the range and excitation keys to change one channel at a time or all channels at once Similar operation is availab...

Page 73: ...it is convenient for these changes to affect all channels at the same time The Model 370 also allows the user to make changes to the input parameters for all channels All channels can be selected for parameters under the Input Setup key by selecting the channel designator All Paragraph 4 7 5 describes how to configure the range and excitation keys to change all channels 4 9 FIRMWARE FILTER The fir...

Page 74: ...xt filter setup screen appears as a prompt for filter settling time Filter Setup Channel 1 Enter A Value For Settling Time 30 s Use the data entry keys to enter a filter settling time between 1 and 200 seconds Press Enter to accept the new selection and continue to the next setting screen Press Escape to restart the setting sequence and enter a new value Press Escape again to cancel the sequence a...

Page 75: ...erating 4 11 1 Temperature Control Modes The Model 370 offers three temperature control modes or the control output can be disabled Each mode requires different control parameters so the control mode must be selected before other parameter values Open Loop Open loop control is less complicated than closed loop control but is also less powerful Open loop control mode allows the user to directly set...

Page 76: ... Control Setup key The first control setup screen appears as a prompt for the control mode Control Setup Select With Control Mode Closed Loop PID Use the s or t key to select a control mode from the list in Paragraph 4 11 1 Press Enter to accept the new selection and continue to the next setting screen Press Escape to cancel the new selection and return to the normal display 4 11 2 2 Control Chann...

Page 77: ...For Setpoint Change Pause Time 25 s Use the data entry keys to enter a change pause time from 1 to 255 seconds Press Enter to accept the new selection and continue to the setpoint ramp feature Paragraph 4 11 7 Press Escape to restart the setting sequence and enter a new value Press Escape again to cancel the sequence and return to the normal display 4 11 2 5 Control Filter During normal operation ...

Page 78: ...accurately display the heater output and manual output in power The instrument does not measure heater resistance so one must be entered for these display values to be meaningful A 100 Ω heater is required for maximum power output but other values can be used If a heater resistance is not known the heater output display should be configured for current The next control setup screen appears as a pr...

Page 79: ...point range to accommodate a variety of sensor types and applications In resistance the setpoint can range from micro ohms to mega ohms In temperature the setpoint can range from milliKelvin to over 1000 Kelvin A setpoint limit in Kelvin can be entered in the temperature response curve This limit is in force for the control channel only and only when operating with setpoint units of Kelvin Setpoin...

Page 80: ...he next setting screen Press Escape to restart the setting sequence and enter a new value Press Escape again to cancel the sequence and return to the normal display 4 11 4 2 Manually Setting Integral I The integral parameter also called reset is the I part of the PID equation It has a setting range of 1 to 10 000 seconds A setting of zero turns I off The default value for I is 20 seconds The next ...

Page 81: ...ual Output 0 000 mW Use the data entry keys to enter a manual output value between 0 and full scale The units multiplier is determined by the heater range and can not be changed Press Enter to accept the new selection and return to the normal display Press Escape to restart the setting sequence and enter a new value Press Escape again to cancel the sequence and return to the normal display NOTE Th...

Page 82: ...small increments that correspond to the ramp rate The ramp rate is entered as a positive number but it can be used for ramping up and down in temperature When the ramp feature is turned on the Ramp annunciator will be shown on the top line of the display During an active ramp the annunciator will blink When the instrument is waiting for a setpoint change the annunciator is steady If the setpoint u...

Page 83: ...X MIN CAPTURE The Max Min feature automatically captures the largest and smallest valid readings taken since the last reset The feature operates at the full update rate of 10 readings per second It is suspended during range or channel change and captured readings are lost when power is turned off The maximum and minimum readings can be displayed in any of the 8 reading display locations Paragraph ...

Page 84: ...ers if this feature is not configured properly For example the setpoint units and reading units for X must match if SP is used in the equation The display resolution can also be misleading For example the scaled error value of 10ΔR does offer more measurement resolution than the normal display reading However increasing the slope M to 100 or 1000 will only increase the display resolution and not t...

Page 85: ...is selected the next setting screen will appear to allow the entry of a value for B Linear Setup Channel 1 Select With B Source Value Use the s or t key to select a source for B as either Value SP or SP Press Enter to accept the new selection and continue to the next setting screen Press Escape to cancel the new selection and return to the normal display The next linear setup screen appears as a p...

Page 86: ...d to sound is any of the alarms are active The relays described in Paragraph 4 15 can also be programmed to follow the alarm feature The alarm feature has two modes of operation latching and non latching The operation of these modes is described below Latching Operation During latching operation if the reading value is ever greater than the high alarm setpoint the high alarm for that channel is la...

Page 87: ...he normal display The next alarm setup screen appears as a prompt for the low alarm setpoint value Alarm Setup Channel 1 Enter A Value For Low Setpoint 0 00000 Use the data entry keys to enter the low setpoint between 1 10 6 and 100 106 depending on selected units Enter the numeric value first Press Enter to accept the new value and advance to the units multiplier Use the s or t key to select a un...

Page 88: ...ress Escape to restart the setting sequence and enter a new value Press Escape again to cancel the sequence and return to the normal display The next alarm setup screen appears as a prompt for alarm On Off If the alarm feature is turned off this will be the first setting screen to appear Alarm Setup Channel 1 Select With Alarm On Use the s or t key to select alarm on or off Press Enter to accept t...

Page 89: ...on and return to the normal display The next relay setup screen appears as a prompt for operating mode Relay Setup Low Relay Select With Mode Alarm Use the s or t key to select the relay mode Manual Off Manual On Alarm or Zone Press Enter to accept the new selection and continue If alarm is selected the next setting screen will appear otherwise the instrument will return to the normal display Pres...

Page 90: ...ading values that correspond to the maximum and minimum output values An example of this mode is given below Zone The analog output is operated with the zone control feature as described in Paragraph 5 3 Still Analog Output 2 is operated manually using the Still Output key as described in Paragraph 4 17 Press the Analog Out key to begin analog output setup The following setup screen appears as a p...

Page 91: ...ss Escape to cancel the new selection and return to the normal display The next analog output setup screen appears as a prompt for input data source Analog Out Setup Analog Out 1 Select With Data Source Kelvin Use the s or t key to select one of three data sources ohms Kelvin or linear result of the linear equation Press Enter to accept the new selection and continue to the next setting screen Pre...

Page 92: ...The Model 370 can provide the small amount of power required to drive the still heater of a dilution refrigerator with analog voltage output 2 None of the analog output hardware changes when it is configured for still operation Paragraph 3 8 3 describes how to estimate the full scale current sourced to a resistive heater When analog output 2 is in still mode the Still key gives direct access to th...

Page 93: ...igit lock code default 123 The instrument returns to the normal display with the keypad locked To unlock the instrument keypad press and hold the Enter key for 5 seconds The following screen appears as a prompt for the 3 digit lock code Enter Code To Unlock Keypad Use the data entry keys to enter the 3 digit lock code default 123 The instrument returns to the normal display with the keypad unlocke...

Page 94: ...y Current Setpoint Ramp Off Heater Resistance 100 ohm Heater Polarity Unipolar Display Format Number of Locations 1 Location 1 Channel Scan Location 1 Data Source Ohms Display Resolution 6 Brightness 75 Excitation and Range Excitation Mode Voltage Excitation 632 mV Resistance Range 63 2 Mohm Autorange Off Input Setup Scan Channel 1 Autoscan Off Scan Dwell Time 10 sec Change Pause Time 3 sec Curve ...

Page 95: ...sensors Limit Temperature control setpoint limit in Kelvin Default is 375 K Enter a setting of 9999 K if no limit is needed Temperature Coefficient The unit derives the temperature coefficient from the first two breakpoints The user does not enter this setting Check for proper entry of the first two breakpoints if the temperature coefficient is not correct A positive coefficient P indicates that t...

Page 96: ...cation parameters associated with the curve is as important as entering the breakpoints Curve header parameters are listed in Table 5 1 Typical parameters for common sensors are listed in Table 5 2 Read this section completely and gather all necessary data before beginning the process NOTE If the curve you wish to enter has similar parameters to an existing curve first copy the similar curve as de...

Page 97: ...he new selection and return to the normal display The next curve entry screen appears as a prompt for the number of the curve to edit The curve name and serial number are displayed below the curve number when available Curve name cannot be changed from the front panel Curve Entry Edit Curve Select With Curve Number 1 User Curve 01 Use the s or t key to select a curve number from 1 to 20 Press Ente...

Page 98: ...Number 0123456789 in log Ω K format The first seven breakpoints are shown and the eighth line is ready for the next breakpoint Curve Entry 1 1 56441 L 1 2000 K Edit Curve 1 2 1 59706 L 1 0950 K User Curve 01 3 1 63050 L 1 0000 K 0123456789 4 1 66000 L 0 9100 K 375 00 K 5 1 67000 L 0 7500 K N 6 1 70000 L 0 8250 K 7 1 79561 L 0 6700 K 8 0 00000 L 0 0000 K When the breakpoint number is highlighted us...

Page 99: ...rve Entry The first curve entry screen appears as a prompt for the curve function Curve Entry Select With Curve Erase Use the s or t key to select Erase Press Enter to accept the new selection and continue to the next setting screen Press Escape to cancel the new selection and return to the normal display The next curve entry screen appears as a prompt for the number of the curve to erase The curv...

Page 100: ...g screen Press Escape to cancel the new selection and return to the normal display The next curve entry screen appears as a prompt for the number of the curve to copy from The curve name and serial number are displayed below the curve number when available Curve Entry Copy Curve Select With From Curve Number 1 User Curve 01 Use the s or t key to select a curve number from 1 to 20 Press Enter to ac...

Page 101: ...zone feature if those features are put into zone mode To enter parameter values into the zone table press Zone Setup The first zone setup screen appears as a prompt for the zone number Zone Setup Select With Zone 1 Use the s or t key to select a zone from 1 to 10 Press Enter to accept the new selection and continue to the next setting screen Press Escape to cancel the new selection and return to t...

Page 102: ...cancel the sequence and return to the normal display The next zone setup screen appears as a prompt for the manual heater output value Manual output must be entered in percent of full scale current Power units are not available within the zone feature Zone Setup Zone 1 Enter A Value For Manual Output 0 0000 Use the data entry keys to enter a manual output value between 0 and 100 The units multipli...

Page 103: ...if the analog output is set to zone mode Zone Setup Zone 1 Enter A Value For Analog Out 1 0 0000 Use the data entry keys to enter a manual output value 100 and 100 in bipolar mode or 0 and 100 in unipolar mode Press Enter to accept the new selection and continue to the next setting screen Press Escape to restart the setting sequence and enter a different value Press Escape again to cancel the sequ...

Page 104: ...s when the setpoint is changed to a value outside that zone If a setpoint value is entered that is greater than the setpoint limit in zone 10 the instrument will use the parameter values from zone 10 Select closed loop PID control mode to turn zone tuning off To select zone tuning mode press Control Setup The first control setup screen appears as a prompt for the control mode Control Setup Select ...

Page 105: ... 0 100 Low Relay On Off High Relay Analog Out1 0 100 Analog Out2 0 100 Heater Range On Off P 0 1 1k I 0 1 1k D 0 200 Manual Output 0 100 Low Relay On Off High Relay Analog Out1 0 100 Analog Out2 0 100 Heater Range On Off P 0 1 1k I 0 1 1k D 0 200 Manual Output 0 100 Low Relay On Off High Relay Analog Out1 0 100 Analog Out2 0 100 Heater Range On Off P 0 1 1k I 0 1 1k D 0 200 Manual Output 0 100 Low...

Page 106: ...Lake Shore Model 370 AC Resistance Bridge User s Manual 5 12 Advanced Operation This Page Intentionally Left Blank ...

Page 107: ...e digital computer which tells the Model 370 which functions to perform Below are Model 370 IEEE 488 interface capabilities SH1 Source handshake capability RL1 Complete remote local capability DC1 Full device clear capability DT0 No device trigger capability C0 No system controller capability T5 Basic TALKER serial poll capability talk only unaddressed to talk if addressed to listen L4 Basic LISTE...

Page 108: ...s Local operations The Model 370 can also be configured for Remote operations via the IEEE 488 interface or the Local key The Local key will toggle between Remote and Local operations During Remote operations the Remote annunciator will appear in the upper right corner of the display and operations from the keypad will be disabled 6 1 3 IEEE 488 Command Structure The Model 370 supports several com...

Page 109: ...rom a digital computer and to transfer measurements to the computer Most device specific commands perform functions also performed from the front panel Model 370 device specific commands are detailed in Paragraph 6 3 and summarized in Table 6 6 6 1 3 4 Message Strings A message string is a group of characters assembled to perform an interface function There are three types of message strings comma...

Page 110: ...CONTROLLER by means of a serial poll SPE to examine the status reports but the BUS CONTROLLER will not be interrupted by the Service Request The QSTB common command will read the Status Byte Register but will not clear the bits Standard Event Status ESB Bit 5 When bit 5 is set it indicates if one of the bits from the Standard Event Status Register has been set Refer to Paragraph 6 1 4 2 Error Bit ...

Page 111: ...rument Instructions for setting up the IEEE 488 board is included in Section 6 1 5 1 Refer to Section 6 1 5 2 for instructions on how to setup the program The Visual Basic code is provided in Table 6 2 A description of program operation is provided in Section 6 1 5 3 While the hardware and software required to produce and implement these programs is not included with the instrument the concepts il...

Page 112: ...Lake Shore Model 370 AC Resistance Bridge User s Manual Figure 6 1 GPIB0 Setting Configuration Figure 6 2 DEV 12 Device Template Configuration 6 6 Remote Operation ...

Page 113: ... Visual Basic 1 Start VB6 2 Choose Standard EXE and select Open 3 Resize form window to desired size 4 On the Project Menu select Add Module select the Existing tab then navigate to the location on your computer to add the following files Niglobal bas and Vbib 32 bas 5 Add controls to form a Add three Label controls to the form b Add two TextBox controls to the form c Add one CommandButton control...

Page 114: ...bject dropdown list select General Add the statement Public gSend as Boolean b Double Click on cmdSend Add code segment under Private Sub cmdSend_Click as shown in Table 6 2 c In the Code Editor window under the Object dropdown list select Form Make sure the Procedure dropdown list is set at Load The Code window should have written the segment of code Private Sub Form_Load Add the code to this sub...

Page 115: ...nd button pressed gSend False Set Flag as False strCommand frmIEEE txtCommand Text Get Command strReturn Clear response display strCommand UCase strCommand Set all characters to upper case If strCommand EXIT Then Get out on EXIT End End If Call ibwrt intDevice strCommand term Send command to instrument If ibsta And EERR Then Check for IEEE errors do error handling if needed Handle errors here End ...

Page 116: ...ill be returned Incorrectly spelled commands and queries are ignored Commands and queries should have a space separating the command and associated parameters Leading zeros and zeros following a decimal point are not needed in a command string but are sent in response to a query A leading is not required but a leading is required 6 1 6 Troubleshooting New Installation 1 Check instrument address 2 ...

Page 117: ...o computers with either 9 or 25 pin connectors Paragraph 8 11 1 gives the most common pin assignments for 9 and 25 pin connectors Please note that not all pins or functions are supported by the Model 370 The instrument serial connector is the plug half of a mating pair and must be matched with a socket on the cable If a cable has the correct wiring configuration but also has a plug end a gender ch...

Page 118: ...is included in each character ASCII letter and number characters are used most often as character data Punctuation characters are used as delimiters to separate different commands or pieces of data Two special ASCII characters carriage return CR 0DH and line feed LF 0AH are used to indicate the end of a message string Table 6 3 Serial Interface Specifications Connector Type Connector Wiring Voltag...

Page 119: ...g at a given time or guarantee timing between messages All of this is the responsibility of the user program When issuing commands only the user program should Properly format and transmit the command including terminators as one string Guarantee that no other communication is started for 50 ms after the last character is transmitted Not initiate communication more than 20 times per second When is...

Page 120: ...oject Menu click Components to bring up a list of additional controls available in VB6 5 Scroll through the controls and select Microsoft Comm Control 6 0 Select OK In the toolbar at the left of the screen the Comm Control will have appeared as a telephone icon 6 Select the Comm control and add it to the form 7 Add controls to form a Add three Label controls to the form b Add two TextBox controls ...

Page 121: ...lean b Double Click on cmdSend Add code segment under Private Sub cmdSend_Click as shown in Table 6 5 c In the Code Editor window under the Object dropdown list select Form Make sure the Procedure dropdown list is set at Load The Code window should have written the segment of code Private Sub Form_Load Add the code to this subroutine as shown in Table 6 5 d Double Click on the Timer control Add co...

Page 122: ...ue Loop until Send button pressed gSend False Set Flag as false strCommand frmSerial txtCommand Text Get Command strReturn Clear response display strCommand UCase strCommand Set all characters to upper case If strCommand EXIT Then Get out on EXIT End End If frmSerial MSComm1 Output strCommand Term Send command to instrument If InStr strCommand 0 Then Check to see if query While ZeroCount 20 And st...

Page 123: ... correctly spelled query without a nothing will be returned Incorrectly spelled commands and queries are ignored Commands and queries should have a space separating the command and associated parameters Leading zeros and zeros following a decimal point are not needed in a command string but are sent in response to a query A leading is not required but a leading is required 6 2 8 Troubleshooting Ne...

Page 124: ...n format term Terminator characters Indicated a parameter field many are command specific state Parameter field with only On Off states NOTE Any number being represented in scientific notation may also be entered as a string of number characters If the number is only represented as a string of number characters it cannot be entered in scientific notation The following example shows two different w...

Page 125: ...on Parameter Query 27 DOUT Digital Output Cmd 27 DOUT Digital Output Query 27 FILTER Filter Parameter Cmd 27 FILTER Filter Parameter Query 28 Command Function Page FREQ Excitation Frequency Cmd 28 FREQ Excitation Frequency Query 28 GUARD Guard Drive Cmd 28 GUARD Guard Drive Query 28 HTR Heater Output Query 28 HTRRNG Heater Range Cmd 28 HTRRNG Heater Range Query 28 HTRST Heater Status Query 29 IEEE...

Page 126: ...s Register To enable an event flag bit send the command ESE with the sum of the bit weighting for each desired bit Refer to Paragraph 6 1 4 2 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 Example To enable event flags 0 4 and 7 send the command ESE 145 term 145 is the sum of the bit weighting for eac...

Page 127: ... a list of status flags Example To enable status flags 2 3 4 and 6 send the command SRE 92 term 92 is the sum of the bit weighting for each bit Bit Bit Weighting Event Name 2 4 Valid Read 3 8 Alarm 4 16 Error 6 64 SRQ 92 QSRE Service Request Enable Register Query Input SRE term Returned bit weighting term Format nnn Refer to Paragraph 6 1 4 1 for a list of status flags QSTB Status Byte Query Input...

Page 128: ...igh alarm if the reading is over 270 activates low alarm if reading is below 0 and latches the alarm when Kelvin reading falls below 270 ALARM Alarm Parameter Query Input ALARM channel term Format nn channel Specifies which channel to query 1 16 Returned off on data source high value low value deadband latch term Format n n nnn nnnE nn nnn nnnE nn nnn nnnE nn n Refer to command for description ALA...

Page 129: ... source high value low value manual value term Format n n nn n nnn nnnE nn nnn nnnE nn nnnnnn Refer to command for definition AOUT Analog Output Data Query Input AOUT analog channel term Format n analog channel Specifies analog output channel 1 2 Returned analog output term Format nnnnnn Refer to command for definition Remarks Returns the percentage of output of the analog control BAUD RS 232 Baud...

Page 130: ...nner is installed CHGALL Input Change All or One Query Input CHGALL term Returned state term Format n Refer to command for description CMODE Temperature Control Mode Command Input CMODE mode term Format n mode Specifies control mode 1 Closed Loop PID 2 Zone Tuning 3 Open Loop 4 Off Example CMODE 3 term Set control mode to Open Loop control CMODE Temperature Control Mode Query Input CMODE term Retu...

Page 131: ...cifies the curve data format 3 Ω K 4 log Ω K setpoint limit Specifies the curve temperature limit in Kelvin coefficient Specifies the curves temperature coefficient 1 negative 2 positive Remarks Configures the user curve header Example CRVHDR 2 DT 470 00011134 3 3 250 1 term Configures User Curve 2 with a name of DT 470 serial no 00011134 data format of Ohms vs Kelvin setpoint limit of 3 25 K and ...

Page 132: ... range 1 8 Refer to HTRRNG for detailed range listing htr resistance Heater load in ohms 1 100 000 Example CSET 16 0 1 30 1 8 100 term The Model 370 controls from channel 16 unfiltered readings The setpoint is in Kelvin with a 30 second setpoint change pause time The heater output is displayed in current The heater maximum range limit is set to 100 mA and the heater load is set to 100 Ω CSET Tempe...

Page 133: ...ighting term Format nn bit weighting Specifies the manual digital output settings 0 31 Bit Bit Weighting Name 0 1 D1 1 2 D2 2 4 D3 3 8 D4 4 16 D5 Remarks This command is only active if no Model 3716 Scanner is installed Example DOUT 21 term Manually sets digital output lines D1 D3 and D5 to logic high and D2 and D4 to logic low DOUT Digital Output Query Input DOUT term Returned bit weighting term ...

Page 134: ... term Format n Refer to command for description GUARD Guard Drive Command Input GUARD state term Format n state 0 Off 1 On Remarks Enables or disables the guard drive GUARD Guard Drive Query Input GUARD term Returned state term Format n Refer to command for description HTR Heater Output Query Input HTR term Returned heater value term Format nnn nnnE nn heater value Heater output in percent of curr...

Page 135: ...alue for the autoscanning dwell time 1 200 seconds pause Specifies a value for the change pause time 3 200 seconds curve number Specifies which curve the channel uses 0 no curve 1 20 user curves tempco Sets the temperature coefficient that will be used for temperature control if no curve is selected 1 negative 2 positive Example INSET 5 1 10 3 0 2 term Enables channel 5 with 10 second autoscan dwe...

Page 136: ...using the equation y mx b The value of m is 1 0 x is set to Kelvin and b is set to SP LINEAR Linear Equation Parameter Query Input LINEAR channel term Format nn channel Specifies which channel to query 1 16 Returned equation M value X source B source B value term Format n nnnnnn n n nnn nnnE nn Refer to command for description Remarks Returns channel linear equation parameter values LOCK Keypad Lo...

Page 137: ... valid reading they receive MODE IEEE Interface Mode Command Input MODE mode term Format n mode 0 local 1 remote 2 remote with local lockout Example MODE 2 term Places the Model 370 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 Output Selection Command Input MONITOR source term Format ...

Page 138: ...tion RAMP Setpoint Ramp Parameter Command Input RAMP off on rate value term Format n nnnnn off on Specifies whether ramping is on or off 0 Off 1 On rate value Specifies setpoint ramp rate in Kelvin per minute from 0 001 to 10 The rate is always positive but will respond to ramps up or down Example RAMP 1 1 5 term When the temperature control setpoint is changed it ramps to the target at 1 5 K minu...

Page 139: ...Voltage Excitation range Resistance range number 1 22 autorange 0 autorange off 1 autorange on cs off 0 excitation on 1 excitation off Example RDGRNG 8 1 9 14 0 0 term Channel 8 in current excitation mode with a excitation of 9 10 0 nA The resistance range is set to 14 which is the 6 32 kΩ range Turn autorange off and excitation on Voltage Range Current Range Resistance Range 1 2 00 μV 1 1 00 pA 1...

Page 140: ...T OVER 7 128 T UNDER RELAY Relay Parameter Command Input RELAY relay number mode channel alarm alarm type term Format n n nn n relay number Specifies which relay to configure 1 low relay 2 high relay mode Specifies relay mode 0 Off 1 On 2 Alarms 3 Zone channel alarm Specifies which channel alarm activates the relay when the relay is in alarm mode 1 16 0 scan channel alarm type Specifies the channe...

Page 141: ... Control Setpoint Command Input SETP value term Format nnn nnnE nn value The value for the setpoint in whatever units the setpoint is using Example SETP 1 5 term Setpoint is changed to 1 5 Kelvin if control units are Kelvin SETP 2 0E 03 term Setpoint is changed to 2 0 kΩ if control units are ohms SETP Temperature Control Setpoint Query Input SETP term Returned value term Format nnn nnnE nn STILL S...

Page 142: ... off 1 on relay high Specifies the High relay state 0 off 1 on analog 1 Specifies the Analog 1 output for this zone 100 to 100 analog 2 Specifies the Analog 2 output for this zone 100 to 100 Remarks Configures the control loop limit band parameters used in conjunction with the Status Byte Register Refer to Paragraph 6 1 4 1 Example ZONE 1 0 25 10 20 0 0 2 0 0 10 50 term Zone 1 is valid to 0 250 K ...

Page 143: ...as shown below 370N AC Resistance Bridge Only Includes a Lake Shore Model 370 AC Resistance Bridge only with no scanner Power is configured as shown below 3716 16 channel scanner for Model 370 3716L Low resistance 16 channel scanner for Model 370 3708 Ultra low resistance 8 channel preamp scanner for Model 370 3708 ARW Ultra low resistance 8 channel preamp scanner for Model 370 Includes 370 upgrad...

Page 144: ...Sensor Input Mating Connector 6 pin DIN plugs for Input connections 2 included G 106 253 DB 25 Plug Quantity of 4 included G 106 264 DB 25 Hood Quantity of 4 included 106 737 Terminal Block Mating Connector 6 pin terminal block for the Alarm Relays output 107 379 Scanner Box Mounting Bracket Used to mount the Model 3716 Scanner 112 374 Cable Assembly Connects Model 370 to optional scanner 3 meters...

Page 145: ...mount cabinet VGE 7031 IMI 7031 Varnish formerly GE 7031 Varnish 1 pint can IMI 7031 Insulating Varnish and Adhesive possesses electrical and bonding properties which when combined with its chemical resistance and good saturating properties make it an excellent material for cryogenic temperatures As an adhesive IMI 7031 bonds a variety of materials has fast tack time and may be air dried or baked ...

Page 146: ...Lake Shore Model 370 AC Resistance Bridge User s Manual 112 374a bmp Cable Wiring bmp Figure 7 1 Model 112 374 Cable Assembly 7 4 Options and Accessories ...

Page 147: ...ales Instrument Service Fax 614 818 1600 614 818 1609 Sales Instrument Service When contacting Lake Shore please provide your name and complete contact information including e mail address if possible It is often helpful to include the instrument model number and serial number located on the rear panel of the instrument as well as the firmware revision information as described in Paragraph 4 19 8 ...

Page 148: ... line voltage is changed WARNING To avoid potentially lethal shocks turn off controller and disconnect it from AC power before performing this procedure 1 Identify the line input assembly on the instrument rear panel See Figure 8 2 2 Turn the line power switch OFF O 3 Remove the instrument power cord 4 With a small screwdriver release the drawer holding the line voltage selector and fuse 5 Slide o...

Page 149: ...lected resistance range or excessive noise on the measurement leads Paragraph 8 7 can be helpful in diagnosing these problems If these messages persist after the input or output is configured properly the instrument may require repair Illegal operation messages remind the operator when a feature is locked out or the instrument is not configured to support a feature Instrument Hardware Defective NO...

Page 150: ...d CSNEG monitoring points The signal voltage at either monitoring point can be viewed on an oscilloscope by using the Monitor output described in Paragraph 4 7 4 Usual causes of this error include 1 An attempt to measure a resistance that is much greater 3 orders of magnitude than the selected range 2 An open connection of the current drive leads I and or I To resolve this condition first verify t...

Page 151: ...n of the phase sensitive detector are several gain stages and a band pass filter If the combination of signal and all differential noise components cause the input to the mixer to exceed 10 V peak the mixer overload error is displayed The overload occurs at the VMIX point in the instrumentation amplifier circuit Refer to Figure 8 3 for the location of the VMIX monitoring point The signal voltage c...

Page 152: ...ved sine wave should be very clean and noise free These signal levels are representative of a balanced resistance measurement If one side of the measured resistance is common to measurement common large deviations from these voltages will be seen Also be reminded that CMR must be turned off in that condition for an accurate measurement As excitation is reduced environmental noise will be seen on t...

Page 153: ...ng CSPOS and CSNEG monitor points This signal shows predominately the controlling sine wave signal applied to the current sampling resistors but will also give good insight in to common mode noise voltages that are reflected back through the current source A level exceeding 10 V peak at these points triggers a CS OVL message 8 7 2 3 Phase Relationship The design of the Model 370 includes a phase s...

Page 154: ...brackets 3 Use a Phillips screwdriver to remove 4 flat head screws centered front rear on the top bottom of the enclosure 4 Use 5 64 hex key to remove 4 screws attaching top panel to unit 5 Use 5 64 hex key to loosen 4 screws attaching bottom panel to unit 6 Carefully remove the back bezel by sliding it straight back away from the unit 7 Slide the top panel back and remove it from the unit INSTALL...

Page 155: ...hese precautions 1 De energize or disconnect all power and signal sources and loads used with unit 2 Place unit on a grounded conductive work surface 3 Ground technician through a conductive wrist strap or other device using 1 MΩ series resistor to protect operator 4 Ground any tools such as soldering equipment that will contact unit Contact with operator s hands provides a sufficient ground for t...

Page 156: ...Lake Shore Model 370 AC Resistance Bridge User s Manual PCB Layout bmp Figure 8 4 Location Of Important Internal Components 8 10 Service ...

Page 157: ...CONNECTOR AND CABLE DEFINITIONS The SCAN CONTROL INPUT REFERENCE MONITOR HEATER OUTPUT ANALOG OUTPUT 1 and 2 STILL ALARM RELAYS and RS 232 DTE connectors are defined in Figures 8 5 thru 8 11 Scan Control bmp Pin Name Description 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Body Scan Present Digital Common Digital Common Unused Analog Common Analog Common Analog Common 15 V Scan 1 Scan 2 Scan 3 Scan 4 Scan ...

Page 158: ... V Voltage I Current 6 None Not Used None Not Used Figure 8 6 Resistor Sensor INPUT Connectors MonitorRefOutputs bmp Pin Description Center Shell Signal Ground Figure 8 7 REFERENCE and MONITOR Connector Details Heater Output bmp Pin Description Center Shell Signal Ground Figure 8 8 HEATER OUTPUT Connector Details Analog Outputs bmp Pin Description Center Shell Signal Ground Figure 8 9 ANALOG OUT 1...

Page 159: ...y Normally Closed Figure 8 10 ALARM RELAYS Terminal Block Serial Connector bmp Model 370 AC Resistance Bridge Typical Computers DE 9P DTE DB 25P DTE DE 9P DTE Pin Description Pin Description Pin Description 1 No Connection 2 TD out 1 DCD in 2 Receive Data RD in 3 RD in 2 RD in 3 Transmit Data TD out 4 RTS out 3 TD out 4 Data Terminal Ready DTR out 5 CTS in 4 DTR out 5 Ground GND 6 DSR in 5 GND 6 D...

Page 160: ...out 7 DTR tied to 4 8 CTS in 8 NC 1 DCD in Model 370 to PC Serial Interface PC with DB 25P Model 370 DE 9P Standard Null Modem Cable DE 9S to DB 25S PC DB 25P 5 GND 7 GND 2 RD in 2 TD out 3 TD out 3 RD in 1 NC 4 RTS out 7 DTR tied to 4 5 CTS in 8 NC 8 DCD in 6 DSR in 20 DTR out 4 DTR out 6 DSR in Model 370 to PC Interface using Null Modem Adapter Model 370 DE 9P Null Modem Adapter PC DE 9P 5 GND 5...

Page 161: ...re 8 12 shows the IEEE 488 Interface connector pin location and signal names as viewed from the Model 370 rear panel IEEE Connector bmp PIN SYMBOL DESCRIPTION 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 DIO 1 DIO 2 DIO 3 DIO 4 EOI DAV NRFD NDAC IFC SRQ ATN SHIELD DIO 5 DIO 6 DIO 7 DIO 8 REN GND 6 GND 7 GND 8 GND 9 GND 10 GND 11 GND Data Input Output Line 1 Data Input Output Line...

Page 162: ... values If the old values are saved they can be reloaded in the case of accidental loss of data during calibration New calculated calibration coefficients should be very similar to the old values Discrepancy between the old and new values of more than 0 1 of gain calibration coefficients or 0 1 of range for zero coefficients could indicate an error in the calibration procedure or a hardware failur...

Page 163: ...e range 63 2 MΩ 10 nA for the highest range 4 Use the CALZ and CALG queries to read and record the coefficients for the selected voltage range A safety step to revert to the original calibration if necessary 5 Set the CALZ and CALG coefficients for the selected Voltage range to default 0 and 1 The current source CALG coefficient does not have to be set to default 1 for this operation 6 Read the sh...

Page 164: ...ent resistor of known value to the input of the instrument with short leads 4 Use the CALG query to read and record the gain coefficient for the selected current A safety step to revert to the original calibration if necessary 5 Set the CALG coefficient for the selected current to default 1 6 Read the resistance from the instrument with the RDGR query 7 Calculate the gain coefficient value for the...

Page 165: ...sation factor must be entered into the Model 370 so it can accurately subtract the gain of its pre amplifier when a scanner is used This calibration is separate from the gain calibration done to the scanner itself When both the instrument and scanner are calibrated properly the calibrations do not interact so scanners and instruments can be interchanged without loss of accuracy To calculate the sc...

Page 166: ...equency of 13 7 Hz 2 Calibrate all voltage zero offsets Follow the procedure described in 8 12 2 1 Be sure to set all voltage gain coefficients to default 1 3 Calibrate the 632 mV voltage gain only Follow the procedure described in 8 12 2 2 Small measurement errors in this step will not contribute to the final resistance measurement accuracy 4 Calibrate current gains from 31 6 mA through 1 μA Rema...

Page 167: ...nge Setting Coefficient Resistor Voltage Filter Actual RDGR Coefficient 4 a 31 6 mA Gain CALG 1 22 20 Ω 632 mV 10s 4 b 10 mA Gain CALG 1 21 60 Ω 632 mV 10s 4 c 3 16 mA Gain CALG 1 20 200 Ω 632 mV 10s 4 d 1 mA Gain CALG 1 19 600 Ω 632 mV 10s 4 e 316 μA Gain CALG 1 18 2 kΩ 632 mV 10s 4 f 100 μA Gain CALG 1 17 6 kΩ 632 mV 10s 4 g 31 6 μA Gain CALG 1 16 20 kΩ 632 mV 10s 4 h 10 μA Gain CALG 1 15 60 kΩ ...

Page 168: ...ntly of each other and their calibration is independent of the measurement input A DC voltmeter with accuracy of 1 mV on a 10 V range and cable to connect to the analog output are required A zero offset and gain coefficient must be calculated for each output The method used for calculating these coefficients provides the most accurate calibration of the DAC used in the instrument To calibrate the ...

Page 169: ...ranges perform the following sequence of operations 1 Configure the Model 370 for Open Loop control Refer to Paragraph 4 11 2 1 2 Set the heater output to the highest range of 100 mA 3 Set the heater calibration coefficients to their defaults of 0 and 1 with the following commands CALZ 3 1 0 and CALG 3 1 1 4 Attach a nominal 20 Ω resistor of known value across the heater output 5 Set the Manual Ou...

Page 170: ...Resistance 8 12 5 Calibration Commands The following interface commands are only used during calibration and are in addition to those listed in Chapter 6 CALG Gain Calibration Constant Command Input CALG input range value term Format n nn nnn nnnE nn input Specifies the input or output to assign the gain calibration constant 1 Current Excitation range 2 Voltage Excitation range 3 Heater range 4 An...

Page 171: ...ormat n nn nnn nnnE nn input Specifies the input or output to assign the zero offset calibration constant 1 Not Used Reserved for Current Excitation 2 Voltage Excitation range 3 Heater range 4 Analog Output range Specifies the calibration range 1 12 for Voltage Excitation range calibration Reference RDGRNG 1 8 for Heater range calibration Reference HTRRNG 1 2 for Analog Output calibration value Ze...

Page 172: ...rement accuracy To calibrate the scanner perform the following sequence of operations 1 Remove the calibration access cover on the front panel of the scanner NOTE The scanner does not have to be disassembled for calibration 2 Attach the scanner to a Model 370 3 Attach a near 20 kΩ resistor of known value to the scanner input designated channel 1 4 Configure the Model 370 to read Channel 1 continuo...

Page 173: ...0 0100 0 2546 40 0 00314 0 07987 ambient temperature The temperature of the surrounding medium such as gas or liquid which comes into contact with the apparatus 1 ampere The constant current that if maintained in two straight parallel conductors of infinite length of negligible circular cross section and placed one meter apart in a vacuum would produce between these conductors a force equal to 2 1...

Page 174: ...netic material to zero coercivity generally used to designate the magnetic field strength H required to reduce the magnetic induction B in a magnetic material to zero from saturation The coercivity would be the upper limit to the coercive force common mode rejection CMR The ability of an amplifier to cancel a common mode signal while responding to an out of phase signal 1 cryogen See cryogenic flu...

Page 175: ...conductive electrostatic discharge ESD A transfer of electrostatic charge between bodies at different electrostatic potentials caused by direct contact or induced by an electrostatic field error Any discrepancy between a computed observed or measured quantity and the true specified or theoretically correct value or condition 2 excitation Either an AC or DC input to a sensor used to produce an outp...

Page 176: ...rent system of units in which the following seven units are considered basic meter kilogram second ampere Kelvin mole and candela The International System of Units or Système International d Unités SI was promulgated in 1960 by the Eleventh General Conference on Weights and Measures For definition spelling and protocols see Reference 3 for a short convenient guide interpolation table A table listi...

Page 177: ... in understanding material properties A small highly magnetic sample can have exactly the same moment as a larger weakly magnetic sample see Magnetization Measured in SI units as A m2 and in cgs units as emu 1 emu 10 3 A m2 magnetic units Units used in measuring magnetic quantities Includes ampere turn gauss gilbert line of force maxwell oersted and unit magnetic pole magnetization M This is a mat...

Page 178: ...ymbol 10 1 deci d 10 2 centi c 10 3 milli m 10 6 micro µ 10 9 nano n 10 12 pico p 10 15 femto f 10 18 atto a 10 21 zepto z 10 24 yocto y probe A long thin body containing a sensing element which can be inserted into a system in order to make measurements Typically the measurement is localized to the region near the tip of the probe proportional integral derivative PID A control function where outp...

Page 179: ...at a time rather than one byte character at a time as in a parallel interface RS 232C is the most common serial interface SI Système International d Unités See International System of Units stability The ability of an instrument or sensor to maintain a constant output given a constant input still A device used to evaporate liquids heat is applied to the liquid and the resulting vapor is condensed ...

Page 180: ... force between the two is 1 dyne volt V The difference of electric potential between two points of a conductor carrying a constant current of one ampere when the power dissipated between these points is equal to one watt 2 volt ampere VA The SI unit of apparent power The volt ampere is the apparent power at the points of entry of a single phase two wire system when the product of the RMS value in ...

Page 181: ...onomer Fahrenheit Abbreviation F A temperature scale that registers the freezing point of water as 32 F and the boiling point as 212 F under normal atmospheric pressure Originally devised by Gabriel Fahrenheit 1686 1736 a German physicist residing in Holland developed use of mercury in thermometry Kelvin Abbreviation K An absolute scale of temperature the zero point of which is approximately 273 1...

Page 182: ... 48 116 67 243 67 153 15 120 240 151 11 122 04 239 67 150 93 122 22 238 150 123 15 230 145 56 127 59 229 67 145 37 127 78 225 67 143 15 130 220 140 133 15 219 67 139 82 133 33 210 134 44 138 71 209 67 134 26 138 89 207 67 133 15 140 202 130 143 15 200 128 89 144 26 199 67 128 71 144 44 190 123 33 149 82 189 67 123 15 150 184 120 153 15 180 117 78 155 37 179 67 117 59 155 56 171 67 113 15 160 170 1...

Page 183: ...A quick comparison between LHe and LN2 is provided in Table C 1 Table C 1 Comparison of Liquid Helium and Liquid Nitrogen PROPERTY LIQUID HELIUM LIQUID NITROGEN Boiling Point 1 atm in K Thermal Conductivity Gas w cm K Latent Heat of Vaporization Btu liter Liquid Density pounds liter 4 2 0 083 2 4 0 275 77 0 013 152 0 78 C3 0 HANDLING CRYOGENIC STORAGE DEWARS Cryogenic containers Dewars must be ope...

Page 184: ...every effort to protect eyes and skin from accidental contact with liquid or the cold gas issuing from it Protect your eyes with full face shield or chemical splash goggles Safety glasses even with side shields are not adequate Always wear special cryogenic gloves Tempshield Cryo Gloves or equivalent when handling anything that is or may have been in contact with the liquid or cold gas or with col...

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