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16

Calibration

Open Dewar Calibration

the cryogenic liquid is under pressure. For this type of approximate calibration, the
substitute

reference liquid

will be the

target liquid

at atmospheric pressure — see

page 19 for a detailed discussion of the approximate calibration method. If any
questions exist in regard to calibration issues, contact AMI for assistance in
determining the optimal calibration strategy.

Open Dewar Calibration

The instrument should be energized with the sensor connected to the instrument via
the oscillator (see the system diagram on page 5).

1. Slowly insert the sensor into the liquid until the level rests approximately one

inch below the top sensor hole and then press the MAX push-button through
the small hole provided on the instrument front panel. When the calibration
point has been accepted, the display will show "bbb.b" and the push-button
can then be released. The location of the liquid level on the sensor when the
MAX button is pressed becomes the 100% level. The 100% level should
always be lower than the upper hole to ensure the instrument will always
reach 100% in the event the overall sensor capacitance changes slightly due to
component drift, pressure variations, fluid impurities, etc.

2. Slowly withdraw the sensor out of the liquid to be measured until the level is

approximately even with the bottom hole in the sensor and then press the MIN
push-button through the small hole provided in the instrument front panel.
When the calibration point has been accepted, the display will show "bbb.b"
and the push-button can then be released. The location of the liquid level on
the sensor when the MIN button is pressed becomes the 0% level. This
completes the calibration procedure.

Note

Having a small amount of liquid on the sensor at the MIN calibration level
helps stabilize the sensor capacitance for 0% level indication.

3. Permanently install the sensor in the vessel and proceed to the

Operation

section for directions for configuring the instrument.

Closed Dewar Calibration

A calibration can be performed in a closed dewar system by monitoring the liquid
level while transferring the target liquid to an initially empty (or near empty) dewar at
a constant rate. In order to insure success with the closed dewar technique, it is
necessary to prepare the instrument by presetting the calibration MIN and MAX
points outside the estimated level range. If the instrument is not prepared in this
manner before the calibration procedure, it is possible to reach the MAX calibration
point of the instrument before the target vessel is at the desired maximum level point.

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Содержание 186

Страница 1: ...CONTROLLER INSTALLATION OPERATION AND MAINTENANCE INSTRUCTIONS Rev 3 Dec 1996 PO Box 2509 112 Flint Road Oak Ridge TN 37831 2509 Tel 423 482 1056 Fax 423 482 5472 American Magnetics Inc EXCELLENCE IN MAGNETICS AND CRYOGENICS ...

Страница 2: ...ers or percent as selected by a front panel switch A front panel switch allows the user to adjust the instrument length quickly and easily for a specific active sensor length The sensor active length can be entered in either inches or centimeters This length adjustment only effects the display and does not change the calibration of the instrument Level control The instrument has four level setpoin...

Страница 3: ...2 Introduction ...

Страница 4: ...ch 5 A level LED control band upper limit 13 Control mode rotary switch 6 B level LED control band lower limit 14 Raise lower toggle switch 7 LO level LED 15 Units mode toggle switch 8 Power toggle switch HI LEVEL LO LEVEL ACTIVITY POWER OFF RAISE LOWER INCH CM MAX MIN CAL HI LO LENGTH SILENCE Model 186 Liquid Level Controller AMI AUTO OFF ON FILL A B INTERVAL A B SET POINTS 4 8 9 10 11 13 14 15 1...

Страница 5: ...ry DB 9 connector see Appendix for pinout 5 Power cord connector 3 RG 59 U coaxial connector to oscillator unit via the extension cable LINE VOLTAGE 250 VA 2A MAX RESISTIVE LOAD CONTROLLER OUTPUT COMMUNICATIONS 50 60 Hz SELECTOR SW INSIDE J5 J2 AMERICAN MAGNETICS INC OAK RIDGE TN U S A INPUT POWER RS 232 J8 S11 ON 115 VAC 230 VAC 2 3 5 1 4 ...

Страница 6: ...5 Introduction Instrument Sensor System Diagram Model 186 instrument control valve and sensor system diagram ...

Страница 7: ...ive load Readout accuracy 0 1 Dimensions 3 8 H x 8 4 W x 11 1 D Standard 3 475 H x 19 W x 11 1 D Rack Mount Weight 3 6 lbs Standard 4 3 lbs Rack Mount Operating environment 15 50 C non condensing Analog Output Specifications 25 C Integral non linearity 0 012 Resolution 16 bits Total error 0 25 for 4 20 mA output 0 5 for 0 10 V output Current drift 4 20 mA 75 ppm C Voltage drift 0 10 V 100 ppm C ...

Страница 8: ...ud rate control 30 Data logger output interval 30 Echo function 31 Data logger function 31 RS 232 Command Set Reference 32 Commands for controlling the units of measurement 32 Commands for configuring permanent memory 33 Commands for querying the configuration 34 Command for returning a level measurement 34 Error Codes 35 5 IEEE 488 Communication Option 37 Command return termination characters 37 ...

Страница 9: ...lizing the GPIB VI 51 Interacting with the running VI 52 Running multiple GPIB devices 53 7 Troubleshooting 55 LED display not on 55 Erratic or erroneous level reading 56 Controller output does not energize 57 Unit not responding to communications 57 WARRANTY 58 RETURN AUTHORIZATION 58 Appendix 59 4 20 mA current loop option 59 Auxiliary connector J2 pinout 60 RS 232 cable DB 25 to DB 9 translatio...

Страница 10: ...y If component replacement is required return the instrument to AMI facilities as described in the Troubleshooting section of this manual 1 Unpack the instrument Carefully remove the instrument sensor oscillator and interconnecting coaxial cables from the shipping carton and remove all packaging material A rack mounting kit is supplied if the instrument was purchased with the rack mount option Not...

Страница 11: ...ecessary Note The coaxial interconnecting cables and the oscillator are temperature sensitive and should be mounted in such a manner as to avoid large temperature changes such as those encountered in the path of dewar vents 4 Connect the oscillator cable to the AMI sensor Connect the oscillator to the sensor using a supplied 6 foot RG 59 U coaxial cable Ensure the oscillator is connected in the co...

Страница 12: ... control valve with the Model 186 ensure the valve is configured for the operating voltage of the Model 186 Failure to do so will result in faulty operation and may also result in valve damage 7 Connect the instrument to the appropriate power receptacle Warning The Model 186 operates on 50 60 Hz power and may be configured for 115 or 230 VAC 100 or 200 VAC for Asian markets The power requirements ...

Страница 13: ...12 Installation Configuring power ...

Страница 14: ... corresponding to the MAX and MIN calibration points The measured value for the length will be used in configuring the instrument for operation Calibration methods The most straightforward calibration method is the Open Dewar Calibration which requires the customer to have access to a filled dewar where the full active length of the sensor can be dipped The Closed Dewar Calibration method can be p...

Страница 15: ...ensor are purchased as a Figure 2 1 Calibration method selection diagram Instrument sensor purchased together START Verify sensor specifications Verify calibration sticker on bottom of instrument Perform Open Dewar Calibration Is factory calibration correct Can Open Dewar Calibration be performed in target liquid Can Closed Dewar Calibration be performed in target liquid Perform Closed Dewar Calib...

Страница 16: ... capacitance based method for determining liquid level such a change in the dielectric of the liquid will result in a shift in the level reading of the instrument The calibration procedures described herein are most accurate when applied in situations where the operating conditions of the cryo vessel are relatively constant i e the operating pressure and temperature of the cryo vessel are relative...

Страница 17: ...ions fluid impurities etc 2 Slowly withdraw the sensor out of the liquid to be measured until the level is approximately even with the bottom hole in the sensor and then press the MIN push button through the small hole provided in the instrument front panel When the calibration point has been accepted the display will show bbb b and the push button can then be released The location of the liquid l...

Страница 18: ...the factor Cadj using the following equation where Ltotal is the total sensor length in inches Lactive is the active sensor length in inches and e is the dielectric constant of the target liquid 4 Enter Cadj into the instrument by placing the front panel control mode rotary switch in the SILENCE position By using the RAISE LOWER toggle switch and holding it in the up or down position adjust the di...

Страница 19: ...fluctuations in the displayed liquid level The liquid level trace will also start to show an increasing profile with positive slope Once the indications of the contact between the sensor and liquid become readily apparent press the MIN push button through the small hole provided in the instrument front panel When the calibration point has been accepted the display will show bbb b and the push butt...

Страница 20: ...sensor in inches This technique can be used assuming the sensor was built as a standard sensor If the sensor was made in a custom configuration refer to the sensor documentation and or drawing or contact AMI Example 20 active length sensor When the sensor is calibrated by the closed dewar procedure the actual length of calibration will be 21 distance between the bottom and top holes in the sensor ...

Страница 21: ...low the top hole Note the physical location of the liquid level on the sensor at the maximum insertion depth While the sensor is submerged at the maximum depth press the MAX push button through the small hole provided in the instrument front panel When the calibration point has been accepted the display will show bbb b and the push button can then be released 4 Measure the distance between the bot...

Страница 22: ...libration procedure Note The approximate calibration factor should only be entered once without resetting the MAX and MIN calibration points Example Purchased a 100 active length sensor for operation in liquid argon at atmospheric pressure however only liquid nitrogen is available for calibration at a maximum depth of 30 First the sensor is dipped as far as possible into the liquid nitrogen and co...

Страница 23: ...22 Calibration Approximate Calibration ...

Страница 24: ...t is normally calibrated at the factory for the specific sensor supplied with the unit for use in a target liquid If the need arises for recalibration see the Calibration section 2 Configure the active length setting After calibration the instrument must be configured for the active length of the sensor in order to scale the measurement to meaningful units of length for display For a standard cali...

Страница 25: ...ensor length The HI and LO setpoint adjustments are compatible with all three units modes a When the measured liquid level reaches or exceeds the HI setpoint the HI LEVEL LED on the front panel is energized and a set of relay contacts are closed on the 9 pin D connector J2 on the rear panel see the Appendix for the pinout When the level falls below the HI setpoint the LED is extinguished and the r...

Страница 26: ... set from 0 to 100 of the LENGTH setting as long as A B 5 Select the operational mode of the controller output receptacle The operation of the CONTROLLER OUTPUT receptacle of the instrument is controlled by the fill toggle switch Operation of the fill toggle switch is as follows a OFF With the power on and the fill switch in the OFF position the instrument serves only as a level monitor giving a l...

Страница 27: ...function the fill toggle switch must be momentarily placed in the ON position to complete the filling process manually or power to the instrument must be momentarily turned off Note The INTERVAL function is disabled when the INTERVAL setting is 0 Adjusting the INTERVAL setting to 0 will also terminate any in progress functions of the INTERVAL timer The INTERVAL setting can be adjusted by placing t...

Страница 28: ...re is not taken to ensure the sensor is in a proper environment Cold sensors exposed to humidified air can show erroneous high level readings due to the fact that the air contains moisture which can condense between the cold sensing tubes A small film of water can cause a shorted or partially shorted condition which results in false level readings As the sensor warms the moisture may evaporate and...

Страница 29: ...28 Operation Sensor contamination ...

Страница 30: ...e transmit on pin 2 and receive on pin 3 the requirements for a DTE or Data Terminal Equipment device If a serial to parallel converter is used it must be capable of receiving data on pin 3 or the cable connected to the Model 186 must interchange the wires between pins 2 and 3 Command return termination characters All commands are transmitted and received as ASCII values and are case insensitive T...

Страница 31: ...odel 186 baud rate is controlled by switches 6 through 8 of the communication DIP switch on the rear panel The unit is shipped with the baud rate set at 9600 The switch settings for various baud rates are on 1 or the up position Data logger output interval The interval between successive output from the data logger function is controlled by switches 3 through 5 The unit is shipped with the data lo...

Страница 32: ...r function generates a time relative to instrument power up and a corresponding level The units of the level output are set by the units mode toggle switch The time and corresponding level are formatted and output to the host device at regular intervals as specified by the switches 3 through 5 The settings for the data logger function are The host device can be a standard dot matrix printer connec...

Страница 33: ...and the INCH command selects inches The PERCENT command sets the units of measurement to the percentage of active sensor length that is immersed in liquid The units of measurement selected through the RS 232 interface are controlled independently from the units mode toggle switch used for controlling the front panel display The default units are centimeters when the Model 186 is first powered on T...

Страница 34: ...measurement The LENGTH command does not configure the Model 186 if the units of measurement are PERCENT The INTERVAL command sets the fill timer in minutes as described in the Operation section on page 26 Setting the value of INTERVAL to 0 disables the fill timer function The SAVE command saves the HI LO A B INTERVAL and LENGTH settings to permanent memory Saved settings are then recalled each tim...

Страница 35: ...rrent units selected through the communication interface Command HI Function Returns the HI setpoint limit in the current units Returns value CR LF Command LO Function Returns the LO setpoint limit in the current units Returns value CR LF Command A Function Returns the A setpoint limit in the current units Returns value CR LF Command B Function Returns the B setpoint limit in the current units Ret...

Страница 36: ...t of error codes their meaning and any associated limits Error Code Meaning Valid Range 1 LO setpoint out of range 0 LO LENGTH 2 B setpoint out of range 0 B A 3 A setpoint out of range B A LENGTH 4 HI setpoint out of range 0 HI LENGTH 5 Attempted to set or query for LENGTH in PERCENT units mode 6 Invalid argument value out of maximum calibration range 1 cm value 650 cm 7 INTERVAL setting out of ra...

Страница 37: ...36 RS 232 Communication Data Logger Option Error Codes ...

Страница 38: ...al characters are case insensitive and character encoding is in accordance with IEEE 488 2 Communicating with the Model 186 The use of a single buffer for both input and output is a result of memory limitations in the Model 186 In order to keep the external IEEE 488 interface from sending successive commands faster than the Model 186 can respond the Model 186 uses the Serial Poll Service Request S...

Страница 39: ...mmunication Option Communicating with the Model 186 N Y Y N SRQ Asserted Send Command Begin Get Response Error Error Routine End N Another Command Y Wait for SRQ Basic communication flow diagram for IEEE 488 commands ...

Страница 40: ...roller cards in external computers will use address 0 The bus address for each Model 186 should be unique with respect to other Model 186 units or any other devices on the bus The switch settings for the various addresses are on 1 or the up position DIP switch Primary bus address 1 2 3 4 5 off off off off off 0 off off off off on 1 off off off on off 2 off off off on on 3 off off on off off 4 off ...

Страница 41: ...ent a full complement of IEEE 488 2 commands nor does it conform to the Standard Commands for Programmable Instruments SCPI protocol These limitations are due to memory constraints in the microprocessor board design Device clear DCL command The Model 186 responds to the device clear DCL command from a host IEEE controller The device clear resets the instrument The default units are centimeters and...

Страница 42: ...or controlling the front panel display The default units are centimeters when the Model 186 is first powered on The last unit command remains in effect until the unit is powered off The setting is not saved in permanent memory The UNIT command returns a one character value and termination indicating the current units C for centimeters I for inches or for percentage Command CM Function Sets the uni...

Страница 43: ...GTH command does not configure the Model 186 if the units of measurement are PERCENT The INTERVAL command sets the fill timer in minutes as described in the Operation section on page 26 Setting the value of INTERVAL to 0 disables the fill timer function The SAVE command saves the HI LO A B INTERVAL and LENGTH settings to permanent memory Saved settings are then recalled each time the power is turn...

Страница 44: ...e liquid level in the current units selected through the communication interface Command HI Function Returns the HI setpoint limit in the current units Returns value Command LO Function Returns the LO setpoint limit in the current units Returns value Command A Function Returns the A setpoint limit in the current units Returns value Command B Function Returns theB setpoint limit in the current unit...

Страница 45: ...error codes their meaning and any associated limits Error Code Meaning Valid Range 1 LO setpoint out of range 0 LO LENGTH 2 B setpoint out of range 0 B A 3 A setpoint out of range B A LENGTH 4 HI setpoint out of range 0 HI LENGTH 5 Attempted to set or query for LENGTH in PERCENT units mode 6 Invalid argument value out of maximum calibration range 1 cm value 650 cm 7 INTERVAL setting out of range 0...

Страница 46: ...the table below Note The fill mode indication is only accurate if the fill mode toggle switch on the front panel is in the AUTO position There is no remote indication available for the OFF or ON manual override selections Bit ON OFF 1 HI relay on HI relay off 2 A relay on A relay off 3 B relay on B relay off 4 LO relay on LO relay off 5 Fill mode off controller output de entergized Fill mode on co...

Страница 47: ...46 IEEE 488 Communication Option Serial Poll Status Byte ...

Страница 48: ...provided VI s are supplied on one 3 5 1 44 MB diskette The VI s require version 3 1 or above of LabVIEW and a minimum of a 256 color display The VI s are stored in one LabView VI Library LLB file which contains the multiple VI s needed for operation of the instrument as a whole AMI s provided VI s are designed for continuous operation under the control of LabVIEW and do not conform to the instrume...

Страница 49: ...etup by the user The figure below illustrates the available controls The Initialize State from Instrument switch allows the user to select whether the instrument is initialized from the current settings of the actual instrument or from the controls available from the VI VI Function 186 Alarms vi Manages alarm functions for 186 Config 186 via Serial Port vi Initializes actual instrument from VI con...

Страница 50: ... panel operation of the actual instrument See the Operation section of this manual for instructions on operating the front panel controls however please note that there are some minor differences discussed below The RAISE LOWER toggle switch functions slightly different in the VI If the RAISE LOWER toggle switch is moved from the center position to the RAISE or LOWER position then the display chan...

Страница 51: ... for the IEEE 488 virtual instrument contains the following files VI Function 186 Alarms vi Manages alarm functions for 186 Config 186 via GPIB vi Initializes actual instrument from VI configuration Convert from CM vi Displays inches or percentage given input in cm Counter vi Timer function for the virtual display Get 186 Level via GPIB vi Updates virtual display with current level Init from 186 v...

Страница 52: ...hronized The only exceptions to this rule are calibration procedures or operation of the fill toggle switch if manual override becomes necessary both of which are functions that are not available from the VI Any function available from the VI should be normally be set by using the VI and not the front panel of the instrument Launching and initializing the GPIB VI First make sure the Model 186 is c...

Страница 53: ...the RAISE or LOWER position the display will begin incrementing or decrementing by tenths After approximately 12 additional seconds the display will begin incrementing decrementing by ones Move the RAISE LOWER toggle switch back to the center position to stop the incrementing or decrementing function The virtual instrument s FILL LED indicator is only accurate if the fill toggle switch is in the A...

Страница 54: ...should be set to a unique primary address In addition to modifications required to use other devices present on the bus the user should modify the Non exclusive loop control vi to both initialize and then execute the Model 186 via GPIB vi at a regular interval The longer the interval between execution the less responsive the VI will appear This is due to the fact that the VI assumes periodic execu...

Страница 55: ...54 Virtual Instrument Operation Running multiple GPIB devices ...

Страница 56: ...er receptacle Failure to do so could result in personnel coming in contact with high voltages capable of producing life threatening electrical shock a Ensure the instrument is de energized by disconnecting the power cord from the power source Disconnect the power cord from the connector located on the rear panel of the instrument b Remove the instrument top cover and check the fuse F1 for continui...

Страница 57: ...treme temperature changes of the oscillator unit can cause readout errors 5 Rapidly varying or sloshing liquids will sometimes make one think the instrument is in error when it is actually operating properly 6 Capacitance based sensors used in cryogenic liquid systems are sometimes exposed to humidified air when the cryogenic vessel is emptied This often happens when a cold trap runs out of liquid...

Страница 58: ... rating Caution Installing fuses of incorrect values and ratings could result in damage to the instrument in the event of component failure 2 Replace the fuse and securely fasten the instrument top cover Reconnect the power cord Unit not responding to communications 1 Verify your communications cable integrity and wiring See the Appendix for DB 25 to DB 9 translation for RS 232 cables 2 Check to m...

Страница 59: ...lem cannot be located contact an AMI customer service representative at 423 482 1056 for assistance Do not send the unit back to AMI without prior return authorization WARRANTY All products manufactured by AMI are warranted to be free of defects in materials and workmanship and to perform as specified for a period of one year from date of shipment In the event of failure occurring during normal us...

Страница 60: ...from connector J2 is not available The figure below shows the wiring diagram and the voltage requirements for the power supply and receiver Caution It is extremely important to observe all polarities and to not exceed 32 VDC for the loop power supply in order to prevent damage to the 4 20 mA driver circuit Receiver AMI Level Instrument Loop Power Supply 12 to 32 VDC RL ILOOP J2 pin 1 J2 pin 2 ...

Страница 61: ...d LO level contacts will be closed which is a state unique to the power off condition The following table provides the specifications for the relay contacts Pin Function 1 4 20 mA current loop input optional feature 2 4 20 mA current loop output optional feature 3 0 10 VDC output optional feature 4 0 10 VDC output common optional feature 5 6 Lo level relay contacts dry 7 8 Hi level relay contacts ...

Страница 62: ...32 cable DB 25 to DB 9 translation RS 232 cable DB 25 to DB 9 translation All other pins on the DB 25 connector are unused This is standard PC modem cable wiring DB 25 Pin DB 9 Pin 2 3 3 2 4 7 5 8 6 6 7 5 8 1 20 4 22 9 ...

Страница 63: ...ic pressure unless otherwise noted a Reference Weast Robert C Ph D Editor CRC Handbook of Chemistry and Physics 67th Edition CRC Press Inc Boca Raton FL 1986 pgs E 49 through E 53 Liquid Dielectric constanta Argon A 1 53 191 C Carbon dioxide CO2 1 60 20 C 50 atm Hydrogen H2 1 228 20 4 K Methane CH4 1 70 173 C Nitrogen N2 1 454 203 C Propane C3H8 1 61 0 C Oxygen O2 1 507 193 C ...

Страница 64: ...guration 11 M method of measurement 13 R rack mounting 10 rear panel layout 4 return authorization 58 S sensor connection 10 sensor contamination 27 sensor installation 10 serial communications baud rate 30 commands 32 data logger 31 DIP switch 30 echo function 31 error codes 35 interactive communication 29 terminators 29 serial port connector cables 29 specifications 6 system diagram 5 T troubles...

Страница 65: ...64 Index ...

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