Lake Shore 475, Руководство пользователя

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Lake Shore Model 475 Gaussmeter User’s Manual
8-14 Service
8.11.3 Temperature Measurement Calibration
This section performs the calibration on the temperature measurement. The Model 475 has three excitation currents for
temperature measurement. Each one of these is used to measure the appropriate 0.1% resistor. Calibration constants and
offsets are calculated and sent to the Model 475.
1. Set the Temperature Gain Correction Factor to 1 and the Offset Correction Factor to 0. (CALG 5,3,1;CALZ 5,3,0)
2. Connect the 2 k
Ω
resistor to the DVM using a proper 4-lead connection.
3. Read the resistor using the DVM. Store as TEMPDESIRED.
4.
Connect a short across the temperature input of the Model 475 using a proper 4-lead connection.
5. Configure temperature current source for 1mA amplitude, manual mode (CALTEMP 1,3)
6. Read the resistor using the 475 (RDGTRES?). Store as TEMPOHMOFFSET.
7. Send the Offset Calibration Factor (OCF) to the Model 475 (CALZ 5,3,TEMPOHMOFFSET).
8. Connect the 2 k
Ω
resistor across the temperature input of the Model 475 using a proper 4-lead connection.
9. Read the resistor using the 475 (RDGTRES?) Store as TEMPACTUAL.
10. Calculate the Gain Calibration Factor (GCF) as TEMPDESIRED/TEMPACTUAL. Test this factor to be 1.0, ±2%
11. Send the Gain Calibration Factor (GCF) to the Model 475 (CALG 5,3,<GCF>)
12. Read the resistor using the 475 (RDGTRES?). Verify the reading to be TEMPDESIRED, ±0.05%.
13. Repeat steps 1 thru 12 for the remaining two current excitations using the following table guidelines.
Current Command Nominal Resistance Expected Cal Constant Verify Reading
1 mA CALTEMP 1,3 2 k
Ω
1.00 ±2% DVM Measure ±0.05%
100 uA CALTEMP 1,2 22.1 k
Ω
1.00 ±2% DVM Measure ±0.05%
10 uA CALTEMP 1,1 200 k
Ω
1.00 ±2% DVM Measure ±0.05%
14.
Configure the 475 for temperature autoranging (CALTEMP 0,3).
15. Send the CALSAVE command to save the calibration constants into non-volatile memory.
8.11.4 Analog Output 2 and 3 Calibration
This section will perform the actual calibration of Analog Output 2 and 3. This involves reading the positive and
negative full-scale output voltages of each output, calculating correction constants for gain and offset of each output and
writing them back to appropriate calibration locations in the Model 475. These values are to be used whenever the
outputs are accessed. The gain and offset values should also be checked to assure that they are reasonable in value and
reject them if they fall outside a given range. Analog Output 2 uses slightly different full-scale range since it is a ±5 volt
output that will never exceed ±3.5 volts in normal operation.
8.11.4.1 Analog Output 2 Calibration
1. Set Analog Output 2 Gain Correction Factor to 1 (CALG 4,2,1) and Offset Correction Factor to 0 (CALZ 4,2,0).
2. Connect the DVM to Analog Output 2.
3. Configure Analog Output 2 to manual mode, -90% (MOUT 1,-90).
4. Read the voltage using the DVM. Record as VMIN.
5. Configure Analog Output 2 to manual mode, +90% (MOUT 1,90).
6. Read the voltage using the DVM. Record as VMAX.
7. Calculate the Gain Correction Factor (GCF) = 9 / (VMAX – VMIN). Note: Gain is calculated over the full span of
the output. Test this factor to be 1.0, ±1%. Record this value.
8. Send the Gain Correction Factor (GCF) to the Model 475 (CALG, 4,2,<GCF>).
9. Configure Analog Output 2 to manual mode, 0% (MOUT 1,0).
10. Read the voltage using the DVM. Record as VZERO.
11. Calculate the Offset Correction Factor (OCF) = -(VZERO) * (100% / 5). Note: The offset voltage is expressed as a
percentage of Full Scale. Test this factor to be between -1 and 1. Record this value.
12. Send the Offset Correction Factor (OCF) to the Model 475 (CALZ 4,2,<OCF>).