Lake Shore 625, User Manual

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Lake Shore Model 625 Superconducting MPS User’s Manual
7-18 Service
7.13.3.8 Calibrate Voltage Reading Gain
1. Add the larger load resistor in series with the shunt resistor.
2. Set the Model 625 output compliance limit to 5 V.
3. Send “CALG 5, 1”. To set the output voltage reading gain constant to 1.
4. Set the Model 625 output current to I = – (0.18 + (4.5/R load)).
(For example, if R load = 1

, set the Model 625 output current to –4.68 A).
5. Wait 30 seconds.
6. Measure the Model 625 actual output voltage at the output terminals and record (V
measuredneg
).
This voltage must be between 4.0 and 5.0 volts, (4.5 V nominal).
7. Get the Model 625 output voltage reading (by front panel or interface) and record (V
readingneg
).
8. Set the Model 625 output current to I = 0.18 + 4.5/R load.
(For example, if R load = 1

, set the Model 625 output current to 4.68 A).
9. Wait 30 seconds.
10. Measure the Model 625 actual output voltage at the output terminals and record (V
measuredpos
).
This voltage must be between 4.0 and 5.0 volts, (4.5 V nominal).
11. Get the Model 625 output voltage reading (by front panel or interface) and record (V
readingpos
).
12. Calculate gain constant per Equation 4.
Equation 4
13. Verify the gain factor to be 1, ±0.02.
14. Send “CALG 5, gain constant”.
15. Verify the Model 625 output voltage reading to match the actual output voltage within, ±0.0005 V.
16. Set the Model 625 output current to 0 A.
17. Send “CALSAVE” to write this calibration to non-volatile memory.
7.13.3.9 Calibrate Remote Voltage Sense Reading Gain
1. Connect the PSH output in parallel with the DVM, a 100

resistor (as a load) and the remote voltage sense lines.
2. Send “CALG 6, 1”. To set the remote voltage sense reading gain constant to 1.
3. Set the PSH switch heater to 50 mA and turn on the PSH output to provide a 5.0 V DC level to be measured by the
remote voltage sense lines.
4. Measure the PSH output voltage and record (V
measured
).
5. Verify V
measured
= 5.0 ±0.1 V.
6. Get the Model 625 output voltage reading (by front panel or interface) and record (V
reading
).
7. Calculate the gain constant per Equation 5.
Equation 5
8. Verify the gain constant to be 1 ±0.02.
9. Send “CALG 6, gain constant”.
10. Verify the Model 625 remote voltage sense reading to match the measured PSH output voltage within, ±0.0005 V.
11. Send “CALSAVE” to write this calibration to non-volatile memory.
12. Turn off the PSH output.
 
 
measuredpos measuredneg
readingpos readingneg
V V
Voltage Reading Gain Constant
V V



measured
reading
V
Voltage Sense Gain Constant
V
