Lake Shore 625, User Manual, Page: 121 / 132

Lake Shore Model 625 Superconducting MPS User’s Manual
Service 7-19
7.13.3.10 Calibrate External Current Programming Voltage Reading Gain
1. Connect the PSH output in parallel with the DVM, a 100

resistor, (as a load) and the external current
programming input lines.
2. Send “CALG 7, 1”. To set the external programming voltage 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 VDC level to be measured by the
external current programming input 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 external programming voltage reading and record (V
reading
).
NOTE: To get this reading from the Model 625, press and hold the Status key on the front panel until the
display goes dark (

3 seconds). When the key is then released, a diagnostics display will be seen.
The upper right reading, “REMOTE I”, is the reading needed for this step.
7. Calculate the gain constant per Equation 6.
Equation 6
8. Verify the gain constant to be 1, ±0.02.
9. Send “CALG 7, constant”.
10. Verify the Model 625 external programming voltage 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.
7.13.4 Calibration-Specific Interface Commands
The following interface commands are only used during calibration and are in addition to those listed in Chapter 5.
CALG
Gain Calibration Constant Command
Input:
CALG <type>, <value>[term]
Format: nn, ±nnnnnnn
<input> Specifies the item to calibrate. Valid entries are:
0 = Output Current Reading
1 = Bias A Reading *
2 = Bias B Reading *
3 = CM Voltage Reading *
4 = Out Control Reading *
5 = Output Voltage Reading
6 = Remote Voltage Reading
7 = External Programming Voltage
8 = Temperature *
9 = Raw Supply Voltage *
10 = Actual Output Current
<value> Gain calibration constant value.
Remarks: Items marked with a * are for internal diagnostic use only and should always be set to a value of 1
(default).
measured
reading
V
Programming Voltage Gain Constant
V
