CALIBRATION
M9B-HFS INTERFACE
4-4
Release 1.0 (97/10)
4.3.3
Current Readback Calibration Procedure
1. Connect the current shunt to the power supply as shown in Section 4.3.1 Current Calibration Setup.
Connecting a DVM is optional.
2. Activate calibration mode by sending software command CMODE ON to the power supply.
3. Send command IRLO; VRLO to the power supply. Wait for the supply to settle. Measure and record the
voltage output shown on the external meter. Send IRLO again.
4. Send command IRHI; VRHI to the supply. Wait for the supply to settle. Measure and record the output
voltage as shown on the external meter. Send IRHI again.
5. Calculate IRLO and IRHI from the voltages taken from the external meter and the shunt resistance.
I=V/R.
6. Send the command IRDAT <ilo>,<ihi> where <ilo> and <ihi> are the current values obtained by sending
the commands IRLO and IRHI to the supply. When the power supply is calibrated, the low to high
current readback calibration values are stored as constants. Refer to the current readback accuracy
specification in Appendix A.
7. Use commands ISET and IOUT? to confirm that the calibration was successful and that linearity is
observed. Refer to the voltage readback accuracy specification in Appendix A.
8. Turn off calibration mode by sending the command CMODE
OFF to the power supply.
4.4 Over Voltage Protection (OVP) Calibration
We recommend that you perform OVP calibration every six months. Connecting a digital voltmeter as in Section
4.2.1 Voltage Calibration Setup is optional.
1. Disconnect any load from the supply.
2. Ensure that jumper J66 on the interface PCB is installed to enable remote OVP calibration. (Jumper J66 is
installed at the factory). See
Figure 2.7-1 for the location of jumper J66.
3. Activate calibration mode by sending command CMODE ON to the supply.
4. Send the command OVCAL to the supply. The ADDR LED will light during OVP calibration. Calibration
is complete when the ADDR LED turns off. This may take a few minutes.
5. Use the OVSET, OVSET?, and VSET commands to trip the OVP level, confirming that the calibration
was successful. When you trip the OVP level, the red OVP LED will light and the voltage will drop to
zero. Send the command RST to clear the OVP condition. Refer to the OVP program accuracy
specification in Appendix A.
6. Turn off calibration mode by sending the command CMODE
OFF to the supply.
