Verification and Calibration Appendix B
Series N8700 User’s Guide 103
Constant Current Tests
Refer to the appropriate test record in the following section for the
instrument settings for each of the following tests.
Current Programming and Readback Accuracy
Test category = performance, calibration
This test verifies that the current programming and measurement
functions are within specifications.
1 Turn off the power supply and connect the current shunt directly
across the output. Connect the DVM across the current shunt.
2 Turn on the power supply and program the output voltage to its
full-scale value and the output current to zero. The CC
annunciator should be on and the output voltage reading should
be approximately zero.
3 Divide the voltage drop (DVM reading) across the current shunt
by its resistance to convert to amps and record this value (Iout).
Also record the current measurement readback. The readings
should be within the limits specified in the test record for the
appropriate model under Current Programming and Readback,
Minimum Current Iout.
4 Program the output current to its full-scale rating.
5 Divide the voltage drop (DVM reading) across the current shunt
by its resistance to convert to amps and record this value (Iout).
Also record the current measurement readback. The readings
should be within the limits specified in the test record for the
appropriate model under Current Programming and Readback,
High Current Iout.
CC Load Effect
Test category = performance
This test measures the change in output current resulting from a
change in output voltage from full scale to short circuit.
1 Turn off the power supply and connect the current shunt, DVM,
and electronic load as shown in figure B. Connect the DVM
directly across the current shunt.
2 To ensure that the values read during this test are not the
instantaneous measurement of the AC peaks of the output
current ripple, several DC measurements should be made and
averaged. With an Agilent 3458A, you can set the voltmeter to do
this automatically. From the instrument’s front panel, program
100 power line cycles per measurement. Press NPLC 100 ENTER.
3 Turn on the power supply and program the output current to its
full-scale value and the output voltage to its maximum
programmable value (Vmax).
4 With the electronic load in CV mode, set it for the output’s full-
scale voltage. The CC annunciator on the front panel must be on.
If it is not, adjust the load so that the voltage drops slightly.
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