20 Verification
Table 2-5. Constant Current (CC) Tests (continued)
Action
Normal Result
Current Sink (CC-) and Readback Accuracy (cont)
4 Observe the DVM voltage reading. Divide this by the resistance of the
current monitor resistor to obtain the current sink value.
5 Subtract the current value obtained in Step 4 from the current reading on
the power supply display. Record the difference as the Current Sink
Display Readback.
Value within Current Sink Display
Readback limits.
CC Noise (PARD)
Periodic and random deviations (PARD) in the output (ripple and noise) combine to produce a residual ac current
superimposed on the dc output current. This test measures CC PARD, specified as the rms output current over the frequency
range of 20 Hz to 20 MHz.
1 Turn off the power supply and connect the current monitoring resistor and
rms voltmeter (see Figure 2-1). Make the test leads as short as possible to
reduce noise pickup.
2 Measure the residual noise on the RMS voltmeter with the power supply
turned off. Noise generated by other equipment may affect this
measurement and should be removed or factored out.
3 Turn on the power supply and program the current to its full scale value
and the voltage to its maximum programmable value (see Table 2-2).
4 Adjust the load in the CV mode for full-scale voltage (see Table 2-2) as
shown on the front panel display.
The power supply output current should
be at its full-scale value and the CC
annunciator on. If it is not, adjust the
load to slightly reduce the output
voltage until the annunciator comes on.
5 Observe the reading on the rms voltmeter. Divide this voltage by the
resistance of the current monitoring resistor to obtain the rms noise
current.
Current is within the specified PARD
rms limits.
CC Load Effect
This test measures the change in output current resulting from a change in load from full-load voltage to a short circuit. It is
recommended that you use averaged readings for Steps 4 and 5 of this test (see Averaging AC Measurements at the end of
this chapter).
1 Turn off the power supply and connect a DVM across the current
monitoring resistor (see Figure 2-1).
2 Turn on the power supply and program the current to its full scale value
and the voltage to its maximum programmable value (see Table 2-2).
3 Set the Electronic Load to CV mode and its voltage to full scale as
indicated on its front panel display.
Power supply output current is full scale
and its CC annunciator is on. If not,
reduce the Electronic Load voltage
slightly until the annunciator comes on.
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