Keysight 669 A Series, Service Manual

Page: 20 / 106

Verification 17
Table 2-5. Constant Current (CC) Tests
Action Normal Result
Current Programming and Readback Accuracy
This test verifies that the current programming and readback are within specification.
1
Turn off the power supply and connect the current monitoring resistor as
shown in Fig. 2-3. Connect a DVM across the resistor .
2 Turn on the power supply and program the output for 5 volts and 0
amperes.
3 Short the load.
4 Observe the DVM voltage reading. Divide this by the resistance of the
current monitor resistor. Record the result as the Low Current value. Value within specified Low Current
limits.
5 Record the front panel display readback. Value within specified readback limits.
6 Program output current to full scale (see Table 2-2).
7 Repeat Steps 4 and 5.
Both current readings within specified
High Current and readback 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 5 and 6 of this test (see Averaging AC Measurements at the end of
this chapter).
Note
: Refer to Figure 2-3. If you are using Keysight N3306A electronic loads, a series DC power source is required to
supply the minimum 3 volt input required by the Keysight N3306A electronic loads. The series DC source must be capable
of 3VDC
at a current level that is greater than the output current of the supply being tested . A switch can be used in
place of the series supply if the electronic loads are used in place of a load resistor as shown in Fig. 2-3(b).
1
Turn off the power supply and connect a DVM across the current
monitoring resistor (see Fig. 2-3).
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. Set the series supply for 3VDC and a
current greater than that being tested. Series source should be in CV mode. 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.
4 Observe the DVM reading. Divide this by the resistance of the current
monitoring resistor to obtain the output current. Record the result.
You may want to use an averaged
reading for this measurement.
5 Program the Electronic Load input to 3 volts or short the Electronic Load
input and repeat Step 5.
You may want to use averaged reading
for this measurement.
6 Check the result.
The difference between the current
readings taken in Step 5 and Step 6 must
be within specified “Load Effect” limits
(see Table 2-2).