Step 5. Short the electronic load. Divide the voltage drop (DMM reading) across the current shunt by
the shunt resistance to convert to amps and record this value. The difference in the current readings in
steps 4 and 5 is the load effect, which should not exceed the value listed in the test record for the
appropriate model under “CC Load Effect”.
Current Sink Capability Verification
This test checks the ability of the power supply to sink up to 10% of its rated output current. If one or
more Keysight N7909A Power Dissipators are connected, this test verifies that the power supply can
sink up to 100% of its rated output current.
Step 1. Turn off the power supply and connect an external power supply to the + and - output
terminals (see Test Setup D). Connect the power dissipator as shown if you are verifying 100 % of the
current sinking capability the power supply.
Step 2. Set the external supply as follows: Voltage setting = 100 % of the rated output voltage of the
power supply under test. Current limit setting = 110 % of the rated output current of the power supply
under test.
Step 3. Turn on the power supply under test. Set the operating mode to Current Priority. Program the
instrument settings as described in the test record under “Current Sink Verification”.
Step 4. Check the front panel display of the power supply and verify that the supply is sinking either
10% or 100 % of its rated current. Divide the voltage drop (DMM reading) across the current shunt by
the shunt resistance to convert to amps and record this value. The readings should be within the limits
specified in the test record form for the appropriate model under “Current Sink Tests”.
If you are checking the current sink capability of a 2 kW unit connected to only one
power dissipator unit (@ 50% of the power supply's rated current), divide the 100%
values in the test record form in half.
Keysight N6900/N7900 Series Operating and Service Guide 315
7 Verification and Calibration
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