Chapter 3 Calibration Procedures
Constant Current (CC) Verifications
61
3
CC Line Regulation
This test measures the immediate change in output current that results from a change
in ac line voltage from the minimum value (10% below the nominal input voltage) to
the maximum value (10% above nominal voltage).
1 Turn off the power supply and connect the output to be tested as shown in Figure 3-1
with the digital voltmeter connected across the current monitoring resistor (R
M
).
2 Connect the ac power line through a variable voltage transformer.
3 Turn on the power supply and select the desired output to be tested using the meter
and adjust selection key on the front panel. Enable the outputs and set the display to
the limit mode. When the display is in the limit mode, program the voltage to the
maximum programmable value and the current to the full rated value (see Table 3-2).
4 Operate the electronic load in constant voltage mode and set its voltage to the full
rated value of the output to be tested (see Table 3-2). Check that the CC annunciator
remains lit. If not lit, adjust the load so that the output voltage drops slightly until the
CC annunciator lights.
5 Adjust the transformer to low line voltage limit (104 Vac for nominal 115 Vac, 90
Vac for nominal 100 Vac, or 207 Vac for nominal 230 Vac). Record the output current
reading by dividing the voltage reading on the digital voltmeter by the resistance of
the current monitoring resistor.
6 Adjust the transformer to 10% above the nominal line voltage (110 Vac for a 100 Vac
nominal input, 127 Vac for a 115 Vac nominal input or 253 Vac for a 230 Vac nominal
input). Record the current reading immediately by dividing the voltage reading on the
digital voltmeter by the resistance of the current monitoring resistor. The difference
between the current readings in step (5) and (6) is the load regulation current. The
difference of the readings during the immediate change should be within the limit
specified below for each output tested.
7 Repeat steps (1) through (6) for the remaining outputs.
Output Difference
+6V 0.75 mA
+25V 0.35 mA
-25V 0.35 mA
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