Appendix Service Information
Constant Voltage (CV) Verifications
171
Service
Information
CV Source effect (Line Regulation)
This test measures the change in output voltage that results from a change in
ac line voltage from the minimum value (10% below the nominal input voltage)
to maximum value (10% above the nominal input voltage).
1 Turn off the power supply and connect a digital voltmeter between the (+) and
(-) terminals of the output to be tested as shown in Figure A-1.
2 Connect the ac power line through a variable voltage transformer.
3 Turn on the power supply. Select the high voltage range (20V/1.5A)
†
, enable
the output, and set the display to the limit mode. When the display is in the
limit mode, program the current to the full scale rated value (1.5 A)
†
and the
voltage to full scale rated value (20.0 V)
†
.
4 Operate the electronic load in constant current mode and set its current to
(1.5 A)
†
. Check that the CV annunciator remains lit. If not lit, adjust the load
so that the output current drops slightly until the
CV 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
reading on the digital voltmeter.
6 Adjust the transformer to high line voltage (127 Vac for nominal 115 Vac, 110
Vac for nominal 100 Vac, or 253 Vac for nominal 230 Vac). Record the voltage
reading on the digital voltmeter. The difference between the digital voltmeter
readings in steps (5) and (6) is the CV line regulation. The difference of the
readings should be within the limit of (5 mV)* or (9 mV)**.
CV PARD (Ripple and Noise)
Periodic and random deviations (PARD) in the output (ripple and noise)
combine to produce a residual ac voltage superimposed on the dc output
voltage. CV PARD is specified as the rms or peak-to-peak output voltage in the
frequency range from 20 Hz to 20 MHz.
• VRMS measurement techniques:
When measuring Vrms ripple and noise, the monitoring device should be
plugged into the front of the terminals at (A) in Figure A-2. Use the vertical
mini-probe socket and the "1:1 voltage probe" to connect the monitor device
to the power supply. To reduce the measurement error caused by common
mode noise, it is recommended to twist the connection wire between the mini-
probe and the output terminals. The load resistor is connected to the terminal
at (B) in Figure A-2. Twisted leads between the load resistor and the power
supply helps reduce noise pickup for these measurements.
*For E3640A/42A/44A models. **For E3641A/43A/45A models.
†
For E3640A model, and see Table A-3
for other models
