Keysight RP7970 Serie Manuel D'utilisation page 268

6 Verification and Calibration
Step 1. Turn off the unit under test. Connect the RP79xxA load unit, differential amplifier, and an
oscilloscope (ac coupled) to the output (see
Step 2. As shown in the diagram, use the differential probes to connect the differential amplifier to the
+ and - output terminals. Connect the shields of the two probes together. Connect the output of the
differential amplifier to the oscilloscope with a 50 Ω termination at the input of the oscilloscope.
Step 3. Set the probe to 1:100 and set the inputs of the differential amplifier to match the probe
setting. Set the inputs to ac coupling. Set the input resistance to 1 MΩ . Set the oscilloscope's time
base to 5 ms/div, and set the vertical scale to the maximum sensitivity without clipping the waveform.
Turn the bandwidth limit on (usually 20 MHz), and set the sampling mode to peak detect.
Step 4. Turn on the unit under test and program the instrument settings as described in the in the test
record form under "CV Ripple and Noise". Turn the output on. Program the RP79xxA load as shown in
the test record card and turn the output on. Let the oscilloscope run for a few seconds to generate
enough measurement points. On the Keysight Infiniium scope, the maximum peak-to-peak voltage
measurement is indicated at the bottom of the screen on the right side. The result should not exceed
the peak-to-peak limits in the test record form under "CV Ripple and Noise, peak-to-peak".
If the measurement contains any question marks, clear the measurement and try
again. This means that some of the scope data received was questionable.
Step 5. Disconnect the oscilloscope and connect an rms voltmeter in its place. Do not disconnect the
50 ohm termination. Divide the reading of the rms voltmeter according to the differential amplifier
setting. The result should not exceed the rms limits in the test record form for the appropriate model
under "CV Ripple and Noise, rms".
Transient Recovery Time
This test measures the time for the output voltage to recover to within the specified value following a
50% change in the instrument's rated load current.
Step 1. Turn off the unit under test. Connect an oscilloscope with the specified probe across the sense
terminals (see Test Setup
Step 2. Turn on the unit under test and program the instrument settings as described in the test record
form under "Transient Response".
Step 3. Set the RP79xxA load's list generator to generate a 100 Hz current waveform with a duty cycle
of 50%. If using 2 - RP797xA units as a load, set one unit in CC to pull a constant current, and use the
second unit to create the current step. Use the following commands to program the list:
FUNC:CURR - specifies current priority
VOLT:LIM MAX - specifies the voltage limit
DIAG:OF:CURR:BWID:LEV 3 - specifies bandwidth level 3, which generates a 40 μs risetime step in the load list
CURR:MODE LIST - specifies current priority
LIST:CURR <low_value>,<high_value> - refer to test record card for low and high current values
LIST:DWEL 0.005, 0.005 - specifies a 100 Hz current waveform with a 50% duty cycle
LIST:COUN INF - sets the list count to infinity
INIT:TRAN - initiates the transient system
TRIG:TRAN - triggers the transient system
OUTP:ON - turns on the load
268
Test Setup
A). Connect the RP79xxA load unit to the output terminals.
Keysight RP7970 & RP7980 Series Operating and Service Guide
C).