Specifications

Performance Verification
Constant Voltage Ripple and Noise
Periodic and random deviations in the output combine to produce a residual AC voltage superimposed on the DC. This
residual voltage is specified as the rms or peak-to-peak noise in the indicated frequency range (see Specifications).
Step 1. Turn off the power supply and connect an electronic load, differential amplifier, and an oscilloscope (ac coupled)
to the output (see Test Setup C).
Step 2. As shown in the diagram, use the differential probe to connect the differential amplifier to the + and - output
terminals. The shields of the two probes should be connected 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 inputs of the differential amplifier to match the probes. Set the inputs to AC coupling. Set the input res-
istance to 1 MΩ. Set the oscilloscope’s time base to 10 ms/div, and the vertical scale to the maximum sensitivity
without clipping the waveform. Turn the bandwidth limit on (usually 20 or 30 MHz), and set the sampling mode to peak
detect.
Step 4. Program the power supply to the settings indicated in the test record form for the appropriate model under “CV
Ripple and Noise” and enable the output. Let the oscilloscope run for a few seconds to generate enough measurement
points. The result should not exceed the peak-to-peak limits in the test record form for the appropriate model 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. Use the oscilloscope to measure the rms noise if it has the ability to measure rms with a 300 kHz bandwidth.
Otherwise, disconnect the oscilloscope and differential amplifier. Connect an rms voltmeter directly to the output ter-
minals (see Test Setup A). 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 10% to 90%
change in the load current.
Step 1. Keep the connections as in Constant Voltage Ripple and Noise. If an rms meter was connected, disconnect it
and reconnect the oscilloscope (see Test Setup C).
Step 2. Turn on the power supply and program the instrument settings as described in the test record form under
“Transient Response”.
Step 3. Set the electronic load to operate in constant current mode. Program its transient generator to the values of
output current as described in the test record form under “Transient Response”.
Step 4. Set the transient generator to 50 ms for both the first and second current values (this is the same as a 10 Hz
frequency at 50% duty cycle).
Step 5. Adjust the oscilloscope for a waveform similar to that shown in the following figure.
Agilent N8900 Series Operating and Service Guide 125