Constant Voltage Ripple and Noise (all except N679xA )
Test category = performance
Periodic and random deviations in the output combine to produce a residual AC voltage superimposed
on the DC output voltage. This residual voltage is specified as the rms or peak-to-peak noise in the
frequency range specified in the Keysight N6700 Modular Power System Family Specifications Guide.
Step 1. Turn off the power system and connect a load resistor or electronic load, differential amplifier,
and an oscilloscope (ac coupled) to the output (see Test Setup C).
Step 2. For models N6751A/52A, N6761A/62A, and N678xA SMU - use an appropriate load resistor to
keep the power system at the instrument setting specified in the test record form under “CV Ripple
and Noise”. For all other power modules - use an electronic load to keep the power system at the
instrument setting specified in the test record form under “CV Ripple and Noise”.
Step 3. As shown in the diagram, use two BNC cables to connect the differential amplifier to the + and
− output terminals. Each cable should be terminated by a 50 Ω resistor. The shields of the two BNC
cables 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 4. Set the differential amplifier to multiply by ten, divide by one, and 1 MΩ input resistance. The
positive and negative inputs of the differential amplifier should be set to AC coupling. Set the
oscilloscope’s time base to 5 ms/div, and the vertical scale to 10 mV/div. Turn the bandwidth limit on
(usually 20 or 30 MHz), and set the sampling mode to peak detect.
Step 5. Program the power system to the settings indicated in the 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. On the Keysight Infiniium scope, the maximum
peak-to-peak voltage measurement is indicated at the bottom of the screen on the right side. Divide
this value by 10 to get the CV peak-to-peak noise measurement. 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 6. 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 by 10. The result should not exceed the
rms limits in the test record form for the appropriate model under “CV Ripple and Noise, rms”.
Step 7. For models N6781A, N6782A, and N6784A only. Repeat steps 2 through 6 for the 6 V range.
6 Verification and Calibration
336 Keysight N6700C Operating and Service Guide
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