Keysight N6705 Service Manual page 15

NOTE
Model N6705 Service Guide
CV Ripple and Noise
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.
1
Turn off the DC Power Analyzer and connect a load resistor or
electronic load, differential amplifier, and an oscilloscope (ac
coupled) to the output (see Test Setup C).
2
For models N6751A/52A, N6761A/62A, and N678xA SMU - use an
appropriate load resistor to keep the DC Power Analyzer 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 DC Power
Analyzer at the instrument setting specified in the test record form under
"CV Ripple and Noise".
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.
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.
5
Program the DC Power Analyzer 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.
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".
7
For models N6781A, N6782A, and N6784A only. Repeat steps 2
through 6 for the 6 V range.
Performance Verification 2
15