Cc Noise (Pard) - Agilent Technologies 6631B Service Manual

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2 – Verification and Performance Tests

CC Noise (PARD)

Periodic and random deviations (PARD) in the output combine to produce a residual ac current, as well, as

an ac voltage superimposed on the dc output. Constant current (CC) PARD is specified as the rms output

current in a frequency range 20 Hz to 20 Mhz with the supply in CC operation.

Turn off the supply and connect the load, monitoring resistor, and rms voltmeter across the monitoring

resistor as shown in Figure 2-1a. The Current Monitoring resistor may have to be substituted by one

with a higher resistance and power rating, such as a 1 ohm 50 W current shunt in series with the

appropriate 3, 24, or 99 ohm resistor for the 6632B and 66332A , 6633B or 6634B respectively , to

get the RMS voltage drop high enough to measure with the RMS voltmeter (For the 6631B use the 0.1

ohm shunt and a 0.9 ohm resistor). Leads should be as short as possible to reduce noise pick-up. An

electronic load may contribute ripple to the measurement so if the RMS noise is above the specification

the resistive loads described above may have to be substituted for this test.

Check the test setup for noise with the supply turned off. Other equipment (e.g. computers, DVMs, etc.)

may affect the reading.

Turn on the supply and program the current to full scale and the output voltage to the maximum

programmable value.

The output current should be at the full scale rating with the CC annunciator on.

Divide the reading on the rms voltmeter by the monitor resistor to obtain rms current. It should not

exceed the values listed in the performance test record card under CC NOISE (RMS).

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