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B - Performance and Calibration Procedures
94
Ripple and Noise Tests
Voltage Priority Ripple and Noise
Periodic and random deviations (PARD) in the output (ripple and noise) combine to produce a residual
ac voltage superimposed on the dc output voltage. PARD is specified as the rms or peak-to-peak output
voltage in the frequency range specified in Appendix A.
Action Program Commands
1. Turn off the dc source and connect the output as shown in Figure B-1d
to an oscilloscope (ac coupled) between the HI and LO terminals. (You
can use the Model URE3 P-P Voltmeter in place of the scope.)
Remember to include a 50 ohm series resistor at the dc source end of the
cable. Also connect a 20 ohm load resistor across the HI and LO
terminals. Set the scope's bandwidth limit to 20 MHz. Use shielded
cable < 1 meter in length if possible. Attach the cable as close to the dc
source connector as possible.
“*RST”
2. Turn on the dc source and program the Voltage Priority mode (this is the
default mode). Program the output voltage to the full-scale value
(10.0V), and the current limit to the maximum value (0.5125A).
“OUTP ON,(@1)”
“VOLT 10,(@1)”
“CURR:LIM 0.5125,(@1)”
3. Note that the waveform on the oscilloscope should not exceed the peak-
to-peak limit in the performance test record card under Voltage Priority
PARD Voltage (peak to peak).
4. Disconnect the oscilloscope and connect an ac rms voltmeter in its
place. The rms voltage reading should be within the rms limit in the
performance test record card for the appropriate model under Voltage
Priority PARD Voltage (rms).
5.
Program the output voltage to the maximum positive value (+10.25V),
and the current limit to 0.45A.
“VOLT 10.25,(@1)”
“CURR:LIM 0.45,(@1)”
6.
Read back the N3280A status to be sure that it’s in the +
CL mode. This
query should return a Bit value of “
2” for +CL mode.
If it is not in +CL mode, decrease the current limit setting slightly.
“STAT:OPER:COND? (@1)”
7. Divide the voltage reading of the ac rms voltmeter by 20 (the value of
the load resistor). The result should be within the limit in the
performance test record card under Voltage Priority PARD Current
Limit.
8.
Program the output voltage to the maximum negative value (–10.25V).
“VOLT −10,(@1)”
9.
Read back the N3280A status to be sure that it’s in the
−CL mode. This
query should return a Bit value of “4” for −CL mode.
If it is not in − CL mode, decrease the current limit setting slightly.
“STAT:OPER:COND? (@1)”
10. Divide the voltage reading of the ac rms voltmeter by 20 (the value of
the load resistor). The result should be within the limit in the
performance test record card under Voltage Priority PARD Current
Limit.