Fluke 5820A, Service Manual

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Calibration and Verification
Calibration and Verification of Square Wave Voltage Functions
3
3-7
output. In general, the HP 3458A is setup to make an analog-to-digital conversion after
receiving the falling edge of an external trigger. The conversion does not take place until
a time determined by the 3458A “DELAY” command. The actual integration time is set
according to the frequency that the DMM is measuring. Table 3-2 below summarizes the
DMM settings required to make topline and baseline measurements. Figure 3-1 shows
the proper equipment connections.
Table 3-2. Voltage HP3458A Settings
Voltage HP 3458A Settings
Input Frequency NPLC DELAY (topline) DELAY (baseline)
100 Hz .1 .007 s .012 s
1 kHz .01 .0007 s .0012 s
5 kHz .002 .00014 .00024
10 kHz .001 .00007 .00012
For all measurements, the HP 3458A is in DCV, manual ranging, with external trigger
enabled. A convenient method to make these measurements from the HP 3458A’s front
panel is to program these settings into several of the user defined keys on its front panel.
For example, to make topline measurements at 1 kHz, you would set the DMM to
“NPLC .01; DELAY .0007; TRIG EXT”. To find the average of multiple readings, you
can program one of the keys to “MATH OFF; MATH STAT” and then use the
“RMATH MEAN” function to recall the average or mean value.
Note
For this application, if making measurements of a signal > 1 kHz, the HP
3458A has been known to have .05% to 0.1% peaking. For these signals,
lock the HP 3458A to the 1V range.