60 Chapter 3 Configuring for Measurements
select the integration time that provides adequate speed while maintaining
an acceptable amount of resolution and NMR. The specifications tables in
Appendix A show the relationship of integration time to digits of resolution
and NMR for DC and ohms measurements.
Specifying Integration Time
Directly
For DC or ohms measurements, you can specify the integration time directly
(in seconds) using the APER (aperture) command. For example, to specify
22 ms of integration time, send:
OUTPUT 722;"APER.022"
Note When using the APER command, the multimeter does not average readings
for long integration times as it does with the NPLC command. For example,
if you specify
60=PLCs (1 second of integration time at a 60 Hz = line frequency) using
the NPLC command, the mulitmeter averages six 10 PLC readings. If you
specify 1 second of integration time using the APER command, the
multimeter integrates a single reading for 1 second.
With the APER command, you can specify integration time from 500ns to
1s in increments of 100ns. The APER command is most commonly used
when sampling a specific part of a signal (such as a pulse) or for digitizing.
You can also use the APER command to reject a noise signal of a specific
frequency from the input signal. To do this, set the integration time equal to
an integral multiple of the period of the signal to be rejected. For example,
to reject noise at 100Hz (period = 10ms), specify an integration time of 10ms,
20ms, 30ms, etc.
Specifying Resolution You specify the measurement resolution as the last parameter of a function
command (FUNC, ACV, DCV, etc.) or the RANGE command.
1
This
parameter is called
%_ resolution since you specify it as a percentage of the command's
max._input parameter (see Specifying the Range earlier in this chapter). The
multimeter multiplies the specified %_resolution parameter times the
max._input parameter to determine the measurement resolution. To compute
the %_resolution parameter, use the equation:
%_ resolution = (actual resolution/maximum input)
× 100
For example, suppose the maximum expected input is 10 VDC and you need
1 mVDC of resolution. The equation evaluates to:
%_ resolution = (0.001/10)
× 100 = 0.01
If you default the %_resolution parameter, the integration time will be that
specified by the last APER or NPLC command executed.
1. You can also specify resolution using the RES command. Refer to the RES command in Chapter 6 for
examples showing its usage.
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