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4-12
Aperture
Aperture is a different way to specify the integration rate. As previously explained, 1 PLC
sets the integration rate to 16.67msec (assuming 60Hz line power). You can instead use an
APERture command as follows to set the same integration rate:
:APERture 16.67e-3
Bandwidth
There are three bandwidth settings for ACV and ACI measurements; 3 (3Hz to 300kHz),
30 (30Hz to 300kHz), and 300 (300Hz to 300kHz). To achieve the best accuracy for ACV
and ACI measurements, use the bandwidth setting that best reflects the frequency of the
input signal. For example, if the input signal is 40Hz, then a bandwidth setting of 30
should be used.
To set bandwidth, simply specify (approximately) the frequency of the input signal. The
instrument will automatically set the bandwidth as follows:
<NRf>
klqb
Rate and bandwidth conflict error
For bandwidth settings of 3 and 30, the normal A/D conversion method is not used for
ACV and ACI measurements. Therefore, integration rate commands (:NPLCycles and
:APERture) for these bandwidth settings will cause a settings conflict error (-221) and not
be executed.
For a bandwidth setting of 300, the normal A/D conversion method is used, therefore the
integration rate commands can be used.
The default bandwidth setting is 30 for both ACV and ACI. If you want to set an integra-
tion rate for an AC function, you will have to first set the bandwidth to 300. Failure to do
so results in an error -221, Settings Conflict.
Rate and bandwidth programming examples
Example #1 — The following command sequence sets ACV rate to 5 PLC. In order to set
rate for an AC function, bandwidth must first be set to 300:
VOLT:AC:DET:BAND 300
VOLT:AC:NPLC 5
Model 2790 SourceMeter
= 3 to 29
3Hz to 300kHz
= 30 to 299
30Hz to 300kHz
= 300 to 300e3
300Hz to 300kHz
A rate command (:NPLCycles or :APERture) for ACV and ACI is only valid if
the bandwidth for that AC function is set to 300 (300Hz to 300kHz). See
and bandwidth conflict
error" below for details.
' Set ACV bandwidth to 300.
' Set ACV rate to 5 PLC.
®
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"Rate
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