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11.. . A
PPENDIX
F: F
ILTERING
O
PTIONS
U
SING
T
HE
OMP-MODL 11-124
The above plot demonstrates the performance of the 50Hz software filtering. The
plot is from actual data collected by a OMP-MODL (which utilizes the same digital
signal processing) during the development and testing of the software filtering
feature. A 5Vp-p AC swept frequency was super-imposed on a 2.5VDC and input
into a OMP-MODL equpped with an HLIM-1 The input channel was configured with
the 50 Hz filtering enabled. As can be seen from the plot, at 50 Hz, the amplitude of
the noise is radically reduced.
As with all filtering, a compromise is involved. Line Rejection filtering adds
approximately 8.5 mS for 60 Hz rejection (10mS for 50Hz) to the measurement and
processing time required for a reading.
If the desired sampling rate allows, enable Line Reject filtering by selecting 50 or 60
Hz depending on the power line frequency used in the installation locale. In the
USA, 60 Hz should be selected.