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6.15 Pre-Processing Aids
The meter has several registers that can aid in pre-processing or post-processing
data that may need secondary operations.
Snap Thresholds
The signal to noise ratio of the meter is above 80 db at full scale (1 part in 10,000).
When the signal amplitude becomes so small that it is indistinguishable from noise, it
is better to record 0 than a small random value. Snap Threshold registers (Advanced
tab in Power Meter Viewer Utilities) tell the meter when to record 0 instead of the
measurement result. The factory defaults for CT’s are expressed in percentages,
and have a default value of 0.04% full scale. The voltage thresholds are in absolute
value, the recommended minimum voltage is 1.0 volt.
Multipliers
The meter has registers that allow potential transformers and series current
transformers to be used with the VerifEye
®
meter. These registers allow for
transformer winding ratios or other scaling adjustments included in the meter
processing to eliminate post-process scaling. Adjustments to voltage are global
to the meter, while CT’s can be adjusted channel by channel. The multiplier is
a oating-point number and can also be used for post installation calibration, if
needed. The default value is 1.0.
CT Phase Shifts
Current transformers experience a small magnetizing current that is out of phase
with the measurement current. Phase shift registers are available on a per channel
basis, and allow corrections of +/- 3 degrees. The Power Meter Viewer Utilities
software loads the default phase shift for the CT types available in the picker list.
If no phase shift information is available, then enter the accuracy class in degrees
(e.g., 1% = 1.0 degree).
Demand
VerifEye
®
meters use a 15 minute sliding window to keep track of electrical
demand. The Peak Demand and Present Demand registers contain the highest
average power consumption in any 15 minute interval and the average power
consumption in the last 15 minute interval. Use the Clear Peak Demand register to
reset the peak demand detector.
6 COMMUNICATION AND VERIFICATION
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