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RMS Variation Limit
RMS Variation Limit
RMS variation
setup properties
RMS stands for root mean square, a mathematical formula used to compute the
equivalent value of the voltage and current. Voltage and current changes are measured
and checked against the programmed limits. Thresholds are set as high limits (threshold
above the programmed limit) and low limits (threshold below the programmed limit).
RMS variations result whenever voltage or current rms value rise above or fall below
the programmed threshold limits. The limits determine how sensitive the instrument
should be (note that statistical and trending information is always captured regardless
of the limit settings, so the user will never be without a data even if he/she did not set
the limits to the ideal values).
The 4400 allows users to set the limits for each of the triggers, as well as the amount of
rms sample (cycles) to record before and after trigger cycle.
RMS trigger
parameters
In order for the instrument to trigger on rms variation, any one of the measured
quantities for which a trigger is enabled must go above the High Limit or below the
Low Limit for a period of at least one rms sample point (which are taken twice per
cycle with a one cycle sliding integration window).
The disturbance end point is defined as the cycle when all channels for which triggers
are enabled have come back within limits (plus hysteresis) for a minimum duration of
Cycles specified in range to end event. Until this criteria is met, any subsequent
excursions beyond the thresholds are considered part of the original disturbance. To
minimize the number of triggers recorded for a sequence of closely spaced
disturbances, hysteresis is employed in both voltage and time for the begin-event and
end-event thresholds.
NOTE: Hysteresis values assigned to limits are set by the system and not
programmable by the user.
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