EPQ DataNode Series User’s Guide
3
Operation
3-3
RMS Trigger Parameters
The following parameters are required do define how an RMS variation is triggered:
Low Limit
High Limit
Cycles in range to end event (fixed at 1)
The programmable tab allows the user to enter the thresholds in absolute volts or in percentage of a specified nominal.
In order for the Monitor 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 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 point when all channels for which triggers are enabled have come back with-
in limits (plus a little internally calculated hysteresis) for a minimum duration of Cycles in range to end event. Until this
criteria is met, any subsequent excursions beyond the threshold are considered part of the original disturbance. To mini-
mize the number of triggers recorded for a sequence of closely spaced perturbations, hysteresis is employed in both volt-
age and time for the begin-event and end-event thresholds.
Figure 3.1 RMS Triggering on Low Voltage
How RMS Disturbances Are Recorded
Once an event has been triggered, the following information is needed to define how and what information is to be
stored:
Pre-event start RMS samples (cycles) - the number of cycles of instantaneous (twice per cycle) RMS samples
to record before event start (the trigger point). Maximum is 8 cycles.
Pre-event start waveform samples (cycles) - the number of cycles of instantaneous point-on-waveform data
(128 points per cycle) to record before event start (the trigger point). Maximum is 7 cycles.
Post-event start RMS samples (cycles) - the number of cycles of instantaneous (twice per cycle) RMS samples
to record after event start (the trigger point) before switching to min/max/average recording mode. Maximum is
512 cycles.
Post-event start waveform samples (cycles) - the number of cycles of instantaneous point-on-waveform data
(128 points per cycle) to record after event start (the trigger point). Maximum is 15 cycles.
Pre-event end waveform samples (cycles) - the number of cycles of instantaneous point-on-waveform data (128
points per cycle) to record before event end point. Maximum is 8 cycles.
Post-event end waveform samples (cycles) - the number of cycles of instantaneous point-on-waveform data
(128 points per cycle) to record after the event end point. Maximum is 15 cycles.
Post-event end RMS samples (cycles) - the number of cycles of instantaneous (twice per cycle) RMS samples
to record after the event end point. Maximum is 15 cycles.
Threshold
- Hysteresis
+ Hysteresis
Event
Trigger
Event
End
Cycles
to
Trigger
Cycles
to
End
Time
V
RMS
