7.4.3
How Much Data do I Record?
It takes about 18 minutes to fill up 128 MB of waveform flash with the
six input channels - three voltages and three currents. Decide how much
waveform data you really need to record following an event. A few seconds
of data is should be ample for each record, however the 128 MB allows for
additional event recordings, providing the postfault data is kept short. For
example, if each record includes one half second of prefault data and one
second of post fault data (90 cycles), the 933A could provide approximately
720 fault records.
When selecting one of the event records by number, use the numeric keypad
or enter key. The 933A will immediately open the waveform view at the
time of the event and allow you to scroll forward and backward with the
cursor keys to inspect the waveform. Use the right and left cursor keys to
locate and examine specific points on the waveforms. Instantaneous values
are computed where the cursor and the waveforms intersect and tabulated
at the bottom of the screen.
Press the COMPRESS WAVEFORMS or EXPAND WAVEFORMS soft
keys to view more or less of the captured event waveforms.
7.4.4
Event Capture Example
The waveform screen shown in Figure 7.12 is an example of an event caught
through setting a power quality trigger on C-phase voltage. The voltage
limit was set for 85 Volts rms, and trigger with
x < Limit
. The 933A also
caught a one-half second of the prefault waveform data, which is about 30
cycles.
Figure 7.12: Captured
Event Waveform
By using the Expand or Compress soft keys and the right and left cursor
keys you can review specific points of the event chronologically.
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