Amprobe ACDC-620T Clamp-On-Multimeter - Manual (Page 32)

c DISTRIBUTION TRANSFORMER MEASUREMENT
You can measure current, phase imbalance between phases, and true RMS neutral
current. True RMS measurement yields the effective value.
1) Set the rotary switch to " A ".
2) Clamp around a phase wire of the transformer. Be sure the jaws are completely
closed or measurement will not be accurate.
3) Observe the display for true RMS current.
4) Repeat your measurement for each phase to determine balance. Imbalanced
phases and/or harmonics can cause neutral currents.
5) Observe the display for true RMS current reading. If the phases are balance, any
significant current flow on the neutral may indicate the presence of harmonic cur
rents.
6) Press the HOLD/MAX ● MINbutton to freeze the digital display.
7) Press and hold the SHIFTbutton (>I sec) to enter the PEAK mode (DH MAX dis
played). Measure the half cycle PEAK current. Divide first reading into the sec
ond reading to determine crest factor. Acrest factor other than 1.4 is an indication
of harmonic current.
8) Press and hold the SHIFT button (>11 sec) to exit the PEAK mode.
9) Press and hold the HOLD/MAX
● MIN (> 1 sec) to enter dynamic recording
mode. Momentarily press HOLD/MAX ● MIN button to review recorded maxi
mum, minimum, and average values.
10) Press and hold the HOLD/MAX ● MIN button (> 1 sec) to exit recording.
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