Amprobe ACD-330T Clamp-On-Multimeter - Manual (Page 25)

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 sig-
nificant current flow on the neutral may indicate the presence of harmonic currents.
6) Press the HOLD/ MAX • MIN button to freeze the digital display.
7) Press and hold the SHIFT button (>lsec) to enter the PEAK mode (DH MAX dis-
played). Measure the halfcycle PEAK current. Divide first reading into the second read-
ing to determine crest factor, A crest factor other than 1.4 is an indication of harmonic cur-
rent.
8) Press and hold the SHIFTbutton (>lsec) to exit the PEAK mode.
9) Press and hold the HOLD/ MAX • MIN (>lsec) to enter dynamic recording mode.
Momentarily press HOLD/ MAX • MIN button to review recorded maximum, minimum,
and average values.
10) Press and hold the HOLD/ MAX • MIN button (>lsec) to exit recording.
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