5
CAUTION
(Application and removal of the Clamp-on meter)
For non-invasive ACA current measurements, press the jaw trigger and clamp the
jaws around only one single conductor of a circuit for load current measurement. Make
sure the jaws are completely closed, or else it will introduce measurement errors.
Enclosing more than one conductor of a circuit will result in differential current (like
identifying leakage current) measurement. Locate the conductor(s) at the Jaws center
as much as possible to get the best measuring accuracy. For removal, press the jaw
trigger and remove the jaws from the conductor(s).
Adjacent current-carrying devices such as transformers, motors and conductor wires
will affect measurement accuracy. Keep the jaws away from them as much as possible
to minimize influence.
THD%-F Total Harmonic Distortion - Fundamental function (model 157 only)
Total Harmonic Distortion - Fundamental (THD%-F) function is designed to give basic
indication on the presence of Harmonics. It is the percentage ratio of the Total
Harmonics RMS value to the Fundamental RMS value of a voltage or current signal,
and is given by the expression:
THD%-F = (Total Harmonics RMS / Fundamental RMS) x 100%
An ideal sinusoidal waveform has a theoretical value of 0 THD%. A badly distorted
sinusoidal waveform may have a much higher THD% value of even up to several
hundreds. It is thus a good parameter to identify the degree of “cleanness” on power
systems.
When the meter is in ACV or ACA function, THD%-F values will be displayed in the
secondary mini display automatically. Press
THD%-F
button momentarily toggles
THD% readings to main display.
