E N G L I S H
33
Press the MIN-MAX pushbutton to
cycle through the readings, including
a position where
the blinks.
In this mode, readings may be taken
without disturbing the values held in
memory. To restart recording, press
the HOLD pushbutton. Then, RECORD
blinks.
When using HOLD and RECORD,
note that when RECORD is blinking,
this Meter is recording values; when
RECORD is not blinking, this Meter is
not recording values.
When
is blinking, the
digital display is showing a real
measurement; when
is not
blinking, the digital display is
showing a recorded measurement.
HOLD and RECORD apply to the
digital display only. The bar graph
shows a real measurement only at all
times.
If you press the MIN-MAX pushbutton
to start recording while in the HOLD
mode, RECORD is not blinking
because this Meter is not recording
values. And if you cycle through the
MAX, MIN, and AVG readings, this
Meter displays just - - - -.
Press the MIN-MAX pushbutton for 2
seconds and then release in order to
exit RECORD (or HOLD and RECORD
it selected). This Meter acknowledges
with a beep sound and RECORD is no
longer displayed.
6. MEASUREMENT
APPLICATIONS
6.1 Non-Linear Loads
True-RMS current flow is very
important because it directly relates
to the amount of heat dissipated
in wiring, transformers, and system
connections.
Most ammeters in the market
measure average current flow, not
true rms current flow, even if this
average current flow is displayed on a
scale calibrated in rms. These average-
sensing ammeters are accurate only
for a pure sign-wave current.
All current waveforms are virtually
distorted in some way.
The most common is harmonic
distortion caused by non-linear
loads such as household electrical
appliances, personal computers or
speed controls for motor drives.
Harmonic distortion caused
significant current flow at frequencies
that are at odd multiples of the power
line frequency. Harmonic current
flow gives a substantial impact on the
neutral wires of star (wye)-connected
power distribution systems.
In most countries a power
distribution system uses commercial
3-phase 50Hz/60Hz power applied to
transformer with a delta-connected
primary, and a star (wye)-connected
secondary.
The secondary generally provides
120V AC from phase to neutral, and
208V AC from phase to phase. To
balance the loads for each phase
was a big headache for the electrical
system designer, historically.
