Non-sinusoidal waveforms may cause :
– Overheated tansformers, generator and motors to burn out faster than normal
– Circuit breakers to trip prematurely
– Fuses to blow
– Neutrals to be overheated due to the triplen harmonics present on the neutral
– Bus bars and electrical panels to vibrate
Crest Factor
Crest Factor is the ratio of the Crest (instantaneous peak) value to the True RMS
value, which is commonly used to define the dynamic range of a True RMS DMM.
A pure sinusoidal waveform has a Crest Factor of 1.414.
A badly distorted sinusoidal waveform normally has a much higher Crest Factor.
NMRR (Normal Mode Rejection Ratio)
NMRR is the
DMM’s ability to reject
unwanted AC noise ef
f
ect which
can cause
inaccurate DC measurements. NMRR is typically specified in terms of dB (decibel).
The Meter has a NMRR specification of > 60dB at 50Hz/60Hz, which means a good
ability to reject the effect of AC noise in DC measurements.
CMRR (Common Mode Rejection Ratio)
Common mode voltage is voltage existing on both
t
he COM and Voltage input
terminals of
a DMM, with respect
t
o ground. CMRR is a DMM’s ability to reject
common
mode voltage
effect which can cause digit rattle
or offset in voltage
measurements. The Meter has a CMRR specification of > 60dB at DC to 60 Hz in
AC volts measurement function and > 120 dB at DC, 50Hz and 60Hz in DC volts
measurement function.
Burden Voltage
Burden voltage is a voltage drop across the input terminals of a current-measuring
device, caused by internal shunt resistance.
Burden voltage contributes measurement error, and should be as low as practical.
Temperature Coefficient
Temperature Coefficient is a fac
t
or
used to calculate the change in indication or
output of an instrument with changes in temperature.
Uncompensated changes in temperature contribute uncertainty by an amount
determined by the temperature coefficient to instrument.
Analog Bar-graph
The analog bar graph provides a visual indication of measurement like a traditional
analog me
t
er’s needle. It
is excellent
in detec
t
ing faulty contacts, identi
f
ying
potentionmeter’s clicks and indicating signal spikes during adjustments.
Turning the Meter On
To turn the meter on, turn the rotary switch from OFF to any switch setting.
If you want a view of the full display (all segments illuminated), press and hold the
HOLD button while turning the meter on. Release the button after viewing the full
display.
Rotary Switch
Turn the meter on by selecting any measurement function. The meter presents a
standard display for that function (range, measurement units, on screen menu bars,
etc.).
The display may also be influenced by
some of the choices made in on
screen menu selection.
Use the on
screen menu selection buttons
to select any
ro
t
ary swi
t
ch alternate
function.
Y
ou can also use other bu
t
tons to choose modifiers for the selected
function.
When you turn the rotary switch from one function to another, a display for the new
function appears.
Button choices made in one function do not
carry over into
another function.
OFF. Turns the meter off. Setup parameters and stored measurements are
saved.
.Millivolts ac rms and dc measurement. Compatible with various adaptors.
.Volts ac rms, Volts dc, Volts ac+dc total rms, Volts ac dc dual display,
dBm, and dB.
Hz . Frequency measurement. Duty cycle and pulse width are also
displayed if they are turned on in the on screen menu.
4. ROTARY SWITCH AND PUSHBUTTON OVERVIEW
76
