1.Safety Information
True RMS AC Measurements
The AC measurement of the multimeter has true RMS response. Power dissipated
in a resistor is proportional to the square of an applied voltage, independent of the
wave shape of the signal. This multimeter accurately measures true rms voltage
or current, as long as the wave shape contains negligible energy above the
meter’s effective bandwidth.
The effective AC voltage bandwidth of the multimeter is 1 kHz, while the effective
AC current bandwidth is 1 kHz.
Waveform
Shape
Crest Factor
(C.F.)
AC RMS
AC+DC RMS
0
V
0
V
0
V
t
T
(50% duty cycle)
1
The multimeter's AC voltage and AC current functions measure the AC-coupled
true rms value, the RMS value of only the AC components of the input waveform
are measured (DC is rejected). As seen in the figure above; for sine waves,
triangle waves, and square waves, the AC–coupled and AC+DC values are equal,
because these waveforms do not contain a DC offset. However, for non–
symmetrical waveforms (such as pulse trains) there is a DC voltage content,
which is rejected by the multimeter’s AC–coupled true rms measurements.
The AC coupled true RMS measurement is especially useful for measuring small
AC signals in the presence of large DC offsets. For example, this situation is
common when measuring AC ripple present on DC power supplies. However,
there are situations where you might want to know the AC+DC true RMS value.
You can determine this value by combining results from DC and AC
measurements, as shown below:
For the best AC noise rejection, you should select "Low" measurement speed to
35
