8
AC Measurement
AC measurements are usually displayed as RMS (root mean squared) values. Two
methods of AC measurement are
average-responding RMS calibrated
and
true
RMS-reading.
The average-responding RMS calibrated method takes the average value of the input
signal, multiplies it by 1.11, and displays the result. This method is accurate if the
input signal is a pure sine wave.
The true RMS-reading method uses internal circuitry to read the true RMS value. This
method is accurate, within the specified crest factor limitations, whether the input
signal is a pure sine wave, a square wave, sawtooth wave, half wave or signal with
harmonics. The ability to read true RMS provides much more measurement versatil-
ity. The Greenlee CMT-90 is a true RMS meter.
The Waveforms and Crest Factors table shows some typical AC signals and their
RMS values.
Waveforms and Crest Factors
Waveform
RMS Value
100
100
100
100
Rectified Value
90
100
87
64
Crest Factor*
(
x
)
1.414
1
1.73
2
* The crest factor is the ratio of the peak value to the RMS value; it is represented
by the Greek letter
x
.
Summary of Contents for Greenlee CMT-90
Page 11: ...11 CMT 90 Typical Measurements Voltage Measurement Resistance Measurement ...
Page 12: ...12 Typical Measurements Continuity Check Diode Measurement Forward Bias Reverse Bias ...
Page 26: ...26 Mediciones más comunes Medición de tensión Medición de resistencia ...
Page 32: ...32 ...
Page 42: ...42 Mesures types Mesure de la tension Mesure de la résistance ...