Ac Measurement - Greenlee DM-100 Instruction Manual

AC Measurement

AC measurements are usually displayed as RMS (root-mean-square) values. Two AC
measurement methods 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 Greenlee DM-100 is an average-responding meter.
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, triangle wave, half wave or signal with harmonics. The ability to read
true RMS provides much more measurement versatility. The Greenlee DM-110 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
Average Value
Crest Factor*
( )
* The crest factor is the ratio of the peak value to the RMS value; it is represented by the
Greek letter .
8
100
90
1.414
100 100
100
1 1.73
100
87 64
2