SDM3055 Series Digital Multimeter User Manual
98 int.siglent.com
Chapter 4 Measurement Tutorial
True RMS AC Measurement
The AC measurement of the Multimeter has true RMS response. The power dissipated in a resistor
within a time is proportional to the square of the measured true RMS voltage, independent of wave
shape. The instrument can accurately measure true RMS voltage or current, as long as the wave
shape contains negligible energy above the effective bandwidth.
The AC voltage and AC current functions measure the “AC coupled” true RMS value, which is to
measure the RMS value of the AC component (DC component is rejected) of the input signal. For
sine waves, triangle waves, and square waves, the AC and AC+DC values are equal since these
waveforms do not contain a DC offset. See the following table 5-1.
Table 4-1 True RMS AC Measurement of Sine, Triangle and Square waves
Non-symmetrical waveforms, such as pulse trains, contain DC voltages which are rejected by AC
coupled true RMS measurements.
An AC coupled true RMS measurement is desirable in situations where you are measuring small AC
signals in the presence of DC offsets. For instance, measuring AC ripple present on DC power
supplies. There are situations, however, 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 the following
shows. You should perform the DC measurement using 5.5-digit mode for best AC rejection.
To Next Page
Loading...
Need help?
General
