# Rms voltage

1. Aug 14, 2012

### mishraneel

Suppose at a test point in my circuit ,I need to measure rms voltage, how I should measure it with DMM?

2. Aug 14, 2012

### I_am_learning

DMM provide rms voltage when set to measure AC voltage. If Set to measure DC Voltage they measure Average.

3. Aug 14, 2012

### psparky

Peak to peak voltage (non-RMS) typcially only shows up on an oscilloscope.

4. Aug 15, 2012

### Carl Pugh

Some DMM measure RMS voltage and some DMM measure average voltage.

Check the manual for your DMM and if it reads average voltage, get a DMM that reads RMS voltage.

5. Aug 15, 2012

### uart

Voltmeters that don't describe themselves as being "true RMS" generally measure scaled average voltage. That is, they display the average voltage times $\pi / \sqrt{8}$, (approx 1.11). This scaling factor makes the average voltage equal the RMS voltage, but only for a sinusoidal waveform.

6. Aug 19, 2012

### mishraneel

In one of replies to my post, I got an answer that AC voltmeters measure rms voltages, further I want to know that at AC volt position 1V RMS will be shown as what, 1v or less or more?

7. Aug 19, 2012

### Staff: Mentor

Providing you are measuring a sinewave, and there is no DC component, then on the AC scale your meter will read 1.00v for a sinewave having an RMS value of 1.00v

DMM probably work reliably only for sinewaves up to a few kHz.