08-03-2016, 12:26 PM
My Fluke 87 computes true RMS but I don't think it measures the DC component. It would be useful to have an AC/DC coupling switch as on a scope.
Then there's form factor and frequency to consider. All RMS instruments will have an upper frequency limit which is typically in the audio range. For the same reason they will tend to underread spiky waveforms (high form factor).
Traditionally, meters were calibrated in RMS but measured the mean. Hence they were only correct for a sine wave. A square wave would overread by 11%. Most lowe cost DMMs are also like this.
Then there's form factor and frequency to consider. All RMS instruments will have an upper frequency limit which is typically in the audio range. For the same reason they will tend to underread spiky waveforms (high form factor).
Traditionally, meters were calibrated in RMS but measured the mean. Hence they were only correct for a sine wave. A square wave would overread by 11%. Most lowe cost DMMs are also like this.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
