DVM rms?

[KevinTams]

Can anyone tell me if the Vac reading on Fluke DVM's are true rms for all frequencies? If they are an approximation how close?

Thanks
Kevin

 

[burbeck]

hi there,
all depends on which model you have ?
regards
bob

 

[richie00boy]

As said, depends on model. If you read the manual it will tell you 😀 If you don't have a manual I'm sure you could get one from Fluke easy enough. My 187 is true RMS all the way.

 

[dhaen]

"True RMS" is a claim that the meter will give the RMS value for any wave shape, so it'll only be a true RMS reading for all waveforms if the meter claims it.
For a sinewave any meter will give a true RMS reading if the frequency is within the meter's range.
The Flukes (older ones) I've used have been flat from 50Hz to 1KHz, and not far out at 10KHz.
I'd throw away any meter that couldn't do 1KHz. Can't imagine there are many.

 

[peranders]

I must correct you, not any waveform, some waveforms defined with the parameter "crest factor", often not too extreme wave forms. Consult the manual for the DVM.

 

[dhaen]

Per,

I accept your correction, but I used the term "wave shape" not waveform with this in mind.
What I should have said that it will give give RMS readings for various distortions of sinewaves.

Always read the manual..... 😉

 

[KevinTams]

THanks

Thanks Guys

MY meter is my companies calibrated newish Fluke, I don't have the manual. I wanted to get an accurate RMS reading at 1KHz sine wave to work out the power output of my amp. The question has been answered, many thanks.

Kev

 

[richie00boy]

You won't get a very accurate result with that method. You need an oscilloscope because you will have little idea if you are clipping the amp.