DVM rms?

KevinTams · 20th April 2005, 08:13 PM

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 · 21st April 2005, 11:22 AM

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

richie00boy · 21st April 2005, 11:29 AM

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 · 21st April 2005, 12:53 PM

"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 · 21st April 2005, 01:08 PM

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 · 21st April 2005, 01:30 PM

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 · 21st April 2005, 03:39 PM

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 · 21st April 2005, 03:58 PM

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.

20th April 2005, 08:13 PM	#1
KevinTams diyAudio Member Join Date: Sep 2004 Location: A bloke from Stoke	DVM rms? 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

21st April 2005, 11:22 AM	#2
burbeck diyAudio Member Join Date: Aug 2004 Location: Ratae Coritanorum	hi there, all depends on which model you have ? regards bob __________________ regards bob

21st April 2005, 11:29 AM	#3
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	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. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

21st April 2005, 01:08 PM	#5
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	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. __________________ /Per-Anders (my first name) or P-A as my friends call me

21st April 2005, 03:39 PM	#7
KevinTams diyAudio Member Join Date: Sep 2004 Location: A bloke from Stoke	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


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

21st April 2005, 12:53 PM	#4
dhaen diyAudio Moderator Emeritus Join Date: Jun 2002 Location: U.K.	"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.

21st April 2005, 01:30 PM	#6
dhaen diyAudio Moderator Emeritus Join Date: Jun 2002 Location: U.K.	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.....

21st April 2005, 03:58 PM	#8
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	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. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read