True RMS multimeter?

Started by Andy February 3, 2018
I bought an Excel XL 830L multimeter with the understanding that it was a RMS
voltmeter.

I also have UEI ElectroMate DM 200.

When I checked the output of my APC unit with both meters, the readings were about
the same.

Is there a way to tell if a meter is an RMS type?

Thanks,
         Andy 
On Fri, 02 Feb 2018 16:02:52 -0800, Andy wrote:

> I bought an Excel XL 830L multimeter with the understanding that it was > a RMS voltmeter. > > I also have UEI ElectroMate DM 200. > > When I checked the output of my APC unit with both meters, the readings > were about the same. > > Is there a way to tell if a meter is an RMS type?
Simplest way is take a reading of the mains electricity in your house. If you're in europe it should come out at about 230-240VAC and the meter (if it's true RMS) will agree with that. I think in America and Japan the domestic mains voltages are very different but you will no doubt know what it should be in your own home country and a true RMS meter will agree with it. -- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.
Andy wrote:

---------------
> > I bought an Excel XL 830L multimeter with the understanding that it > was a RMS voltmeter. >
** Can you see the term "true RMS" on the meter or handbook?
> I also have UEI ElectroMate DM 200. >
** Not a true RMS type.
> When I checked the output of my APC unit with both meters, > the readings were about the same. >
** OK.
> Is there a way to tell if a meter is an RMS type? >
** The maker will tell you. .... Phil
Cursitor Doom wrote:

----------------------
>> > > > Is there a way to tell if a meter is an RMS type? > > > Simplest way is take a reading of the mains electricity in your house. If > you're in europe it should come out at about 230-240VAC and the meter (if > it's true RMS) will agree with that. I think in America and Japan the > domestic mains voltages are very different but you will no doubt know > what it should be in your own home country and a true RMS meter will > agree with it. >
** Any multimeter with AC ranges will give correct results on low frequency sine waves, like the mains power. ..... Phil
On Friday, February 2, 2018 at 6:33:38 PM UTC-6, Cursitor Doom wrote:
> On Fri, 02 Feb 2018 16:02:52 -0800, Andy wrote: > > > I bought an Excel XL 830L multimeter with the understanding that it was > > a RMS voltmeter. > > > > I also have UEI ElectroMate DM 200. > > > > When I checked the output of my APC unit with both meters, the readings > > were about the same. > > > > Is there a way to tell if a meter is an RMS type? > > Simplest way is take a reading of the mains electricity in your house. If > you're in europe it should come out at about 230-240VAC and the meter (if > it's true RMS) will agree with that. I think in America and Japan the > domestic mains voltages are very different but you will no doubt know > what it should be in your own home country and a true RMS meter will > agree with it. > > > > > > -- > This message may be freely reproduced without limit or charge only via > the Usenet protocol. Reproduction in whole or part through other > protocols, whether for profit or not, is conditional upon a charge of > GBP10.00 per reproduction. Publication in this manner via non-Usenet > protocols constitutes acceptance of this condition.
116 - 118V Andy
They are all off base here. Actually I am surprised Phil didn't mention it. 

Compare the readings with the same peak to peak value o a sine wave and a square
wave. If they read the same it is not true RMS. If it is true RMS on a square wave
it will read approximately ½ the P-P value but on a sine wave it will read
lower, 0.70711 of ½ the P-P value. Almost any meter has the resolution to
discern 1 volt from 0.71 volt. 

You do have a scope right ? If not you'll have to figure out a way to clip a sine
wave. You don't need any power behind it, a Zener or stack  of diodes will do. A
scope is the best way though. If you have to wing it come back and I will try to
figure out the easiest way.
>"Simplest way is take a reading of the mains electricity in your house."
That won't tell you jack shit. Non true RMS meters are calibrated for a sine wave. A volt will read 0.7071 anyway.
>"> I also have UEI ElectroMate DM 200. >
** Not a true RMS type. " That should be all he needs then. Some sort of variable AC supply and some diodes or something to match the P-P value. Ba da bing, ba da boom. (well not boom hopefully, he only needs a volt, and one volt because it is convenient)
On Fri, 2 Feb 2018 16:02:52 -0800 (PST), Andy
<andrewkennedy775@gmail.com> wrote:

>I bought an Excel XL 830L multimeter with the understanding that it was a RMS
voltmeter.
> >I also have UEI ElectroMate DM 200. > >When I checked the output of my APC unit with both meters, the readings were about
the same.
> >Is there a way to tell if a meter is an RMS type? > >Thanks, > Andy
True RMS is for wave shapes other than pretty sine waves.
default wrote:

---------------
> > True RMS is for wave shapes other than pretty sine waves.
** Careful, true RMS works for sine waves too. .... Phil