# True RMS



## EBFD6 (Aug 17, 2008)

99cents said:


> I have only used True RMS meters. Last week I was stuck for a meter on a job and bought a cheap Klein clamp meter just to get by. It's not TRMS and voltage readings seem to be quite bizarre, actually.
> 
> I know, I know! You get what you pay for  .
> 
> Anyway, I could see myself using a compact little meter. I was thinking of buying a T5-1000 but it's not TRMS either. Will that be an issue with the Fluke?


I don't know what type of work you're doing, but for most electricians there is really not a need for a true rms meter. Most of what we do a measurement that's a couple volts off one way or another doesn't make a difference. Do you really care of it's 117 volts or 122 volts? Does it really matter if it's 10.4 amps or 11.2 amps? Sometimes it does, but most of the time not. If you do a lot of technical work true rms might be necessary, but for the average electrician who just needs basic readings it's probably overkill. I would say an averaging meter is going to get you in the ballpark which is all most construction electricians need.

It's like the guys who spend a ton of money on an 87v when all they really needed was a pair of wiggy's. The fancy meter might be nice, but they'll never use it to it's full potential. It's just a waste of money.


All of this being said, I'm still an advocate of buying the best meter you can afford. You never know what kind of work you'll be doing in the future. You may need that 87v someday.


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## Big John (May 23, 2010)

I think for most circuit troubleshooting, you'll be fine with non-RMS. I've got a T+ Pro that I really like and it's an averaging meter.

But I like to have a low-impedance true RMS available when troubleshooting equipment (lots of stuff now days has electronic power supplies), or for headscratcher problems, because knowing for sure that your voltages are accurate is one less worry.


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## HARRY304E (Sep 15, 2010)

99cents said:


> I have only used True RMS meters. Last week I was stuck for a meter on a job and bought a cheap Klein clamp meter just to get by. It's not TRMS and voltage readings seem to be quite bizarre, actually.
> 
> I know, I know! You get what you pay for  .
> 
> Anyway, I could see myself using a compact little meter. I was thinking of buying a T5-1000 but it's not TRMS either. Will that be an issue with the Fluke?


I use the T-5-1000 too , it's great for many things.

If you want a true RMS meter.

Here you go.:thumbsup:

http://www.newark.com/jsp/search/pr...NC-GPLA&mckv=%7Cpcrid%7C27153109821%7Cplid%7C

.


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## HackWork (Oct 2, 2009)

99cents said:


> I have only used True RMS meters. Last week I was stuck for a meter on a job and bought a cheap Klein clamp meter just to get by. It's not TRMS and voltage readings seem to be quite bizarre, actually.
> 
> I know, I know! You get what you pay for  .
> 
> Anyway, I could see myself using a compact little meter. I was thinking of buying a T5-1000 but it's not TRMS either. Will that be an issue with the Fluke?


What were you measuring that the voltage seemed bizarre? 

What type of work do you do? What are you usually measuring?


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## EBFD6 (Aug 17, 2008)

I'll also second either the t+pro or t5-1000.

I carry both in my front line bag and they handle 95% of my needs.


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## HARRY304E (Sep 15, 2010)

EBFD6 said:


> I'll also second either the t+pro or t5-1000.
> 
> I carry both in my front line bag and they handle 95% of my needs.


:thumbsup::thumbsup:


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## HackWork (Oct 2, 2009)

I use the T5-600. It would be great if Fluke put a LoZ feature in it like they did with their 117.


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## retiredsparktech (Mar 8, 2011)

HackWork said:


> What were you measuring that the voltage seemed bizarre?
> 
> What type of work do you do? What are you usually measuring?


I bought a Sears Craftsman true RMS meter. I need it for some of my projects dealing with Capacitive and inductive reactance and semi-conductor voltage drops.


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## 99cents (Aug 20, 2012)

HARRY304E said:


> I use the T-5-1000 too , it's great for many things.
> 
> If you want a true RMS meter.
> 
> ...


I have a high priced Fluke already; just like the idea of having a small, knock around meter available that I can throw into a tool bag.


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## 99cents (Aug 20, 2012)

HackWork said:


> What were you measuring that the voltage seemed bizarre?
> 
> What type of work do you do? What are you usually measuring?


I was getting about 20V on a stone cold circuit. Maybe I'll return it and get my money and buy the T5.

Normally I don't do work where super accurate readings are important but that's a little too bizarre. At first I thought that this meter really sucked until I realized DC is the default setting.


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## Big John (May 23, 2010)

99cents said:


> I was getting about 20V on a stone cold circuit...


 In fairness to Klein, the problem there isn't true-RMS, it's that there is 1MΩ of resistance between the meter leads and it can't bleed off the capacitive coupling in the circuit. Even an $800 Fluke would likely do the exact same thing when in high-impedance mode.


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## EBFD6 (Aug 17, 2008)

Big John said:


> In fairness to Klein, the problem there isn't true-RMS, it's that there is 1MΩ of resistance between the meter leads and it can't bleed off the capacitive coupling in the circuit. Even an $800 Fluke would likely do the exact same thing when in high-impedance mode.


Yep, you need a meter with low Z feature. True rms wouldn't help in that situation.


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## 99cents (Aug 20, 2012)

EBFD6 said:


> Yep, you need a meter with low Z feature. True rms wouldn't help in that situation.


Gotcha. I'm learning things today. Thank you  .


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## Voltage Hazard (Aug 10, 2009)

For resi work, and most small commercial jobs, I agree that a True RMS DMM is not needed. But, with all the LED and Fluorescent lighting in use today, I believe everyone should be using TRMS clamps now. Current draws on Fluorescent lighting can be off 30% just using RMS meters.

With that said, I agree with the others about your issue. It is related to impedance, and not RMS.


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## chicken steve (Mar 22, 2011)

I'm of the opinion my True RMS meters _lie_ as much as any other meter.....~CS~


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## Jlarson (Jun 28, 2009)

I do ok with a T5-1000 every day. It and 1587 ride in my tool bag, I have stupid amounts of 1000 amp fluke clamps and clamp attachments for the DMMs and scopes for when the T5 is out of it's element. The T+ pro is my back pocket meter along with a lenox 9-1 screwdriver.

You can never have too much fluke stuff. :laughing:


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## mattd88 (Aug 3, 2013)

EBFD6 said:


> I don't know what type of work you're doing, but for most electricians there is really not a need for a true rms meter. Most of what we do a measurement that's a couple volts off one way or another doesn't make a difference. Do you really care of it's 117 volts or 122 volts? Does it really matter if it's 10.4 amps or 11.2 amps? Sometimes it does, but most of the time not. If you do a lot of technical work true rms might be necessary, but for the average electrician who just needs basic readings it's probably overkill. I would say an averaging meter is going to get you in the ballpark which is all most construction electricians need.
> 
> It's like the guys who spend a ton of money on an 87v when all they really needed was a pair of wiggy's. The fancy meter might be nice, but they'll never use it to it's full potential. It's just a waste of money.
> 
> ...


Very true.I've got a 87v but I never use it.My wiggy gets the job done most of the time and it fits perfectly into the side pocket of my pants.


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## chicken steve (Mar 22, 2011)

Is that a wiggy in your pocket , or are you just looking for something on the side Matt? ~CS~


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## BBQ (Nov 16, 2010)

EBFD6 said:


> I'll also second either the t+pro or t5-1000.
> 
> I carry both in my front line bag and they handle 95% of my needs.


I agree, T5-1000 in the tool bag for everyday chores, good meters in truck for when I need them.


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## uconduit (Jun 6, 2012)

t+pro vs t5-1000?


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## EBFD6 (Aug 17, 2008)

uconduit said:


> t+pro vs t5-1000?


That depends on what you're looking for in a tester. I carry both, they both serve different purposes. Which one I use depends on the situation. I do use the t+pro more however.

T+pro:

*Pro's*
Low impedance
Audible and Vibration when testing voltage
resistance to 10K ohms
reads voltage without batteries installed
phase rotation (using 2 leads, works fairly well with the right technique)
GFCI tester

*Con's
*No amp clamp
voltage only to 600v
I don't trust it when reading higher DC voltages, sometimes it reads as AC voltage and gives weird values






T5-1000:

*Pro's
*Voltage to 1000v 
Amps to 100A
very reliable on AC or DC

*Con's
*Resistance only reads to 1K ohms
High impedance (can be a pro or con depending on the situation)
Doesn't work if the batteries are dead 
No audible voltage indication


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