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Author Topic: Clamp ammeter on 12/3 cable  (Read 3554 times)

Kevin_Tisdall

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Clamp ammeter on 12/3 cable
« on: February 18, 2023, 03:12:03 PM »

Id like to start having some idea of how much power my system is pulling from the usual spread of 2-3 20 amp nema outlets.   

Will a typical low-end fluke or klein tool lowes-purchased clamp on meter do that?  Or do you need to clamp on to just a hot wire such as from a distro?

Looking to spend $100 or less. 

--kevin
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Brian Jojade

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Re: Clamp ammeter on 12/3 cable
« Reply #1 on: February 18, 2023, 03:27:08 PM »

Clamp on meters need to go around just the hot wire. You won’t be able to clamp around the 12/3 as a whole.

Yo can make a short extension of individual conductors to put inline, o buy a prebuilt meter that does that.
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doug johnson2

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Re: Clamp ammeter on 12/3 cable
« Reply #2 on: February 18, 2023, 04:16:03 PM »

There are lots of fairly cheap panel mount voltage/amperage meters on Amazon.  Build a short extension cord with one in a box, in-line.
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Jeff Lelko

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Re: Clamp ammeter on 12/3 cable
« Reply #3 on: February 18, 2023, 10:08:02 PM »

Will a typical low-end fluke or klein tool lowes-purchased clamp on meter do that?  Or do you need to clamp on to just a hot wire such as from a distro?

The short answer within the context of sound equipment is generally no.  In the world of lighting where current draw is much more consistent you can get an accurate measurement without anything special, however with sound equipment - particularly amplifiers - the momentary transients are much too brief for the average ammeter to get a good reading.

As already mentioned though - regardless of what you're trying to measure, a clamp-on ammeter won't work on 12/3 or any other multiconductor wire.  The right work-around will depend on your particular application but I'd first sort out what specifically you're trying to measure first.  Hope this helps!   
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Tim McCulloch

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Re: Clamp ammeter on 12/3 cable
« Reply #4 on: February 19, 2023, 12:09:19 AM »

You seek a "Kill-a-Watt."  Some are direct-reading Ammeters and others are a 'break out loop' you can clamp around.

Jeff is spot on about fast current changes that your meter is unlikely to display but you'll still get a idea of how much current is used.
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Bob Taylor

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Re: Clamp ammeter on 12/3 cable
« Reply #5 on: February 19, 2023, 10:56:15 AM »

The way I have done this is with my Fluke 33. It will give average, instantaneous, and minimum RMS amperages. It's a discontinued meter but I'm sure there are similar out there. This will let you know what that Bass Drum is actually pulling for that punch and let you plan how much current you need to keep Sub Amps from dropping out or that Genny from tripping.

And another thing that can be done while measuring low currents on a high current meter, wrap the wire thru the jaws twice and divide the reading by 2. Or 3 times and divide by 3...

Bob T
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Stephen Swaffer

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Re: Clamp ammeter on 12/3 cable
« Reply #6 on: February 22, 2023, 12:56:18 PM »

They are are out of the OP's price range but Fluke has added a Fluke Connect feature that bluetooth's to a smart phone-the meters have an FC suffic in their model number.  Not much more than an equivalent non-FC meter but it is incredibly powerful for the cost-from "watching" a meter from 200' feet away to recording a reading over a time period I find them very handy.  (Using a display adapter with the phone allows you to project a live meter reading making for a useful teaching tool).
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Steve Swaffer

Kevin_Tisdall

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Re: Clamp ammeter on 12/3 cable
« Reply #7 on: February 25, 2023, 11:49:53 AM »

You seek a "Kill-a-Watt."  Some are direct-reading Ammeters and others are a 'break out loop' you can clamp around.

Jeff is spot on about fast current changes that your meter is unlikely to display but you'll still get a idea of how much current is used.


Thanks all for the education.   I saw the kill-a-watt units but im a little reluctant to put something that might fail between my speakers and the power source.  Are they pretty reliabl at least to keep passing power through?

--kevin
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Jeff Lelko

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Re: Clamp ammeter on 12/3 cable
« Reply #8 on: February 25, 2023, 02:50:40 PM »


Thanks all for the education.   I saw the kill-a-watt units but im a little reluctant to put something that might fail between my speakers and the power source.  Are they pretty reliabl at least to keep passing power through?

I’ve had mine for probably 15 years now and it still works like day one.  However, I view the Kill-o-watt as a bench testing tool and not something that belongs inline with equipment on a job.  For that you’d either want to use your clamp-on meter around a single conductor if possible, or utilize an UPS or power distro that gives realtime current measurements.  Even then you’ll need to use common sense to determine if the measurements you see are “valid”.  Hope this helps!
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Kevin_Tisdall

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Re: Clamp ammeter on 12/3 cable
« Reply #9 on: February 26, 2023, 11:29:13 AM »

I’ve had mine for probably 15 years now and it still works like day one.  However, I view the Kill-o-watt as a bench testing tool and not something that belongs inline with equipment on a job.  For that you’d either want to use your clamp-on meter around a single conductor if possible, or utilize an UPS or power distro that gives realtime current measurements.  Even then you’ll need to use common sense to determine if the measurements you see are “valid”.  Hope this helps!

Thanks Jeff.  My feelings pretty much the same.

--kevin
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Re: Clamp ammeter on 12/3 cable
« Reply #9 on: February 26, 2023, 11:29:13 AM »


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