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Author Topic: best way to measure amp draw with meter  (Read 6063 times)

Jeff Bankston

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Re: best way to measure amp draw with meter
« Reply #10 on: May 21, 2017, 02:56:40 am »

Any time you are using a clamp meter, the ideal situation is to have the conductor centered in the clamp,  often this can be difficult/impossible.

When metering and monitoring multiple legs-especially if you are looking at phase relationships, I could see where having all of the CTs the same direction could affect the final reading.  The Emon is designed to monitor multiple phases for voltage and current simultaneously.  Apples to oranges when compared to the typical single phase clamp meter.

By definitition Alternating Current flows one direction half of the time and the opposite the other half of the time-I do not see how the direction could affect the reading when you are concerned about a single phase AC load-which is what the OP is about.
I have installed a few Emons that measure one hot leg. The hot leg is the current carrying conductor. The neutral is the return. You can touch the neutral buss and nothing will happen. You can touch the hot buss and get shocked. I am not the guy that designed the way ct's work but I am the guy that wired up many many buildings and read the directions.
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Lyle Williams

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Re: best way to measure amp draw with meter
« Reply #11 on: May 21, 2017, 04:10:36 pm »

Buy a $20 "green" power meter.  Plug you gear in through it.  Read the numbers off the LCD.  Done.
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Jeff Bankston

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Re: best way to measure amp draw with meter
« Reply #12 on: May 21, 2017, 09:10:10 pm »

Buy a $20 "green" power meter.  Plug you gear in through it.  Read the numbers off the LCD.  Done.

BINGO !

http://www.youtube.com/watch?v=YqAyz1coj44
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Brian Jojade

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Re: best way to measure amp draw with meter
« Reply #13 on: May 22, 2017, 12:26:18 pm »

I've added these to all of my distros:

http://www.ebay.com/itm/US-100A-AC-Digital-LCD-Current-Monitor-Energy-Panel-Meter-Ammeter-Voltmeter-CT-/112352366647?hash=item1a28b91037:g:aEUAAOSwXYtY3GCJ

On 240v distros, I put one on each leg.  The overload feature is neat, that you can set a threshold, and the display will start to flash if you are over.  Setting the threshold at a point below disaster can be extremely helpful.

Having the energy reading over time is extremely useful as well. While the meter can show peaks or current at any point in time, you can also see what your average draw is.  The way breakers work is based on current over time.  A very brief peak won't trip the breaker. However, if you are running close to threshold continuously, that same exact peak may in fact be enough to push you over the edge.
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Brian Jojade

Jim Layton

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Re: best way to measure amp draw with meter
« Reply #14 on: June 01, 2017, 11:55:56 am »

I picked up a new Fluke clamp meter to test out the idea of measuring draw during a show. I used one of those Extec splitters, made for measuring with clamp meters. I was running a PRX XLF sub, PRX 635 3-way cab plus four Chauvet Slim Par Pro LEDS off that circuit. It was a small room so I only had drums and vocals in the PA. With drums slamming (Pop punk) and yelling vocals plus LEDs the meter was showing a steady 2.5 amps.

I understand the meter is not able to show the millisecond transients. I was surprised (but not surprised based on your comments) how low the draw was. I could have run both sides of the PA and lights off than 20-amp circuit.

This explains why, years ago, how we got away with running an entire show off multiple outlets that was really only one circuit.
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Between Allentown & Philadelphia

Stephen Swaffer

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Re: best way to measure amp draw with meter
« Reply #15 on: June 01, 2017, 09:39:11 pm »

Something else that is rarely brought up in a discussion like this is that a 20 amp breaker is not just a 20 amp breaker.  Breakers from different manufacturers have different trip curve characteristics.  One manufacturer in particular has a reputation among electricians as being one you can "weld" with if you short 2 wires.  From a practical standpoint, it doesn't matter much-but you might want to keep this in mind if you decide to walk too close to the edge.  What you might get by with on one dedicated circuit might not work on another.
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Steve Swaffer

Jim Layton

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Re: best way to measure amp draw with meter
« Reply #16 on: June 02, 2017, 10:53:35 am »

  What you might get by with on one dedicated circuit might not work on another.

I have experienced that!
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Between Allentown & Philadelphia

ProSoundWeb Community

Re: best way to measure amp draw with meter
« Reply #16 on: June 02, 2017, 10:53:35 am »


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