# Clamp Meters



## Diarmuid (Dec 24, 2007)

I've had a question hanging around in the back of my head for quite a while...

My understanding of a clamp meter, is that you just take a cable, put the cable in between the jaws of the clamp and then it tells you the current going through the cable,and dependent upon how good the clamp meter is, it tells you the voltage etc.

Is that right?

The reason for all this confusion, is that we have a clamp meter at school, and when we clamp it around a cable, it doesn't work... and the rather ambiguous instructions don't say whether they refer to a complete cable, or just one conductor of that, as in a live wire...

It might just be that our clamp meter is dodgy, but I thought I'd make sure, before I get one in the post christmas sales..

Thanks for your help!


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## derekleffew (Dec 24, 2007)

First, the clamp meter must be used only around a single wire conductor, not around cable. Second, the clamp meter will only tell you amperage, not voltage, without physical contact using the included probes. *Disclaimer: Always use every available precaution when working around live electrical circuits! * Here's the one I use, Fluke 30--it's not the best, but adequate for my purposes. It has been replaced by the Fluke 333A, MSRP $149.95 US.

Sounds like yours is not a very good manual. Out of curiosity, what make and model is your meter? Here is a link to the manual for the Fluke 333. It will probably help clear up your confusion.


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## SteveB (Dec 24, 2007)

derekleffew said:


> First, the clamp meter must be used only around a single wire conductor, not around cable. Second, the clamp meter will only tell you amperage, not voltage, without physical contact using the included probes. .



I believe an Amp meter, as a clamp around a single HOT conductor meter is called, will only do a reliable test on loads whose sine wave is not distorted in some fashion - I.E. they don't work to get you the load of a Sensor 96 dimmer rack (or any dimmer rack, for that matter).

Or am I thinking of something else ?.

Steve B.


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## derekleffew (Dec 25, 2007)

I certainly hope you are mistaken, SteveB, as I've used my Fluke 30 to measure amperage loads on many touring dimmer racks and ML Distros, and never been challenged on the results. I think you may be confused on the measurement of output voltage of a given dimmer, for which you need a "true RMS" (Root Mean Square) meter.


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## Diarmuid (Dec 25, 2007)

I'm not sure the make and model of ours, because it is at school, but I'll try and find out...

And if it can only be clamped around the live conductor, would I be right to suggest that in most applications it can't be much use? I guess if you had like a 3 phase system, with all the different phases on seperate inputs, then it would be ok... but as it can't be used for actual cables, for installed systems and such, it can't be used very effectivley?

Thanks for the help.


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## David Ashton (Dec 25, 2007)

Clamp meters do have practical limitations in getting to the single conductor which generally involves getting close to live wires, a clamp on meter loses accuracy on dimmed settings as the waveforms become too complex to analyze accurately and they do not read the dc content of the waveform, but they are near enough for all practical purposes.There are cheap rms meters on the market which are perfectly useful for the type of work we do.


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## STEVETERRY (Dec 25, 2007)

Diarmuid said:


> I'm not sure the make and model of ours, because it is at school, but I'll try and find out...
> And if it can only be clamped around the live conductor, would I be right to suggest that in most applications it can't be much use? I guess if you had like a 3 phase system, with all the different phases on seperate inputs, then it would be ok... but as it can't be used for actual cables, for installed systems and such, it can't be used very effectivley?
> Thanks for the help.



If you want to measure the current in a single-phase, two wire plus ground branch circuit or feeder, just make yourself a male-female adaptor with the outer jacket of the cable removed so that you can get the clamp around the insulated hot or neutral conductor.

BTW, the clamp meter does not care if it's measuring the neutral or hot conductor--the current is the same in both for a single-phase circuit.

For higher current feeder applications where you may be clamping around live conductors on equipment with the covers off, you are now under the rules of NFPA 70E "Standard for Electrical Safety in the Workplace" in North America. This defines the protective gear you must wear, and the various boundaries and voltages where different rules apply. DO NOT ATTEMPT THIS without training and expert help!

Of course, this does not apply if you are clamping around insulated, single conductor feeder cables or branch circuit conductors outside equipment or switchgear.

ST


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## Diarmuid (Dec 25, 2007)

STEVETERRY said:


> If you want to measure the current in a single-phase, two wire plus ground branch circuit or feeder, just make yourself a male-female adaptor with the outer jacket of the cable removed so that you can get the clamp around the insulated hot or neutral conductor...


 
Would I be right to assume that removing the insulation from a cable, to just leave the insulation on the wires, wouldn't be possible to do in a way that would pass electrical safety testing? Basically would it be safe to do it, or could it be put through a junction box or something like that to make it safer?

Thanks


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## SteveB (Dec 25, 2007)

Diarmuid said:


> Would I be right to assume that removing the insulation from a cable, to just leave the insulation on the wires, wouldn't be possible to do in a way that would pass electrical safety testing? Basically would it be safe to do it, or could it be put through a junction box or something like that to make it safer?
> Thanks



There's no need or purpose in removing any insulation. A clamp around Amp-meter will measure the current with insulation intact. It's measuring the EMF.

As further clarification, the typical clamp around amperage measuring meter - here's a photo of an Amp-Probe model, has a set of jaws that open to allow you to wrap the jaws around an insulated conductor, the jaws then close to create a loop around the conductor. There's usually a few inches of clearance between the conductors and the insulated jaws of the meter. Care and attention needs to be in place to do this measuring safely and Steve T. has listed a link as to the methods now required.

As to usage. One typical example would be attempting to get a rough measurement of the normal load on an electrical panel that has space(s) for additional breakers, but whose existing loading is undetermined. Removing the panel cover and testing the hot legs, presumably while the loading is as close to maximum current usage, would then yield a reading.

SB


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## SteveB (Dec 25, 2007)

To Steve Terry

By the way - a Merry Christmas to all you folks at ETC !.

A question arose as to whether a clamping amp-probe will accurately measure a dimmed load ?. Does the distorted sine-wave affect the readings ?. That's what I was told years ago and is why I stopped using my personal Amp-Probe to measure portable dimming systems.

Steve B.


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## Diarmuid (Dec 25, 2007)

I wasn't refering to removing the insulation from the induvidual wires, just removing it from the cables, so as to make a jumper, like the one SteveT mentioned above, allowing me to measure the current draw of a single phase cable. Because otherwise, it would only be used for about one job a year, in which case I could spend the money better elsewhere.


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## JD (Dec 25, 2007)

Most, if not all "amp-probes" will not give you a true reading on distorted waveforms, but will give you a pretty accurate idea of the thermal load on the cable. For instance, clamp it on a non-power factored 100w HPS ballast and you will read about 2 amps. Connect the power factoring capacitor in the ballast, and watch as the meter drops to 0.9 amps. Same power going to the lamp, but as we know, non-power factored ballasts will heat the wiring up more than those with power factoring. (please don't try this if you arte not trained, don't want any deaths on my conscious at Christmas!) So, the end result is the amp-probe will give you a good ballpark figure about how the wire feels about it's loading.


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## derekleffew (Dec 25, 2007)

One time my amprobe proved invaluable: I had a 50gallon trash can full of unlabeled PAR64 lamps, a mixture of 500W and 1000W. The manufacturers' printing was either faded or worn off. I did as STEVETERRY suggested and made an Edison to 2P&G adaptor, using the Blk,Wht,Grn inner wires from a 2' piece of 12/3 SOOW. Clamped around the hot or neutral wire, when the meter read 8.3A or so, I knew I had a 1000W; when it was just was over 4.0, I knew I had a 500W. I could ascertain by looking whether it was WFL, MFL, or NSP. After testing each lamp, I wrote "1K MFL" or "500 NSP" or whatever on the ceramic with black Sharpie™. Since then I've always written on the ceramic as soon as I open a new PAR64 lamp box.


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## SteveB (Dec 25, 2007)

derekleffew said:


> Since then I've always written on the ceramic as soon as I open a new PAR64 lamp box.



Ooooo.... I like that Sharpie on the ceramic trick. Going to remember that one, so a thanks is in order.

SB


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## derekleffew (Dec 25, 2007)

For GE 4552 and 4559s, there's no ceramic, so I've had to write on the glass, but that burns/wears off over time. Every place I've worked seems to have had a mixture of 4552 and 4559, never on the same bar, of course.

ship and len are probably too young to remember HiLights, a major R&R company of the '70s and '80s. I bought all their PAR lamps when they finally folded. They had engraved "HLI" in the back of every lamp, with an electric engraver. Taking it a tad too far, if you ask me.


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## avkid (Dec 26, 2007)

derekleffew said:


> They had engraved "HLI" in the back of every lamp, with an electric engraver. Taking it a tad too far, if you ask me.


I can do that in about 40 seconds, no big deal.
Good intern task.


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## STEVETERRY (Dec 26, 2007)

SteveB said:


> To Steve Terry
> By the way - a Merry Christmas to all you folks at ETC !.
> A question arose as to whether a clamping amp-probe will accurately measure a dimmed load ?. Does the distorted sine-wave affect the readings ?. That's what I was told years ago and is why I stopped using my personal Amp-Probe to measure portable dimming systems.
> Steve B.



The original Amprobe is not a true-RMS responding meter, so it's fairly useless on phase-control dimmers. However, there are a number of fairly inexpensive true-RMS-responding clamp meters with decent crest factors. I have a 200A one made by Greenlee that cost me about $100.

Happy holidays to you too!

ST


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## STEVETERRY (Dec 26, 2007)

JD said:


> Most, if not all "amp-probes" will not give you a true reading on distorted waveforms, but will give you a pretty accurate idea of the thermal load on the cable. For instance, clamp it on a non-power factored 100w HPS ballast and you will read about 2 amps. Connect the power factoring capacitor in the ballast, and watch as the meter drops to 0.9 amps. Same power going to the lamp, but as we know, non-power factored ballasts will heat the wiring up more than those with power factoring. (please don't try this if you arte not trained, don't want any deaths on my conscious at Christmas!) So, the end result is the amp-probe will give you a good ballpark figure about how the wire feels about it's loading.



Err..sorry, I don't agree.

A current waveform with 50% THD-I (Total Harmonic Distortion in current that is typical on a dimmer feeder with most dimmers set near half) is going to under-report the RMS current by a big amount on a non-True-RMS responding instrument. First clue: the breaker trips! Nowadays, with True-RMS meters costing so little, I don't see a reason to keep other types in service around the type of gear we deal with on a daily basis. 

ST


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## SteveB (Dec 26, 2007)

STEVETERRY said:


> The original Amprobe is not a true-RMS responding meter, so it's fairly useless on phase-control dimmers. However, there are a number of fairly inexpensive true-RMS-responding clamp meters with decent crest factors. I have a 200A one made by Greenlee that cost me about $100.
> Happy holidays to you too!
> ST



Which would explain why I stopped using my very original (30 year old ?) Amp model amp-probe a long time ago. 

Nice to know there are true RMS versions now. I might find one useful.

SB


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## JD (Dec 26, 2007)

STEVETERRY said:


> Err..sorry, I don't agree.



Ummm... What are you not agreeing with now? That an amp-probe will not give you a true reading? Isn't that what I just said? Let me expand that statement: Any magnetically coupled meter (wrap-around type) will not give you a true reading because (the important part-) they are magnetically cupped. As the frequency rises (square = sine plus every harmonic) the transfer ratio increases, producing more voltage in the secondary loop (same reason a 60 cps transformer is much bigger than a 400 cps transformer, like those used in plains.) and that RF broadcasting works. 

The "true RMS" meters work well but are a far cry for accurate if they are magnetically cupped. To get an accurate reading, you must break the circuit, introduce a passive, frequency independent resistance, then monitor the drop across the resistor. Any magnetic involvement screws the equation as you have introduce an inductive element which will not be liner to frequency. To make matters worse, the type of waveform that is produced by a dimmer is part sign and part square, dividing at the chop point. 

I must further state that amp-probe was not a term describing a brand of meter, but a type of meter, specifically a "non-intrusive clamp on meter." I am aware of the old style magnetically operated Amprobe" as a brand, but the spelling is different, which is why I spelled it out amp-probe.

My own current unit is this one- http://www.lashen.com/vendors/fluke/336.asp I would trust it to give me a good ballpark thermal load reading.


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## STEVETERRY (Dec 26, 2007)

JD said:


> Ummm... What are you not agreeing with now? That an amp-probe will not give you a true reading? Isn't that what I just said? Let me expand that statement: Any magnetically coupled meter (wrap-around type) will not give you a true reading because (the important part-) they are magnetically cupped. As the frequency rises (square = sine plus every harmonic) the transfer ratio increases, producing more voltage in the secondary loop (same reason a 60 cps transformer is much bigger than a 400 cps transformer, like those used in plains.) and that RF broadcasting works.
> The "true RMS" meters work well but are a far cry for accurate if they are magnetically cupped. To get an accurate reading, you must break the circuit, introduce a passive, frequency independent resistance, then monitor the drop across the resistor. Any magnetic involvement screws the equation as you have introduce an inductive element which will not be liner to frequency. To make matters worse, the type of waveform that is produced by a dimmer is part sign and part square, dividing at the chop point.
> I must further state that amp-probe was not a term describing a brand of meter, but a type of meter, specifically a "non-intrusive clamp on meter." I am aware of the old style magnetically operated Amprobe" as a brand, but the spelling is different, which is why I spelled it out amp-probe.
> My own current unit is this one- http://www.lashen.com/vendors/fluke/336.asp I would trust it to give me a good ballpark thermal load reading.



1. Any non-true-RMS meter will give you an inaccurate reading on a non-linear current waveform. The clamp-on current transformer has almost nothing to do with the inaccuracy.

2. Almost all field current measurement on AC line circuits are accomplished with clamp-on or toroidal current transformers, not by breaking the circuit and measuring across a resistance. That is just not practical in most cases.

3. Good true RMS clamp-on meters are capable of quite high accuracies even when presented with high-harmonic content waveforms. For example, the Fluke 345 clamp-on meter is capable of +/- 3% of reading on crest factors between 1.1 and 3, and +/- 5% of reading on crest factors between 3 and 5. This is pretty darned accurate.

4. Typical instruments have frequency response of 15 Hz to 1kHz for the meter and clamp-on transformer combination. The accuracies above are measured across that frequency range. This takes care of the instrument response to harmonic frequencies in no-sinusoidal waveforms like a phase-control dimmer.

The bottom line: magnetically coupling the meter to the conductor under measurement does not introduce gross inaccuracies, even when the waveform is harmonic-rich. Gross inaccuracies come from using a non-true-RMS instrument on a non-sinusoidal current waveform. That was the point I was originally trying to make.


ST


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## church (Dec 26, 2007)

removing the outer insulation on a cable to expose te insulated conductors on a permament electrical installation is consider an unlawful modification in many jurisdictions. here in Ontario the individual who performs such an act is liable to be personally fined - likewise their employer can b e fined and they can be made to pay a victim surcharge plus pay for the repairs. A recent case resulted in a cable TV installer being fined $10,000 and his em^ployer was fined a similar amount. Fortunately no one was injured by this action of stripping away 1 inch of outer sleeving of a piece of Romx outside of an approved box.

To be honest when I read this post the questions that are being asked about the use of basic electrical test equipment indicate that the person doing this type of measurement should stop and find someone who is a competant (legal word here) to show them how to do this type of measurement safely. It is very easy to suffer serious second and third degree burns or lose your life by performing these types of measurements incorrectly (using the wrong setting and or euipment, slipping with a probe etc etc).

it is good to ask the questions and want to learn however the next step is to get someone to show you and take the training. Good luck.


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## icewolf08 (Dec 26, 2007)

The easiest, and possibly safest way to use your clamp on ammeter is to buy something like this. Sure, you spend a few extra bux, but in the end, your theatre probably already has edison to stage pin adapters. Then there is no need to construct your own electrical devices and no need for "creative" solutions to using your equipment. Did I mention it was safer?


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## Diarmuid (Dec 26, 2007)

icewolf08 said:


> The easiest, and possibly safest way to use your clamp on ammeter is to buy something like this. Sure, you spend a few extra bux, but in the end, your theatre probably already has edison to stage pin adapters. Then there is no need to construct your own electrical devices and no need for "creative" solutions to using your equipment. Did I mention it was safer?


 
Thank you, very much for finding that, I think that typa thing is just what I needed, though I need to try and find a 13A plug version, which I'm sure there'll be somewhere on the internet. Thanks for the find.


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## derekleffew (Dec 26, 2007)

While that's a nice item icewolf08, do I really need to buy something, for $14.99 US, that I already have the parts for, AND since our original poster, Diarmuid, is UK-based, he would need to build TWO adapters to use it? EDIT-answered by the post above, for the most part. Diarmuid , do you see the Edison, NEMA 5-15, PBU, plug and connector in the UK, often?


STEVETERRY, as I am a (sometimes) House Electrician of an arena, are you suggesting I should throw away my Fluke 30 and purchase a Fluke 345 (or equivalent) for $1395.00 US?! Yikes. Would a Fluke 334A, for $164.95 US, be acceptable? 

Has my Fluke 30 _really_ been giving me inaccurate readings of ETC Sensor™ Touring Racks all these years? Does the level of the dimmers matter (as to the amount of inaccuracy)? [I usually take a reading with ALL Dimmers at Full before the show, and sometimes a couple of readings during the show, if I suspect the load is approaching 400a/leg, on that particular service.]


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## STEVETERRY (Dec 26, 2007)

derekleffew said:


> While that's a nice item icewolf08, do I really need to buy something, for $14.99 US, that I already have the parts for, AND since our original poster, Diarmuid, is UK-based, he would need to build TWO adapters to use it? EDIT-answered by the post above, for the most part. Diarmuid , do you see the Edison, NEMA 5-15, PBU, plug and connector in the UK, often?
> STEVETERRY, as I am a (sometimes) House Electrician of an arena, are you suggesting I should throw away my Fluke 30 and purchase a Fluke 345 (or equivalent) for $1395.00 US?! Yikes. Would a Fluke 334A, for $164.95 US, be acceptable?
> Has my Fluke 30 _really_ been giving me inaccurate readings of ETC Sensor™ Touring Racks all these years? Does the level of the dimmers matter (as to the amount of inaccuracy)? [I usually take a reading with ALL Dimmers at Full before the show, and sometimes a couple of readings during the show, if I suspect the load is approaching 400a/leg, on that particular service.]



Your Fluke 30 meter, while a fine tool, is the wrong meter for the job in that it's not a true-RMS device. In the same price range, the Fluke 32 is the ticket, or equivalent. Your readings have been "close", since you test with all dimmers at full, where the current waveform is almost a sine-wave. Had you wanted to measure the current in the neutral with all dimmers at half (a useful test), you would have gotten much more inaccurate (low) readings.

I was using the specs on the more-accurate Fluke 345 simply to make the point that current transformer clamps are not inherently inaccurate, as a previous post suggested.

As for the line splitter--Icewolf08 is right--it's the right tool for the job. It preserves the 600V insulation rating of the cable and it's UL-Listed. If I had remembered these devices, I would have suggested them earlier. Thanks, Alex!


ST


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## derekleffew (Dec 26, 2007)

STEVETERRY said:


> Your Fluke 30 meter, while a fine tool, is the wrong meter for the job in that it's not a true-RMS device. In the same price range, the Fluke 32 is the ticket, or equivalent. Your readings have been "close", since you test with all dimmers at full, where the current waveform is almost a sine-wave. Had you wanted to measure the current in the neutral with all dimmers at half (a useful test), you would have gotten much more inaccurate (low) readings....


Watch ebay soon for a Fluke 30 meter, in very good condition, and still have the original box. Ordering a Fluke 32 (or equivalent) now. Thank you, Mr. Terry. There goes my Xmas money.


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## JD (Dec 26, 2007)

STEVETERRY said:


> 1. Any non-true-RMS meter will give you an inaccurate reading on a non-linear current waveform. The clamp-on current transformer has almost nothing to do with the inaccuracy.



Actually, it has everything to do with the inaccuracy. An inductor by nature (of which transformers are, and that is what you really are using in a clamp on meter) is frequency dependant. (see below)


STEVETERRY said:


> 2. Almost all field current measurement on AC line circuits are accomplished with clamp-on or toroidal current transformers, not by breaking the circuit and measuring across a resistance. That is just not practical in most cases.



In no case am I suggesting you break the line in field application. My referral is to lab measurements. Most all electric company meters (that I've ever seen) do indeed measure by use of a torad, with the exception of domestic meters.


STEVETERRY said:


> 3. Good true RMS clamp-on meters are capable of quite high accuracies even when presented with high-harmonic content waveforms. For example, the Fluke 345 clamp-on meter is capable of +/- 3% of reading on crest factors between 1.1 and 3, and +/- 5% of reading on crest factors between 3 and 5. This is pretty darned accurate.



I am not arguing this point. see below.


STEVETERRY said:


> 4. Typical instruments have frequency response of 15 Hz to 1kHz for the meter and clamp-on transformer combination. The accuracies above are measured across that frequency range. This takes care of the instrument response to harmonic frequencies in no-sinusoidal waveforms like a phase-control dimmer.



And there in lies the problem! The output from a dimmer is not one frequency. If has a low frequency element (60cps) but also has high frequency harmonics all the way up to whatever filtering limit is on the dimmer! I am sure at any given frequency, your meter is accurate. The problem is the nature of taking multiple readings at multiple frequencies at the same time. 


STEVETERRY said:


> The bottom line: magnetically coupling the meter to the conductor under measurement does not introduce gross inaccuracies, even when the waveform is harmonic-rich. Gross inaccuracies come from using a non-true-RMS instrument on a non-sinusoidal current waveform. That was the point I was originally trying to make.



And this is what is confusing me. I never said otherwise! I am perfectly happy using the meter I am using.


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## STEVETERRY (Dec 26, 2007)

derekleffew said:


> Watch ebay soon for a Fluke 30 meter, in very good condition, and still have the original box. Ordering a Fluke 32 (or equivalent) now. Thank you, Mr. Terry. There goes my Xmas money.




I just looked up the 334, and it has the same problem--it's not true-RMS.

Cheers

ST


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## JD (Dec 26, 2007)

The 336 is. 
http://www.lashen.com/vendors/fluke/336.asp

About $299 list, and you can get good discounts on that elsewhere.


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## STEVETERRY (Dec 26, 2007)

In an earlier post, you said:

"Let me expand that statement: Any magnetically coupled meter (wrap-around type) will not give you a true reading because (the important part-) they are magnetically cupped. As the frequency rises (square = sine plus every harmonic) the transfer ratio increases, producing more voltage in the secondary loop (same reason a 60 cps transformer is much bigger than a 400 cps transformer, like those used in plains.) and that RF broadcasting works."

True-RMS meters with good crest factors get around this problem. They are designed to measure non-sinusoidal waveforms with high harmonic content while preserving true-RMS accuracy. That includes those types with clamp-on current transformers.

ST


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## ship (Dec 27, 2007)

It was once upon the big boss’s visiting a show site that there was a wee problem in balancing the load, and further discovered that not one of the crew possessed a clamp meter so as to help solve or diagnose the problem. It was than mandated into corporate rule that any employee that wished to do shows should possess a clamp meter. Ya’ know how simple could that be, I even had one while a carpenter by trade...

Given this mandate which has a bit fallen to the wayside in requirement level until next time by way of active memory in what could happen... I set out as the shop tool person to find and study the clamp meter at the same time as my B&K clamp meter was starting to give me problems or limited for what I needed.

Did a study of the following:
Model # Brand True RMS AC Amps DC Amps AC Voltage DC Voltage Resistance Capacitance Continuity Temperature Frequency Peak/Hold Jaw Size


Of this there were a few defining features important. First the seperation of True RMS that on a computer dimmer will counter the non-wattage effect, and jaw size - a 4/0 type SC feeder cable has a specific diamater and those clamp meters that will not fit over the cable won’t work so well. Add to that amperage rating of 400A and less, features such as peak hold and max hold, ability to test voltage both AC and DC, frequency, resistance and have a beep for it, etc. and you have what will be an all around multi-meter. Add to this some Fluke add on/replacable jaws to one’s probes and you have a really useful multi-meter. As long as bananna clip style probe as another limitation. Beyond this was accuracy and features available.

Below is what I studied and the starting prices from 2003: (given this is a Word Perfect table and it does not translate so well to the net.... Perhaps print if really interested in what I found in this study of most brands of clamp meter.)

SEE PDF posted below...



Since than, those of the upper tier of people such as me bought the best Ideal (above Fluke) in spec choice for clamp meter. While we had to get used to it taking a bit longer to settle down in zeroing, for the most part it is a good easy to use true RMS meter. Those stating out seem in the other extreme of budget most often settle for non-tru RMS meters of the Extech brand and there is nothing really wrong with them. Accuracy, RMS and features are at times less but for the price they work well. For those following the rule, it is a good meter even if the jaws are a bit small in just able to fit the cable. While one co-worker was waiting for the Ideal clamp meter simillar to mine was waiting for the thing to just settle down and zero out he sent me an E-Mail about the thing... What is this crap you specified over Fluke... it won’t zero. Did a study of my own and it does take it’s own time in zeroing, but on the other hand is much more cost effective, accurate and more important yet does offer more features than the Fluke line of product. I was really disappointed in what Fluke for clamp meters had to offer. This not to say that Fluke and other brands don’t have a place, just that for the best, at times it is not Fluke. I did the best and they also have full warranty in one lens breaking under use and it being replaced.

Still beyond clamp meters there is multi-meters that measure amperage. One can even test such a thing thru a figure eight with one’s probes. Bought thru McMaster Carr a Extec multi-meter non-clamp meter or two now that will meter thru the probes 20 amps and that’s sufficient and necessary to test a follow spot.. Master ballast testing prociedure for a Lycian 924 ballast is with a multi-meter that tests up to 20 amps by way of probes into the multi-pin plug. Far different than testing 400A range on a show this testing with the probes the multi-pin plug to ensure it will as a ballast provide the proper amperage. At minimum at work now, I now have two types of amperage meters and ones that the common standard to the industry Fluke #77 won’t do. One to do feeder cable in the 400A range, plus is true RMS and very accurate, one that tests ballasts, than one that is analog. Something not mentioned above is the analog meter.

In an expert in the induststry coming to visit where I work in giving a class, he requested a meter. Gave him mine, it was not sufficient. Gave him the shop’s old analog meter and he was satified. Why would one choose an analog meter over a digital meter? Analog meters have a sort of resistance that compensates for computers, computer meters I learn don’t. Going for a clamp meter... go with the best or go simply analog I learn as often even better yet. The old timers use analog clamp meters if they use them - they often don’t in already having solved problems, but non the less it is their magic. Yet to buy one but it is on my own shopping list such an analog clamp meter. No... Not such a thing as a Radio Shack type meter in considering it accurate, more like a Spherry type brand and one well respected.

Still the expert in the industry recognized my meter and did his thing given it’s limitations and slowness to zero. True RMS and not True he explained etc. in teaching how to use such a meter. Beyond buying a multi-meter, this much less just as if multi-meter, one that beyond what the multi-meter does, one that will also tell amps about a cable, one needs physical instruction in how to use it. This much less at least a knowledge of what “True RMS” is or its use for our purposes where appropriate or in need or necessity dependant upon the person using it.

Multi-meters are a science, beyond this are clamp meters that do what a multi-meter will do yet go beyond that. Cannot imagine the need for say a Fluke #77 these days when a clamp meter will do what it did in our world plus more.

It’s possible that if one buys a good enough multi-meter, one can also buy the accessory amp clam for it and it’s going to work the same, but one needs to buy a good meter in the first place, than invest further into it. Cannot see any rational in a plug in feature that does the same as a meter that alredy does it however.

On Fluke on the other hand, Fluke #TL 223... It’s a sort of probe type accessories kit that will work with most brands of quality banana plug type mult-meter and has a number of probes that disconnect and reconnect. Great idea - others have similar but not as good. Add onto it with other styles of clip and you now have ease in testing stuff. Clip the alligator clip onto one pin and probe with the other. This as opposed to attempting to hold a probe on one pin and test to another without much ease.

Me, I’m an Ideal meter person in having replaced my discontinued B&K clamp meter that I loved and was great. Hz, amps AC and DC amps and volts, ohms and continuity. Add to this True RMS, ability to clamp the cable, peak and max hold, than after those options accuracy and you now have a great multi-meter for our industry.


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## ship (Dec 27, 2007)

derekleffew said:


> For GE 4552 and 4559s, there's no ceramic, so I've had to write on the glass, but that burns/wears off over time. Every place I've worked seems to have had a mixture of 4552 and 4559, never on the same bar, of course.
> ship and len are probably too young to remember HiLights, a major R&R company of the '70s and '80s. I bought all their PAR lamps when they finally folded. They had engraved "HLI" in the back of every lamp, with an electric engraver. Taking it a tad too far, if you ask me.



Yep too young.. besides I'm not a rock and roller by hart and a carpenter by trade.... yea.. that worked out well for me these days in the end. Yes, I stock 547 different types of lamp having just done my year 2007 $250,000+ inventory for lamps. Major headache in trying to make the Word Perfect table preform as if Excell so as to make sumtotals but I did do so - screw Excell.

I know $4552 lamps and $4559 lamps, don't have the latter in stock though I wish I did so as to see. Len on the other hand... them might be fighting words with him.

Still engraving HLI on the back of the lamps. Could be brilliant or could be really stupid in weakening the glass. Paint marker for the glass and graphite for the porcelain works for me - this and yelling at my vendors that supply inks that wear off.


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## derekleffew (Dec 27, 2007)

ship said:


> Major headache in trying to make the Word Perfect table preform as if Excell so as to make sumtotals but I did do so - screw Excell.
> 
> I know $4552 lamps and $4559 lamps, don't have the latter in stock though I wish I did so as to see. Len on the other hand... them might be fighting words with him.


Hey, ship, do you have the ability to generate a .pdf document from Word Perfect, or Excel for that matter? Your posting is just gibberish due to the lack of formatting, and a PDF would solve that. Also, could you not have exported your WordPerfect document to Excel to do the calculations? Both are easy on a Mac, someone else will have to explain how to do it under Windows.

The 600w ACLs are brighter enough for me to overlook the (perceived, in my opinion) lag in response time due to the larger filament. Len, which do you prefer, and why?


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## ship (Dec 27, 2007)

Here is the rest of the 2002/2003 list of tools at one point I worked up as useful. This in attempt to post a PDF by way of experiment.


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## soundlight (Dec 27, 2007)

Hey ship - if you have any of the information in tables, you can use a program called PDF Creator. Free program. Basically, you just install it as a printer, and then you just print like you would to any hard copy printer - but it will just print it as a PDF to a file. I find alot of the posts useful, but if you already have the information in a table, that would be even more useful! I use this all the time when sending "official" stuff, so that none of the original formatting gets lost, and PDF is basically the standard file format for finalized text document transfers.


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## derekleffew (Dec 27, 2007)

ship, that is a fantastic tool list. I'm starting a new thread in the "general advice" forum with that as the "flagship", no pun intended.


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## Charc (Dec 27, 2007)

Great presentation value Ship.


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## Van (Dec 27, 2007)

I may have missed it, there's so much good info in this thread, But did someone post the solution to the main question yet ? The trick with a clamp on amp-probe is to build a little jummper. Edison male on one end female on the other. connect everything together with 10-12 gauge single wires. thnn, or just the inside conductors from a standard cable. Plug the device you are checking into the female end and the male end into the wall, dimmer etc. This adapter allows you to clamp onto just one conuctor at a time. I have several of these in my tool kit with varying gauges of wire, and connectors. Obviously you don't need an adapter if you are chaecking the legs of feeder cable, but it's good to have a four wire setup and a couple of three wire set-ups. Remember when making the adapters, and using them, to use a properly rated connector and wire gauge e.g. don't use a 16ga wire on something you think might have 20 amps running through it, that would be bad.


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## David Ashton (Dec 27, 2007)

My concern was that this query is from a school student in a country with 240/440 volt system.
basically if you don't know how to work a clamp meter it is probably irresponsible for this site to try and explain, already we have seen talk about stripping off insulation and I know what is meant but if someone gets the wrong idea.........
Sorry to be a kill joy, I usually as irresponsible as the next man but I have a bad vibe about making these suggestions to someone with a clamp meter at school.


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## STEVETERRY (Dec 27, 2007)

allthingstheatre said:


> My concern was that this query is from a school student in a country with 240/440 volt system.
> basically if you don't know how to work a clamp meter it is probably irresponsible for this site to try and explain, already we have seen talk about stripping off insulation and I know what is meant but if someone gets the wrong idea.........
> Sorry to be a kill joy, I usually as irresponsible as the next man but I have a bad vibe about making these suggestions to someone with a clamp meter at school.



I agree, and shame on me for suggesting the "strip off insulation" technique without considering the audience.

Get the adapter suggested by Icewolf08!

ST


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## ship (Dec 27, 2007)

Van said:


> I may have missed it, there's so much good info in this thread, But did someone post the solution to the main question yet ? The trick with a clamp on amp-probe is to build a little jummper. Edison male on one end female on the other. connect everything together with 10-12 gauge single wires. thnn, or just the inside conductors from a standard cable. Plug the device you are checking into the female end and the male end into the wall, dimmer etc. This adapter allows you to clamp onto just one conuctor at a time. I have several of these in my tool kit with varying gauges of wire, and connectors. Obviously you don't need an adapter if you are chaecking the legs of feeder cable, but it's good to have a four wire setup and a couple of three wire set-ups. Remember when making the adapters, and using them, to use a properly rated connector and wire gauge e.g. don't use a 16ga wire on something you think might have 20 amps running through it, that would be bad.



Best way to test amperage is with a clamp meter. Given a clamp meter needs to surround one conductor (neutral / hot doesn’t always matter on single phase) one’s best way of doing this is with a commercially available figure eight clamp meter tool. Not only does it allow a reading but for a more accurate reading it allows for a x10 reading which once one changes the decimal point will more accurately read the current. This in a safe way.

This granted I have my own 208v jumpers for metering it and even three phase jumpers with wire between two plugs. Most often in doing this I would use type MTW wire rated for the amperage of the circuit and outer jacket further insulate the conductors to exposure by way of rubber or vinyl tubing over the conductor. While type MTW over stranded THHN wire has a thicker jacket and is more flexible, it still is not designed to be handled or exposed - further jacketing of the individual conductors than makes it a bit more safe.


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## ship (Dec 27, 2007)

allthingstheatre said:


> My concern was that this query is from a school student in a country with 240/440 volt system.
> basically if you don't know how to work a clamp meter it is probably irresponsible for this site to try and explain, already we have seen talk about stripping off insulation and I know what is meant but if someone gets the wrong idea.........
> Sorry to be a kill joy, I usually as irresponsible as the next man but I have a bad vibe about making these suggestions to someone with a clamp meter at school.



I agree with this and it is a constant balance to be done on the website - this safety verses what is tech. Stripping away of or even percing the insulation and testing when not properly trained and supervised is a good note to make in not doing so.


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## ship (Dec 27, 2007)

Below is the PDF version of my study into various clamp meters if of help. Also the six meters that within pricing/quote for a bulk order and spec I thought were best.


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## derekleffew (Dec 31, 2007)

I rec'd my Fluke 336 today and it's great. Many significant improvements over the Fluke 30, besides being trueRMS. Only disadvantage is the jaws are only 1.25", as opposed the to Fluke 30's 1.5". Still should fit around any 4/0 feeder cable I encounter, (I hope). Advantage of smaller jaws is easier to get into tight places, which is seldom a problem for my use. I regret somewhat not spending the $40 more and getting the Fluke 337, which adds Hz, goes to 1000A (which I'd better never need!), and a min/max display.

I'll be testing the 336 against my 30 this weekend and will post the results.

Another word about safety, which cannot be stressed enough:
Here's the link to the Fluke meter's Safety Sheet PDF, applicable to all brands and types of Multi-Meters/DMMs, in 20 different languages!


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## derekleffew (Jan 5, 2008)

So wouldn't you just know it, the first show on which I try my new Fluke 336 meter contains no dimmers, just lots of VL3000Spots, VL3500Wash, VL2500Spots, and LED fixtures.

The attached PDF shows the results of my Fluke Shootout readings. Note that these readings were taken during programming, with all lights on, but not necessarily moving, which would increase the power draw slightly. I could not see the stage from where I was taking the readings in the electrical room, so couldn't tell what was happening "at the other end" of the feeder, which was all brand new 4/0 by the way. Ah, that new feeder smell, almost as good as the new Leko smell.


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## STEVETERRY (Jan 5, 2008)

derekleffew said:


> So wouldn't you just know it, the first show on which I try my new Fluke 336 meter contains no dimmers, just lots of VL3000Spots, VL3500Wash, VL2500Spots, and LED fixtures.
> The attached PDF shows the results of my Fluke Shootout readings. Note that these readings were taken during programming, with all lights on, but not necessarily moving, which would increase the power draw slightly. I could not see the stage from where I was taking the readings in the electrical room, so couldn't tell what was happening "at the other end" of the feeder, which was all brand new 4/0 by the way. Ah, that new feeder smell, almost as good as the new Leko smell.




OK, no material differences. Now try it on a dimmer system set at 50% and let us know.

ST


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## STEVETERRY (Jan 11, 2008)

derekleffew said:


> So wouldn't you just know it, the first show on which I try my new Fluke 336 meter contains no dimmers, just lots of VL3000Spots, VL3500Wash, VL2500Spots, and LED fixtures.
> The attached PDF shows the results of my Fluke Shootout readings. Note that these readings were taken during programming, with all lights on, but not necessarily moving, which would increase the power draw slightly. I could not see the stage from where I was taking the readings in the electrical room, so couldn't tell what was happening "at the other end" of the feeder, which was all brand new 4/0 by the way. Ah, that new feeder smell, almost as good as the new Leko smell.




OK, we're not letting you off the hook, here. Where are some dimmer readings?




ST


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## derekleffew (Jan 11, 2008)

I've had the same show with no dimmers in my building for a week now. And, in fact, is the first show I can recall that has not a single item made by ETC. 

IF the show next week has dimmers, I'll post the new readings.


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## Van (Jan 11, 2008)

Derek, Did you get the cool tutorial/safety video with your meter? I have a VHS that came with mine. One instance shows what happens when a transient spike occurs as this guy is metering line voltage on a transformer. The result is a "Plasma Fire" a giant 10' ball of energy that just fries the entire electrical room. That vid will always do a good job of keeping you on your toes.


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## derekleffew (Jan 11, 2008)

Alas no video included with my meter. But I think I may have found that to which you are referring. Is it the CD/DVD in this link? VHS? What's that?


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## Van (Jan 12, 2008)

derekleffew said:


> Alas no video included with my meter. But I think I may have found that to which you are referring. Is it the CD/DVD in this link? VHS? What's that?


 
Yeah. My Fluke is OLD, from pre-dvd days. When the pictures for the magic box came on a tape.


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## STEVETERRY (Jan 12, 2008)

Van said:


> Derek, Did you get the cool tutorial/safety video with your meter? I have a VHS that came with mine. One instance shows what happens when a transient spike occurs as this guy is metering line voltage on a transformer. The result is a "Plasma Fire" a giant 10' ball of energy that just fries the entire electrical room. That vid will always do a good job of keeping you on your toes.




This is the whole thrust of the new NFPA 70E standard for Electrical Safety in the Workplace. The current thinking is that arc flash provides at least as much risk as electrocution. The standard requires wearing various protective gear and non-flammable clothing when working on an open panel. These techniques were just not considered 5 or 10 years ago.

Part of the ESTA ETCP Electrician Certification exam is understanding the rules and requirements of NFPA 70E. I recommend that everyone get a copy.

ST


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## JD (Jan 12, 2008)

STEVETERRY said:


> The current thinking is that arc flash provides at least as much risk as electrocution.



About time someone recognized that! Of the 2200 some shows I have done, and equal number I have helped on over the years, all of power related injuries I have seen or heard of involved burns, burned clothing, or eye damage from arc flash. (Excluding linemen stories) Yes, electrocution is a real and present danger at all times, but burns are far more likely due to what can happen with a simple tool drop. Although you have to be pretty unlucky to get nailed by a lightning hit or transient spike as Van described in the video, it is easy to deceive yourself into thinking everything is safe because you are holding a non-intrusive or insulated probe. 

Fact is, once a panel is open (or in some cases the act of opening it), you are at risk. The saying in pyrotechnics is "Always treat explosives like they are about to go off." I believe death and injury are just as close when you are working with distribution. In fact, I have heard louder explosions from distribution equipment then most pyrotechnics can produce.


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## Charc (Jan 12, 2008)

Quick note, that safety video is 100% free, if you get it on CD. No shipping, no tax, no credit card required.


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## derekleffew (Feb 10, 2008)

FINALLY had a show with dimmers. Three racks of Sensor 48x2.4Kw, driving 28x 1K-PAR64 6Lamp-Bars, 30-some single cans as truss warmers, 8x 8-Lights, and 8x 4552 ACL bars. Plus two 24-way Moving Light Distro's. All four services were 400A, with 100' of 4/0 feeder. One of the Sensor racks had a 1993 serial number! Below are readings taken with all dimmers at FULL, moving lights (34x VL3000s, Spots and Washes) moving all their motors; and all dimmers at HALF, moving lights lamped ON, but not moving.

Based on the data, it appears that: at FULL, the Fluke 30 is nominally close to the 336. However, with dimmers at 50%, the Fluke 30 UNDER-READS by about 15 to 30%: Consistent across phases in each rack, but varies from rack to rack. Notice that the neutral is approximately 1.33 times higher than any hot phase, hence the reason for the double neutral on Touring Racks, that I personally have never seen used, but might consider it if I exceeded 300A on 4/0 feeder. 

I suspect the Blue phase of the 336 is a fluke, as it's really hard to take a reading while the numbers are jumping all over the place, basically watching the bally-hoo on the meter.

So as much as it kills me to admit it, STEVETERRY is correct. One must use a trueRMS meter to get accurate readings with a less-than-100% level, but the Fluke 30 is accurate enough at measuring total load. So I still have mixed emotions as to whether it was worth it for me to buy a new meter. I still think I should have bought the model 337.

On a different topic, this just arrived a few days ago. And one of my House Electricians didn't know what it was!


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## STEVETERRY (Feb 10, 2008)

derekleffew said:


> FINALLY had a show with dimmers. Three racks of Sensor 48x2.4Kw, driving 28x 1K-PAR64 6Lamp-Bars, 30-some single cans as truss warmers, 8x 8-Lights, and 8x 4552 ACL bars. Plus two 24-way Moving Light Distro's. All four services were 400A, with 100' of 4/0 feeder. One of the Sensor racks had a 1993 serial number! Below are readings taken with all dimmers at FULL, moving lights (34x VL3000s, Spots and Washes) moving all their motors; and all dimmers at HALF, moving lights lamped ON, but not moving.
> Based on the data, it appears that: at FULL, the Fluke 30 is nominally close to the 336. However, with dimmers at 50%, the Fluke 30 UNDER-READS by about 15 to 30%: Consistent across phases in each rack, but varies from rack to rack. Notice that the neutral is approximately 1.73 times higher than any hot phase, hence the reason for the double neutral on Touring Racks, that I personally have never seen used, but might consider it if I exceeded 300A on 4/0 feeder.
> I suspect the Blue phase of the 336 is a fluke, as it's really hard to take a reading while the numbers are jumping all over the place, basically watching the bally-hoo on the meter.
> So as much as it kills me to admit it, STEVETERRY is correct. One must use a trueRMS meter to get accurate readings with a less-than-100% level, but the Fluke 30 is accurate enough at measuring total load. So I still have mixed emotions as to whether it was worth it for me to buy a new meter. I still think I should have bought the model 337.
> On a different topic, this just arrived a few days ago. And one of my House Electricians didn't know what it was!



Interesting to note that the delta-connected 208V Vari*Lites also show a wide disparity in readings between meters due to their switchmode power supplies that have a harmonic-rich current waveform. Note the near-zero neutral current (probably electrical noise), because VL PD's don't use the neutral. So, this would be a case where the equipment is "at full" all the time, and the only way to get an accurate reading is to use a true-RMS meter.

All in all, with the relatively small difference in cost between average and True-RMS meters, I recommend that anyone in the entertainment industry pony up for the right tool: the true-RMS meter. Just look at the numbers in Derek's study, and you'll see why.

I rest my case.



ST


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## JD (Feb 10, 2008)

STEVETERRY said:


> Interesting to note that the delta-connected 208V Vari*Lites also show a wide disparity in readings between meters due to their switchmode power supplies that have a harmonic-rich current waveform.



Switch mode supplies throw an even more interesting curve into the picture. Basically, power entering the supply goes through a full wave rectifier, a storage capacitor, then to a drive transistor (Usually a power MOSFET) which drives a transformer using PWM and FM to achieve a regulated secondary. The system accurately compensates for variations in line voltage by adjusting the current draw over a wide range of voltages. The thing that makes powering them interesting is that front end rectifier. As the diodes in the bridge only turn on after the input waveform exceeds the voltage stored in the capacitor, and turn off once the voltage drops below, the supplies only draw power near the peak of the waveform. Example, if the cap has a charge of 200 volts, no current passes from the supply line except during the portion of the waveform that is above 201.2 volts. (diodes drop about 1/2 volt.) The result is a current draw that is unlike any other. It almost looks like an abbreviated square wave with a rounded top. What this also means is that the supply must grab all of it's operating power out of a small portion of the AC waveform. 

How does this affect us? Keep in mind that all of your switch mode supplies on a given phase leg are drawing power at the same time, and it is a multiple of what the wattage would suggest. Although cable heating is not an issue due to the duty cycle, voltage drop may be. In this case, the RMS ratings go out the window. A supply driving a 575w lamp may be drawing the RMS equivalent of 5+ amps, but in actuality, it is drawing 0 during most of the waveform, and 15+ amps at the top of the waveform. Three units may run just fine off of a 20 amp breaker, and clock in on the meter at under 20 amps, but during the critical portion of the waveform where the supplies are grabbing all their power, the actual load may exceed 45 amps. Again, this is not a thermal issue, but a voltage drop issue, and suggests up-gauging would be recommended. 

In conclusion, I am not sure the industry has dealt, or even paid much attention to this issue. It is a well know problem on computer server farms due to the fact that computer supplies are switch mode as well. As the supplies generally work over a wide range of voltages, it may ultimately be a non-issue except with extremely long runs. One must always remember the other name for wire- Resistor.

NOTE: PWM - Pulse Width Modulation. FM - Frequency Modulation. Switching supplies use both, dropping the frequency under heavy load. As the old service saying goes, "if you can hear it, pull the plug! (but you're probably too late!)"


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## derekleffew (Feb 10, 2008)

JD said:


> ... Three units may run just fine off of a 20 amp breaker, and clock in on the meter at under 20 amps, but during the critical portion of the waveform where the supplies are grabbing all their power, the actual load may exceed 45 amps. Again, this is not a thermal issue, but a voltage drop issue, and suggests up-gauging would be recommended. ...


Good point, JD. While I have never "three-fered" 575W Movers, I have, due to budget or laziness, "two-fered" them. But I don't like that practice because, if a unit needs a hard reset during the show, TWO units are lost while they recal and then, depending on the fixture and mode, must be "lamped ON" again. With this show, all of the 1200W VL3000s were single circuited, and the designer/programmer DID ask for a hard reset on one light during the performance.


STEVETERRY said:


> Interesting to note that the delta-connected 208V Vari*Lites also show a wide disparity in readings between meters due to their switchmode power supplies that have a harmonic-rich current waveform. ...


Please elaborate, as the feeder is, of course, Wye-connected. Or are you saying "delta-connected" because the neutral is unused/unwired? 


STEVETERRY said:


> ...All in all, with the relatively small difference in cost between average and True-RMS meters, I recommend that anyone in the entertainment industry pony up for the right tool: the true-RMS meter. Just look at the numbers in Derek's study, and you'll see why.


Well, who can argue with that point? But also look for features such as min/max, peak-hold, and though not as critical, but sometimes handy, frequency.

By the way, before anyone says anything about balancing the legs, *I* did not plan the patch. I believe the rule of thumb is no one leg should be more than 25% off from the others. I also feel it's somewhat of a moot point, as no one can guarantee that during every cue the legs will remain balanced. In fact, we're positive they WON'T remain balanced. 

Another thing I learned during this exercise is how much energy a moving light's motors use, but again, it's a very remote possibility that every motor inside a light will be working simultaneously.

Others, please try this experiment for yourselves and post the results!


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## JD (Feb 10, 2008)

derekleffew said:


> I also feel it's somewhat of a moot point, as no one can guarantee that during every cue the legs will remain balanced. In fact, we're positive they WON'T remain balanced.



Interesting that you should mention that.... A bit of a tangent here, but I've been thinking lately, due to the nature of IGBTs one could design a dimmer system that actively remains in complete balance across all three phase legs no matter what the scene. To do so, the unit would use a master 3 phase power supply that produced a + / G / - buss output (much like a power amp.) Each IGBT PWM sign wave dimmer would the operate off the rails. No matter what circuits were loaded, the draw would be balanced on all three phase legs perfectly. I wonder if anyone is working on this?

end tangent.


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## STEVETERRY (Feb 10, 2008)

JD said:


> Interesting that you should mention that.... A bit of a tangent here, but I've been thinking lately, due to the nature of IGBTs one could design a dimmer system that actively remains in complete balance across all three phase legs no matter what the scene. To do so, the unit would use a master 3 phase power supply that produced a + / G / - buss output (much like a power amp.) Each IGBT PWM sign wave dimmer would the operate off the rails. No matter what circuits were loaded, the draw would be balanced on all three phase legs perfectly. I wonder if anyone is working on this?
> end tangent.



We could do that. However, we'd like to be heading in the other direction, cost-wise, in order to drive down the cost of IGBT or MOSFET sine wave dimmers.

ST


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## STEVETERRY (Feb 10, 2008)

derekleffew said:


> Please elaborate, as the feeder is, of course, Wye-connected. Or are you just saying "delta-connected" because the neutral is unused?



Yes, a VLXX Moving Light (How does one format strikethru?)-DL. PD will not connect the neutral in North America. So it does not matter that it's a wye secondary, the load is delta- connected.

ST


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## phil000 (Feb 10, 2008)

I would just like to thank everyone who contributed to this thread. I have learned so much in this past 30 minutes (nearly took notes!)...

They taught us the basics in our advanced lighting technology class (which is currently going on this semester), but it really helps to see people talk about it back and forth to really help comprehend it, so, thank you 

Phil


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## derekleffew (Feb 10, 2008)

phil000 said:


> I would just like to thank everyone who contributed to this thread. I have learned so much in this past 30 minutes (nearly took notes!)...


If you have found the information presented on ControlBooth useful, consider donating today. ...Oh wait, you already did!


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## STEVETERRY (Feb 10, 2008)

derekleffew said:


> If you have found the information presented on ControlBooth useful, consider donating today. ...Oh wait, you already did!



OK, I just gave some cash.

ST


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## derekleffew (Feb 10, 2008)

STEVETERRY said:


> OK, I just gave some cash.
> 
> ST


Steve, your expertise and experience is contribution enough. But I know dvsDave appreciates the cash also.


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## derekleffew (Feb 16, 2008)

icewolf08 said:


> The easiest, and possibly safest way to use your clamp on ammeter is to buy something like this. Sure, you spend a few extra bux, but in the end, your theatre probably already has edison to stage pin adapters. Then there is no need to construct your own electrical devices and no need for "creative" solutions to using your equipment. Did I mention it was safer?


Icewolf08 wins again...



...actually, with *SAFETY FIRST, EVERYONE WINS!*


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## LavaASU (Feb 12, 2014)

Okay, whats the favorite? Excluding all forms of no-name made in china ones. I had two (I was smart and bought a spare), but alas one has grown legs and the other got broken by a so claimed licensed electrician that tried to meter resistance on a live circuit. I'm hoping to get a true RMS one this time (old ones weren't), it needs to be at least Cat III 300V, AAC 400A, plus the usual resistance, VAC and VDC.

Yes, I'd like to get a fluke, but it's way too much given that others end up using mine (and sometimes taking or breaking!).


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## JonCarter (Feb 12, 2014)

I like my Amprobe. Had it for something like 30 yrs now and it never failed me.


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## jhochb (Feb 12, 2014)

the FLUKE T5 -1000
it's a FLUKE & under $150
AC amps, AC/DC volts, continuity
no boot time.

I like my AMPROBE too


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## gafftapegreenia (Feb 12, 2014)

I got a Milwaukee one a few years ago, but in hindsight I should have just got a Fluke. I guess I just feel more comfortable with a company thats known an respected for meters, especially at such high voltages and amps. Not that the Milwaukee is bad, just should have bought once and been done with it. As another factoid, most meters, even relabeled ones by Craftsman or Klein, are made by Extech and UEi.

The T-5-1000 is nice, but its technically a fork meter, and can it accept 4/0?


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## Dover (Feb 12, 2014)

I haven't had to replace any of my meters recently but I have a 80$ Greenlee I picked up some years back that has served me well. When I replace it I will probably get another Greenlee or one of the new Milwaukee meters. One of my coworkers has a Milwaukee, and it is a well built unit. I hear good things about Ideal meters as well.

Hope this helps
Dover


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## LavaASU (Feb 13, 2014)

If you guys want to laugh, of the dead ones (or broken enough I don't use) are a Sperry (voltage readings are all over the place), Extech (I don't remember what was wrong with it I know frequency didn't work, but I think there was something else too), and TPI (resistance is dead due to the "electrician" metering a live circuit). The Sperry and Extech are both normal ones, the TPI is a clamp meter.


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