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Detecting current in twin plus earth


 
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Blitherer

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PostPosted: Sat Jul 30, 2011 3:21 pm Reply with quote

I realise that one can use a current clamp meter to measure current in a single conductor, but is there anyway to measure current in twin plus earth without disconnecting it or cutting it?

Thanks

M.
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fireman22

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PostPosted: Sat Jul 30, 2011 3:48 pm Reply with quote

well if you loosen the accesory box you can use a mini clamp meter and clip it around one of the live conductors, i have done this to test immersion heaters inside the switched spur, otherwise outside say a twin & earth the answer is no
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holmslaw

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PostPosted: Sat Jul 30, 2011 3:53 pm Reply with quote

..


Last edited by holmslaw on Wed Apr 11, 2012 4:26 am, edited 1 time in total
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Wontdothatagain

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PostPosted: Sat Jul 30, 2011 4:07 pm Reply with quote

http://www.megger.com/uk/products/ProductDetails.php?ID=656&Description=

Will measure the current in flat and round multi core cable. Is great for measuring current draw on wasing machines.
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The following user says thank you to Wontdothatagain for this useful post:
holmslaw (30 Jul 2011)
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holmslaw

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PostPosted: Sat Jul 30, 2011 4:18 pm Reply with quote

..


Last edited by holmslaw on Wed Apr 11, 2012 4:26 am, edited 1 time in total
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doni

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PostPosted: Sat Jul 30, 2011 4:33 pm Reply with quote

holmslaw wrote:
I wonder how it does that?


"Unlike conventional clamp meters, the Megger MMC850 Multi-core Clamp Meter has a complex array of planer magnetic sensor coils to calculate the current flowing in the conductors of multicore cables with either 2 cores or 3 cores, and in either flat or round section cable, up to 100 A. The convenience and potential time saving from using the Megger Multi-Core Clamp is considerable."

?
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fireman22

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PostPosted: Sat Jul 30, 2011 4:56 pm Reply with quote

must admit i havent seen one of these, does anyone know how accurate the reading it gives is?
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martinxxxxxx

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PostPosted: Sat Jul 30, 2011 4:59 pm Reply with quote

fireman22 wrote:
must admit i havent seen one of these, does anyone know how accurate the reading it gives is?


I don't think Megger would lie so consult the MI online, someone might do it for you.
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cumbriahandyman

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PostPosted: Sat Jul 30, 2011 5:01 pm Reply with quote

fireman22 wrote:
must admit i havent seen one of these, does anyone know how accurate the reading it gives is?


Not sure of the accuracy but at up to 145 each + 25 for a calibration cert, they are not for the DIYer.
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JohnW2

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PostPosted: Sat Jul 30, 2011 5:20 pm Reply with quote

martinxxxxxx wrote:
fireman22 wrote:
must admit i havent seen one of these, does anyone know how accurate the reading it gives is?
I don't think Megger would lie so consult the MI online, someone might do it for you.

They claim that it has a resolution of 0.1A and an accuracy of 5% + 10d, such that it is 'reasonable' for currents in the range 2A - 100A, but pretty useless for currents <2A.

I've seen talk of these before, and must say that I'm rather intrigued by the described technology, and rather surprised that it can give anything approaching accurate results; at the least, I would have expected it to be very orientation-sensitive.

Kind Regards, John
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fireman22

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PostPosted: Sat Jul 30, 2011 5:24 pm Reply with quote

i wasnt saying megger would lie i just meant how accurate is reading as the jaws have a centralising bit and wondered how critical it would be to have a true reading on a flat twin & earth cable, has anyone used it?
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RF Lighting

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PostPosted: Sat Jul 30, 2011 7:42 pm Reply with quote

Just knocked this together in my workshop



icon_biggrin.gif
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The following 2 users say thank you to RF Lighting for this useful post:
EFLImpudence (31 Jul 2011), martinxxxxxx (31 Jul 2011)
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martinxxxxxx

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PostPosted: Sun Jul 31, 2011 7:35 am Reply with quote

RF Lighting wrote:
Just knocked this together in my workshop



icon_biggrin.gif


That is brilliant, thanks for going to the trouble and to think I couldn't even be bothered to do a google for the MI.

I have a question are all of the instuments "in calibration"? Oh and I can't read the left hand one. icon_redface.gif

Thanks Martin

PS we'll have to think of more things for you to knock up and photo - your experiments are one of the best things about this forum - that someone is prepared to do something practical to add to a discussion. Well Done
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EFLImpudence

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PostPosted: Sun Jul 31, 2011 10:51 am Reply with quote

martinxxxxxx wrote:
I can't read the left hand one.

It says 01.9 as well.
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RF Lighting

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PostPosted: Sun Jul 31, 2011 1:52 pm Reply with quote

Unfortunately none of the instruments are calibration. I have never needed a clamp meter that is bang on accurate, so con't justify 40 a year on it.

The load was a 500W halogen lamp, so the readings are possibly a little on the low side, but they are near enough.

The meter on the left says 1.9A too. It's my meter I use at work and has got quite sratched so is a little difficult to read in the picture.
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