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Old Nov 21, 2009, 08:05 AM
lazy-b is offline
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How to make a DC Clamp amp meter ?


How to make a DC Clamp meter ?

Guys, do you have any idea how to make a DC Clamp meter ? most Clamp meter is can only measure AC.

or do you have any suggestion to convert an Ordinary AC Clamp Amp meter to allow measurement of DC current.

I need to measure a DC Current up to 500 Amps for my electric Forklift project.
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Old Nov 21, 2009, 08:45 AM
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Fluke Instruments of Fremont Ca. did it first. They inject a DC pulse into one side of the clamp & then detect it on the other side. There is a polairty (direction) the clamp has to be oriented with respect to the current flow. How to make one? Very hard without a scope and allot of circutry. I would wire in a full time shunt (.01 ohm) 200 Amp and leave it there. It would act like an extra 20 feet or so of wire that you could measure the voltage drop across, and thus current flowing. Or from what I've seen recently....pawn shops have been carrying a cheaper Fluke model that will measure DC Current. Look for the clamp on meters (Fluke) that have the words "in & out" molded on each side of the clamp. You could always test it on your car battery when you're there.

Sorry, in my mind, it would be kinda hard to DIY, but have faith. Lets see what the others think. Good catch on the "in line DC Current" sensing topic!

Best, Doug
Last edited by 43851E; Nov 21, 2009 at 10:30 AM.
Old Nov 21, 2009, 08:53 AM
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"Simplify, then add lightness"
Would be extremely difficult to build one and get it calibrated. Best to just buy one. http://ph.farnell.com/jsp/search/bro...26catalogId%3D
Old Nov 21, 2009, 10:58 AM
Acetronics is offline
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Quote:
Originally Posted by lazy-b View Post
How to make a DC Clamp meter ?

Guys, do you have any idea how to make a DC Clamp meter ? most Clamp meter is can only measure AC.

or do you have any suggestion to convert an Ordinary AC Clamp Amp meter to allow measurement of DC current.

I need to measure a DC Current up to 500 Amps for my electric Forklift project.
Hi, Ellion

Why not parallell 3 ACS 758/200 Amps sensors ( see Allegro Application notes, they show How ...)
http://www.allegromicro.com/en/Produ...0758/index.asp

Friendly Thoughts

Alain
Old Nov 21, 2009, 11:20 AM
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You might be able to DIY one.
Go to http://www.major-tech.com/products/m...=Clamp+Meters# and click on "Measurement Principle of AC/DC Clamp Meter"
Pat MacKenzie
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Old Nov 21, 2009, 01:14 PM
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You can try using a low permeability material core such as a ferrite core to catch the magnetic field lines produced by the DC current and pass them through a hall sensor.
This will require a slit in the ring that is difficult to make, so 2 half circular cores may be the answer.

Hell-e-Guy
Old Nov 21, 2009, 04:19 PM
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The LEM serie of current transducers does just that(Hall effect sensor) for DC or AC. Very easy to use but requires +/- 15V supply:
http://www.datasheetcatalog.com/data...HAL100-S.shtml
Available from 50<600 amps. Just download the pdf for application
Old Nov 21, 2009, 04:55 PM
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Neat part. Less than $20 at Mouser for similar ones that only need +5 volts to operate:
http://www.mouser.com/Sensors/Curren...rd=hal&FS=True

- But no stock

A bit more than $20 at Digikey , and in stock

http://search.digikey.com/scripts/Dk...name=MT7180-ND


Pat MacKenzie
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Old Nov 23, 2009, 08:43 AM
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Guys, thanks to all your suggestion......look like Bruce Abotts's cirucits is simple to make..........look like if we can find a smaller Core, I guess it can be use for our Electric Plane/Helicopter.

Alain, Thats a very nice current sensor perfect for my next project........Data Logger for electric Helicopter.

Ellion
Old Nov 23, 2009, 11:55 AM
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"Simplify, then add lightness"
That article Bruce linked is probably the same design as this kit. http://www.altronics.com.au/index.as...=item&id=K2582

Kit is cheap enough, but I imagine shipping would be high.


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