Electronics > Beginners

Is there a way to make a cheap multimeter into a contactless amp meter?

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Beamin:
This seems like it would be simple: Take on of the probes and connect it to a small device using a transistor to amplify the current its seeing and run the device off 1.5 or3 volts. You could add a coil to make it more sensitive and useless components/simpler design. Hard part might be getting the scale right on the meter display although if it was just one or two decimal places off you could just read 0.001 as 0.1 in your head.


ow would this be done with current instead of volts? Ideally it wouldn't require you to make a metal +/- contact with the device but could if it's too hard.

Giaime:
Are you talking about measuring mains current, like those clamp-on meters?

If yes, consider safety: what you are proposing is dangerous.

There are cheap clamp-on meters, but they work on AC only. Another alternative is to use a current transformer, a sense resistor and connect that to your multimeter (again, AC only).

Could you clarify what kind of currents, at what voltage levels, in which kind of circuits are you trying this?

MosherIV:
Hi, Yes.

As Glaime says - turn you DMM into a clamp meter.

Just like this :
http://tronixstuff.com/2011/04/12/kit-review-current-clamp-meter-adaptor/

It is as safe as using any clamp meter.
This kit also allows measuring DC current. Not sure what the range is like in the low currents ie wheather it can measure down to 1mA

Giaime:
The picture attached summarizes why IMHO that kit is not safe: the clamp is uninsulated. Better get a cheap, off the shelf clamp meter, at least they have plastic covered clamp. When trying to insert the clamp into a tight distribution panel you can touch by mistake some live wires...

If you only work with low voltages then it's fine.

BradC:

--- Quote from: MosherIV on August 02, 2018, 06:46:23 am ---Just like this :
http://tronixstuff.com/2011/04/12/kit-review-current-clamp-meter-adaptor/
--- End quote ---

I've built two of those over the years. They do a credible job but I sure as shit wouldn't put them anywhere near uninsulated mains.

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