Is there a way to make a cheap multimeter into a contactless amp meter? - Page 1
Forum section: electronics / beginners

author: Beamin
author_rank: Super Contributor
timestamp: August 02, 2018, 05:14:31 am
content: 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.

author: Giaime
author_rank: Regular Contributor
timestamp: August 02, 2018, 06:34:52 am
content: 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?

author: MosherIV
author_rank: Super Contributor
timestamp: August 02, 2018, 06:46:23 am
content: 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

author: Giaime
author_rank: Regular Contributor
timestamp: August 02, 2018, 07:22:43 am
content: 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.

author: BradC
author_rank: Super Contributor
timestamp: August 02, 2018, 08:35:04 am
content: Quote from: MosherIV on August 02, 2018, 06:46:23 amI'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.

author: drussell
author_rank: Super Contributor
timestamp: August 02, 2018, 03:24:32 pm
content: Quote from: Giaime on August 02, 2018, 07:22:43 amWho said he wanted to probe distribution panels with his homemade current meter?

author: lordvader88
author_rank: Frequent Contributor
timestamp: August 07, 2018, 07:18:32 am
content: I have generic Hall effect sensors, I haven't had time to try them at all yet. I want to make a non-contact current probe and see how well it works.I figured that would be easier/less expensive than trying to make a clamp meter that uses really fine wire coil.

author: iainwhite
author_rank: Unknown
timestamp: August 08, 2018, 08:20:00 pm
content: Quote from: drussell on August 02, 2018, 03:24:32 pmWho assumed OP was male?

author: Beamin
author_rank: Super Contributor
timestamp: August 09, 2018, 11:18:21 am
content: I wouldn't trust my life or risk fire to any DIY, or Chinese/ebay device for that matter, but I was thinking some type of resistor voltage divider set up where you can move a decimal point visually and get a reading on a DC source without cutting wires. Maybe I should study ohms law a bit more.

author: Karlo_Moharic
author_rank: Regular Contributor
timestamp: August 09, 2018, 12:10:24 pm
content: You can buy add-on clamps so yes , I guess , depending what your definition of cheap is