# Non-invasive Low Current Measurement

I've been tasked with non-invasively measuring a 200 mA pulse signal through a wire. The solutions that come to mind are using a current clamp or a hall effect sensor. I don't need an accurate reading, I just need to sense when the pulse is there. Any suggestions?

• what bandwidth is needed for the measurement, what risetime do you want to resolve on the edges of the pulse? – Neil_UK Feb 13 at 7:39
• For DC, I'd go hall-effect. And since you don't need accuracy or precision, that recommendation goes double, I think. Bandwidth may be an issue. But you didn't mention it, so I'm guessing you'll be okay. – jonk Feb 13 at 7:48
• Thank you for the replies. Well, the only details given to me were that the pulse is around 100 ms long, and it's not periodic, since it comes from a "totalizer." My worry is that most current clamps I find are at least 5 A in rating, and if I can find a hall effect sensor that can measure such a very weak magnetic field. – Ronnel Tehrence Paclibar Feb 13 at 8:00
• A current clamp is used for ad-hoc current measurements. If it is a permanent fixture you would use a current transformer. I found one which went down to 125mA (and there is a 500mA one too: digikey) – Oldfart Feb 13 at 8:16

Other than hall effect sensor, if you have a current probe..

1. set it to the best possible settings.. (just an example: 2A per 1V instead of 2 A per 100mV)..

2. Roll the wire 10 times around the clamp in the same direction. Now, on the oscilloscope you will measure $$\10 X\$$ the actual current through the wire.

For the update:.

If you are planning for multiple, hall sensor is cheaper and practical.

• Thank you for the suggestion. :) Unfortunately, I want to interface several of these to an Arduino, and current probes are expensive. – Ronnel Tehrence Paclibar Feb 13 at 8:30
• @RonnelTehrencePaclibar you've asked for suggestions then you start putting constraints on what you want. Put all constraints down in the question. I mean all of them like size, cost, bandwidth, type of conductor to sense, voltage on that conductor, accuracy, drift.... and add these constraints to your question. This isn't a forum it's a Q and A site and we expect questions to be(come) fully formed and unambiguous. – Andy aka Feb 13 at 10:45