I'm sensing the output current of a transformer which can get up to 250A. However, I'm only interested in turning on a separate circuit if this current exceeds 10A. If I use a 0-15A hall effect sensor and the current goes to 250A, will the sensor be damaged? I can't find any info on the max amount of current through a sensor before damage, only the max amount it can read accurately. I haven't chose a sensor yet, but it does need to be the type where it clamps around an existing wire.

  • \$\begingroup\$ Why would your transformer start outputting 250A? If you can put a fuse or some physical limit on the output, you can safely get away with a lower rated current hall sensor. That tends to be a good idea in general: put in all the protection you can. \$\endgroup\$
    – Puffafish
    Commented Sep 24, 2020 at 12:56
  • \$\begingroup\$ Sorry, maybe it wasn't so clear. The output of the TX will vary from 0-250A when the circuit is working normally. I need to add an additional circuit that triggers when the current goes past 10A. I'm not really interested in anything other than whether the current is > or < 10A. My concern is if I use a 10A sensor, will it be damaged when the current hits 250A? \$\endgroup\$
    – Thomas C.
    Commented Sep 24, 2020 at 13:01
  • 3
    \$\begingroup\$ There are many kinds of Hall sensors. Please edit to include a picture and a link to the datasheet of the unit you are considering. Note capital 'H' for Hall. It's the chap's name not a sensor for detecting halls. \$\endgroup\$
    – Transistor
    Commented Sep 24, 2020 at 13:03
  • \$\begingroup\$ You will saturate the core material of the hall sensor as well as maximum current admissible, it's not a good idea. Well, you are on the secondary side of the transformer you don't need an isolated sensor why not use a current shunt sensor ? \$\endgroup\$
    – Delphesk
    Commented Sep 24, 2020 at 13:19
  • \$\begingroup\$ It would be easiest to measure with something I can loop around the existing wire rather than trying to safely add a mount for a shunt because there is not much room. I don't have a sensor yet, looking into which one to get. I will probably just go with a 250A sensor and use a comparator to give a signal when it goes above 10A. \$\endgroup\$
    – Thomas C.
    Commented Sep 24, 2020 at 13:55

1 Answer 1


I haven't chose a sensor yet, but it does need to be the type where it clamps around an existing wire.

Hall effect sensors work by detecting magnetic fields. I've never heard of a magnetic field sensor being damaged by too strong of a magnetic field. (Within reason - of course if it was extremely strong like an MRI then it might suck the sensor in and smash it to bits)

The only reason why the sensor might be damaged, that I know of, is if the wire is part of the sensor and you overload the wire so it burns. But since you're only looking at sensors where the wire isn't part of the sensor, that can't happen.

  • \$\begingroup\$ So just to clarify, both the question and this answer: If I wanted to make a current direction sensor for a car starter battery, and that's all I care about, then I could put a split ferrite ring around the thick battery cable, put a hall effect sensor in the gap with a sensitivity that works out to maybe 1A or less full-scale, feed that to an analog comparator and nothing else, with a threshold near half the supply voltage which (usually) corresponds to 0A. And then I could run the starter motor (several hundred amps) through that same sensor without damaging it? \$\endgroup\$
    – AaronD
    Commented Sep 19, 2023 at 3:43
  • \$\begingroup\$ @AaronD sounds fine to me. I found one page that says "There is no upper limit to the magnetic field strength that may be applied to a Hall-effect sensor." Obviously make sure the wire is thick enough for the current. \$\endgroup\$ Commented Sep 19, 2023 at 12:25

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