I want to buy this current sensor from eBay. I couldn't find how it works, but I presume it works like the other ones through induction. On many sites it says it has a maximum current of 5 amps, but I'm wondering what would happen if a higher current would be used? Specifically I'd like to sense something up top 15 amps.

  • \$\begingroup\$ If you only want to know if the appliance is on or not, why not make your own sensor. It should be easy to get a few mV of AC, either from a simple transformer made from a metal ring, or a Rogowski coil wound from thin wire. I've even had some luck just placing a 100 turn coil adjacent to one of the conductors. \$\endgroup\$ – tomnexus Jun 8 '15 at 4:15
  • \$\begingroup\$ I tried to make one, but it didn't work. I used some piano wire (the only thing ferrous that I had at hand) and some thin multifilar wire. It was also pretty big. I want to buy one ready made to eliminate my possible (probable :)) construction faults (and also to make it fit better in a junction box) \$\endgroup\$ – rslite Jun 8 '15 at 13:00

The core will tend to saturate so you'll lose accuracy. How much is anyone's guess, but if it really works down to 20Hz/5A it might not be too bad at 60Hz/15A. I have doubts- would not be gobsmacked if it reads 30 or 40% low at 15A. Otherwise they put 2x ~ 3x as much core in there as they needed.

  • \$\begingroup\$ So if I don't need the accuracy I could use it? I just need to know if an appliance is on, not to calculate the current. I was worried that I might cause overheating or something :-) \$\endgroup\$ – rslite Jun 8 '15 at 3:10
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    \$\begingroup\$ It should work well for that purpose. It won't overheat so long as you put a wire capable of 15A through the hole. \$\endgroup\$ – Spehro Pefhany Jun 8 '15 at 3:20
  • \$\begingroup\$ I'm thinking of a 14 AWG wire from an extension cord that will be connected to an outlet. \$\endgroup\$ – rslite Jun 8 '15 at 3:45
  • \$\begingroup\$ Should be okay if the cord is rated for that current. \$\endgroup\$ – Spehro Pefhany Jun 8 '15 at 4:11

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