[Resolved] CTs larger than 600A?


I was just wondering if anyone has used CTs larger than what’s available on the IoTaWatt store? I’ve come across some CTs elsewhere but they didn’t have the headphone jack connection, which is what I’m interested in. I haven’t done any kinda of wiring/soldering/etc so I’m looking for an out of the box solution.

If that’s not possible, happy to hear about any online resources on how to wire a male headphone jack to a CT.


Large CTs up to 2500 Amps are available special order. Current lead time is 3-4 weeks.

1 Like

Just on this, are you also open to sorting smaller Amp CTs but physically larger than what’s in the store?

I’m looking for a 200A CT with a 36mm diameter. I spotted that the 400A CT you have in the store has a 200A version. If the 200A version has a 1-200A accuracy range and is cheaper, then that’d be ideal.

That size CT is the same price for any capacity, moreover, anything low quantity special order is more expensive. I would say just use the 400A.

the accuracy range is important though, do you know if the 200A version is accurate between 1-200A or is it like the others and only 5-200A? also roughly how much would 3 of them cost?

I’m more of an empirical engineer looking to match real-world results with user needs and expectations. The data-sheets indicate the range where the accuracy is guaranteed, but do not say anything whatsoever about what to expect when you go outside of that range.

So I took a stock 400A x 36mm CT and clamped it around one of my test circuits that measures a computer load. For comparison I placed an AccuCT 50A and an echun 50A on the same cable. The statistics below the graph show that all three measured exactly the same current, and that the average current was 1.33A which is 2.6% of scale for the 50A CTs and 0.33% of scale for the 400A. This is with a stock IoTaWatt and stock CTs right out of the box, no calibration of any kind performed.

Ah this is very helpful, yes you’re right there’s 0 indication of how accurate it is outside of the specified range but this looks like the 400A CT should suit my needs.

Thanks for taking the time out to do the test, much appreciated.

FYI, I remembered that I had some 400A CTs I ordered from you before and tested this out myself, comparing it against two 100A CTs I also have. The graph below has the 3 CTs measuring the current of a cable connected to my 3D printer as it was printing. It initially spiked and stayed high to reach the specified temperature for the print but then the rest of the print was just to maintain temp. All 3 CTs reported virtually the same results which is promising.