EmonTX measuring strange values

I have connected the CT sensor to the live wire and plugged the AC-AC adapter. From the UART interface, I can see the EmonTX logging data, which is the following:

When there is one 40W lamp connected to the live:

When there is no load:

The question is why ct1 is measuring 9 when there is no load, and ct1 is measuring -35 (minus 35) when there is a 60W load?

Hi Alexandre,

The FAQ section has answers to both of those questions.

In addition to that, you need to use a load much larger than 40 or 60 Watts to get meaningful output from the EmonTX. That’s covered in the FAQ as well.

Hi Bill, that’s great. Thank you very much for the information. The power measurement is working fine now.

After calibrating with a load of 850W, the power reading when there is no load has been reduced to 3W. I’ll try to calibrate using the recommended load of 2000W.

Or you can cheat. If you wind several turns of wire through your c.t., you multiply your load by the number of passes through the core. That’s how I can get 100 A for testing - though actually it is the same 5 A going through the c.t. twenty times, so it looks like and reads 24 kW.

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Thanks Robert for reminding about the Faraday’s law of induction. :slight_smile: