Measuring voltage with CT clamp

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I’m planning to asses the performance of my electric water heater the EmonPi with single phase power metering at my house panel. However, the additional provision I want to do is measure the voltage of my thermostat in an attempt to estimate the internal water temperature. I’ll be doing this via a relation using ohm/temperature tables. My question is, how can I left the CT clamp measure and show voltage or resistance readings of my desired circuit?

I’m a newbie so sorry if I missed anything.
Thank you

There are a few things about your question that I’m not clear about.

A current transformer can only measure current. You will need an a.c. adapter - essentially another transformer that reduces the mains voltage to a safe level, to measure the mains voltage. To measure the power going into your heater accurately, you must have both.

Now the part I don’t understand - your thermostat. A thermostat is a switch which is operated by temperature, but from what you write, that is not what you have. Could you give the maker and the model number of the device that you are referring to? It sounds to me as if it might be a thermistor - that is a resistor that changes its resistance according to temperature; or it might be a themocouple - a junction of two different metals that generates a minute voltage depending on temperature.

And don’t worry about being a newbie - we were all one of those once.