I am trying to make a very basic energy meter that is basically an Arduino (a random microcontroller) attached to a Current Transformer (CT) that I can clamp around an electric cable in an electric board (one for each phase).
For what I've understand I will have a function that, according to each CT specification, will translate me the current Arduino is measuring in one end of the CT, with the current the CT is measuring in the other end (the electric cable I want to measure).
I can estimate energy consumption over time if I assume that the voltage is constant (240VAC for eg.). However this is not always true and I want to be able to measure voltage as well, using this same CT.
How can I do that with a CT? Does the CT voltage outputted to Arduino vary in a way that I can correlate with the voltage on the measured cable?
The connection diagram is the following:
simulate this circuit – Schematic created using CircuitLab
Best Answer
A CT clamp will measure current taken by the load from the supply it is being fed. So, if the supply voltage is 240 VAC and the load is 240 ohms then the CT will produce a signal indicative of 1 amp RMS flowing.
If the supply were 200 VAC and the load were 200 ohms, the CT would also indicate 1 amp RMS flowing.
In other words, no, the CT doesn't have any facility to indicate what the supply voltage is nor what the load is. You cannot measure power or energy without both a current and voltage measurement device.