Sensor to sense 2000w current???


I have an electrical watter cilinder that has a 2000w resistor. I have no idea when it turns on and off (it depends on its internal thermostate). I'd like to build an arduino application that somehow logs when the resistor is on and off. For that, I'll need some kind of sensor, but I have no idea which kind. I was thinking in applying somekind of galvanometer around the cilinder electrical wire, that could change a logical level when current flows.

Does anyone knows what kind of sensor can be used for this?

Thanks in advance, Joaoabs

How about a current sensor on the power supply to the water heater? Such as this:

I would make my own:

You need a small toroid transformer like this:

You can remove one like this from an old PC powersupply.

Connect the wires so you have 1 winding, mount an LED across the coil, one each way (there will be AC current on the output) so you need the LED's to clamp the voltage both ways.

Connect this to an analog input, and then you can sense when the heater is on.

Another option is to use an opto coupler as shown on the first link.

// Per.

Not what you asked, I know... but maybe an answer to what you want...

How about putting a temperature sensor in the best spot you can get to? Insulate it, as best you can, from the external environment. If a 2kW heater is switching on and off, there ought to be a temperature spike to detect!

Is there a neon or LED "on" indicator on the water heater? A photo-detector "looking" at that would be easy.

I suggest a current switch from the likes of Cr magnetics. Much lower cost, easy to interface with arduino and non-contact.