Hello, I recently bought the following CT - ECS10-50 to use it with IottaWatt. Only after installation, I realised that it has voltage output instead of current output. However, for approximate measurements, I am intending to keep it until I get proper CT with current output.
So my idea to use it wit IotaWatt is to set the value of the burden resistor in the IotaWatt setting to the parallel value of both burden resistors (internal IotaWatt burden is 20 Ohms).
However I don’t know the value of the burden resistor inside ECS10-50 with 333mV output.
Experimental measurements with 2kW load and adjusting the value on the IottaWatt gives me about 4 Ohms burden in the ECS10-50 (so the total is 3.333 Ohms as a parallel combination of 4 Ohms and 20 Ohms).
In the IottaWatt setting, I left the other CT setting to ECS1050 (didn’t change it to custom).
Any user can help me with setting the propper values of this setup without hardware modification (removing the burden)?
Precision is not a big deal.
Thank you very much.
Ondrej
I know nothing about iotawrat (other than reports from others), so I suggest you do as you have done and set the value by trial and error. If you already have another c.t, you could put both on the same cable and compare results.
Or do you have a multimeter capable of measuring a.c. voltage or current, which you could use?
If you can measure around 300 mV reasonably accurately, you can calculate the a.c. current from the voltage (with the c.t. unplugged from the iotawatt), then set the calibration to give that value.
Or if it can measure current but only to (say) 2 A, you use a low-power heater and multiply the current the c.t. sees by winding the wire through many times: 10 turns through the c.t. @ 2 A will read 20 A.
Bear in mind it is likely that the manufacturer could adjust the value of the burden on test to give accurate calibration, so a calculated value might still not be absolutely correct.
Hi Rob,
thank you for your reply.
I purchased the ECS1050 here on openenergymonitor so I was hoping maybe somebody from the staff could know manufacturing values.
However, the trial-error method gave me pretty good values. Now I will observe it for longer time to see if I need more adjustments. As this is measurement for the house main power source (three phases here in Europe), I can compare the total measurements with the distributor’s calibrated meter. This will give me the answer, but the longer period for comparation of the values is, the better.
The situation is that I already have proper CT - the SCT-013-000, which is very accurate and works out of the box, but this CT is way too large to fit it around my main house power source wires in the electrical box - so this is why I chose smaller CT, but I didn’t notice it gives output in volts and not amps.