Can we use single calibration for all CT's

Emoncms
1

Hello,
In my project i am using Raspberry pi compute module 4 and i want read the voltage and current, as off now i can able to read the voltage but the actual requirement is i need to use different type of CT’s (like different type of manufacturer or different ranges) so i have calibrated it with general straight line concept like calculating slope and intercept for one CT and if i use for different CT as i mentioned above different manufacturer or different ranges then will it accept the same calibration and give proper output current at the output side or not .??
please let me know if you have any idea on this.
thank you.

2

No.

Every device ever made - electrical, electronic, mechanical or whatever - is subject to manufacturing tolerances. In the particular case of a c.t., that means the amplitude error and the phase error will be different for each and every one that comes out of the factory, even if they are supposedly identical parts. All the manufacturer will tell you is they guarantee the quantity in question will lie within a certain band. If it’s important to you that you know the actual value more precisely, you must calibrate each one.

Continental Control Systems has published a document “CT Accuracy Standards” that you might find useful.

3

For ~10USD more, CCS will calibrate your CT and give you a copy of the cal sheet.

Here’s an example of a cal sheet included with one I bought from CCS:

Accu-CT-Calibration-Certificate.pdf (39.1 KB)

1 Like
4

Hello,
Thanks for your reply, that’s ok if we can’t calibrate the CT with different manufacturer or different ranges then at least can we use same calibration for all CT’s with same ranges with different manufacturer lets say for example 500A/5A with Acrel CT and 500A/5A with Jentor so these are the two same range CT with different manufacturer. Please let me if its possible.??

thank you.

5

If that arrangement gives you adequate accuracy for your purposes, then go ahead. But don’t say I haven’t advised you of the problems and the risk that the value your instrument indicates will differ by an unknown amount from the true value of the quantity you are measuring.