Why do you use a reference voltage for each CT?

Hardware Heatpump
1

First of all sorry for my English it is not as goos as I would like it to be

I need to know the power consumption of several points (14) and I have studied the design of the hardware to optimize it. I have a heatpump board working in Zaragoza (Spain)

My first question is: why do you use a reference voltage for each CT instead of use the same (1,65 V) for all of them (CT1, CT2 and CT3)? I think this has multiple advantages for the hardware but also for the software

Kind regards
Oscar

2

Cost, I think. If you have 14 inputs, then it makes much more sense to use a common 1.65 V bias supply, best provided by an op.amp. See Learn | OpenEnergyMonitor

3

Thanks Robert for your answer. You’re very kind

Let me show you the circuits scheme. I am testing it in the laboratory an it works really well.

Notice the ref_medida is for all the CTs (yhdc sct-013-000) the same

Best regards

4

As the FAQ says:
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5

Sorry Robert but I am trying to upload the file but the system tells me:

“Sorry, new users can not upload attachments”

Please let me know what i have to do to upload the file

Kind regards
Oscar

6

You should be able to do it now, I’ve raised your membership level.

7

This is the schema I was talking about
ciruit_scheme.pdf (78.2 KB)

8

I cannot see an operational amplifier there to give a low impedance voltage source for the mid-point bias supply (ref_medida). I think you might have a problem with the signal on one channel also appearing at a low amplitude on the others.

9

Yes, that’s my concern and that’s why I’m testing the previous circuit but, in the tests I’m doing, the input signal from a CT has no influence on the others.
An operational circuit would be safer but if there really is no difference it does not make sense.

Thank you very much for your support.