I have created a custom board which has a small on-board dedicated voltage transform for measuring the incoming AC voltage.
I based my circuit:
on this part of the EmonPi circuit diagram:
But having now read this page in the Learn section whilst calculating my resistor values, I notice that the circuit shown there:
seems to be different. I am now wondering which is correct, or are they functionally equivelent?
Don’t you think that in all the years that the emonPi and the emonTx (which the arrangement used in the ‘Learn’ article) have been in production and in use, somebody might have noticed if either or both were wrong?
Why don’t you analyse the two and compare what you get at the ADC input in the two cases?
Thanks Robert, I’ll look into it further. It was just that one shows the secondary connected directly to GND, but the other one doesn’t that threw me.
Both are connected to a ground, in one case it’s a solid d.c.& a.c. ground, in the other, it’s a.c. only.
