voltage sensig circuit for energy meter

[lok]

Hai all,


Iam started to doing an energy meter with ade7763 .....In the application note of the ade7763; they recommend a circuit for voltage sensing...which is a resistor divider network; one end of the divider network is connected to live(phase) and the other is connected to ground/common..It is worked fine when I connected the circuit with live and earth(ground).....
but still Iam doubted that Are they show the circuit ground is "earth connection" of my home wiring???

 

[FvM]

Not sure which application note document you'rew referring to.

Using a voltage divider interface for voltage sensing usually involves that the ADE7763 circuit ground is directly tied to mains neutral. Neutral isn't necessary at earth potential. In safety regards, it must be treated like a hot mains wire. All ADE7763 interfaces to external circuits and display/control elements must have safe isolation.

 

[brushhead]

I would be tempted to use a voltage transducer. That will give you galvanic isolation from the mains. LEM do something that may be suitable. Suggest you use that until you are sure you know what you're doing. Mains is lethal (no really).

Rob.

 

[lok]

Iam reffering this document - https://www.analog.com/media/en/technical-documentation/evaluation-documentation/ADE7763EB.pdf

In the voltage sensing section a Jumper (JP10) is connected to ground...Is that one is digital ground?

 

[FvM]

JP10 is connecting mains neutral to the ADE7763 circuit ground, which is common analog and digital ground.

The evaluation board PC interface has optical isolation, the clearance and creepage distances are however not meeting safety standards.

I would be tempted to use a voltage transducer. That will give you galvanic isolation from the mains. LEM do something that may be suitable. Suggest you use that until you are sure you know what you're doing. Mains is lethal (no really).

The problem is that a real energy meter circuit will use voltage dividers both for cost and accuracy reasons. But it can't be tested safely without special means, e.g. safety transformers. Similar problems arise when testing off-mains SMPS. There's no simple solution for this problem. In a student lab, I would probably modify the evaluation board to use low voltage (e.g. 24V) AC.

 

[lok]

when I connect the phase to neutral with a resistance divider network the wave form seem to not a clear sine wave as I early connected to ground...Is the signal is like distorted??

 

[Vbase]

The datasheet shows that you have to connect V2N to Neutral, and Live to V2P via attenuator off 2 X 255K and 1K to AGND.
The distortion could be because of the board filtering.