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Mains voltage data logger with instrumentation op amp

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The attached is our mains voltage data logger. The INA126 is an instrumentation op amp.

There is a loop of current involving the 1MEG input resistances of the IN AMP that must go through the primary of the small mains transformer. This is a relatively large loop of current. Do you think that this will cause noise issues?

If the secondary ground of our schematic was earthed, there would be another loop of current for the current in the R6 (1MEG) resistor which involves going through earth and back into neutral at the point where earth and neutral are connected……this current loop would then go through the secondary of the supply distribution transformer……this is a massive loop of current.

Presumably the secondary of our schematic should not be earthed? If it was earthed then I don’t think the IN Amp would be accurate?

INA126 datasheet


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