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Original question:

Isolation Amplifier

Isolated high AC voltage measurement + zero crossing detection

Alen Barisic
Intellectual 1300 points
Other Parts Discussed in Thread: AMC3330, ISO224

Hi,

1) a customer is searching for a solution for isolated high AC voltage measurement.

- for 180-770VAC/50-60 Hz, accuracy of +-0.25% needed

Which isolated amplifier would be the best fit for this? Is there any ref design / literature for this?

2) they also need zero crossing detection with <100us delay. Positive zero crossing -> negative  flank, negative zero crossing -> positive flank

I have seen ADS7x28 with zero crossing detection module mentioned in sbaa356.

Could this work in combination with an isolated amplifier?

Thanks,

Alen

  • 0
    TI__Mastermind 47625 points

    Hi Alen,

    1. The AMC3330 is going to be our best fit, as it has a bipolar +/-1V input range, high input impedance, and integrated power supply. As for the accuracy, you can see on the product page under design tools & simulation, an AMC voltage sensing excel calculator that can help the customer calculate their errors. We have several cookbook circuits on the ISO224 and AMC1300B pages that may help as well. 

    Is the accuracy requirement of 0.25% for typical error or worst case?

    What kind of calibration is the customer prepared to do?

    2.  This should work given the 100us requirement, there is a slight propagation delay through the isolated amplifier of approximately 3us which does not use much of the time budget.