December 12, 2011
about 2 years ago
When measuring AC current, does it simply give a sine wave output voltage centered on Vcc/2? I didn’t see anything specific in the datasheet about AC input/output, just that the output is above Vcc/2 for positive current and below Vcc/2 for negative current. So that’s why I’m thinking that it just gives me the corresponding sine wave output (again, centered on Vcc/2). If so, has anyone used it with a microcontroller to measure AC current? And if so, how did you rectify the output into a suitable DC voltage for the ADC? I’m guessing the simplest way (which isn’t so simple) is to run the output through an op-amp to stiffen its output impedance (and besides that, I need to amplify the output anyway because I’m measuring fairly low AC current, less than 250mA) with Vcc/2 as one input thereby centering the op-amp’s output signal at ground (the datasheet shows an example of that; also, without split power supply rails, an AC signal into an op-amp would just give me every other “hump” of a half wave output, like one side of a center-tap xformer), possibly cap it to reduce the ripple, and then run that final output into the ADC. The last thing I want to do is bring in split power supply rails just for getting a better rectified AC output. What a mess…
Has anyone does this? I feel the coming pain of lots of testing and screwing around to get this right, so I’m hoping someone’s already done this who’s willing to help a brother out :)
Thanks in advance for any ideas at all! :D
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