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amplify small dc signal sitting on large dc offset

davebullockmbe

Weekend brain teaser?

Hi experts,

I have a sensor that gives a varying dc output with sensed input.

My problem is that the sensor's output has a 'static' dc offset of around 1V d.c. but I need to use the sensor at the low end of it's range meaning that it's output will only swing a couple of millivolts d.c.

The couple of millivolts will then need to be amplified by something like x1000 to fully exercise an arduino ADC.

I am not sure how stable the 'static' dc offset is with time/temperature or how noisy the output is yet as I am just starting to tackle this problem.

Initially I am thinking differential amplifier and cancel the unwanted offset with a separate 1V input, but I imagine device dc drift will come into play?

Clearly it would be ideal if the dc offset could be tracked by the cancelling voltage but the 'wanted' dc signal will be cancelled too as they are both pretty static.

Before I spend time inventing the wheel or disappearing down rabbit holes.......

Has anyone solved any similar problems?

Discovered any suitable low drift devices etc.

Thanks in anticipation......

Dave

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  • in reply to jc2048

    Well spotted! I was wondering where was the Vref out like any decent analog sensor should have. The datasheet mentions TR being Vref so it looks perfect.

    It seems some breakout boards for it, like Sparkfun, didn't think of bringing that out to a pin, but it could easily be wired by soldering onto the capacitor if this is a breadboard prototype etc.