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Isolated sensor to differential amplifier inputs.

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alastair-2010

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Hi,
I want to connect a piezoelectric ultrasonic transducer to the differential inputs of an instrumentation amplifier. I think its easy enough but i'm getting confused when I think about it.

I think of the piezoelectric transducer as an independent voltage source, when it experiences a change in mechanical stress it produces a proportional voltage with respect to the other plate.

If the amplifier is powered from a power source with no reference to the transducer then how can it "see" the signal? I know it will amplify the voltage difference at the inputs but doesn't that have to be relative to the amplifiers power supply?

Will any of the differential circuits work? I think they all will but don't see how!

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Alastair
 

As transducer itself is not referenced to any other voltage, You don't need diferential aplifier. You can use operational amplifier and connect one electrode of transducer to GND and the other to + input. If You use diferential amplifier connect transducer directly to amplifier inputs and also connect one of the inputs to gnd for reference.
 

All circuits with bias resistors will work, without it fail.
 

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