Need help with reference voltage on AD620 Instrumentational Amplifier

[integralx2]

I am designing a circuit that will measure the muscle motion. The part I am stuck on is the reference voltage pin on the AD620. Should that be grounded, to make the reference 0V ?

 

[mneary]

The reference terminal potential defines the zero output voltage and is especially useful when the load does not share a precise ground with the rest of the system.

You could ground it, or it can be connected to the subject (patient). It will help eliminate errors due to potential differences between the subject and actual ground. If the cable to the subject is shielded, this reference can also be connected there.

 

[integralx2]

You could ground it, or it can be connected to the subject (patient). It will help eliminate errors due to potential differences between the subject and actual ground. If the cable to the subject is shielded, this reference can also be connected there.

What does it really mean when it says zero output voltage ?

 

[mneary]

Actually I had it backwards. If you are sending the result elsewhere, you can send this 'reference' there also and use it as the (-) terminal on any differential input that the following instrument may have. I had to read page 18 (Fig 47, 48, and 49) several times before I understood.

 

[ericgibbs]

I am designing a circuit that will measure the muscle motion. The part I am stuck on is the reference voltage pin on the AD620. Should that be grounded, to make the reference 0V ?

hi,
The REF pin on a Inst OPA should be connected to 0V, if you dont want an OFFSET voltage at the OPA output
If you examine the internal circuit diagram of the AD620 you will see that the REF pin is connected to the non inverting pin [via a resistor] of the final OPA, which typically has a gain of 1.
So if you connect the REF to +1V, the output voltage will be +1V when there is NO input voltage differential at the IAopa inputs.
Any signals that are applied to the IAopa inputs will cause the output to swing about +1V.

Do you follow OK.?