ad620 offset and non liniearity

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Waqas_MicroSolutions

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hi,
I am using ad620 as preamp for a load cell resistive bridge, 20mV max output at 5Vcc.Max Load capability of load cell is 100Kg.
I'm having two Problems, When there is no load, It is still giving 0.968 Volts which unacceptable and supposed to be zero at zero Load on Load Cell..
Secondly,in Proteus simulation output does not become linear until input exceeds 5mV..
In Practical, op amp's output gives nonlinear output at all Physical Loads.
Here is my Proteus simulation results and my implemented circuit is the same.
Thanks in advance

 

First thing to look at is your ground situation. The AD620 refers
the output to an applied ground (not necessarily the input
reference), this pin needs to be within a suitable common mode
range and the output measured relative to it, not the input
reference point. Check your input common mode position,
supplies and output ground for sanity vs the datasheet.

Then, I recommend you look at the inputs with a suitably
high impedance DMM and determine whether it's the
instrumentation amp or its input that accounts for the
"no load error".
 

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