hi every one,
I am trying to measure weight using loadcell, op-amp (op177), a low pass filter and icl7660 (4.5 digits)connected to 8051 (At89C52).
I made STAR (seperate)ground, VCC connections to all chips from supply to reduce noice.
i placed 104pf accross all chips power supply. 0.1mf accross power supplies of op177.
Amplified signal from op-amp at dead weight is AROUND 200mv.

Now the problem that has been dragging for about 2 weeks is that output of ADC is different most of the times when power is turned on after a gap of 1 hour. The deviation is about +1 to -1 units of ADC value maximum.

The output of loadcell voltage seems to be constant (trusting my multimeter at really low voltages!!). Output of op-amp is not same when the power is supplied next time.

I need to make ADC output same at dead weight each time the system is powered on.

waiting for ur comments

ramesh