Lm324 offset my input voltage by appx 0.05v

[kein]

I'm connecting the output of adxl330 accelerometer to lm324 input unity gain configuration non-inverting mode. This is to reduce the impedance of 32k inorder to improve PIC 16f877a internal adc(capacitor) charge up time.
By doing so, my zeroG values goes up by approx. 0.05v.
What is happening?
any help, any other OPAM recommendation.
Thanks

[Fabri]

Hi Kein,
You have to adjust offset of LM324 with trimmer to have 0 volt in output or change it with one lower offset. In any case you can set sero by software to calibrate analog scale.

Regards,
Fabri

[Ttelmah]

You may though be able to get closer without adjustment.
What is the impedance of the accelerometer source at the input pin (resistors in line etc.)?. What are the accuracies of your resistors?.
The offset voltage of op-amps, generally gets noticeably worse, if the impedances feeding the two inputs are not a reasonably close match.

Best Wishes

[kein]

the x,y z impedances are 32k each. These are fed into lm324 +input pins while -inputs are shorted to the output pins by wires. No resistors have been used here.

My vref and Vs(supply voltage) of adxl330 are derived from a voltage regulator max667cpa configured for voltage adjustment giving 3.04v. A resistor value of 1M and 1.5M have been used to adjust the voltage to 3.04v.
Thanks

[Ttelmah]

Put a 33K resistor in the feedback, instead of the direct connection then. It may improve things a little.

Best Wishes

[kein]

I'll try that tomorrow. Cheers