I am using a sensor having high impedance and have been suggested by the manufacturer to use a buffer (unity gain buffer) so that when we measure the values on ADC, they don't vary.
Now i am using LM324 Quadruple Operational Amplifier as a unity gain amplifier using this circuit
and this link page 9 (but not using RL and CL).
Input on the V + of the circuit is 1.37 but the output V out is coming to be 1.41 or 1.42 instead of 1.37. I am not able to find out why this gain is coming and how to resolve this.
Best Answer
If the manufacturer says you need a high impedance buffer, I would assume your act of measuring the voltage is in fact changing the value.
You can test this by one of two methods.
Get two meters, check they give equivalent readings on the output, then connect one to the input while maintaining the other on the output. If the meter is affecting the voltage then both meters should now read close to the same lower voltage.
Disconnect the sensor and apply a low impedance test source. Verify the output now matches the input voltage.