I have this problem on my application using AD623. Somehow, the output of AD623 becoming fluctuating after the power turned off and then on again after next 9 hours. It is a simple application actually. I use two divider circuits of thermistor and resistor. Then i meassure the drop voltage difference between the two circuits. I use 200Ohm and 10K divider circuits. The ground return is using the 200 ohm resistor. Then i put 2.5V reference for the AD623 op-amp. I use 5 VDC supply for the divider circuits and also for the AD623.
When this problem is happening, i have already measured with my oscilloscope, the signal from divider voltage circuits is stable. Only that the output showing fluctuation voltage. Please help how to remedy this problem or how to avoid this problem on the future.