I'm currently trying to create a pH sensor glass electrode simulator capable of generating a millivolt output that can be read by a pH sensor. I'm not trying to simulate the pH sensor output, rather the input to the electronics on the sensor that read the glass electrode voltage.
Currently I have set up the circuit shown in the diagram above. This circuit has a microcontroller (Arduino at the moment) controlling a DAC (MCP4725) to create a voltage output between 0V and 1V. When reading this on my oscilloscope the DC output is fine, a nice straight line. When I plug it into my pH sensor electronics however, the sensor reads a value that is in the correct range but jumps around by +- 100mV and has an offset.
To compare this to what I want - when I connect the function generator on my oscilloscope to my pH sensor I get the correct mV value the sensor. For example outputting 300mV on the oscilloscope will show a perfect 300mV on the sensor, but doing the same using my uC and DAC will show 300mV +- 100mV noise on the sensor.
Does anyone know how I can stabilise the output of the DAC to the eyes of the sensor?
