I have been looking around for some time and haven't found helpful information on how this is done. I am working on a project that intends to send data through the headphone jack to be processed by a smartphone. More specifically, I want to measure the temperature of water using an IR sensor. The voltage of the sensor will be sent to a smartphone where it can be analyzed to tell me what the temperature is. Is this a feasible idea?
I don't know too much about how 3.5mm connectors work on smartphones so links would be helpful as well. I know this is a vague description of the project and I'm just looking for some sources to steer me in the right direction. The project requires the usage of the headphone jack on smartphones so I can't use USB.
Side note: I am a novice undergrad engineer that might be in over his head.