What temperature instrument should I use to measure the temperature inside the petri dish?

I am currently doing a research if a bacterial cell releases energy as it multiplies such as an atom. I placed the temperature in the y axis and number of bacterial cells in x axis. My goal here is to find out if bacterial cells release some kind of energy (maybe in the form of heat) after dividing through binary fission. I am going to conduct the experimentation by measuring the temperature inside a petri dish(one bacterial cell after another). What temperature instrument should I use for my data to be accurate(not being affected by any other factor)?