The ion current can be divided into three distinct phases:

- Ignition: is the one, influenced by the last phase of the spark and the measurement circuit current itself.

- Chemistry phase: the one where the current is a function of the ions generated during the initial stage of combustion, rupture of the hydrocarbon molecules.

- Thermal phase: the one where the current is a function of the ions generated by the high temperature of the flame front, typically oxides of nitrogen. This stage approximates the shape and characteristics of the cycle of pressure inside the combustion chamber.