Controlling amount of developer by using output waveform obtained from toner concentration sensor

A non-transitory machine-readable storage medium encoded with instructions executable by a processor, the non-transitory machine-readable storage medium comprising instructions for:

• measuring, using a toner concentration sensor installed in a developing apparatus of an image forming apparatus, a toner concentration of a developer stored in the developing apparatus and obtaining an output waveform corresponding to the toner concentration of the developer;
• calculating, based on the output waveform, a first characteristic value which corresponds to a volume of the developer;
• determining whether to execute a discharge mode for discharging the developer from the developing apparatus based on a comparison of the first characteristic value with a reference value calculated from a reference output waveform;
• and
• when the discharge mode is executed according to a result of the determining, controlling a driving speed of the developing apparatus to discharge a portion of the developer from the developing apparatus.

An image forming apparatus, comprising:

• a developing apparatus comprising a toner concentration sensor to measure a toner concentration of a developer stored in the developing apparatus;
• a driving device to drive the developing apparatus;
• a memory to store instructions;
• and
• a processor to execute the instructions stored in the memory to:
• control the toner concentration sensor to measure the toner concentration of the developer stored in the developing apparatus to obtain an output waveform,
• calculate, based on the output waveform, a first characteristic value which corresponds to a volume of the developer,
• determine whether to execute a discharge mode for discharging the developer from the developing apparatus based on a comparison of the first characteristic value with a reference value calculated from a reference output waveform, and
• when the discharge mode is executed according to a result of the determining, control the driving device so as to control a driving speed of the developing apparatus to discharge a portion of the developer from the developing apparatus.