Image forming apparatus capable of calculating surface potential of image carrier based on development current

An image forming apparatus comprising:

• an image carrier that allows an electrostatic latent image to be formed on a surface thereof;
• a charging device that charges the image carrier;
• a developing device that supplies a toner on the image carrier and develops the electrostatic latent image formed on the image carrier to form a toner image;
• a transfer device that transfers the toner image formed by the developing device to a recording medium;
• a development power supply that applies a predetermined bias voltage to the developing device;
• a current measurement device that measures a development current flowing through the developing device;
• and
• a processor that executes a control program to function as:
• (i) a calculator that calculates a surface potential of the image carrier based on the development current measured by the current measurement device;
• and
• (ii) a controller that controls the charging device, the developing device, the transfer device, and the development power supply,
• the controller setting a tentative transfer current to be flowed through the transfer device while the calculator calculates the surface potential.