MEASURING METHOD OF TONER CONCN. OF TWO-COMPONENT DEVELOPER AND DEVICE THEREFOR

摘要

PURPOSE:To obtain a method and a device by which a stable measured value of the toner concn. is obtd. by controlling the center line average roughness of the surface of a magnetic bridge system concn. sensor to a specified value or smaller. CONSTITUTION:The center line average roughness of the sensor surface of a measuring device to detect the magnetic permeability of a developer with the magnetic bridge system concn. sensor and to measure the toner concn. is specified to <=0.4mumRa. If the center line average roughness of the sensor surface is larger than 0.4mumRa, the frictional coefft. between the sensor surface and the developer increases and it takes time to obtain smooth flow of the developer on the sensor surface. This makes the initial state of the sensor output unstable and the desired value is not obtd. Therefore, in the developing zone of a copy machine using a two-component developer, a stable measured value of the toner concn. is obtd. by the method and the device to measure the toner concn. using a magnetic bridge system concn. sensor having <=0.4mumRa center line average roughness of the sensor surface.