| 摘要 |
PURPOSE:To obtain a detection result the same to that obtained when a sensor part was mounted even when no sensor part is mounted, by connecting the output side terminal of a light receiving transistor to the input terminal of a comparator while earthing the output terminal of a light emitting diode and connecting the same to the reference voltage terminal of a comparator in parallel to the earth. CONSTITUTION:A medium detection apparatus has a sensor part 11 having a light emitting diode 12 and a light receiving transistor 13 and an operation part 14 connected to the sensor part 11 and judging the presence or absence of a medium such as recording paper on the basis of the output from said sensor part 11. The operation part 14 consists of a comparator 15, the resistor circuit R3 adjusting the reference voltage of the comparator 15 and resistor circuits R1-R4 controlling the input voltage of the comparator 15. The resistor circuit R3 is connected between the output side of the diode 12 and earth E and the output side of the diode 12 is connected to the reference voltage terminal of the comparator 15. By this mechanism, a reference voltage value is made variable with the mounting and detachment of the sensor part 11 and different detection results can be obtained with respect to the same input.
|
