| 摘要 |
<p>PURPOSE:To automatically make diagnosis whether a photo-sensor is acceptable (in its remaining life). CONSTITUTION:A photo-quantity changeover circuit 20A electrically changes over, at least at two stages, the photo-quantity of the light L emitted from a light emitting diode 9A constituting a photo-sensor 11A. The photo-quantity of the light L is so set that one of the stages (in case the movable contact 24A of a switch 21A is in connection with stationary contact 22A) is used in normal operation while the other stage (in case the movable contact 24A of switch 21A is in contact with stationary contact 23A is used at the time of diagnosis, wherein the condition is such that the resistance value R1 of a resistor 18A is smaller than that R2 of a resistor 19A. Therefore, diagnosis whether the photo-sensor 11A is acceptable (in its remaining life) can be done automatically by a system controller 25 from the signal level of output signal Q1A of a photo-transistor 10A when the switch 21A is turned.</p> |
