| 摘要 |
<p>PURPOSE:To secure insulation between circuits, and restrain generation of heat by making light from a light emitting device incident on a liquid crystal display on which voltage to be detected is impressed, and receiving transmitted light by a light receiving device. CONSTITUTION:Voltage to be detected is divided by an electric 7 current restricting resistor 4 and a Zener diode 5, and is impressed on a liquid crystal display 1, and the device 1 is turned on. A light emitting part 9 emits pulse light having wave lengths (lambda1 and lambda2), and makes it incident on the device 1 and an optical filter 6 through optical fiber 10. The light incident on the device 1 in an ON condition passes as it is, and in the light incident on the filter 6, only light having a wave length (lambda1) passes, and both and are made incident on a light receiving unit 15 through optical fiber 19. The output signal is separated into pulses having wave lengths (lambda1 and lambda2) by a separator 16, and the pulses having (lambda2) are counted by a detector 17, and when they exceed a prescribed value, it is judged as the voltage to be detected exists. When the pulses having (lambda1) are counted by a detector 18, abnormality of the light emitting part 9, the optical fibers 10 and 19 or the like can be detected.</p> |
