Unambiguous interruption indicating circuitry for output circuit - has LED belonging to opto-coupler having transistor in input current circuit and coupling element for explosion risk area protection

摘要

The circuitry unambiguously indicates an interruption in an output current circuit as a measurement value in an input current circuit. The latter has a measuring arrangement which supplies a process-dependent current to the output circuit via a coupling element. The latter has a Zener diode on both the input and output current sides, the diodes being switched in parallel. The output circuit (1) contains a LED (7) serving as part of an opto-coupler (8). The input circuit (2) is coupled to the output circuit via a transistor (9) serving as part of the opto-coupler and the coupling element (4). A resistor (10) is switched in parallel with the transistor by a push-button (11). An amplifying transistor (12) can be assigned to the transistor. USE/ADVANTAGE - Ensuring that no current capable of causing a spark arises in the output circuit, i.e. current is limited to 4 to 20 mA, to protect area exposed to explosion risk. Fault in output circuit detected with certainty.