An optocoupler or optocoupler consists of an emitter and a photodetector, separated from each other by a layer of air or a transparent insulating substance. They are not electrically connected to each other, which allows the device to be used for galvanic isolation of circuits.
Instructions
Step 1
Connect the measuring circuit to the photodetector of the optocoupler according to its type. If the receiver is a photoresistor, use a regular ohmmeter, and the polarity is not important. When using a photodiode as a receiver, connect a microammeter without a power source (plus to the anode). If the signal is received by an n-p-n phototransistor, connect a circuit consisting of a 2 kilo-ohm resistor, a 3-volt battery and a milliammeter, and connect the battery with a plus to the transistor collector. If the phototransistor has a p-n-p structure, reverse the polarity of the battery connection. To test the photodynistor, make a circuit of a 3 V battery and a 6 V, 20 mA light bulb, connecting it with a plus to the anode of the dinistor.
Step 2
In most optocouplers, the emitter is an LED or an incandescent light bulb. Apply its rated voltage to an incandescent light bulb in any polarity. Alternatively, an alternating voltage can be applied whose rms value is equal to the operating voltage of the lamp. If the emitter is an LED, apply a voltage of 3 V to it through a 1 kΩ resistor (plus to the anode).
Step 3
The optocoupler is operational if, when the emitter is turned on, the readings of the measuring device change, and when it is turned off, the readings become the same as before. The exception is the dinistor optocoupler: after disconnecting the emitter, the photodinistor will be open. To close it, briefly disconnect the power supply to the measuring circuit.
Step 4
After making sure that the optocoupler is working, check its insulation resistance. Disassemble the measuring circuit and then switch the ohmmeter to the most sensitive limit. Connect the test leads of the instrument between the input and output circuits of the optocoupler in all lead combinations and in both polarities. Do not touch the probes with your fingers - an electric shock will not occur, but the readings may be distorted. In all cases, the device should show infinity.
