Part's Required: Multimeter or ohm meter, opto-coupler,100 Ohm resistor,push button,battery or power supply. Now, Connect the multimeter ( X1K Ohm or X10K Ohm ) between emitter and collector like this: red probe to collector and. Using a multimeter, you can perform several tests to assess the functionality of an optocoupler. Each test targets a specific aspect of the optocoupler's operation. An optocoupler tester is a small device that helps verify whether an optocoupler is functioning properly or has failed. An optocoupler is an essential electronic component that transfers signals without a direct electrical connection.