How to Test OPTOCOUPLER?

An opto-isolator contains a source (emitter) of light, almost always a near infrared light-emitting diode (LED), that converts electrical input signal into light, a closed optical channel (also called dielectrical channel, and a photo sensor, which detects incoming light and either generates electric energy directly, or modulates electric current flowing from an external power supply. The sensor can be a photoresistor, a photodiode, a phototransistor, a silicon-controlled rectifier (SCR) or a Triac. Because LEDs can sense light in addition to emitting it,construction of symmetrical, bidirectional opto-isolators is possible.

1. LED ANODE
2. LED CATHODE
3. PHOTO TRANSISTOR COLLECTOR
4. PHOTO TRANSISTOR EMITTER.

(Opto Coupler 6 PIn Type)

optocoupler-4N35-datasheet Click here. photo-interup-datasheet

HOW TEST OPTO-COUPLER WITH DMM—SELECT DIODE MODE IN DMM
OPTO-COUPLER TESTING: 6-PIN TYPE (DMM MEANS (DIGITAL MULTIMETER)

STEP-1: Connect DMM    positive Red test lead to pin-1 (LED ANODE)
Negative black lead to pin-2     (LED CATHODE)
Display reading shows .983v (983 mV)

STEP-2. Connect DMM

Negative Black test lead to pin-1

positive red lead to pin-2

Display reading shows OL
Connect DMM    positive Red test lead to pin-6  (BASE)
Negative black lead to pin-5 = .618V (COLLECTOR)
Negative black lead to pin-4 = .648V (EMITTER)
Display reading shows

STEP-3 .Connect DMM  Negative Black test lead to pin-6
positive red lead to pin-5
positive red lead to pin-4
Display reading shows OL
PIN -3 No connection     (6 PIN TYPE OPTOCOUPLER)

Verification: If the DMM above reading shows the condition is GOOD
Verification:  If you get reading in forward bias as 0000 or OL  or 1, and in reverse bias as 0000 (or) low values the opto coupler can be FAULTY and needs replacement.

(Opto coupler with circuit
Required components:–
1.  R1=470E
2. R2=470E
3. opto=4N35