Channraingsey Yek
ET 360 Instrumentation
October 20, 2013
Experiment 5: Optocoupler
Objective
To get familiar with the optoisolator, which is a hybrid integrated circuit that contains an LED on one side and a photodetector on the other. A low-voltage circuit is used to energize the LED, and the light from the LED is then optically coupled to the detector, which is used to control a secondary circuit. In this exercise, we will use an ohmmeter to determine the condition of the optoisolator. Observe the operation of an optocoupler, and determine the maximum frequency response of the optocoupler. 
Procedure

Optoisolator Output

	
			          
	                                LED ON/OF Condition

At 100 Hz, the output of the transistor is ideal to the perfect square wave.
As the frequency increases more and more, distortion will appear until 
at the point that is no longer acceptable. 

 
  At 1 kHz, there appear to be distortion that is about 3/4 VP. This is the maximum 
  frequency rating for a square wave signal that is applied to its input. Beyond the 
  maximum frequency, the output signal cannot reach a good on or off level before
  the input signal is switched. An acceptable output signal should reach at least 3/4
  of its maximum signal.

   Here is an example of an unacceptable output where the output signal is 
   less than 3/4 of its maximum signal. Here, the frequency is 15 kHz.

            Optocoupler Circuit in MultiSim
Conclusion
Optocoupler is a very unique electronic device that can control the secondary circuit optically. There is no direct contact between the LED and the transistor. Hence, the secondary device is protected if the LED circuit is damaged .