POSITION SENSOR: INCREMENTAL OPTICAL ENCODER

INCREMENTAL OPTICAL ENCODER

it is also a device which can convert the rotational or linear position into the electric signals.incremental optical encoder also used to detect the position of the shaft. 

 

DIFFERENCE BETWEEN  ABSOLUTE ENCODER & INCREMENTAL OPTICAL ENCODER

1. the output of the  absolute encoder indicates the current position of the shaft but the output of the incremental encoders gives the information about the motion of the shaft.

2.absolute encoder have an unique position whereas in incremental encoder position is determined by counting the pulses from the zero reference.


3. absolute encoder are more complex then the incremental encoder.


4.incremental encoder outputs the pulse corresponding  to the rotation angle by code only when in rotation condition. absolute encoder signal of position corresponding to the rotation angle by code.the absolute position from the starting point is measured by the output code data.

 

CONSTRUCTION AND WORKING OF THE INCREMENTAL OPTICAL ENCODER

 
the basic construction of the incremental encoder is shown in fig.
 
there is a disk which is mounted on the shaft. disk can rotates. the periphery of the disk of coded light and dark patterns. these coded patterns have alternative features of opaque and transparent. the photodetectors are placed outside the periphery of the disk.these photo detectors are displaced by 90 degree angle. 
 
 
 



As the disk starts to rotates the light is propagates through the transparent code and received by the photo detectors . these photo detectors generates the electric signal accordingly. in this case pulse is not a square type but it may be in the form of sine and cosine. it is require to place a comparator to change it in the form of square wave.
                        Here you can see their are two channels A & B. you can also see their output signals.signal of channel  B is lagged by A at an angle of 90 degrees. this notation is useful to check or the direction of the rotation of the shaft.

 

 

Leave a Reply

Your email address will not be published. Required fields are marked *