28-06-2013, 02:24 PM
A REPORT ON ENCODERS
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ABSTRACT
This report describes the principle and working of Rotary and Linear Encoder. These two encoders come in two main types namely Absolute and Incremental Encoder. These encoders are simulated using Labview and those simulations are also part of the report. The Rotary Encoder is used to measure the angular displacement of the shaft and Linear encoder is used to measure Linear displacement. Absolute encoders give absolute position of the shaft or absolute linear displacement, while incremental encoder indicates the direction of motion.
INTRODUCTION
The general definition of encoder is as follows: An encoder is a device, circuit, transducer, software program, algorithm or person that converts information from one format or code to another, for the purposes of standardization, speed, secrecy, security, or saving space by shrinking size. In this report we are discussing about rotary encoder and linear encoder which has to convert the motion to binary code.
Rotary Encoder
A rotary encoder, also called a shaft encoder, is an electro-mechanical device that converts the angular position or motion of a shaft or axle to an analog or digital code. There are two main types: absolute and incremental (relative). The output of absolute encoders indicates the current position of the shaft, making them angle transducers. The output of incremental encoders provides information about the motion (direction) of the shaft, which is typically further processed elsewhere into information such as speed, distance, and position. Rotary encoders are used in many applications that require precise shaft unlimited rotation—including industrial controls, robotics, special purpose photographic lenses, computer input devices (such as opto mechanical mice and trackballs), controlled stress rheometers, and rotating radar platforms.
Linear Encoder
A linear encoder is a sensor, transducer or readhead paired with a scale that encodes position. The sensor reads the scale in order to convert the encoded position into an analog or digital signal, which can then be decoded into position by a digital readout (DRO) or motion controller. The encoder can be either incremental or absolute. Motion can be determined by change in position over time. Linear encoder technologies include optical, magnetic, inductive, capacitive and eddy current. Optical technologies include shadow, self imaging and interferometric. Linear encoders are used in metrology instruments, motion systems and high precision machining tools ranging from digital calipers and coordinate measuring machines to stages, CNC Mills, manufacturing gantry tables and semiconductor stepper.
Absolute and incremental encoders
An "absolute" encoder maintains position information when power is removed from the system. The position of the encoder is available immediately on applying power. The relationship between the encoder value and the physical position of the controlled machinery is set at assembly; the system does not need to return to a calibration point to maintain position accuracy. An "incremental" encoder accurately records changes in position, but does not power up with a fixed relation between encoder state and physical position. Devices controlled by incremental encoders may have to "go home" to a fixed reference point to initialize the position measurement. A multi-turn absolute rotary encoder includes additional code wheels and gears. A high-resolution wheel measures the fractional rotation, and lower-resolution geared code wheels record the number of whole revolutions of the shaft.
[attachment=56162]
ABSTRACT
This report describes the principle and working of Rotary and Linear Encoder. These two encoders come in two main types namely Absolute and Incremental Encoder. These encoders are simulated using Labview and those simulations are also part of the report. The Rotary Encoder is used to measure the angular displacement of the shaft and Linear encoder is used to measure Linear displacement. Absolute encoders give absolute position of the shaft or absolute linear displacement, while incremental encoder indicates the direction of motion.
INTRODUCTION
The general definition of encoder is as follows: An encoder is a device, circuit, transducer, software program, algorithm or person that converts information from one format or code to another, for the purposes of standardization, speed, secrecy, security, or saving space by shrinking size. In this report we are discussing about rotary encoder and linear encoder which has to convert the motion to binary code.
Rotary Encoder
A rotary encoder, also called a shaft encoder, is an electro-mechanical device that converts the angular position or motion of a shaft or axle to an analog or digital code. There are two main types: absolute and incremental (relative). The output of absolute encoders indicates the current position of the shaft, making them angle transducers. The output of incremental encoders provides information about the motion (direction) of the shaft, which is typically further processed elsewhere into information such as speed, distance, and position. Rotary encoders are used in many applications that require precise shaft unlimited rotation—including industrial controls, robotics, special purpose photographic lenses, computer input devices (such as opto mechanical mice and trackballs), controlled stress rheometers, and rotating radar platforms.
Linear Encoder
A linear encoder is a sensor, transducer or readhead paired with a scale that encodes position. The sensor reads the scale in order to convert the encoded position into an analog or digital signal, which can then be decoded into position by a digital readout (DRO) or motion controller. The encoder can be either incremental or absolute. Motion can be determined by change in position over time. Linear encoder technologies include optical, magnetic, inductive, capacitive and eddy current. Optical technologies include shadow, self imaging and interferometric. Linear encoders are used in metrology instruments, motion systems and high precision machining tools ranging from digital calipers and coordinate measuring machines to stages, CNC Mills, manufacturing gantry tables and semiconductor stepper.
Absolute and incremental encoders
An "absolute" encoder maintains position information when power is removed from the system. The position of the encoder is available immediately on applying power. The relationship between the encoder value and the physical position of the controlled machinery is set at assembly; the system does not need to return to a calibration point to maintain position accuracy. An "incremental" encoder accurately records changes in position, but does not power up with a fixed relation between encoder state and physical position. Devices controlled by incremental encoders may have to "go home" to a fixed reference point to initialize the position measurement. A multi-turn absolute rotary encoder includes additional code wheels and gears. A high-resolution wheel measures the fractional rotation, and lower-resolution geared code wheels record the number of whole revolutions of the shaft.