How Does a Linear Encoder Work

An encoder is a mechanical motion sensor that creates digital signals when there is a motion. Since it is electro-mechanical device, the encoder can provide motion control system users with information concerning direction, velocity and position. When it comes to encoders, there are two different types: linear and rotary encoder, where the linear one responds to motion along a path, while the rotary encoder responds to rotational motion.

Generally speaking, encoders are categorized by the means of their output. Absolute encoders generate unique bit configurations in order to track positions directly, while the incremental encoders generate a train of pulses that can be used to determine both speed and position.

But let's get back to the matter in hand, what is a linear encoder?

A linear encoder is a sensor, reading-head or transducer that is linked to a scale which encodes position. Moreover, the sensor reads the scale and immediately converts position into digital or analog signal which is transformed into a digital readout. The movement on the other hand, is determined from changes in position with time. Both magnetic and optical linear encoder types operate by using this type of method, but they differ by their physical properties.

The Working Principle Of Linear Encoder

With the help of magnetic sensor redhead and a magnetic scale, the linear encoder system produces TTL or analog output for both Channel A and B. Once the magnetic sensor passes through the magnetic scale, the sensor detects that change in magnetic field and outputs a signal which frequency is proportional to the displacement and measuring speed of the sensor.

A linear encoder detects the change in magnetic field, as well as the interference of light, dust, oil and debris, which means they have no effect on this type of system.

The Working Principle Of Optical Linear Encoder

The lens and light source produce a parallel beam of light that goes through four windows of the scanning reticle, which are shifted 90 degrees apart. After that, the light passes through the glass scale and is detected by photosensors, after which the scale transforms the detected light beam while the scanning unit moves. The detected light of the photosensor produces sinusoidal wave outputs, while the linear encoder system combines shifted signals in order to create two symmetrical sinusoidal wave outputs that are 90 degrees out of phase from each other.

The Use Of Encoders

Encoders can be used in different types of applications like packaging, assembly machines, testing machines, CNC machines, motor feedback, medical equipment and so on, that require feedback of velocity, position, distance, etc.