what is linear encoder?
Hello everyone,
A linear encoder is a type of sensor that measures linear motion. Linear encoders measure the position and/or speed of machine components or motors moving along a straight path. Measurement results are expressed as digital signals. These encoders are widely used in applications requiring precise position control, especially CNC machines, industrial automation systems and robotic applications.
Linear encoders essentially consist of two main components:
+ Measuring scale: A coded strip or bar provides a regularly marked or divided reference along the path of linear motion. These markings can be encoded using optical, magnetic, capacitive or inductive methods. The scale is the component that determines the system's basic precision.
+ Readhead: The readhead detects the markings or divisions on the measuring scale to determine the amount and direction of movement. As it travels along the scale, it derives position and speed information from the detected markings. This data is sent to the control system to provide precise feedback.
How does a linear encoder measure motion?
As the readhead moves along the scale, the A and B signals change. Reversing the motion also reverses the signal sequence.
25.00 mm
5
25 mm
Right →
A = 1 B = 0
Reading the animation: In this incremental encoder example, one A/B period represents 20 mm, giving a 5 mm step with four-edge counting. The controller calculates position as count × 5 mm. The initial reference is defined as 0 mm. The divisions are enlarged to explain the operating principle; they do not represent the resolution of an actual product.
Linear encoders are divided into two main types according to their measurement method:
+ Absolute linear encoders: They generate a unique code for each position and retain position information after a power interruption. These encoders offer high precision and reliability, but their design is more complex and costly. They are therefore preferred in systems requiring high accuracy.
+ Incremental linear encoders: They measure the position and speed of linear motion by tracking increases or decreases between markings. These models provide simpler and more economical solutions. After a power interruption, however, the system needs to return to its starting point to re-establish the reference position.
One of the main advantages of linear encoders is their non-contact measurement principle. This keeps mechanical wear to a minimum and helps extend system life. Particularly on high-speed servo axes, measurement accuracy is maintained despite vibration or voltage fluctuations.
In my experience, optical linear encoders perform very well when repeatable precision is the priority. If the environment contains dust, oil or metal chips, magnetic or capacitive types are more durable. Selecting the right encoder for each application determines the overall performance of the system.
In the future, linear encoder technologies are expected to work together with smart drives and wireless feedback networks. This could allow the same sensor to monitor not only position, but also parameters such as temperature, vibration and changes in speed.