What Are Rotary and Linear Encoders?

Rotary and Linear Encoders – The Rotary Encoder: It is a device that encodes, and sometimes decades, position info about the movement of a shaft. Typically these shafts or axles can be turned by hand or with some kind of mechanism such as a motor.

A rotary encoder has 2 parts: The first part is called the “rotating wheel”. It spins freely on its axis and it has 2 pairs of pins. One pin from each pair points to one direction on either side of the wheel’s centerline; they are referred to as “north” & “south”, for example. A 2^nd part is called the “indexing disk”.

What are rotary encoders used for?

Rotary encoders are used in a variety of applications where accurate and repeatable positioning, speed, and direction information is needed. They are used on paper machines as well as in industrial machinery such as conveyor belts, calenders, die cutters, and folding machines.

How do rotary encoders work?

A rotary encoder has two parts: The first part is called the “rotating wheel” (or “rotor”). It has 2 pairs of pins. One pin from each pair points to one direction on either side of the wheel’s centerline; they are referred to as “north” and “south”, for example. The second part is called the “indexing disk”. The indexing disk spins freely on an axis. The indexing disk has two concentric circles that can be made to show two different (or even the same) positions. The positions, called “north” and “south”, have little tabs (or bumps, depending on the type of encoder) that stick out from each circle.

Rotary encoders have a range from 0 to 127 and can be made so that index points line up with each other and are no farther apart than one-fourth of the indexing disk diameter. The miniature versions of rotary encoders (sometimes called micro-rotators) have even finer resolution.

It is possible to use a rotary encoder to tell if two shafts are oriented in the same direction, but this is not very common because it requires more information than logarithmic divisions would need.

How is the output from a rotary encoder used?

Most of the time, the output from a rotary encoder is simply used to tell how far something has turned. Classically, they were used to tell how many times per revolution something turned. In these applications, the fluctuation in signal as the wheel passed through zero often introduced errors into the signal. The output of an encoder can also be interpreted as a frequency or speed signal if it has been filtered properly and is sampled correctly.

What are linear encoders used for?

Linear encoders are used in many different applications. A wide variety of machines and equipment use them extensively. They are common in paper machines, die cutters, press brakes, fold forming machines, and other industrial machinery. Linear optical encoders are very popular for use on automated assembly lines because they can be made so small (even as small as a pencil point).

How do linear encoders work?

A linear encoder is a device that counts the number of times one mechanical object moves past another object. The “encoder” does this by measuring changes in the distance between two points along its shaft (or the diameter of its wheel). The distance changes occur as the object with the encoder moves past the “analog detector” in its path.

Linear encoders have a range of 0 to 255 and can be made so that index points line up with each other and are no farther apart than one-half of the encoder’s shaft diameter. The miniature versions of linear encoders (sometimes called micro-encoders) have even finer resolution.

The output from a linear or optical encoder is usually used to tell how many times per second one object passes another object, but digital signals can also be used for higher speed applications, to tell how long an object has been passing another object.

What are some typical uses of linear encoders?

Linear encoders are used in a variety of applications where accurate and repeatable position information is needed. Some common applications are on automated assembly lines to tell how long an object has been passing by certain points, or to tell how far each part has moved past some reference point.

Other applications include robotics, machine control, and paper machines. For use in machine control, linear encoders can be used as a crash sensor (for example) by using the zero-counts that they produce as the signal that triggers a switch to stop the motion of potentially dangerous equipment. Another application is as a limit switch.

Linear encoders are used in industrial machinery as well as in paper machines. They are also used to tell how far a shaft has turned. The fluctuation in signal as the wheel passes through zero often introduces errors into the signal. A linear encoder can sometimes be used to tell if two shafts are oriented in the same direction, but this is not very common because it requires more information than logarithmic divisions would need.

How are linear encoders used as limit switches?

Linear encoders are used in industrial machinery as well as in paper machines. They are also used to tell how far a shaft has turned. The fluctuation in signal as the wheel passes through zero often introduces errors into the signal. A linear encoder is sometimes used to tell if two shafts are oriented in the same direction, but this is not common because it requires more information than logarithmic divisions would need. Using a linear encoder as a limit switch actually does not require any additional information; it can be done on one output channel of the encoder alone, without reference oscillator or other auxiliary equipment required.

The use of a linear encoder to tell the distance something has moved is almost the same as the use of a rotary encoder. The main difference is that a linear encoder can be made much smaller than a rotary encoder, so it is more often used in small products such as consumer electronic devices, and industrial equipment like machine tools.