A rotary encoder (shaft encoder), is a sensor, that is capable of detecting electrical signals in response to the rotational movement of the object it is encoding. The signals are in turn used to control the speed or the position of that mechanical device. The encoder is usually used in conjunction with other conversion devices including linear slides and pinions. These encoders can be used on a variety of precision equipment devices, and those items that do require close control and monitoring of the position and the speeds. Some devices that they are used on include robotics, certain medical devices, testing equipment, and certain assembly machines.
Rotary Encoder Types
There are 2 main types of encoders: incremental encoders and absolute encoders. An incremental encoder is going to generate a series of pulses when it is rotating. The output is then measured in the number of pulses per minute, which are then used to measure the speed, or to keep track of the position of the device that is being measured. An absolute encoder is going to generate the output signals by using digital bits. Each of the bits that are measured are corresponding to a known position; this results in the encoder being able to determine the exact position of the device it is monitoring.
Optical Sensing
An encoder that is run via optical sensing is typically used for applications where a high operating speed and high-resolution is going to be required when the output is read. It is also used when the use of the environment and external factors are taken in to consideration for any read out. Since a higher level of precision is guaranteed, you have to use these encoders when trying to find the position at the highest speeds and levels.
Magnetic encoder
A rotary encoder that uses magnetic sensing capabilities is often used with more resistant environmental factors come in to play (such as the dust, moisture, the vibration in a room, mechanical shock, wind, or other external conditions come in to play). Since it is capable of handling more rugged applications, it is going to provide you a more precise reading than the optical sensor, which is more finely tuned, is going to provide to you.
The parts
The rotary encoder is made up of the disk, sensors, and electronics. The function of each is as follows:
- Disks contain a pattern of fine lines on the external teeth.
- The sensor is mounted on the disk, and reads the external teeth; and,
- The electronics make use of an output device, which receive signals from the sensor, and then convert them in to usable figures, to provide you with the speed that is being monitored by the rotary encoder.
The Technologies
The rotary encoder is going to use either magnetic sensor or optical technologies. With the magnetic sensor encoder a magneto sensor is used, and detects changes in the magnetic fields, as the disk rotates. The changes mark the different angles and positions that the disk moves in. With the optical technologies, a light emitting diode is used; it shines a light through thin glass disks, which have a pattern of lines on the surface. A photo detector is then used to receive the signal, which in turn produces the electrical output.
Use
Since there are quite a few sizes you can choose from when purchasing a rotary encoder, they can be used for different purposes. As they also have different levels of resolution, and different features (which include indicator lights, certain custom disks and sized disks, and improved electronic features), you have to consider the use, and what level of precision is required, in order to choose the right encoder. The speed of the rotation that is required is often the leading factor that you have to keep in mind when trying to select the right encoder, so you do have to keep this in mind as you are trying to find the right product, for any specific use.
Regardless of the desired use, or what you are testing, you have to know what factors to look for, what level of precision you need, and where you are going to use the rotary encoder, in order to ensure you use the right one.
