How To Use An Angle Position Sensor
An angle position sensor, also known as a rotary encoder, converts the angular setting of a shaft into an electrical signal for input. One common use is to detect the settings of a knob on an electrical component, such as the station control on an FM radio.
The encoded signal can be either analog or digital. The sensor itself can be either single turn or multiple-turn. A single turn sensor will return a value according to the absolute position of the shaft. In contrast, a multiple-turn sensor will return a value relative to the starting position, in other words, a distance. In addition, by detecting the rotation time, the sensor can also provide a rotational speed.
These types of sensors see many uses including robotics, computer mice, industrial controls, stress rheometers, and rotating radar installations.
Angle Position Sensor Specifications
Sensors are generally buffered electrically, so that they act like either switches for digital outputs, or variable resistors, for analog outputs. Circuit designers can interface to the sensors by providing a voltage source and a voltage level detector. The electronic properties of each type of transducer are standardized, so specifying the electrical portion of the sensor is generally straightforward. It is simply chosen to match the input device, whether it be a microprocessor or a detector circuit.
Designers will generally choose a rotary encoder based mainly on the mechanical properties. The shaft sizes are standard, but the other properties of the shaft can be chosen to present a range of interfaces to the user. For instance, one type of shaft rotates smoothly while another type return clicks as it is spun. The clicks do nothing electrically, but they do give the user tactile feedback to give a stronger impression to the user that he or she is actually doing something with their knob turn. Another example is the use of the angular velocity measurement, which can be used to allow the user to accelerate the adjustment outputs when the knob is turned faster.
The application notes of each type of angle position sensor can help the designer with further details.
