Anyone who has heard about position sensors may deduce the meaning directly from what the word ‘position’ implies. Essentially, it is a device that is used to measure the movement or displacement of an object with reference to its initial position. Position sensors can measure linear, angular, or rotary motion. While this may be the simplest description for what a sensor does, it is also important to understand the technology and mechanism that distinguishes a sensor used from one application to another.
Potentiometric position sensor
This type of sensor operates through the resistive effect principle. In a potentiometric linear position sensor, there is a resistivetrack which will serve as the sensing device. This track is coupled with a wiper that is attached to the body of the object of which the movement will be measured. This wiper is connected to both the track and the body of the object.
When the wiper moves along with the object, the resistance of the track with the connecting end to the wiper also changes. This resulting resistance will then become the function of the position of the wiper. The measurement of change per unit in wiper positioninrelation to the change in resistance is the linear motion of the object.
The resistive track can be modified in order to measure angular motion depending on the requirement of the device. One advantage of this type of sensor is that it is easy to use.
Capacitive position sensor
There are two configurations to which capacitive sensors operate under:
- Change in dielectric constant.The dielectric material in between two plates is connected to the body of the device or machine whose movement is going to be measured. As the object moves, the plates will produce a dielectric constant which results from air and dielectric elements.
- Change in overlappingInstead of being connected to the two plates, the object is only connected to one of the plates. There is an area between these plates that overlapsand changes along with the movement of the object. This change will then result in capacitance change between the two plates.
Magnetostrictive Position Sensor
The primary components of this type of sensor are aposition magnet, electronics module, waveguide, and magnetostrictive position sensor that is used to measure the distance between the end of the sensingrod and position magnet.
There are other types of position sensors such as hall-effect based magnetic position sensors and optical position sensors which also use a different mechanism. Each type of sensor is suitable for specific applications but in general, position sensors are applied in the following:
- Machines used in packaging
- Medical equipment
- Aircraft systems
- Other industrial and mechanical machinery
Recent developments in sensing technology have paved the way in developing more compact, and reliable devices that are used in extreme and hazardous conditions such as in mining. In fact, the preference of most industries using position sensors is for contactless sensing devices that are not prone to regular wear and tear, moisture, and friction. Non-contact sensors have a longer life-span and are robust enough for submerged applications.