What is a position sensor and what are their types

What is a position sensor

A position sensor is a device that can measure the distance a body has moved from its reference and after that, the output will be given to the control system. The motion of the movement can be linear and curvilinear and so that to measure that linear or angular position sensor can be used. Position sensors use different methods to measure the movement of the body. According to these sensing methods these sensors can be classified into contacting or non-contacting position sensors. The contacting sensor will be in contact with the body so that it can measure the linear or angular position. While the non-contacting sensor won’t be in contact with the body and it will measure the linear or angular position.

How do position sensor work

Position sensors are capable to detect the position of an object, the movement of the object can be a straight line or angular so to detect these movements linear or rotational sensors are used. The position of the object will be measured from its reference or from a fixed point.

What are the types of position sensor

Linear variable differential transformer (LVDT)

LVDT is a linear position sensor, and it can measure small movements. LVDT has a single primary winding and two secondary windings. These windings will be wounded on a cylindrical bobbin and it is a non-magnetic insulating material. The secondary windings are placed on either side of the primary winding and the primary winding is connected to an AC source. In the bobbin, there is a movable soft iron core which would help to measure the movement. This method is very accurate and reliable, LVDT is fixed in a place and the ferrous core is attached to the moving element on the piece of equipment for position feedback.


It is a simple device which can be used to measure the position, these are mostly used in robots. It will check the angular and linear position. This device can be constructed by winding a resistive element in a coil configuration. While applying the DC voltage across the entire resistance, the output voltage is proportional to the linear or rotary distance of the sliding contact from the reference point. The potentiometer is a non-optical position sensor.



Synchro is a rotary transducer that can convert angular velocity into an AC voltage or the reverse. This device is made up of certain three-phase components such as control transmitter, control transformer, and control differential transmitter. Most of these components work according to the principle of the rotating transformer. Two or three components measure the angular position.

Optical position sensors


The optical method can be used to measure the distance traveled, and it won’t have problems related to mechanical switches. A transparent disk will be placed between the light emitter and a light receiver or sensor and the transparent disk would have one dark sector. A binary signal is used to detect the endpoint of the travel.

Proximity sensor

The proximity sensors can detect the presence of an object without any point of contact. This device won’t have any contact between the object and the sensor. These sensors have a long life, high reliability. There are many types of proximity sensors such as inductive proximity sensors, capacitive and ultrasonic, photoelectric and hall effect sensors. A proximity sensor emits an electromagnetic field and waits for the return signals or changes in the field.


Resolvers are similar to synchros, they can provide accurate angular and rotational information. They are widely used for factory applications and they are small in size. High accuracy and long term reliability. Absolute position measurement is possible by this, this device can be used for angle measurement and positioning.

Inductive sensors

Inductive sensors have more than one coil with variable inductance. The principle of this sensor is that it influences the quality to be measured by the inductance of the coil. Change in inductance can be measured by using a suitable measuring bridge. Inductive proximity sensors can be used to measure the distance between the sensor and an approaching object and they can be used for distance measurement.

Capacitive sensors

Capacitive sensors can detect the object because of the ability of the object to electrically charge. We can detect the non-conductors by using these sensors because they can also hold the charge. So any object can be detected by using this sensor.