What is Position Sensor : Working & Its Applications

The sensor is an essential component in any measurement system because they gather data from the physical parameter or environment and changes into an electrical signal to provide input to the systems. There are different types of sensor available in the market which operates based on different sensing principles and are used in different applications. Among them, position sensor plays a key role in various systems like drive-by-wire cars, injection molding machines, medical equipment, fly-by-wire aircraft systems, bullet trains, packaging machines, etc. So this article discusses an overview of the position sensor and its working with applications.

What is a Position Sensor?

Position sensor definition: It is a sensor that is used to detect the object’s movement & convert it into signals which are suitable for transmission, control, or processing. These sensors are normally used for measuring the distance of the body from the reference position. So it detects how far the body has moved from one position to another and this output is frequently used as feedback to the control system to take appropriate action.

The position sensor working mainly depends on providing motion control, counting & encoding different tasks through determining the existence or nonexistence of a target or otherwise by detecting its speed, direction, distance, or motion.

The specific parameters of a position sensor will define its performance but they may change based on the type of sensor being selected. Some main specifications of position sensors include a range of measurement, accuracy, resolution, linearity, and repeatability.

Position Sensor Types

There are different types of position sensors available in the market which are discussed below.

Capacitive Displacement Sensor

These sensors are non-contact devices, used for measuring any conductive target’s high-resolution of the position & position change. These sensors are also used for measuring the density or thickness of non-conductive materials.

Capacitive displacement sensors are used in different applications like semiconductor processing, precision equipment assembly like measurements of precision thickness, disk drives, assembly line testing & machine tool metrology.

Eddy Current Sensor

Eddy current sensor uses the eddy current formation principle to detect displacement. These types of sensors are used to measure the displacement of the shaft within rotary machines & they offer manufacturers high-speed measurements, high resolution & high linearity.

Eddy current sensors are applicable in harsh industrial environments because of their higher tolerance for dirt, oil, moisture dust, etc. These sensors are available in small & sub-miniature models which can be used mainly for measurement within a space wherever area is limited.

Hall Effect Sensor

A Hall Effect sensor is also known as a Hall sensor, which is used to detect the magnitude & presence of a magnetic field through the Hall Effect. These sensors are applicable in different applications like positioning, proximity sensing, detection of speed & current detecting.

Please refer to this link to know more about Hall Effect Sensor.

Inductive Sensor

An inductive sensor uses the electromagnetic induction principle to sense or measure different objects. Generally, these sensors are used in harsh environments because they are strong & deliver steady signals even in aggressive environments. These sensors are highly reliable and have longer life because they use the contactless principle.

Please refer to this link to know more about Inductive Sensor.

Linear Variable Differential Transformer

The LVDT or linear variable differential transformer is the most frequently used electromechanical sensor. This sensor is mainly used for converting vibrations or mechanical motion, particularly rectilinear motion into electric signals.

Please refer to this link to know more about LVDT.

Potentiometer

Potentiometers are either rotary or linear position sensors that use thermoplastic damped wipers & a resistive track to measure displacement very effectively. Linear type potentiometers measure displacement linearly whereas rotary type measures rotating displacement.

The construction of both the potentiometers is the same where each type includes a wiper & a track or conductive element. But the shape of the track is different in each type of potentiometer. In linear type, the track is straight whereas in rotary type it is circular. The wiper simply moves with the track to determine the displacement through the input voltage.

Cable Extension Transducer

These transducers are linear position sensors that measure large ranges of position by using a spring-loaded spool & a cable. These sensors are compact, so applicable where space is restricted. These are called with different names like string pot, draw-wire sensor, string encoders, or yo-yo pot.

Cable extension transducers are used in different industries for different displacement measuring applications like Telescopic ram, Hoists, handling materials, leveling platform, positioning hydraulic cylinder, controlling crane, equipment in industrial & agriculture, etc

Ultrasonic Sensor

Ultrasonic sensors are one type of position sensor which detects and generates ultrasound energy. These sensors are mainly used for the detection of reliable position & exact continuous measurement of distance for solids, liquids & powders. They send & receive sound signals within the ultrasonic range.

Fiber-Optic Position Sensors

These position sensors utilize an optical fiber through a set of photodetectors which are arranged at every finish of the fiber. These sensors are mainly for the displacement measurement & vibration of objects provides high precision within difficult environments.

Optical Position Sensors

An optical position sensor mainly works through using two principles. So, in the first principle, from an emitter, light transmission can be done to a receiver of the sensor whereas, in the second principle, the signal of emitted light can be reflected from the object being checked & returned to the light source. So, a change within the characteristics is utilized to create information regarding the position of an object.

Magnetostrictive Position Sensors

These sensors are called non-contact linear position sensors which utilize the quick interaction of two magnetic fields to generate a strain signal that moves through a waveguide. The first field is from a magnet that moves along the exterior of the waveguide whereas another field is from the waveguide.

These position sensors provide complete measurements which generate a unique signal for every point through the travel axis. The main benefit of this sensor is, it is non-contact, there is no friction or wear & not affected through vibrations. The main drawback is the dead band on both faces of the sensor, so cannot be decreased to zero.

String Potentiometer

A string potentiometer is one type of position sensor which is used to measure & detect velocity & linear position through a flexible cable & a spool loaded with the spool. Alternate names of this sensor are cable-extension transducer, string pot, yo-yo sensor & draw-wire sensor.

Proximity Sensor

A proximity sensor is a position sensor, used to detect the existence of nearby objects with no physical contact. This sensor frequently generates an electromagnetic radiation signal or an electromagnetic field & seems for changes within the field.

Proximity sensors have high reliability and long functional life due to the lack of mechanical parts & physical contact between the sensor & the object. These sensors are mainly used for monitoring the vibration of a machine to measure the difference within the distance between a shaft & its support bearing.

Position Sensor Circuit Diagram & Working

A common type of position sensor that is used to monitor rotary or linear motion is known as a potentiometer. It is a voltage divider that provides a changeable DC voltage reading for the computer. These types of sensors are normally used to determine the position of the air conditioning unit door, a valve, a seat track, etc. A potentiometer sensor circuit is used to measure the sum of voltage drop to find out the position.

Generally, the potentiometer includes a wire wound resistor including a movable wiper in the center. A stable voltage value like 5 volts is given to the ‘A’ terminal. If the wiper is connected close to the ‘A’ terminal, then the voltage drop will be low, which is denoted through a high voltage signal back to the computer throughout the ‘B’ terminal. When the wiper moves in the direction of the ‘С’ terminal, then the sensor voltage signal toward the ‘В’ terminal will be decreased.

Here, the computer interprets various voltage values into various shaft positions. Once the wiper moves across the resistor, then the unit position can be tracked through the computer. Since voltage applied must flow throughout the whole resistance, then temperature & other factors do not make incorrect & false sensor signals toward the computer. A rheostat is not precise & its use is limited within computer systems.

Advantages

The advantages of position sensors include the following.

• Potentiometric sensors are Inexpensive & high accurate.
• LVDT or RVDT sensors provide high accuracy & Heavy-duty and are less sensitive to harsh environments.
• Optical sensors are highly accurate and have high resolution.
• Magnetic & Hall effect sensors are less sensitive to liquid and heavy-duty.
• The magnetostrictive sensor is accurate especially for long lengths and heavy-duty.

Disadvantages

The disadvantages of position sensors include the following.

• Potentiometric sensors are sensitive to dust, extreme temperatures, high wear & tear.
• LVDT or RVDT is expensive, heavy & bulky.
• Optical type sensors are sensitive to dust, temperatures, and delicate.
• Magnetic & Hall effect sensors are responsive to impact, interrupted through electrical wires, magnetic materials & Hysteresis.
• Magnetostrictive type sensors are sensitive to changes in temperature, lack of accuracy for small lengths & expensive

Where are Position Sensors Used/Applications?

The applications of position sensors include the following.

• These sensors are essential devices to measure rotary or linear positions.
• These sensors are used where measurement of movement is required.
• These sensors are used in different industries like Automotive, Hydraulics, Motorsport, medical, Mobile Vehicle, Aerospace, etc.
• Some of the other applications mainly include medical equipment, packaging machines, Drive-by-wire cars, Fly-by-wire aircraft systems, Injection molding machines, etc.

What type of devices are engine position sensors?

Engine position sensors are a particular type of sensor that provides information regarding the present state of your automobile. The most frequently used engine position sensor is the crack sensor.

What is a potentiometer position sensor?

A potentiometer position sensor is used to measure the displacement of an object within any direction & convert it into an electrical signal.

What are the symptoms of a bad crankshaft position sensor?

Bad crankshaft position sensor symptoms are Uneven acceleration, issues while starting the vehicle, intermittent Stalling, engine vibrates or misfires, gas mileage can be reduced, etc.

Is a potentiometer a contact type position sensor?

Potentiometers are mainly involved in physical contact through the object being detected. So, these are known as contact position sensors.

When would you use a potentiometer as a position sensor?

The potentiometer can be used as a position sensor where displacement needs to be measured in any direction. So, it is used as a position sensor by connecting the moveable object to the rotational shaft/slider of the potentiometer directly.

Thus, this is all about an overview of a position sensor, working, types, and its applications. The considerations while selecting a position sensor mainly include size, weight, the information provided by the sensor like incremental or absolute, range of operating temperature, accuracy, environment, time for response, ease of installation, initial cost, etc. Here is a question for you, what is RVDT?