What is Capacitive Transducer : Principle, Working, Advantages/ Disadvantages Its Applications

Hello readers welcome to a new post in this post we will discuss What is Capacitive Transducer. Capacitor transducer is a transducer type or sensor that operates on the principle of capacitance change.  Different fields such as automotive, and vision, medical devices use these transducers extensively. The design, functioning, benefits, limitations, and uses of capacitive transducers will be explained in this post. Let’s Get started with Capacitive Transducer

Introduction to Capacitive Transducer

A passive transducer that is used for measuring pressure, displacement, and other physical parameters is known as a capacitive transducer. This type of transducer requires more power to work. The working principle of the capacitive transducer is based on variable capacitances. Its capacitance varied due to many causes like overlapping of capacitor plates, distance variation between plates, and dielectric constant.

Capacitive Transducer Construction

This type of transducer comes with two parallel metallic plates that are separated through a dielectric medium such as air, liquid, gas, or any metal. The distance between the two plates of the capacitor is not varied and in the capacitive transducer, it changed. This transducer uses capacitance to vary mechanical motion in the signal. Input varies capacitance and is measured directly with the use of a transducer.

The capacitor measures both fixed and dynamic chacnes. Also, displacement can be measured directly by connecting computable devices to a capacitor variable plate. it operated on two modes such as contacting & non-contacting.

Principle of Operation

capacitive transducer working based on the principle of capacitance changes according to the physical parameter being measured. if an external force such as displacement or pressure is applied to the transducer distance between its conductive plates changes and as a result capacitance changes. Changes in capacitance are directly proportional to the physical quantity measured, that are main point for the operation of the transducer working.

Capacitive Transducer Working Principle

 

What is a Capacitor Polarity – Construction, Its Types, Function & Applications

Capacitance of the Capacitive Transducers

The capacitance C is between two let’s of capacitance transducer is as.

C = εo x εr x A/ d

In this equation, C is capacitance or variable capacitance transducer.

• εo is the absolute permittivity
• εr is the relative permittivity The product of
• εo & εr is also called as the dielectric constant of the capacitive transducer.
• A is the area of the plates
• d is the distance between the plates

From this equation, we know that the capacitance of a capacitive transducer is based on the area of plates and the distance between plates and it varies with a change in the dielectric constant of the dielectric material used.

Based on features that vary capacitance transducer, that are listed here
 Changing Dielectric Constant type of Capacitive Transducers

• In this capacitive transducer, the electrical material in two plates varies due to the capacitance of the transducer also varies. If there is a change in input that has to be measured. value of dielectric constant changes offering variation in capacitance of capacitive transducer. This capacitance-measured input quantity directly provides the value of the measured quantity
• This feature is used to measure the level of the hydrogen container, where a change in the level of hydrogen between two plates casues in variation in the dielectric constant of the capacitance transducer. it also used to measure humidity and air moisture

 Changing Area of the Plates of Capacitive Transducers

• The capacitance of the variable capacitance transducer also varied with the area of the two plates. This is used in the torque meter for measuring torque on the shaft. It comes with a sleeve that has teeth cut axially and a matching shaft tha is like teeth at its periphery.

 Changing Distance between the Plates of Capacitive Transducers

In this capacitive transducer distance between plates is varied, and the area of the plate and dielectric constant is constant. it is a commonly used type of variable capacitance transducer. To measure the displacement of bodies one plate of capacitance trans
For measurement of the displacement of the object, one plate of the capacitance transducer is moved it result in variation in distance between two plates and a change in capacitance. The variated capacitance is measured and its value is found for input that is displaced and kept fixed, while the other is connected to the object. When the object moves, the plate of the
capacitance transducer also moves, this results in a change in the distance between the two plates
and the change in the capacitance. The changed capacitance is measured easily and it is displacement. This principle is also used to measure pressure, acceleration, and velocity.

Types of Capacitive Transducers

Parallel plate transducers:

it is also called a flat capacitive transducer. It has one fixed plate and the other plate is moveable. Due to motion of place distance or area changes that also vary the capacitance value

Cylindrical capacitor transducers: 

The cylindrical capacitive transducer is also used for measuring linear displacement. It comes with two cylindrical electrodes. One cylindrical electrode is fixed and the other cylindrical electrode is movable

Semicircular parallel plate transducers:

This transducer comes with a high value of capacitance when two capacitive plates are overlapped with each other. it is used where high capacitance is needed.

What is a Capacitive Pressure Transducer

Capacitive pressure transducers are used for the conversion of pressure into an electrical signal by measuring variations in capacitance.

This type comes with a sensing component and reference element parted with the diaphragm. When pressure is provided to a diaphragm, it causes deflection that varies the distance between the sensing and reference components, which in turn varies capacitance.

This capacitance change is then transformed into an electrical signal and sent to a data system for processing and analysis.

Capacitive pressure transducers is used in industries, automotive, aviation, and medical devices, that need correct and reliable pressure. It provides high accuracy, stable and linear function, and works for different values of of pressures and temperatures.

Advantages of Capacitive Transducers

• It needs less power for operation
• it is highly sensitive
• Its frequency response is good
• the high impedance at the input
• Use in a stray magnetic field
• It has a high-resolution

Disadvantages of Capacitive Transducers

• A complicated circuit is needed at the output because of the high output impedance.
• For decreasing pickup changes, electrostatic screening must be defined for these devices.
• The change in external parameters such as humidity, and temperature hold capacitance for the transducer.
• Its capacitance can change due to dust and moisture.
• it is temperatue sensitive so many temperature changes can affect operation.
• it has linear operation due to edge effects. So to reduce this effect guard ring is required.
• If the cable is connected to a transducer for measuring small physical changes then causes of error.
• The output impedance of this device is high due to the lower capacitance value that causes the loading effect.

Applications of Capacitive Transducers

Capacitive transducer is used for differnt applications that are explained here

• It used to measure linear and angular displacement with high sensitive level
• It is used for measuring pressure and force. it first changes in linear displacement then the displacement is measured with the use of a transducer.
• it is also used for measuring gauges of levels of volume, density, and liquid. These features are also measured with the use of mechanical modifiers.
• it is used to measure pressure where variation in pressure causes a change in a dielectric medium in two plates of capacitors.
• The dielectric constant gases modify with humidity. As a result, the transducer can measure humidity in gases through the use of variation in capacitance since the change in the principle of dielectric constant.

Read Also:

• What is the Difference Between: Ceramic vs Electrolytic vs Tantalum Capacitors
• What is a Capacitor Polarity – Construction, Its Types, Function & Applications
• What is the Role of Capacitor in a Ceiling Fan?
• Electrolytic Capacitor Symbol, Working, Types, Construction & Uses
• What is Synchronous Condenser (Capacitor)

What is the working principle of a capacitive transducer?

The capacitive transducer’s working principles are based on changes in the capacitor’s capacitance. Change in capacitance can be due to changes in overlapping plate area, changes in distance between plates, and dielectric constant change

Is a capacitive transducer active or passive?

The capacitive transducers a passive transducers that operate on variable capacitance rules. it is used for measuring physical quantities like displacement, pressure, etc.

What are the three types of capacitive transducers?

• Parallel plate capacitive transducers
• Semi-circular capacitive transducers
• Cylindrical capacitive transducers

What is a capacitance transducer used to measure?

Capacitive transducers are used for finding the value of displacement, and pressure. The capacitive transducer  comes with two parallel metallic plates that are parted with dielectric material like air, which is called a dielectric material

 How accurate are capacitive transducers?

Capacitive transducers are best-shorted distance. The value measured is a change in capacitance between the surface of the sensor head and the target surface with the use of a homogenous electric field

 Can capacitive transducers measure both static and dynamic pressures?

The capacitive transducer has a feature to measure both static and dynamic changes. so, they are used for measuring force and pressure.

 Can capacitive transducers be used in harsh environments?

Sensors are simple and can be rugged with stable output, making them best for use in harsh conditions. Capacitive sensors are  tolerant of temporary over-pressure conditions

What are capacitive transducers normally used for?

it is used for dynamic measurements, measure displacement, pressure, etc

Are capacitive transducers sensitive to temperature variations?

All capacitance sensors are affected by changes in capacitance in surrounding conditions. Humidity changes or temperature can affect the operation of sensors or transdcuers .

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