In this u will study about
1.Working Principle
2.Parameter for CTT
3.Applications (in details)
4.Advantages
5.Disadvantages
of Capacitive Type Transducer
3. Introduction
Moreover, the capacitive transducer or
sensor is nothing but the capacitor with
variable capacitance
“Capacitive type means using capacitance and
transducer means a device that converts variations
in a physical quantity, into an electrical signal”
4. Working principle
The capacitive transducer comprises of two parallel metal plates that are separated
by the material such as air, which is called as the dielectric material. In the
typical capacitor the distance between the two plates is fixed, but in variable
capacitance transducers the distance between the two plates is variable.
5. The capacitanceC between the two plates of capacitive transducers is
given by:
C= (ε0 x εr xA)/ d
Where,
C -The variable capacitance transducer
ε0 - absolute permittivity
εr - relative permittivity
The product of ε0 & εr is also called as the dielectric constant of the
capacitive transducer.
A - area of the plates
D - distance between the plates
6. Changing Area of the Plates of CapacitiveTransducers
Changing Distance between the Plates of Capacitive
Transducers
Changing Dielectric Constant type of Capacitive
Transducers
Parameters for Capacitive
Transducers
7. Application of capacitive
transducer
Capacitive type transducers has wide range of applications in
which s0me of them are:
In Microphones
In Semiconductor Industries
In Detecting Dynamic Motion
8. In Microphones
An increase of distance between the parallel plates will
decrease the capacitance value correspondingly.
This transducer is used to convert the value of displacement
or change in pressure in terms of frequency.
9. • As shown in the figure , A capacitive transducer has a
static plate and a deflected flexible diaphragm with a
dielectric in between.When a force is exerted to the outer
side of the diaphragm the distance between the
diaphragm and the static plate changes.This produces a
capacitance which is measured using an alternating
current bridge or a tank circuit.
• A tank circuit is more preferred because it produces a
change in frequency according to the change in
capacitance.This value of frequency will be
corresponding to the displacement or force given to the
input.
10. Capacitive sensors are used for the precise
positioning of semiconductor down to nanometer
level for exposure in different electrical and
electronic circuits.
Semiconductor industry
11. Capacitive transducers are ideal for the
measurement of dynamics of a continuously
moving target such as rotating spindles or
vibrating element like in disc drive spindles.
Detecting Dynamic Motion
12. Liquid level measurement by changing the
capacitance between two conductive plates.
Capacitors are common force sensors.
Commonly used forThickness measurement in a
noncontact fashion.
13. Advantages
High sensitivity
Can detect upto 10^-14 m displacements
Low power requirement
High resolution
Low cost
Easy to integrate into ICs
14. Disadvantages
Performance is severely effected by dirt and
other contaminants.
The metallic part must be insulated from
each other.
Affected by temperature and humidity
Sensitivity to noise
Difficulties in designing
Non-linearity
