Construction & Working Principle of Sensors & Transducer

In today's electronics world we have 3 types of devices. We can say this is the origin of all electronic devices and equipment they are namely the Resistor, Capacitor, and Inductor, here our Transducer working principle depends on these 3 electronic elements. Now we will see how our transducers work on these elements and what is the mechanism behind this. 

Resistive Transducer: here we can understand the resistive transducer with the help simple resistive formula, and here we can say that " The resistance of conductive rod is directly proportional to its length and  inversely proportional to its cross-sectional area, so we would say that the resistance of conductor change with change in its length and cross-sectional area
R= ρL/A

L is the length of the conductive rod 
A is the cross-section area of the conductive rod
ρ Resistivity 
R is the resistance of the Conductive rod
so here we can consider our conductive rod as the transducer and the change in the environmental cause 
change in length, area, and resistivity of the transducer, we can use a resistive transducer to measure the temperature, displacement, pressure, and force.

Capacitance principle-based transducer: In this capacitive principle-based transducer, the capacitance of the transducer change due to a change in the physical quantity, the capacitor-based transducer is made of two conducting parallel metal plates separated by a dielectric medium, here we can understand the capacitive transducer with the help of simple capacitive formula.

C=\frac{\in A}d

ϵ is the permittivity of the medium,
A is the area of the plates
d is the distance between two plates.

The capacitance between these two plates is


Where C is the capacitance and
f is the frequency of excitation.

The capacitance between two plates can be varied by a change in physical quantity and this can change the various  parameter of the capacitive transducers

we can also measure the physical parameter using the

  1. change the distance between two plates (d)

  2. change the permittivity of the dielectric medium (ϵ)

  3. change the area of overlapping plates (A)

the capacitive-based transducer can use to measure the Force, Displacement, Level, etc.

Piezoelectric principle-based transducer: piezoelectric is a transducer which use to measure physical quantities like Stress, pressure, force, and Displacement which can not measure directly it is an electroacoustic transducer that converts the pressure or mechanical stress into another electrical force or signal.

Pierre & Jacques curie has discovered the piezoelectric effect, the piezoelectric transducer work on the principle of the piezoelectric effect, the principles state that when mechanical force or stress is directly applied to a quartz crystal of transducer so due to electrical phenomena its generate some electrical charges on the quartz crystal surface. The mechanical force or stress is directly proportional to the rate of change in electrical charge on the quartz crystal surface, when the mechanical force or stress is more than the voltage will also become more.
the piezoelectric transducer can also perform a reverse operation it can convert the electrical signal into mechanical displacement or force too.

Hall effect Principle base Transducers

The hall effect based transducer is used to measure the magnetic field by converting it into the Emf. so we can not measure or determine the straight of the magnetic field directly so for this purpose we use the hall effect transducer . and this transducer typically converts the magnetic field into electrical quantity like voltage and current and we can measure this electrical quantity into analog and digital form as well.

The principle of the Hall effect transducers is that if we place a current-carrying strip in the crosswise magnetic field so the EMF will be generated in that current-carrying conductor. Some voltage will be developed on the conductor edge, the magnitude of the developed voltage or emf depends on the density of flux or magnetic field, and this all phenomena or conductor is called the hall effect, The hall effect factor is mainly used for magnetic determination and for sensing the current, the hall effect phenomena of any metal and semiconductors depend on their densities and electrons mobility. 

Selection criteria of transducers

  • Principle of operation:- Transducer must be working on the resistor, Capacitor, and Inductor mechanism so that we can easily measure any physical parameter

  • Availability:- Transducer should be available on the local market so in the case of failure of any component of transducer we can easily import it from the market.

  • Cost:- Cost of a transducer must be below as much as possible so any industry and person can purchase it for their use like automation and processing.

  • Sensitivity:- sensitivity of the transducer must be very high so that it can sense any small variation in any physical or mechanical parameter

  • Accuracy:- Accuracy of the transducer should be high as possible and as per our requirement

  • Operating range:- operating range of the transducer must be high and it should be our requirement

  • Loading effect:- The transducer input impedance must be high and output impedance must be as must as low so that it can easily reduce or avoid the loading effect

  • Error:- Error of transducer must be low or less and their output must be very high and accurate