Transducers Technology and Working Principle of the Devices
As properties of the transducer biology, Transducers are the machine which is to be used as energy converter to converts one energy form to another energy form.Another way, the device by which non-electrical input quantity to be converted into electrical quantity is called Electrical Transducer.
The explanation is the based on the INSTRUMENTATION ENGINEERING
BLOCK DIAGRAM OF TRANSDUCERS
From the above image, there are exist two parts Sensing Element and Transduction Element.Non-Electrical input quantity is to be detected & measured by Sensing Element. Transduction Element converts it’s to suitable electrical output quantity.
The transducers with signal conditioning equipment(s) which provide a pure electrical signal at output directly without ripple, noise & other unwanted components are to be said Smart Transducers.
Classification of Transducer OR Types of Transducers and their Applications ( based on the instrumentation engineering ):-
- Primary & Secondary Transducers: Whenever the non-electrical input signal is directly detected and measured by transduction element and the physical phenomenon is to be converted into an electrical signal such transducer is to be said primary transducer.When the non-electrical input signal is sensed by sensing element and this sensor output is to be transformed into suitable electrical signal such transducer is to be said Secondary Transducer.
Ex: The Bourdon tube transfers the input pressure into a displacement, as a primary transducer and the LVDT converts this displacement into an analogous voltage, a secondary transducer.
- Analog & Digital Transducers: Analog Transducers are machines converts non-electrical input signal to electrical output signal which continuous function of time, such LVDT, thermistor, strain gauge, thermocouple. Digital Transducers are devices converts non-electrical input signal to electrical output signal which dis-create function of time OR in Pulse form.Digital signal becoming more popular day by day because it can be transmitted over long distance without distortion due to amplitude variation and phase shift.
- Transducers & Inverse Transducers: Transducers machine converts the non-electrical input signal to electrical energy at the output. Inverse-Transducer is a machine converts electrical input quantity to non-electrical output quantity.
Transducer types based on principles:-
- Capacitive Transducer: It is a passive transducer where applied pressure force between two plates is to be converted into Capacitance.
- Resistive Transducers: It is a passive transducer, If physical properties (Lenght & Cross-Sectional Area) of conductor wire become changes then the resistance of such wire become changes too.
- Inductive Transducer: It is either Active OR Passive transducer.
- In case active transducer, it utilizes basic generator principle.When there is relative motion between magnetic field, the voltage is induced in the conductor. As an example, Tachometer directly converted into speed /velocity into an electrical signal.
- Transducer Classification based on Application of Transducer below:-
- Active Transducers: The transducer device OR transducer machine which could make energy conversion from one form to another form without operating auxiliary external power supply source, meaning it creates its own power supply source during conversion, such transducers are to be said Active Transducer. NOT require external power supply source, so they also are known as self-generating powered transducers.Examples:-
- Photo-Voltaic Cell: When radiates light on p-n junction then as a phenomenon voltage change occurs.This voltage change is to be a measured value of the solar cell or light intensity.The voltmeter is calibrated in terms of light intensity at the output.
- Thermopile: When two dissimilar metals are connected then voltage change across the junction is the measured value of temperature, heat or flow, detected by voltmeter calibrated in terms of temperature, heat or flow’s parameters’ units.
- Piezo-electric transducers: When an external force is applied to quartz crystal then occurs changes in voltage across the surface area.The value of changed voltage is the measurement of sound or vibration.The voltmeter is calibrated in terms of sound or vibration at the output.
- Moving Coil generator: The changes of voltage in a magnetic field is the measurement value of vibration or velocity, detected by voltmeter which is calibrated in terms of velocity.
- Passive Transducers: The transducer machine which strictly required external power supply source during energy conversion from one form to another form, such devices are to be said Passive Transducers. so they are known as externally powered transducers. A simple example of a passive transducer is a device containing a length of wire and a moving contact touching the wire.Selection of transducer is based on accuracy, precision, the speed of response, negligible error factor, the sensitivity of measurement, linearity, hysteresis, threshold, resolution & loading effect.
- Resistance Variation Type: The variation of input electrical resistance in the transducer device system is to be the corresponding measured value of non-electrical parameters (mechanical, thermal, optical etc.) at the output.
Examples: Resistance Strain Gauge, Resistance Thermometer, Thermistor, Resistance Hygrometer, Hot Wire Meter, Photoconductive cell & Potentiometer.
- Capacitance Variation Type: The variation of input electrical capacitance in the transducer device system is to be the corresponding measured value of non-electrical parameters (mechanical, thermal, optical etc.) at the output.
Examples: Dielectric Gauge, Capacitor Microphone,Variable Capacitance pressure gauge.
- Inductance Variation Type: The variation of input electrical inductance in the transducer device system is to be the corresponding measured value of non-electrical parameters (mechanical, thermal, optical etc.) at the output.
Examples: Variable Reluctance Transducers, Differential Transformer,Eddy Current Transducers & Proximity Inductance Transducers etc etc.
- Voltage and Current Variation Type: The variation of magnitude and/or direction of input voltage & current in the transducer system are to be the corresponding measured value of non-electrical parameters (electromagnetic, thermal, optical etc.) at the output.
Examples: Ionisation Chamber, Hall-Effect, and Photo-Emissive cell.
Selection of Transducer:-
- Selection of transducer is based on accuracy, precision, the speed of response, negligible error factor, the sensitivity of measurement, linearity, hysteresis, threshold, resolution & loading effect.
- Selection of transducer is based upon physical quality and quantity of input parameter which need to be measured.
- The principle of the transducer should be excellent compatible with given physical input to be measured.
Additionally, Transducers are also classified based on the method of converting the non-electric signal into electric signal and quantity of electrical signal to be generated at the output.