Introduction of Transducer Classification
A transducer is an electronic device that converts energy from one form to another. Common examples include microphones, loudspeakers, thermometers, position and pressure sensors, and antennas. Most transducers convert a nonelectrical physical quantity (such as displacement, force, temperature, light, etc.) to an electrical voltage or current proportional to the magnitude of the physical quantity being measured.
The transducer must be sensitive enough to produce detectable output. Operating Range. The transducer should maintain the range requirements and have a good resolution over its entire range. The rating of the transducer should be sufficient so that it does not break down while working in its specified operating range.
The selection of the proper transducer is an essential factor for ensuring optimum performance in any ultrasonic gauging application. It is necessary to consider the material being measured, the range of thickness that must be covered, part geometry, and part temperature.
In an electric instrumentation system, the functions of a transducer (being the input device) are divided into two types:
Transducer classification
On the basis of energy conversion
- Passive Transducer
- Active Transducer
Passive Transducer
Passive transducers are also classified into different types. It provides help to understand of classification of the transducer and the selection criteria of the transducer.
- Resistive Transducer
- Inductive Transducer
- Capacitive Transducer
Active Transducer
- Thermoelectric Transducer
- Piezoelectric Transducer
- Photo Electric Transducer
There are different types of transducers classified as follows –
Microphone: It is a transducer that converts sound energy into electrical energy.
Solar Cell: It converts light energy into electrical energy.
Quartz Crystal: It converts pressure into electrical energy and the opposite also.
Thermocouple: It converts heat into electrical energy.
Speaker: It is a transducer that converts electrical energy into sound energy.
Thermister: It converts heat into resistance.
Light Dependent Resistor: It converts light into resistance.
Galvanometer: It converts electrical energy into mechanical energy i.e. deflection.
Strain Gauge: It converts strain into electrical energy.
The following factors are to be considered while selecting a transducer for further applications.
Operating range: The range of the transducer should be appropriate for measurement to get a good resolution.
Operating Principle: The transducers are selected on the basis of the operating principle it may be resistive, inductive, capacitive, optical, etc.
Accuracy: The accuracy should be as high as possible or as per the measurement.
Range: The transducer can give good results within its specified range, so select the transducer as per the operating range.
Sensitivity: The transducer should be more sensitive to produce the output or sensitivity should be as per requirement.
Environmental compatibility: The transducer should maintain input and output characteristics for the selected environmental condition.
Loading effect: The transducer’s input impedance should be high and output impedance should be low to avoid the loading effect.
Errors: The error produced by the transducer should be low as possible.
The transducer must be sensitive enough to produce detectable output. Operating Range. The transducer should maintain the range requirements and have a good resolution over its entire range. The rating of the transducer should be sufficient so that it does not break down while working in its specified operating range.
Applications of Transducer
It is used for detecting the movement of muscles which is called an acceleromyograph. The transducer measures the load on the engines. It is used as a sensor for knowing the engine knock. The transducers measure the pressure of the gas and liquid by converting it into an electrical signal.
Transducer frequency is inversely proportional to the depth of penetration of the ultrasound signal into the body and directly proportional to image resolution. The common transducer frequencies for pelvic imaging range from 3.5 to 7.5 MHz.
Transducer design is based on an accurate transducer simulation model such as the electroacoustic KLM transducer equivalent circuit model which is explained in detail in Appendix C. A useful design perspective is that a transducer and/or model has three ports: two acoustic and one electric.