What is the difference between sensor and transducer ?
Sensors and transducers are foundational components in many technological systems, from smart devices to industrial equipment. Though often used interchangeably, sensors and transducers serve distinct functions. A sensor detects changes in the environment, such as temperature or light, while a transducer converts these detected signals into readable outputs. Let us understand what is the difference between sensor and transducer exploring their working principles, roles and common applications.
In a common terms, sensor is basically a device which detects change in physical parameters and converts it into a signal which can be recorder or measured. For example, Thermistor which senses the change in temperature and converts it into resistance change.
The transducer is a device which converts energy in primary form into corresponding energy signal in the different form. the primary forms of energy include mechanical, electromagnetic, thermal, chemical, optical and more. As shown in the figure-1, transducer composed of a sensor and an actuator. As depicted microphone is the sensor which converts acoustic signal into electrical form which is being amplified and fed to the loudspeaker which converts electrical signal back to acoustic waves. Here louspeaker is a actuator which generates signal or the stimulus. Sensor basically detects or measures a signal or stimulus.
As we know world is moving towards having automation in all the industries including our home. Due to boom in the wireless standard compliant devices based on WiFi, Zigbee and Bluetooth home automation has become reality. Home automation relies heavily on sensors of various kinds such as proximity sensor or motion sensor, liquid level sensor, smoke sensor, magnetic sensor, temperature sensor, light sensor and more.
Types of Transducers and sensors
There are two types of transducers viz. passive transducer and self generating transducer.
Passive one requires external power source. For example condenser microphone mentioned in the figure-1 is of passive type.
The output of the passive transducer is measure of variation of parameters such as capacitance and resistance.
The self generating transducer do not need external power to function.
They will produce current or voltage due to stimulation of some physical form of energy.
Thermocouple is self generating type of transducer.
Sensors types are categorized based on the material and functionalities. Sensors are either organic or inorganic. Ogranic sensors are made of materials such as insulator, liquid, gas or plasma etc. Inorganic sensors are made of conductor, semiconductor or biological substances. Based on detection mechanism used in the sensors they are of various types. These include Biological sensor, chemical sensor, physical sensor, temperature sensor, electric or magnetic sensor, light sensor, radioactive sensor etc.
Physical sensors will have following conversion phenomena:
• Thermoelectric
• Photoelectric
• Photomagnetic
• Magnetoelectric
• Electromagnetic
• Thermoelastic
• Electroelastic
• Thermomagnetic
• Thermooptic
• Photoelastic
Chemical sensors will have conversion phenomena such as chemical transformation, physical transformation, electrochemical process, spectroscopy etc. Similarly biological sensors will have biochemical transformation, physical transformation, effect on test organism, spectroscopy and more.
Difference between sensor and transducer
Following table lists out differences between sensor and transducer.
| Parameters | Sensor | Transducer |
|---|---|---|
| Function | It converts physical quantity to electrical signal. | It converts one form of energy to another form of energy. |
| Output | Electrical signal (e.g. voltage or current) | Various outputs (e.g. electrical, optical, mechanical) |
| Sensing mechanism | Utilize specific physical change or property for detection | Serve as primary sensing element in a system |
| Signal processing | Requires for accurate measurement | May require less as it often directly produces desired output. |
| Output range | Typically has limited output range | It can vary based on application |
| Calibration | It requires calibration for accuracy | It may require calibration depending on use |
| Complexity | Generally simple in structure and function | May be more complex due to energy conversion |
| Cost | Can be cost effective for basic measurements | Cost may vary widely based on complexity |
| Usage | Often used in measurement and control systems | Used in various applications including sensing, measurement and actuation |
| Examples | Temperature sensor, pressure sensor | Microphone, loudspeaker, light sensor |
Selection Parameters and Vendors
Following are the typical specifications of sensors to be considered before purchase:
• Sensitivity
• Stimulus range (span)
• Stability (short and long term)
• Resolution
• Accuracy
• Selectivity
• Speed of response
• Environmental conditions
• Overload characteristics
• Linearity
• Hysteresis
• Dead band
• Operating life
• Output format
• Cost
• size
• weight
The reputed manufacturers of sensors and transducers are Silicon Labs, Analog Devices and more. Refer IoT Sensors and IoT components pages for IoT compliant sensors and various IoT components and manufacturers.
Conclusion
In summary, sensors and transducers are crucial for detecting and translating physical signals into useful data across a range of applications. While sensors focus on sensing environmental changes, transducers convert these signals into usable electrical forms. Recognizing the unique roles of each helps in designing efficient systems, from IoT applications to industrial automation. As technology evolves, sensors and transducers will continue to be at the core of data driven innovations across industries.