Difference Between Sensor and Transducer

Main Difference – Sensor vs. Transducer

In the field of electrical engineering, the terms sensor and transducer both refer to components which convert energy into different forms. The main difference between sensor and transducer is that a transducer is a device that can convert energy from one form to another, whereas a sensor is a device that can detect a physical quantity and convert the data into an electrical signal. Sensors are also a type of transducers.

What is a Sensor

A sensor is a device which detects one form of energy and converts the data to electrical energy. A microphone is a good example. Sound consists of vibrating molecules. Whenever you speak, you set up vibrations in air molecules. A microphone has a membrane which also vibrates, as air molecules collide with it. The membrane is connected to an electrical circuit so that oscillations of the membrane cause the electrical current and voltage in the circuit to vary. In this way, the original sound energy gets converted into electrical energy.

A sensor’s task is complicated by the fact that there is always noise: Noise includes the information that the sensor picks up which is not useful (like a microphone picking up the sound made by air conditioners in a studio). Sometimes, noise can be produced from within the sensors, as well. A signal-to-noise ratio (SNR) is a useful quantity which is used to describe the strength of the desired signal compared to the strength of the noise.

The quality of a sensor depends on how weak a signal it can “pick up”. Minimum discernible signal describes the lowers signal that can be picked up by a sensor. Merely having the ability to register weak signals is not good enough either: the sensor should also have the ability to distinguish that signal from the noise. The term sensitivity describes a sensor’s ability to do this. Resolution of a sensor describes how good the sensor is at differentiating between two different levels of the signal.

What is a Transducer

A transducer is a device which converts one form of energy into another. So sensors are, in fact, a type of transducer. However, transducers also consist of devices that convert energy into other forms, such as actuators. An actuator is something that can convert a different form of energy into motion.

A transceiver is a device that both detects and gives out signals. A good example for this is the ultrasonic transducer used in ultrasound imaging. The device works by sending out high-frequency pulses of sound (called ultrasound because the frequency of this sound is too high for humans to be able to hear it). The sound pulses enter a patient’s body, and as the pulse travels through the patient, a fraction of it gets reflected at boundaries of various organs on its way. The transducer then picks up the reflected signals. Using the time interval and the strength of the reflected signals, an image of the internal organs could be built up.

An ultrasound transceiver used in medical imaging

Difference Between Sensor and Transducer

A microphone is a transducer and a sensor, which converts sound energy to electrical energy. A loudspeaker is a transducer, converting electrical energy to sound energy.

Function

A transducer is a device which converts one form of energy into anther form.

A sensor is a device which detects a physical quantity and produces an electric signal based on the strength of the quantity measured.

Feedback

A sensor merely measures a quantity and cannot, by itself, give feedback to the system.

Since transducers can convert between any forms of energy, they can be used to provide feedback to the system.

Image Courtesy

“ Medical Ultrasound linear array Probe/scan head/transducer. By Daniel W. Rickey 2006” Original uploader was Drickey at en.wikipedia (Transferred from en.wikipedia; transferred to Commons by User:Shizhao using CommonsHelper) [CC BY-SA 2.5], via Wikimedia Commons

“Microphone” by Ernest Duffoo (Own work) [CC BY 2.0], via flickr (Modified)

“Loudspeaker” by Richard King (Own work) [CC BY 2.0], via flickr (Modified)

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