A transducer is a component that converts one type of energy to another for information transfer. Transducers are central to the operation of many electronic devices and can be separated into three categories.

Sensors for Measuring

A sensor is a type of transducer that measures one form of energy and reports it in another, usually a digital or electrical signal such as an analog voltage or current output. The output can be run to a measuring device such as a frequency meter or data logger to measure the incoming energy.

The incoming signal can be from any form of energy including mechanical, magnetic, acoustic or others. Users can make precise measurements of these energies rather than trying to judge them subjectively. Examples of sensors include tachometers, pH probes and photoresistors, thermocouples and transformers.

Sensors can be used to do more than just activate a needle on a gauge. A microphone is a sensor that converts acoustic energy into electrical signals. These signals are transmitted or recorded and turned back into acoustic energy by an actuator.

Actuators for Action

An actuator is a transducer that converts an input, typical electrical, into an output, typically non-electrical. It can be used to convert input signals generated by device controls into actions. The user pushes a button or turns a dial, and the input is translated into concrete tasks.

A very simple example of an actuator is a light bulb. Electrical energy is converted to visible light. Switching the current on and off causes the same change in the light, and current can be varied to dim or brighten the light.

A loudspeaker or transmitter is another common example of an actuator. Electrical signals generated by a microphone sensor are translated into acoustic energy by a loudspeaker or radio waves by a transmitter.

Sensors and Actuators Working Together

Often, electrical or digital signals are intermediaries in a device and both types of transducers are used. A microphone sensor and a loudspeaker actuator are both needed for a public address system or bullhorn. A camera sensor transmits a signal to a CRT actuator, converting visible light to a signal then back to visible light.

Since most modern devices, even very simple ones, are likely to contain a number of transducers it is important to use efficient ones. An inefficient transducer makes an inefficient device and a series of inefficient components multiplies inefficiency geometrically. Typically, a given type of component has a limit to how efficient it can be.

Going back to the example of the light bulb, incandescent bulbs are fundamentally inefficient converters thus the current movements to find more efficient transducers such as fluorescent or LCD bulbs to generate visible light. Devices that incorporate inefficient components may benefit from a redesign that replaces low efficiency elements with high efficiency alternatives.