Transducers are electric or electronic devices that transform energy from one form to another. For example, a stereo speaker converts the electrical signals of recorded music into sound. Many people think of a transducer as being a complicated, technical device designed to gather or transfer information. In reality, however, anything that converts energy can be considered a transducer.
Sensors and Actuators
There are many different types of transducers, but at their most basic, they can be divided into two groups: input (sensor) and output (actuator). Input transducers take some sort of physical energy — such as sound waves, temperature, or pressure — and converts it into a signal that can be read. A microphone, for example, converts sound waves that strike its diaphragm into an electrical signal that can be transmitted over wires. A pressure sensor turns the physical force being exerted on it into a number or reading that can be easily understood.
Actuators take an electronic signal and convert it into physical energy. A stereo speaker works by transforming the electronic signal of a recording into physical sound waves. Electric motors are another common form of electromechanical transducer, converting electrical energy into mechanical energy to perform a task.
Combining Transducers
Many devices work by combining sensors and actuators to convert energy from one form to another and then back again. Audio cassettes, for example, are created by using a transducer to turn the electrical signal from the microphone pick-up — which converted the sound waves into an electrical signal — into magnetic fluctuations on the tape head. These magnetic fluctuations are then read and converted by another transducer — in this case, the stereo system — to be turned back into an electrical signal. This signal is then fed by wire to speakers, which turn the electrical signal back into audio waves.
Ultrasound imaging also works by converting energy multiple times. A piezoelectric transducer is used to convert electricity into high frequency sound waves (ultrasound), which are focused by the machine and aimed at body tissues. These waves bounce back to the machine, where a transducer converts them into electrical signals again. The signals are processed and sent to a monitor to produce an image of the body tissues.
Other everyday tasks are possible through the use of energy that is transformed multiple times. Turning on an electric light requires electrical energy to be converted into visible light. That electrical energy first had to be generated, however; an electrical generator is a type of transducer that turns mechanical (or kinetic) energy into electricity that can then be used by other devices.
Efficiency
As in all energy conversions, some energy is lost when transducers operate, but some are more efficient than others. A radio antenna, which turns radio frequency power into an electromagnetic field, is one example of an efficient transducer. When the antenna is operating well, this process can be more than 80% efficient. Most electrical motors, by contrast, are less than 50% efficient, while regular incandescent light bulbs, because of the amount of energy that is lost as heat, are less than 10% efficient.