Sensor

Definition

An electrical sensor (also called an electronic sensor) is a device that detects a physical parameter of interest (e.g. heat, light, sound) and converts it into electrical signal that can be measured and used by an electrical or electronic system.

The detected quantity is usually a form of energy that is analog (continuous) in nature and is converted into electrical energy using a transducer (e.g. a microphone is a transducer that converts sound energy into electrical energy).

How Are Sensors Used?

The signal generated at the output of an electrical sensor is typically used for the purpose of making a measurement which can then be used to trigger a subsequent response. For example, a temperature sensor could be used to measure the temperature of a room and convert it into an electrical signal. If the measured room temperature is too low (below a pre-determined threshold) this information could be used by an electronic system that automatically switches on a heater to increase the temperature of the room back towards the pre-determined threshold. Alternatively, if the measurement from the sensor indicates that the room is too hot (above a pre-determined threshold), the system could automatically switch on an air-conditioning unit to reduce the room temperature. The common name for a sensor used to measure temperature is a thermometer.

Nowadays, the output signal from an electrical sensor is usually processed by a digital processor. To make this possible, the continuous analog electrical signal must first be converted into a discrete digital representation using an Analog-to-Digital converter.

Types of Sensors

Apart from heat and sound, electrical sensors can be used to detect and measure other quantities including light, pressure, speed, acceleration, and mass. The size of the signal produced by a sensor depends on the application e.g. Industrial sensors produce electrical signals typically between 20 and 30V while biosensors, used in health and fitness wearables (Figure 1) and which are used to make human body measurements, typically produce electronic signals of only a few millivolts or even smaller.