Sensors are often used to detect objects and devices. In response to a specified measurement, a device produces a usable output. A physical parameter is obtained and converted into a signal as a result of the sensor for detecting specific physical properties in any device or material. The sensor's output is a signal that is converted to a human-readable form, such as changes in characteristics, resistance, capacitance, and impedance. A transducer is a device that transfers a signal from one physical structure to another. It transforms one type of energy into another. It could be used as an actuator in a variety of systems.
There are three types of sensors: Indicators, Counters, and Measurements.
Indicators are simple - they are either turned on or off. They indicate when something has occurred, such as when a panel has been opened and accessed.
A counter can record a series of events. A tachometer measures the number of shaft or axle revolutions. Indicators and counters are examples of digital sensors. Their job is to keep track of and report on discrete events. This type of sensor is relatively simple.
Measuring sensors are becoming more sophisticated. A physical entity or an environmental attribute, such as temperature, is reported. Rather than reporting discrete events, continuous scales report where a person is at any given time.