What is a sensor?

A sensor is a device that measures a physical quantity and converts it into a ‘signal’ which can be read by an observer or by an instrument. For example, a mercury thermometer converts the measured temperature into the expansion and contraction of a liquid which can be read on a calibrated glass tube. Video cameras and a digital cameras have an image sensor.

In the broadest definition, a sensor is an object whose purpose is to detect events or changes in its environment and sends the information to the computer which then tells the actuator (output devices) to provide the corresponding output. A sensor is a device that converts real world data (Analog) into data that a computer can understand using ADC (Analog to Digital converter).

Sensors are used in everyday objects such as touch-sensitive elevator buttons (tactile sensor) and lamps which dim or brighten by touching the base, besides innumerable applications of which most people are never aware. With advances in micromachinery and easy-to-use micro controller platforms, the uses of sensors have expanded beyond the most traditional fields of temperature, pressure or flow measurement, for example into MARG sensors. Moreover, analog sensors such as potentiometers and force-sensing resistors are still widely used. Applications include manufacturing and machinery, airplanes and aerospace, cars, medicine, robotics and many other aspects of our day-to-day life.

A sensor’s sensitivity indicates how much the sensor’s output changes when the input quantity being measured changes. For instance, if the mercury in a thermometer moves 1 cm when the temperature changes by 1 °C, the sensitivity is 1 cm/°C (it is basically the slope Dy/Dx assuming a linear characteristic). Some sensors can also affect what they measure; for instance, a room temperature thermometer inserted into a hot cup of liquid cools the liquid while the liquid heats the thermometer. Sensors need to be designed to have a small effect on what is measured; making the sensor smaller often improves this and may introduce other advantages. Technological progress allows more and more sensors to be manufactured on a microscopic scale as microsensors using MEMS technology. In most cases, a microsensor reaches a significantly higher speed and sensitivity compared with macroscopic approaches.

Types of Sensors

  • Photo electric sensors (Diffuse, retro-reflective, emitter-receiver, fibre-optic)
  • Ultrasonic sensors (Digital, analog, near and far)
  • Temperature sensors (T-gauge sensor with Teach facility)
  • Register mark sensors (Bulletproof R58 Expert, fibre-optic)
  • Vision inspection systems (iVU Optical Recognition sensor with Teach facility, no PC required)
  • Wireless communication systems (Dataradios, DX70, DX80, digital or analog signals)
  • LED work lights and indicators (Tower lights, multicolour, audio-alarms, working area strip lights)
  • Machine safety solutions (Safety curtains, controllers, relays, door and hinge-switches)

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