Proximity & Presence Sensors

 These sensors are able to detect the presence (or absence) of objects, without actually touching them. The type of technology used depends on the application – what it needs to detect, how it needs to detect it, and what the range (nominal range) could potentially be For example to be able to detect metal objects within close proximity you could use an inductive sensor, but this would be ineffective with any plastic objects … for those you could potentially use a capacitive sensor.
The different types include:
  • Capacitive
  • Capacitive displacement sensor
  • Doppler effect (sensor based on effect)
  • Eddy-current
  • Inductive
  • Laser rangefinder
  • Magnetic, including Magnetic proximity fuse
  • Passive optical (such as charge-coupled devices)
  • Passive thermal infrared
  • Photocell (reflective)
  • Radar
  • Reflection of ionising radiation
  • Sonar (typically active or passive)
  • Ultrasonic sensor (sonar which runs in air).


An inductive sensor video from Baluff …

Condition Sensors

These sensors typically include systems to ensure machinery is operating within its “ideal” operating conditions. They inform operators / systems of the conditions so that preventative maintenance or procedures can be carried out to avoid machine failure. These typically include:
  • Pressure Sensors
  • Temperature Sensors
  • Level Sensors
  • Flow switches
  • Rotation Switches
  • Speed Sensing Switches
  • HVAC Sensors

Measurement Sensors

Typically, the most common sensors available measure:
  • Temperature
  • Strain
  • Sound
  • Vibration
  • Position and Displacement
  • Pressure
  • Force
There are various sensors that can deliver results within each category, a good explanation of the various types can be found in this National Instruments White Paper