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Position sensors- inductive, capacitive, magnetic, laser, and photo sensors

In typical automation position detection switches are used for all types of applications. Some examples are position sensing, axis limits, motor speed detection, rotary positioning, part detection and more. Proximity switches come in many shapes, sizes, forms and types. This is a general over view showing the most common types of position sensors available and typical applications.

Types of Position detection sensors available

Inductive sensors

Inductive proximity switches detect metallic targets and are generally used for position sensing. Some sensors have the option for an optical setting aid.

Magnetic sensors

Ideal for applications for position detection at high and low speeds applications. Typical maximum sensing range of around 80mm.

Capacitive sensors

Good for position detection of non-metallic targets like plastic, glass, paper, wood etc.. Preferably do not use where coolant may heavily coat the switches. Capacitive is like the sensor pad on a laptop. If your finger is wet it will not sense properly.

Photo electric

Infrared and red light sensors are great for non contact sensing. Some of these sensors should also be avoided where sensors frequently are coated with coolant.

Typical configurations

  1. Through beam
  2. Retro reflective
  3. Diffuse reflection
  4. Infrared heat sensors

Laser sensors

Laser sensors are good for applications where small objects need to be detected or where very accurate positioning is required. The light beam is also visible for easy adjustment.

Typical configurations

  1. Through beam
  2. Retro reflective
  3. Diffuse reflection

Fiber optics and controllers

Fiber optic controllers and sensors provide reliable detection of small targets and can be used to control multiple applications.

Typical configurations

  1. Light on
  2. Dark on

Linear position transducers

Analog type position detection gives accurate linear position and comes in almost infinite lengths based on the application

Position sensor specification and considerations

Type of Voltage required for sensors

Standard switches

  1. 12vdc
  2. 24vdc
  3. 100vac
  4. 115vac

Analog switches- Voltage range required

  1. 0-10vdc
  2. -5 to +5 vdc
  3. -10 to +10vdc
  4. 4-20mA
  5. 0-20mA

Interface voltage PNP (sourcing) or NPN (sinking)
  1. Is it PNP?
    2-wire-Positive voltage in Positive out to machine PLC as an input
    3-wire-Positive and negative in from power supply Positive out to machine input

  2. Is it NPN?
    2-wire-Positive voltage in Positive out to a Machine PLC as an Input
    3-wire-Negative and positive in from power supply Negative is output to machine input

Proximity Body styles

Typical diameters (most common)- 8 mm, 12 mm, 18 mm, and 30 mm

Sensing distance required

Sensing distances (most common)-3 mm, 4 mm, 5 mm, 8 mm, 12 mm, 18 mm, and 30 mm

Material construction

  1. Metal
  2. Plastic

Typical sensor Environments to consider
  1. Oils and coolants
  2. magnetic fields
  3. Hygienic and wet areas
  4. Mobile applications
  5. Food applications
  6. Caustic and acid solutions
  7. Shock resistance
  8. Electrical noise
  9. Dust or debur type applications


Another great maintenance tool to have is a Proximity Tester