What are Proximity and Position Sensors?

Meet the Connector: Proximity and Position Sensors

Robotics and control systems depend on proximity and position sensors employing methods such as infrared, ultrasonic, or capacitive sensing to correctly park, position, and orient their motion in relation to the environment around them.

STMicroelectronics VL53L1X Time-of-Flight (ToF) proximity sensor from Mouser Electronics is a state-of-the-art laser-ranging sensor. This long-distance ranging miniature ToF sensor offers accurate ranging up to 4 m and fast ranging frequency up to 50 Hz. The VL53L1X sensor is housed in a miniature, reflowable package and integrates a SPAD receiving array, a 940nm invisible Class 1 laser emitter, physical infrared filters, and optics for the best ranging performance. The VL53L1X sensor uses ST’s latest generation ToF technology which allows absolute distance measurement.

Proximity sensors

Proximity sensors detect the presence of nearby objects, often called targets, without any physical contact. Often this is done by emitting an electromagnetic field or beam of electromagnetic radiation, such as infrared. Changes in the field or return signal indicate the target’s proximity. Different types of sensors are used, depending on the target.

A plastic target might require a capacitive proximity sensor or photoelectric sensor. Capacitive, or capacitance, sensing technology is based on capacitive coupling that can detect and measure anything that is conductive or has a dielectric constant different from air. A photoelectric sensor uses a light transmitter to determine the distance, absence, or presence of an object.

A metal target requires an inductive proximity sensor. When an electrical current flows through an inductor, a magnetic field develops. Alternatively, a current will flow through a circuit containing an inductor when the magnetic field through it changes.

Proximity sensors are also used to monitor machine vibration. They measure variations in distance between a shaft and its support bearing. This is useful in large steam turbines, compressors, and motors with sleeve-type bearings. Proximity sensors adjusted to a very short range are used as touch switches.

Because they don’t have mechanical parts and don’t require contact with the target, proximity sensors are generally considered high reliability and have long functional lives.

Proximity sensors can recognize air gestures and hover manipulations. In mobile devices they are used in the lock screen to detect the target (i.e, the user’s hand). The device goes into sleep mode when no user is detected and awakens when the user’s hand is within range or engages with the device.

Proximity sensors are useful in many applications, including mobile phones, recycling plants, automobiles and other vehicles (parking sensors, self-driving capabilities), anti-aircraft systems, manufacturing (production and assembly lines).

TE Connectivity’s HR Series general purpose LVDTs provide the optimum performance required for a majority of applications. The large 1/16 inch [1.6mm] bore-to-core radial clearance provides for ample installation misalignments and therefore reduces the application costs. Featuring a high output voltage and a broad operating frequency range, these versatile and highly reliable LVDTs deliver worry-free and precise position measurements. The HR windings are vacuum impregnated with a specially formulated, high temperature, flexible resin, and the coil assembly is potted inside its housing with a two-component epoxy, providing excellent protection against hostile environments such as high humidity, vibration, and shock.

Position sensors

Position sensors detect and measure the location (actual position) or displacement (relative position) of an object and provide feedback on the object’s position in terms of linear travel, rotational angle, or three-dimensional space. Some sensors provide incremental measurements from one point to another, while others provide absolute position information relative to a specific reference point.

Position sensing is vital for many applications, such as conveyor belts, monitoring the swaying of wind turbine towers and robot chain drives. Position sensors can be linear, rotary, angular, absolute, incremental, contact (less expensive), and non-contact (more reliable). They can be static or dynamic (measuring speed and acceleration). Specialized sensors can determine positions in three dimensions.

Various technologies are used for position sensing.

Magneto strictive position sensors use the change in size and shape of ferromagnetic materials in the presence of an applied magnetic field to establish position.

Sensata’s ACW4 and TCW4 rotary Hall effect sensors from Heilind Electronics enhance industrial automation with IO-Link connectivity. The ACW4 offers single-turn measurement, while the TCW4 adds multi-turn capability. Both integrate seamlessly into Industry 4.0 and IoT environments, ideal for robotics, conveyors, and material handling, ensuring easy integration and real-time data exchange.

Hall effect-based magnetic position sensors measure changes in Hall voltage as an indicator of the object’s position.

Fiber-optic position sensors measure optical power using optical fiber with photodetectors at each end to calculate the distance of the object from the end of the fiber and thereby determine the object’s position.

Optical position sensors use a change in wavelength, intensity, phase, polarization, or other light characteristics to gain information about the object’s position.

Ultrasonic position sensors use changes in high-frequency sound waves to determine an object’s position. These sensors work with target objects of different materials and surface characteristics and can detect small objects over large distances. They are resistant to vibration, ambient noise, EMI, and infrared radiation.

Design Notes 

Markets

Industrial, Automotive, Transportation, Telecom, Aerospace & Defense, Healthcare, Test & Measurement

Applications 

Mobile phones, recycling plants, automobiles and other vehicles (parking sensors, self-driving capabilities), agricultural machinery, drones, anti-aircraft systems, industrial automation (production and assembly lines), robotics, medical devices, imaging equipment, robotic surgery systems, test equipment, consumer products, HVAC systems, smart buildings

Suppliers 

TE Connectivity, Sensata Technologies Inc. (Heilind Electronics), STMicroelectronics (Mouser Electronics), Amphenol Corporation, ams-OSRAM AG, Omron, Honeywell International Inc., TDK Corporation, SICK AG, Texas Instruments Incorporated, Analog Devices Inc., CTS Corporation, Infineon Technologies AG, Microchip Technology Inc., Vishay Intertechnology Inc., and Novotechnik U.S. Inc.

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