Motion sensors – find manufacturers and suppliers

Motion sensors detect movements of people, objects or machine components within a defined detection area.

They are used to control lighting, doors, alarm systems, machine functions or automated processes as required. Depending on the measuring principle, they respond to thermal radiation, electromagnetic waves, ultrasound, optical changes or the movement of magnetic or mechanical components.
Typical applications can be found in building automation, security technology, industrial automation, conveyor technology, robotics, vehicle technology, machinery and production plants.
The selection of a suitable motion sensor depends on factors such as the type of movement, required range, detection angle, environmental conditions and desired output signal.
The following provides an overview of typical designs, applications, advantages, limitations and important selection criteria for motion sensors.

Types of motion sensors

Passive infrared sensors

Passive infrared sensors, commonly known as PIR sensors, detect changes in thermal radiation within their monitoring area.
When a person or warm object moves through several detection zones, the received infrared signal changes. The sensor interprets this change as movement.
PIR sensors are frequently used in lighting controls, alarm systems and building automation systems. They do not require an active radiation source and are characterised by comparatively low energy consumption.
Their performance can, however, be affected by small temperature differences between the object and its surroundings or by unfavourable directions of movement.

High-frequency and radar sensors

High-frequency sensors emit electromagnetic waves and analyse their reflections.
When an object moves within the detection area, the frequency or phase of the reflected signal changes. This allows the sensor to detect movement.
Radar sensors can detect very small movements and may also operate through thin, non-metallic materials.
They are suitable for building automation, automatic doors, industrial presence detection and mobile applications. High sensitivity can, however, cause movements outside the intended area to be detected.

Ultrasonic motion sensors

Ultrasonic sensors emit sound waves above the range of human hearing and analyse the reflected signals.
If the propagation time or frequency of the reflections changes, the sensor detects movement.
Ultrasonic sensors can detect even small movements and are suitable for rooms or enclosed areas where optical sensors have limited effectiveness.
Air currents, major temperature differences, sound-absorbing materials or unfavourable room geometries can affect detection.

Optical motion sensors

Optical motion sensors use visible or infrared light to detect moving objects.
Depending on the design, they operate with photoelectric barriers, reflective sensors, cameras or image-processing methods.
Simple sensors detect whether a light beam is interrupted. More advanced systems compare image data and can determine the direction, speed, size or shape of an object.
Optical motion sensors are used in conveyor systems, access systems, traffic monitoring and quality control, among other applications.

Inductive and magnetic motion sensors

Inductive motion sensors detect moving metallic objects through changes in an electromagnetic field.
Magnetic sensors respond to the movement of a magnet or magnetic component.
These sensors are frequently used to monitor pistons, shafts, gears, flaps, doors and other machine components.
They provide robust, non-contact detection but require metallic or magnetically detectable target objects.

Acceleration and vibration sensors

Acceleration sensors detect changes in the movement of a component in one or more spatial directions.
They can detect starting, braking, inclination, impacts and oscillations.
Vibration sensors are used particularly for condition monitoring of motors, bearings, pumps and other rotating machinery.
They can identify unusual movement patterns and provide indications of wear, imbalance or mechanical damage.

Combined motion sensors

Combined sensors use several measuring principles, such as passive infrared and high-frequency technology.
Depending on the design, movement is reported only when both measuring principles produce matching results.
This can reduce false triggering or improve the reliable detection of different types of movement.
Such systems are frequently used in security technology, building automation and demanding monitoring applications.

Applications of motion sensors

Building automation

In buildings, motion sensors control lighting, ventilation, heating and other technical installations according to actual use.
Lighting can be switched on automatically when a person enters a room and switched off again after a defined period without detected movement.
This can improve both convenience and energy efficiency.

Security and monitoring technology

In alarm systems, motion sensors detect people or vehicles within protected areas.
They can trigger acoustic or visual warnings, transmit signals to a control centre or activate cameras.
For outdoor applications, sensors must be able to distinguish relevant movements from influences such as animals, plants, precipitation or changing temperatures.

Mechanical and plant engineering

In machines, motion sensors monitor slides, shafts, flaps, tools and other moving components.
They can determine whether a movement has started, ended or been completed correctly.
The detected signals are used for sequence control, position detection, fault diagnosis or safety monitoring.

Automation and assembly technology

In automated production systems, motion sensors detect workpieces, transport containers, grippers and handling equipment.
They support the synchronisation of individual process steps and report missing, blocked or incorrectly moving components.
Short response times and reliable switching signals are particularly important at high machine cycle rates.

Conveyor and logistics technology

Motion sensors monitor transported goods on conveyor belts, roller conveyors and sorting systems.
They detect product movement, congestion, standstill or inadmissible distances between individual objects.
In warehouse systems, they can also detect vehicles, lifting equipment and moving load units.

Automatic doors and access systems

At automatic doors, motion sensors detect people, vehicles or transport equipment approaching the entrance.
The sensor signal initiates the opening of the door and can also prevent it from closing while someone is passing through.
The detection area and response time must be designed to ensure reliable and safe access.

Vehicle and traffic technology

In vehicles and traffic systems, motion sensors detect movements of vehicles, people or components.
They are used for parking assistance, interior monitoring, door control, traffic-flow measurement and obstacle detection, among other applications.
In mobile applications, they often have to withstand strong vibrations, temperature changes and varying environmental conditions.

Condition monitoring

Acceleration and vibration sensors monitor machines and plants during operation.
Changes in vibration behaviour can indicate bearing problems, imbalance, loosened components or other mechanical faults.
Continuous monitoring supports condition-based maintenance and can reduce unplanned downtime.

Advantages of motion sensors

• Non-contact detection of people, objects and machine components
• Automatic control of technical processes
• Reduced need for manual operation
• Support for energy-efficient building and lighting control
• Monitoring of motion sequences and machine conditions
• Rapid response to changes within the detection area
• Integration into controllers, alarm systems and communication systems
• Detection of faults, standstill and inadmissible movements
• Use in indoor areas, outdoor environments and industrial plants
• Adaptation to different ranges and detection angles

Limitations of motion sensors

• Passive infrared sensors primarily detect changes in thermal radiation. If a person moves directly towards the sensor or if the temperature difference from the surroundings is very small, detection may be limited.
• High-frequency sensors can detect movement through thin walls, doors or other non-metallic materials. This may result in false triggering outside the intended monitoring area.
• Ultrasonic sensors can be affected by air currents, open doors, sound-absorbing surfaces or unfavourable reflection conditions.
• Optical sensors require an unobstructed view of the detection area. Dust, dirt, fog, ambient light or concealed objects can impair their performance.
• Moving plants, animals, curtains, machine components or heat sources can cause unintended switching, depending on the sensor type.
• Many motion sensors do not detect people or objects that remain completely still. Applications requiring presence detection without clear movement need more sensitive presence sensors or combined systems.
• A motion sensor is not a substitute for a complete safety system where machinery or movement poses a hazard. Safety-related applications require appropriately tested components.

Important selection criteria for motion sensors

Type of movement to be detected

The first step is to define whether people, vehicles, workpieces, machine components or vibrations are to be detected.
The direction of movement, speed, object size and temperature difference from the surroundings also influence the choice of measuring principle.
Very slow or slight movements impose different requirements from fast transport or machine movements.

Range and detection area

The required range depends on the size of the area to be monitored.
In addition to the maximum distance, the detection angle, shape of the detection zone and possible blind spots must be considered.
The sensor should be positioned so that relevant movements are detected reliably while adjacent areas are excluded as far as possible.

Sensitivity and response behaviour

High sensitivity allows small movements to be detected but can also increase the risk of false triggering.
The response time must suit the respective process. Automatic doors and fast machine sequences require shorter response times than simple lighting controls.
Adjustable sensors often allow the sensitivity, switch-off delay and switching threshold to be adapted.

Mounting position

Walls, shelves, machine housings, glass panes and other obstacles can influence the detection area.
The mounting height and alignment must be matched to the measuring principle and the intended movement.
With PIR sensors, movement across the detection zones is generally detected more reliably than direct movement towards the sensor.

Environmental conditions

Temperature, humidity, dust, precipitation, sunlight, vibration and electromagnetic interference can affect performance.
For outdoor areas and industrial environments, a suitable degree of protection, robust housing and adequate temperature resistance are required.
Special materials and approvals may be necessary in hygienic, corrosive or potentially explosive environments.

Output signal and interfaces

Motion sensors can provide relay contacts, transistor outputs, analogue signals or digital communication data.
The output signal must be compatible with the controller, building management system, alarm system or evaluation unit.
Fieldbus, wireless or Ethernet interfaces may be required for networked applications.

Power supply and energy consumption

The power supply must be compatible with the existing installation.
In addition to mains-powered sensors, battery-operated and low-energy wireless sensors are available.
For battery operation, range, transmission frequency, temperature and desired service life must be considered.

Parameterisation and diagnostics

Adjustment options make it easier to adapt sensors to different rooms, objects and motion sequences.
Depending on the sensor, range, sensitivity, switching delay, switch-off delay and detection zones can be configured.
Diagnostic functions support commissioning and can indicate contamination, communication faults or signal interference.

Summary

Motion sensors detect movements of people, objects or machine components and provide signals for control, monitoring and automation.
Depending on the application, passive infrared, high-frequency, ultrasonic, optical, inductive, magnetic or acceleration-based measuring principles are used.
The main selection criteria include the type of movement, range, detection angle, sensitivity, response time, environmental conditions and interfaces.
The limitations of the respective measuring principle must be considered during planning and installation in order to avoid false triggering and detection gaps.

Motion sensors are available from various manufacturers and suppliers. Comprehensive information about manufacturers and suppliers of motion sensors from around the world can be found on Exportpages.