STEINEL Ultrasonic Motion Sensors

Sept. 20, 2011 - PRLog -- Ultrasonic sensors are based on measuring the properties of sound waves with frequency above the human audible range. They are based on three physical principles: time of flight, the Doppler effect, and the attenuation of sound waves. Ultrasonic sensors are non-intrusive in that they do not require physical contact with their target, and can detect certain clear or shiny targets otherwise obscured to some vision-based sensors. On the other hand, their measurements are very sensitive to temperature and to the angle of the target.

Ultrasonic sensors “are based on the measurement of the properties of acoustic waves with frequencies above the human audible range,” often at roughly 40 kHz

They typically operate by generating a high-frequency pulse of sound, and then receiving and evaluating the properties of the echo pulse.Three different properties of the received echo pulse may be evaluated, for different sensing purposes.

They are:

▪   Time of flight (for sensing distance)

▪   Doppler shift (for sensing velocity)

▪   Amplitude attenuation (for sensing distance, directionality, or attenuation coefficient)

Some homeowners choose to use motion detectors as a security measure. Motion detectors survey a certain area and activate other measures, such as alarms, if they detect motion. One such device, ultrasonic motion sensor, detects motion using sound waves. As movement disrupts air and sound waves, these sensors are able to sound alerts of intrusions. Two types of sensors fit this category, active and passive. Active sensors emit sounds at pitches beyond the capacity of human ears to hear. Passive sensors consist only of receivers that listen for sounds. They are among the most sensitive of detection systems. Thus, they are also among the most expensive.

Active Sensors

Active ultrasound sensors emit sound waves from quartz-crystal transducers. The waves strike objects within the field of detection and as long as there are no movement the waves are not disrupted. However, when movement occurs the sound wave is disrupted and is reflected back to the system's receiver.

The receiver then relays the signal to the electronic control unit, and depending on its sensitivity and calibration, the electronic control unit determines if the signal disruption warrants inordinate movement. If so, it then relays the signal to the alarm component, which triggers the alarm. The sound waves create a complete field of detection, so that any point within the field falls within its range. The field of detection weakens with distance. However, motion is generally detectable up to a distance of about forty feet.

Passive Ultrasonic Motion Sensors

Passive sensors operate on the principle of sounds such as breaking glass or metal striking metal to trigger alarms. These sounds produce waves detected by the sensors that, like the active sensors, relay them to electronic control units to determine if the sound wave pattern falls within established normal parameters. Since skilled burglars know how to pass through space without making highly audible sounds, many people use these sensors in conjunction with passive infrared sensors to increase sensitivity. Newer models combine both technologies within one system.

Maintenance

Most systems have a life span of approximately twelve to fifteen years; however, control units may have life spans as short as six to as much as ten years. High temperatures and humidity may cause premature system deterioration.

Disadvantages

The sensitive detection abilities of these sensors offer obvious advantages to consumers who wish to monitor property. Nevertheless, this sensitivity can also cause many false alarms. Highly sensitive active detectors may trigger false alarms when detecting innocuous objects such as passing insects or birds. Gusts of wind or vibrations caused by airplanes passing overhead may also trigger false alarms.

Also, ultrasound cannot penetrate solid objects such as furniture or boxes and these areas cause gaps in the sensor's detection field. In addition, precise, slow movements by a burglar may not trigger an alarm. Passive detection units may falsely detect pipe discharges and ringing telephones.

On the other hand, some systems are calibrated to not detect such noises but they also do not detect drilling through doorknobs. Objects such as furniture may also obfuscate sounds, which the sensor may not detect. These systems utilize advanced technology and are among the most thorough of detection systems.

An active system detects everything within its range. Nevertheless, they are expensive, and under some conditions prone to false alarms. If you live in an area with an unusual amount of noise such as an airport, industrial area, or near a construction zone then these systems may not suitable for your needs. Also, passive systems do not provide complete detection in areas with large objects and in those cases another type of detection system may be required to compliment the ultrasound system.

With the STEINEL Professional range providing hi-tech for everyday use, we are the world's first company to have researched and developed high-frequency sensor systems for application in lighting automation. Perfected and suitable for routine tasks, it's now available to you.

High-frequency sensors in theory

High-frequency sensors actively scan your detection zone. The signals are emitted; reflected as an echo and received again a moment later  any change in echo means a movement is registered. This takes place instantly and irrespective of temperature  in other words, without direction of movement or temperature restricting sensitivity.

High-frequency sensors in practice

High-frequency sensors can be used to provide rooms with uninterrupted, reliable coverage. Walking direction is irrelevant. High-frequency sensors are highly sensitive and extremely precise in the way they respond. Detecting any movement immediately, the sensor switches light 'ON'. In comparison to good-quality PIR sensors, HF-sensors need not necessarily be given preference nor must they be dismissed.

Their use always depends on the particular room and on the specific detection task they are required to perform. STEINEL Professional offers the right sensor technology for every situation.

Benefits of HF

•   Uninterrupted coverage

•   Electronically adjustable reach

•   Detection through glass, wood, walls etc.

•   "Invisible" sensor that can be integrated in lights

•   Can be concealed behind trim panels

•   Uninterrupted signal propagation

•   Good quality of detection, even in long rooms, stairwells etc.

•   Extremely fast detection of the smallest of movements

•   Operates irrespective of ambient temperature and temperature of objects

•   Reach, twilight threshold and light 'ON' duration can be set to suit individual needs

Steinel Sensor Lights are brilliantly designed using their expertise with the high frequency sensor technology. The sensors can see through the Glass / Acrylic covering by remaining unobtrusive and invisible without compromising on the efficacy of the fixture performance.

These fixtures are essentially installed for indoor applications ranging from corridors, staircases, toilets, washrooms, alleyways etc. The sensor’s detection range is normally 12 to 15 feet on either side as a result of which the area to be detected needs to be small to medium in size about 100 sq. feet would be ideal.

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Pammvi is sole distributor and dealer of Steinel, Germany products for lighting automation and power tools in India, Bangladesh, Sri Lanka and other sub-continent countries. Pammvi also deals in FDA certified drugs of abuse test kits and AED.