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Dual Technology Sensors

Dual technology detectors


Security is an important aspect of modern life because it provides a sense of protection from the potential threat people face in their daily lives. Technology advancement has been a key element in improving security around the world, as people find it easy to protect themselves using technological tools due to their efficiency and reliability[ CITATION Ibr14 l 1033 ]. One technological aspect of security is the development of motion sensors, which has become a linchpin of people’s security system[ CITATION Ibr14 l 1033 ]. Motion sensors have an important capability that can transform how people approach security threats. The motion sensor technology functions as detection devices when someone is in people’s homes, offices or commercial premises when they should not be.

Motion sensor technologies have become unique in the security sectors due to its capability of using one or multiple technologies to detect movement in an area[ CITATION Chr12 l 1033 ]. This means if one part of the system sensor is tripped by an intruder, a signal is sent to the security system’s control panel that links to the monitoring center, which alerts security personnel in the monitoring center to a potential threat in the premises. Sensor technologies contains microwave, optical or acoustic sensor that enables the technology to function effectively[ CITATION Chr12 l 1033 ].

There are varieties of dual sensor technologies, which have found wide use in the domestic and commercial applications. Dual sensor technologies are very common in activation of automatic door openers in businesses premises and public buildings. The technology has also been useful in detecting intrusion by activating streetlights or indoor lights in walkways[ CITATION JCa13 l 1033 ]. Dual sensor technologies have also been used with a combination of security alarms and cameras, where the motion detected triggers the alarm to sound and the security camera to record the intrusion. Dual Technology Sensor has become an important aspect of security because they sense intruders and send an alert to the control panel, which alerts the monitoring system[ CITATION Car12 l 1033 ].

In order to improve security accuracy, Dual Technology Sensor has become an ideal security measures for many people and organization. The combination of different sensor technologies into one system not only reduces false detection but also estimates detection probabilities and increased vulnerability[ CITATION JCa13 l 1033 ]. The multiple sensor technologies into the single unit, have to work together in order to trigger an alarm or activate detection.

Types of dual technology detectors and their principles

There are variety of dual sensor technologies that is currently being used for domestic and commercial applications

Occupancy sensors

Occupancy sensors are important for detecting the presence or absence of occupants in a specific space. Occupancy sensor is widely used for turning on or off automatically lights, heating system, ventilation and air condition system[ CITATION Car12 l 1033 ]. They are also very useful in saving energy, providing automatic control and comply with building codes. Occupancy sensors use a combination of passive infrared (PIR) and ultrasonic sensors to function effectively[ CITATION Car12 l 1033 ]. Passive infrared sensor operates by detecting the presence of occupants using the heat emitted by the occupant and that of the background. Passive infrared differentiates the occupant’s heat from that of the background to detect motion[ CITATION Dom11 l 1033 ]. The sensor technology is very effective when the coverage between the occupants and the sensor is aligned together. This means the sensor’s coverage must be well defined to ensure accurate detection of movement within a specific space. Passive infrared are known to be effective in an enclosed space, high ceiling areas and high airflow spaces[ CITATION Dom11 l 1033 ]. This means users can use this sensor technology in areas such as offices, lobbies, warehouse, hallways and storage closet.

On the other hand, ultrasonic sensors function by sending ultrasonic sound waves in space and measure the speed at which the sound is reflected[ CITATION Ste12 l 1033 ]. Usually, the sound waves emitted have high frequency, which is impossible for human ear to hear the sound. Therefore, ultrasonic sensors uses the changes in frequency caused the occupant’s movement to detect presence in a specific space[ CITATION Sha12 l 1033 ]. The unique aspect of ultrasonic sensors is that, unlike passive infrared sensors, they do not need direct line of sight and can detect presence of a person behind objects. Ultrasonic sensors cover a wide area of space, which improves accuracy for detecting presence of an occupant in space. In addition, ultrasonic sensors are sensitive to minor motions such as hand movement[ CITATION Ste12 l 1033 ].

In spaces such as rest rooms, open offices and enclosed hallways where spaces either are partitioned or require a higher level of sensitivity, ultrasonic sensors are suitable in such spaces[ CITATION Ste12 l 1033 ]. This is because they are able to detect motion in areas where direct line of sight is not possible hence compensating for the defaults that might arise due to the use of passive infrared sensors. Despite the wide variety of features that passive infrared and ultrasonic sensors have on improving security, there are minor complications because of using the sensors[ CITATION Ste12 l 1033 ].

Passive infrared sensors are very ineffective during low levels of motion, which can provide the intruder a major loophole for the intruder. In addition, passive infrared sensors are also ineffective when the sensors view is blocked by obstacles[ CITATION JCa13 l 1033 ]. On the other hand, ultrasonic sensors cannot detect motion when the ceilings are higher than 14 feet. This is because ultrasonic sensors cannot provide accurate estimation between the occupant and the sound wave reflected[ CITATION JCa13 l 1033 ]. Ultrasonic sensors are also very ineffective when the airflow is at high levels. This is because airflow causes high levels of vibration, which is a nuisance to ultrasonic sensors, and causes the sensors to switch off[ CITATION Ste12 l 1033 ]. Open spaces are also not a suitable condition for the proper function of ultrasonic sensors. This is because open spaces require selective coverage which is common in controlling of individual warehouses aisles.

In occupancy sensor technology, the combination of passive infrared and ultrasonic sensors literally eliminates the possibility of inaccurate detection by requiring either of the technology to hold the lights on upon detection[ CITATION Ste12 l 1033 ]. However, for the occupancy sensor technology to work, both sensor technologies must simultaneously work together to detect presence of an occupant. Occupancy sensors are used in areas such as classrooms, conference rooms and open spaces where a high degree of detection is required[ CITATION Ste12 l 1033 ].

Security motion sensors

Motion sensors are a combination of passive infrared sensors and microwave sensors used in the detection of movement in restricted areas. Motion sensors are the mostly commonly used security measures by both domestic and commercial applicants[ CITATION Hui10 l 1033 ]. In motion sensor technology, passive infrared and microwave sensors operate on a different spectrum, that is, one is active and the other is passive[ CITATION Udo10 l 1033 ]. Similarly, to occupancy sensors, motion sensors are also used to detect presence by using light to alert the monitoring center[ CITATION Udo10 l 1033 ].

Microwave sensors are unique in the combination of passive infrared sensors in various security devices. The use of microwaves sensors has increased due to the rise in security and surveillance concerns[ CITATION Lam11 l 1033 ]. Microwave sensors function by detecting motion into a specific portion, which triggers the alarm as a result. Microwave sensors produce microwaves, which emits it to a specific region and analyzes the changes of the received microwaves from the reflection of the intruder[ CITATION Law13 l 1033 ]. Based on guiding principle of the Doppler’s effect, microwave sensors consist of three major components, that is, a transmitter, a receiver and an alarm or circuit. The transmitter produces microwaves, which sends it towards a specific direction. The microwaves move at a specific frequency in which the phase of the waves signal can be altered when the velocity of the intruder’s movement strike it[ CITATION ARo11 l 1033 ]. When the receiver recognizes the change in frequency, the microwave sensor triggers the alarm or any other related circuit. In normal circumstances, the change in the frequency of the waves is directly proportional to the velocity of the intruder.

There are various challenges that microwaves sensor faces when signal handedly used. Microwaves sensors are vulnerable to false alarms mainly due to slight interruptions of objects like curtain and swinging signs[ CITATION Ste12 l 1033 ]. However, such shortcomings can be solved by adding receiver diodes into the component of microwave sensors. The receiver diodes function by determining the frequency level through mix up with the transmitted microwave signal. Therefore, the alarm is triggered only when the shift in frequency signal is beyond the estimated change pre-fed into the sensor[ CITATION Ste12 l 1033 ]. Microwave sensors are beneficial as compared to passive infrared sensors, which have many disadvantages.

Microwave sensors are effective even in harsh environmental conditions unlike passive infrared sensors[ CITATION ARo11 l 1033 ]. This means that microwave sensors can work in situations where heat cycles are not regular. This is very useful for outdoor security operations, which is common with many domestic and commercial users. Microwave sensors have capability to penetrate through walls and holes[ CITATION Mar121 l 1033 ]. The sensor uses microwave radiations, which can penetrate through obstacles to detect motion and trigger alarms. This can be very useful in ensuring security across boundaries or closings. Therefore, a combination of passive infrared and microwave sensors is essential in reducing false alarms due to their different spectrum of operation[ CITATION Mar121 l 1033 ].

Microwave sensors have some minor shortcomings that can compromise the security of a specific coverage[ CITATION Meh10 l 1033 ]. They are vulnerable to unnoticed intrusion as the technology does not work continuous but instead work in intervals. Intruders can find a high opportunity to use this vulnerability to their advantage. Microwave sensor relies on continuous power source to remain operation at all times. However, the sensors use high voltage batteries, which are expensive to quire, therefore, majority of these sensors, are ineffective if not sufficiently sourced with enough power[ CITATION Mar121 l 1033 ].

There are some instances where Dual Technology Sensor has been integrated with security cameras to enhance security measures in a specific area. The purpose of placing security cameras in Dual Technology Sensor is to provide a more reliable information about the intrusion, which can be provided as evidence during prosecution[ CITATION Sha12 l 1033 ]. The proliferation of inexpensive digital cameras has made it possible to use motion detectors in surveillance cameras. Cameras offer the capability to record videos triggered by motion detection, which can be essential in taking necessary measures to address the potential security threat[ CITATION Chr12 l 1033 ]. Other than taking pictures and recording videos, cameras do no offer much capability in security systems. This is because camera and computer hardware do not offer technological capability in motion detection. Therefore, cameras and computers are considered passive technology similarly to passive infrared sensors. Camera can be combined with infrared technology to improve vision at night in security surveillance[ CITATION Chr12 l 1033 ].


Dual technology sensor is becoming an effective security measure tool for many domestic and commercial users. Their capability of handling sunlit windows, strong air flows and detect small movements makes the technology an ideal security tool to protect domestic and commercial premises[ CITATION Meh10 l 1033 ]. Dual technology sensor has become very effective in handling various situations by utilizing its pair of technologies sensitive to two different types of disturbance. This concept has enabled the technology very critical in improving security systems by ensuring that each pair sensor supports the weakness of another to eliminate false detection[ CITATION Xia11 l 1033 ].

The effectiveness of dual technology sensor can well be noted during the function of the passive infrared sensor and microwaves sensor[ CITATION Xia10 l 1033 ]. The passive infrared sensors are known to be ineffective with low signal level, which compromise coverage, and security limits. While microwave sensors offer strong detection performance to compensate for the weakness of passive infrared sensors[ CITATION BSm12 l 1033 ]. Microwave can cover a large area and pick up variations between the signal sent and received. This simply means that they can easily detect anything that moves within its proximity[ CITATION Sha12 l 1033 ]. Dual technology sensors are very expensive to acquire but offer much better security solutions than other security measures available today. Dual technology sensors use their technological capability to detect motion beyond human capability.

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