Microwave Sensor
The oldest sensors had only one technology behind them. The faults or drawbacks were analyzed. Specific faults were pinpointed. Technological research discovered that the sensors, if combined could overcome their initial singular faults. The combination that was found to work well was the combination of the passive infra-red and the microwave technologies.
The trend in security systems keep changing for the better. Two or more principles may be applied to create newer sensors. One important combination is the combination of passive infra-red sensors with microwave sensors. The new combined microwave sensor is several times more efficient as security sensors than the components. Low cost light sensors are available. The passive infra-red sensors detect heat emission from a body be it a human being or animal. The microwave sensor or the Doppler Unit operates at a frequency of ten MHz. The Doppler uses a radar signal which causes microwaves to bounce off an object. The frequency of the returning microwaves is then measured. A moving object within the view of the combined microwave sensor will return a frequency higher and lower than the signaled frequency and not the same. Microwave sensors can detect motion from a long distance away. They are reliable to cover greater distances. They can penetrate walls and therefore can be placed anywhere, even behind a wall or cupboard. The disadvantage of a microwave sensor is that it is very sensitive and gets disturbed by the electrical devices like lights and the radio. These micro wave sensors are really too strong for a home security system.
In the combined system, the microwave system used is weaker than when used alone. When combined with PIR it produces a very efficient combined microwave sensor. A combined microwave sensor senses the object in the field of transmission of microwaves by the returning frequencies. The passive infra-red sensor detects the object by virtue of the heat emission from the object. When both sensors can detect the object, only then will there be an alarm. The weaknesses of the two sensors are corrected in the combined microwave sensor.
Combined microwave systems are being used on large scale projects. They are found in the transducers for detecting total ultrasonic solutions. It is also used in some factories with formaldehyde as a product. The combined microwave sensors are used for optic fiber sensing. Magnetic sensors and automotive sensors use the combined microwave systems. Radar level gauges similarly have the use of the combined microwave system.
The military uses combined microwave systems for their surveillance. Their purpose would be on a larger scale but the purpose is still security. Motion detection within the premises will be the aim of the combined microwave system. At times a third technology or a microwave sensor will be again added strengthening the effect of the sensor. The distance and area covered for the detection will be many times more.
A combined microwave sensor known as multi sensor microwave soil moisture remote sensing equipment for measuring temperature is available. It is a combined radar and radiometer system.
There is another multi sensor with ultrasound and microwaves. It is a compact fairly cheap sensor for measurement of the distance of an object, its presence, and velocity of motion. It is actually a superbly performing large motion detector. This combined microwave sensor can differentiate signals produced by a noisy event or other disturbances. The combination has enhanced its function.
Another combined microwave sensor with microwaves and infra-red technologies combined together is used for the measurement of Tropical rainfall in the Tropical Rainfall Measurement Mission. The microwaves help the imaging of the clouds and evaluation of the liquid water path.
The infra-red acts as the scanner for observing the clouds from visible infra-red onwards.
Space borne remote sensors use a combined microwave system with microwaves and infra-red for an optimum performance of the machine which monitors the earth's surface. The satellite communication system thus works well.
There are many more instances of combined microwave systems enhancing the functioning of a machine which previously would have been using a single technology. The single technology would not have produced a good performance.
We find that the combined microwave system is a technology combination being used all over the world for various essential purposes other than home security. This would probably remain for some time now considering the extent to which combinations are being used.
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