Microwave Sensor Applications

Microwave sensor devices have found their way into many applications in today’s world.

Microwave resonator type sensors have been developed to measure the water content in paper. This method is analytically able to determine the weight and moisture content of a number of different materials. Microwave frequencies up to 100 GHz. are becoming commonplace for industrial applications. When these frequencies are coupled to special resonators, specific electrical information such as permittivity and permeability can be determined. When the resonator is employed, sample material is inside of the resonator’s cavity region. This affects the cavity’s center frequency and Q. The permittivity and permeability can be determined by the resonator’s shift of frequency from its normal center frequency. The Q factor is calculated based on the frequencies from 3 dB to the magnitude at resonance. Once the data is generated, it can then be transformed via DSP methods into data the computer can calculate and display. These resonator techniques can measure samples as small as one cubic millimeter at high speed and with accuracies down to 0.1%.

Microwave sensors have also been used for intelligent traffic systems. These microwave sensors typically are composed of vehicle, pedestrian, and mobile radar traffic counters. Traffic data collection radar sensors exhibit reliable and inexpensive technology, are safe and low cost and require little maintenance. Vehicle and pedestrian detectors for intersections can detect approaching vehicles at distances up to 150 meters away. These sensors can also be used for vehicle speed detectors for speed warning signs or the activation of VMS and traffic signs.

Lastly, it is interesting to note that microwave sensors have found their way into the coal industry. Surprisingly, microwave devices are used to measure “how much” coal material is in a bin or hopper. This is done in three (3) possible ways:

1. RF Admittance: This level detector uses a radio frequency signal and monitors the change in RF admittance to indicate either the presence or absence of coal material.

                                                      2. Through-Air-Radar: This is a method using FMCW (frequency modulated continuous wave) or pulse radar technologies. These devices measure empty space distance by measuring the time-of-                                                            flight of radar energy from the moment it is emitted to when the reflected energy is received back.

                                                      3. Guided Wave or TDR: This is a method using guided wave radar (TDR) which is time domain reflectometry. It measures the time-of-flight of radar pulses traveling to the material surface along a                                                             waveguide and the subsequent reflection off the material surface.

So, it can be seen that “point” and “continuous” level sensors are an integral part of the operation of a coal fired power generating plant. Overall, it can be seen that microwave sensors are playing an important role in current industry. Component General, Inc. is poised and ready to develop your microwave sensor based applications.

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