Research On Signal Detection System Of Surface Acoustic Wave Temperature Sensor

High voltage switchgear plays a very important role in power system. It is commonthat high voltage switchgear produces too much heat because of surface oxidation andcorrosion or bolts loose or busbar connections at aging. That will make high voltageswitchgear work abnormally and even lead to serious accidences. So it is necessary tomeasure its temperature. But traditional methods can’t work for its exposed high-voltageand narrow space. Surface acoustic wave(SAW) sensor is suitable to be used in highvoltage switchgear because it is passive and wireless and has a lot of advantages such asstrong anti-interfere ability, high accuracy and low cost. SAW sensor can be also used insome special circumstances such as high temperature， high pressure, flammability,explosibility, strong electropositive, strong magnetic and high speed movement.Signal detection system is vital in application of SAW temperature sensor. Accordingto the sensing signal characteristic of SAW temperature sensor, the power of sensing signalis strongest when the frequency of excitation signal is equated to resonant frequency ofsensor, a signal detecting method scanning frequency in a frequency range was proposed,and the hardware and software design were also implemented.Aiming at those problems, the main work was done as follows.(1)The histories of SAW sensor and signal detection technology of SAW sensor andapplication of SAW sensor were studied. The sensing principle of SAW temperature sensorwas analyzed.(2) Intermittent sinusoidal pulse signal was selected as excitation signal by analysingsignal characteristics of SAW sensor. And hardware and software of signal detectionsystem were implemented. The key technology of hardware and methods used to controlsending and receiving gain automatically of software were used to improve signal-to-noiseratio and accuracy of the whole system.(3)The rationality of the design of the system and the good linear relationship betweenresonator frequency and temperature were proved through experiments. Wireless sensing distance and accuracy of measuring temperature were also got. According to the results, itcould be concluded that passive and wireless system of temperature monitoring based onSAW sensor can be used to measure temperature of high voltage switchgear.(4)The application scheme of passive and wireless system of temperature monitoringused in high voltage switchgear was introduced.