Analysis of two types of passive sensors


Under the continuous support of the National Natural Science Foundation of China, we have studied the wide-area distribution of passive array sensors and passive wireless array sensors to expand the application of piezoelectric characteristics and components in modern detection technology.

Surface acoustic wave (SAW) devices are excellent sensing carriers and passive components. SAW devices operate from 10 to 105 MHZ and are directly coupled to RF electromagnetic waves. Based on this feature, wireless sensing is implemented with SAW devices: non-contact provides sensing energy and non-contact read sensing output. Such a sensor has the advantages of no power supply and signal connection, passive, small size and strong anti-interference ability, and is suitable for applications in complex environments. Such as moving parts, the detection of non-contact objects. SAW sensors with different structures or parameters have different RF excitation gating conditions and only respond to the corresponding wireless query signals. A passive wireless array sensor can be constructed using a plurality of SAW passive wireless sensors with different gating conditions. The sensing elements in the array can be arbitrarily distributed. This is a passive wireless temperature sensor developed using a SAW resonator with frequency selective characteristics. Temperature sensing information is obtained by performing full digital signal processing on the echo signals of the RF query.

A separate array of piezoelectric elements and passive components is used to form a sensor array that can be arbitrarily distributed. Due to the piezoelectric characteristics, the array directly converts the mechanical quantity change of the measured object into an electrical signal to realize distributed sensing without using a power source to supply sensing energy to the array. The array uses a unique network structure and signal control method, which greatly reduces the connection of conventional sensors in spatial distribution applications. The array sensing signals are addressable and can also be scanned. Piezoelectric passive distributed array sensors are especially suitable for real-time no-power or very low-power, long-term uninterrupted monitoring of large-area spatial distribution (tens of meters to hundreds of meters), irregular, and large engineering structures. Piezoelectric passive array sensors have been applied to health and safety monitoring of engineering structures such as bridges. This is a distributed sensing array consisting of 8 × 13 piezoelectric elements. The array has only 8 + 13 lead wires to realize array sensing signal readout and readout control.

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