Zigbee-based micro strain measurement unattended engineering monitoring system

Abstract

The invention discloses a Zigbee-based micro strain measurement unattended engineering monitoring system. The Zigbee-based micro strain measurement unattended engineering monitoring system comprises an integrated displacement sensor, a reduced function device (RFD) module and a coordinator, wherein the integrated displacement sensor is embedded into concrete and comprises a fixed amplitude RC oscillating circuit, a linear variable differential transformer (LVDT) displacement sensor, a phase sensitive detection and signal amplifying circuit and a microprocessor which are connected sequentially; the RFD module is connected with the integrated displacement sensor, is arranged on the ground and comprises a second Zigbee chip and a direct current / direct current (DC / DC) converter; the coordinator is connected with the RFD module and comprises a display screen, a keyboard, and a first Zigbee chip and a general packet radio service (GPRS) module which are connected with the display screen and the keyboard respectively; and the second Zigbee chip is in wireless communication with the first Zigbee chip. The Zigbee-based micro strain measurement unattended engineering monitoring system can realize site-remote end unattended monitoring function.

Description

technical field [0001] The invention relates to an engineering monitoring system, in particular to an unattended engineering monitoring system for micro-strain measurement based on Zigbee. Background technique [0002] ZigBee is a low-power personal area network protocol based on the IEEE802.15.4 standard. It has become increasingly known to everyone. Its biggest feature is low power consumption and networking, especially the networking function with routing. Zigbee is a wireless data transmission network platform composed of up to 65,000 wireless data transmission modules, which is very similar to the existing mobile communication CDMA network or GSM network. Each Zigbee data transmission module is similar to a node of mobile communication. Within the entire network range, they can communicate with each other; the communication distance between each network node can be extended from the standard 75 meters to hundreds of meters or several kilometers; the entire Zigbee networ...

AI Technical Summary

Problems solved by technology

There is an essential difference between Zigbee and mobile communication network. Zigbee network is mainly to realize data transmission and interaction in the automatic control system, while mobile communication network is based on realizing the interaction of voice and image information, and the establishment cost of each mobile node is extremely high. Expensive (generally more than one million RMB), in contrast, the cost of building a Zigbee "node" is often less than 1,000 RMB

[0005] 1) Since the two ends of the steel string are tight and are always under tension, the steel string will undergo natural deformation, resulting in a change in its output natural frequency;

[0006] 2) The consistency of the output signal of the steel string stress gauge is poor, and its output response is related to the tightness of the steel string and the consistency of the steel string material, so each sensor needs to be calibrated independently;

[0008] 4) Steel string sensors usually need an external excitation signal with a certain power energy, so the excitation signal cannot be transmitted wirelessly;

[0009] 5) When measuring the strain of the pile foundation, the steel bar to be tested needs to be cut off, and the steel string sensor is welded between the two fractures of the steel bar. Therefore, when the pile foundation is loaded, if the elastic modulus of the steel string sensor is the If they are inconsistent, the measured value has no meaning to guide the construction;

[0010] 6) The measured value needs to be converted twice through empirical parameters, the accuracy is poor, and it is not comparable and consistent

[0011] From the above analysis, it can be seen that the use of steel string sensors in the measurement of stress and micro-displacement is not suitable for building an unattended monitoring network, and its measured values ​​often cannot withstand scrutiny

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