CN201465278U - Remote Wireless Monitoring System - Google Patents

Abstract

The utility model discloses a remote wireless monitoring system, which comprises a sensor module, a wireless transmission module and a collection terminal connected thereto, wherein the signal output end of the sensor module is connected to the signal input end of the wireless transmission module, and the sensor module includes a A strain gauge bridge circuit and a single-chip microcomputer at the point to be measured, wherein the output end of the strain gauge bridge circuit is connected to the signal input terminal of the single-chip microcomputer through an analog-to-digital converter, and the single-chip microcomputer is connected with a memory chip and a temperature chip. The remote wireless monitoring system described in the utility model can remotely transmit strain information, and realizes remote monitoring of engineering restricted by geological conditions. At the same time, the system is easy to install and operates stably and reliably.

Description

Remote Wireless Monitoring System

technical field

The utility model relates to a remote wireless monitoring system, in particular to a remote wireless monitoring system applied to geotechnical engineering safety monitoring, such as bridges, tunnels, subways, slopes and other geotechnical engineering monitoring fields.

technical background

The resistance strain gauge sensor is a resistance sensor with a resistance strain gauge as the conversion element. The resistance strain sensor is composed of an elastic sensitive element, a resistance strain gauge, a compensation resistor and a casing, and can be designed into various structural forms according to specific measurement requirements. The elastic sensitive element is deformed by the measured force, and deforms the resistance strain gauge attached to it together. The resistance strain gauge then converts the deformation into a change in resistance value, so that various physical quantities such as force, pressure, torque, displacement, acceleration and temperature can be measured. Commonly used resistance strain sensors include strain gauge load cell, strain gauge pressure sensor, strain gauge torque sensor (see torque sensor), strain gauge displacement sensor (see displacement sensor), strain gauge acceleration sensor (see accelerometer) and Temperature strain gauge, etc. The advantages of resistance strain sensors are high precision, wide measurement range, long life, simple structure, good frequency response characteristics, can work under harsh conditions, and are easy to realize miniaturization, integration and variety diversification. It is widely used in water conservancy and hydropower, railway, transportation, and building monitoring.

But the current resistance strain gauge sensor has the following disadvantages:

1) The sensor generally has a large nonlinearity at large strains, and the output signal is weak, resulting in error amplification;

2) The front end of the sensor is the actual measured voltage value, and the measured physical quantity can only be obtained according to the manual calibration curve, which is slow and prone to fatigue and error;

3) The front end of the sensor is an analog signal rather than a digital signal, which cannot be transmitted remotely;

4) The sensor only has manual numbering, and cannot intelligently coexist with the product. It is not convenient for data sorting and classification, and it is easy to confuse.

5) The products are all used in the field with heavy minefields such as steel frame structures or water conservancy dams, and are vulnerable to lightning strikes.

In the monitoring field of geotechnical engineering such as bridges and tunnels, not only on-site inspection is required, but also the difficulty of on-site construction is needed to realize remote wireless real-time monitoring. Therefore, a strain acquisition monitoring system that can realize remote monitoring is urgently needed.

Utility model content

In view of the above-mentioned prior art, the purpose of this utility model is to provide a remote wireless monitoring system, which can remotely transmit strain information and realize remote monitoring of geologically restricted projects. At the same time, the system can be easily installed and operates stably and reliably.

In order to achieve the above purpose, the technical solution adopted by the utility model is a remote wireless monitoring system, including a sensor module, a wireless transmission module and a collection terminal connected thereto, wherein the signal output terminal of the sensor module is connected to the signal of the wireless transmission module Input end, the technical feature of the present utility model is that described sensor module comprises the strain gauge bridge circuit and the one-chip computer that are positioned at the point to be measured, wherein the output end of the strain gauge bridge circuit connects the signal input end of the one-chip computer through the analog-to-digital converter, The single-chip microcomputer is connected with a storage chip and a temperature chip, and can simultaneously detect the temperature of the measuring point and store data.

The above strain gauge bridge circuit can be a bridge structure formed by four strain gauges, or a half bridge structure formed by connecting two strain gauges and two standard resistors.

The DC half-bridge has the following advantages: a high-stability DC voltage source is easy to obtain; the half-bridge circuit can also directly compensate the temperature of the measuring chip through the compensation chip; the adjustment of the balance circuit is simple; the sensor has little influence on the distribution parameters of the measuring circuit. Therefore, the system preferably uses a DC half-bridge circuit.

According to a preferred solution of the embodiment, the temperature chip is a DS18B20 type thermometer chip. What described one-chip computer adopted is chip STC89C58RD.

Conventional wireless transmission modules generally have a relatively large working current, so the wireless transmission module used in this system is SIM300 from Siemens, mainly considering the stable operation of the module and the sleep function of the module, which can save power in harsh outdoor environments. The wireless transmission module of the system includes: SIM300 module and peripheral circuits such as temperature acquisition circuit, storage circuit, lightning protection circuit, input and output circuit and clock synchronization circuit.

The sensor module described in the utility model is that the resistance strain gauge is pasted on the elastic surface of the special steel of the sensor (the steel has a certain degree of elasticity, which can be guaranteed to change with the change of the measuring body, but it is generally stationary and has little change with temperature and external connections. characteristics), the resistance strain gauge is firmly pasted on a certain measuring point of the steel to be tested, and as the steel deforms, its deformation is transmitted to the special steel, so that the resistance value of the strain gauge also changes accordingly. The change of the measured resistance value can be calculated to obtain the line strain value along the direction of the strain gauge at the measuring point. Since the strain at the point to be measured is generally small (on the order of 10 ^-6 ), the change in the corresponding resistance of the strain gauge is also very small, so a half-bridge DC circuit is used for measurement, that is, the strain gauge or the strain gauge and the standard resistance Connected into a bridge circuit, it converts the resistance signal of the strain gauge into a voltage signal.

The sensor module calculates the direct physical quantity based on the collected analog voltage and the calibration table, without secondary conversion. The wireless transmission module then packages the physical quantity and other data and sends them to the nearby mobile wireless network base station. The mobile base station is connected with the internet network, and when the wireless transmission module sends data packets, there is a target address, that is, the ip address of the internet public network.

The data enters the data acquisition software through the corresponding port of the TCP/IP protocol. The software then analyzes the effective fields of the data packet.

An electronic potentiometer can be set in the sensor module to adjust the zero point voltage, so that the range can be adjusted, and the measurement and calculation can also be facilitated. The memory chip in the sensor module also stores a calibration information table, that is, how much strain value occurs corresponds to what voltage difference value. After the sensor module collects the voltage difference, it calculates the strain value by reverse calculation.

The above-mentioned wireless transmission module and the sensor module are installed separately without distance limitation, which is convenient for the operator to adjust according to the site, and each sensor module has a unique number in the world.

On the basis of the original wireless transmission module, this system also realizes the following functions: 1. Clock synchronization function. By keeping time synchronization with the management terminal, the system will automatically collect data from the front-end module when it reaches a certain moment. 2. The scalability interface is added, which can realize the external connection with Zigbee and Ethernet.

To sum up, the remote wireless monitoring system described in the utility model can remotely transmit strain information, and perform remote monitoring on projects restricted by geological conditions. At the same time, the system is easy to install and operates stably and reliably.

Description of drawings

Fig. 1 is a schematic diagram of a strain gauge bridge circuit;

Fig. 2 is a schematic diagram of strain gauge installation in the sensor module;

Fig. 3 is a schematic diagram of the principle of the sensor module;

Fig. 4 is a schematic diagram of the principle of the wireless transmission module;

Fig. 5 is a schematic diagram of a data communication link;

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment the utility model is described further.

A remote wireless transmission monitoring system is composed of three parts: a sensor module, a wireless transmission module, and a monitoring host (data collection and management software). The sensor module is mainly responsible for collecting data, converting the collected data into analog/digital, and adding a communication protocol for remote data transmission. The wireless transmission module is mainly responsible for sending and receiving remote wireless communication data, and maintaining clock synchronization with the monitoring host; the monitoring host collects sensor data in real time by issuing commands, and saves the received data to the background database.

The bridge structure of strain gauges is shown in Figure 1. If R1 and R2 are strain gauges and R3 and R4 are standard resistors, the strain gauges and standard resistors form a half-bridge structure; if R1, R2, R3 and R4 are all strain gauges, It constitutes a full bridge structure. The sensor module in this embodiment is a half-bridge structure composed of strain gauges and resistors.

When the resistance values of the four bridge arms of the bridge meet:

$\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}$

When this relationship exists, the bridge is balanced, that is, there is no voltage between B and D. When one of the resistances changes, the bridge is out of balance, so there is a voltage U _BD between B and D. And the electronic potentiometer is used to ensure that U _BD is positive to amplify the signal. According to the size of U _BD , the corresponding resistance change and the corresponding line strain can be calculated. There is a certain linear relationship between the voltage change U _BD and the deformation of the measured steel. Use the acquisition terminal as the input device to configure the sensor module and set its corresponding parameters, and store the calibration table in the memory chip in the sensor module. The MCU of the sensor module reads the voltage U _BD module every time and then calculates according to the calibration table. The micro-strain of the measured steel measuring point can be measured, so that the force or pressure on the measured steel measuring point can be measured, and the micro-strain can also be directly measured.

The output of the conventional strain sensor is generally the output voltage value, and the physical quantity must be converted to obtain the physical quantity, and the balance adjustment circuit is complicated (manual resistors are more unstable, and the zero adjustment of this module uses an electronic potentiometer), and it cannot be measured. point temperature. The sensor module in this embodiment can effectively solve the above problems, and has the function of temperature compensation, and the measurement accuracy can be improved by a level.

After the sensor module converts the strain into a digital signal, it is sent to the wireless transmission module. The wireless transmission module uses the existing GSM network or CDMA network. The wireless transmission module described in this embodiment utilizes the internal GPRS module to establish a connection with China Mobile (or China Unicom), so as to establish a connection with the Internet by China Mobile, and what the whole tracking information is is exactly the IP address (or domain name), so in the wireless transmission module Data is sent to an IP address (or domain name). After the software terminal and the wireless transmission module establish a link, they can communicate with each other. The wireless transmission module sends the data of the sensor module to the corresponding IP address (or domain name), and then the upper layer software analyzes the data.

The installation method of the strain gauge in the sensor module described in this embodiment is shown in Figure 2. The compensation gauges R3 and R4 are located in the unstrained region of the elastic body, and the strain gauge is located in the strained region of the elastic body. Therefore, when the strain gauge is subjected to a force When the deformation occurs due to the relationship between R1 and R2, the resistance of R1 and R2 will change accordingly with the deformation of the measuring point, and the change of R3 and R4 will be small, resulting in the change of U _BD . In practice, the temperature compensation sheets of R3 and R4 are attached to the components under test The strain gauge on the test piece with the same material but no force is used as a temperature compensation resistor. During the measurement, the compensation plate should be placed near the measured point to ensure that when the ambient temperature changes, the measurement plate and the compensation The resistors R1 and R2 of the chip will have the same change without affecting the balance of the bridge.

The wireless transmission module is connected to the PC through a 485 to 232 or 485 to USB converter for communication, which can facilitate the operator to use the PC as an input device to modify the IP terminal address (or domain name) and the calibration table of the sensor module according to the actual situation setting. At the same time, the wireless transmission module can also be expanded, such as external zigbee or Ethernet.

The sensor module can also be expanded or changed into different products, such as force measuring sensors, pressure measuring sensors and deformation sensors.

The principle of the sensor module in this embodiment is shown in Figure 3:

The voltage collected by the strain gauge in the sensor module is connected to the circuit, and the bipolar signal is added to the single-supply analog-to-digital converter AD623 to output a single-source voltage. The single-supply analog-to-digital converter AD623 can remove the common-mode voltage, and The useful signal in the input signal is amplified by 100 times. The amplified signal is then converted through the 16-bit analog-to-digital conversion chip ADS1100A0IDBVT, communicates with the single-chip microcomputer STC89C58RD through the IIC communication protocol, and inputs the collected strain voltage into the single-chip microcomputer.

A port of the single chip microcomputer is also connected with a thermometer located at the strain position of the strain gauge, which is used to monitor the temperature change at this point in real time, mainly to provide temperature compensation data and further supplement and improve the monitoring data information.

The single-chip microcomputer reads the calibration table stored in the memory chip, combines the collected strain voltage, and finally outputs the deformation amount.

The input end of the strain gauge is connected with an electronic potentiometer. The operator can achieve the effect of adjusting the bridge balance by adjusting the resistance of the electronic potentiometer to ensure that the initial reading voltage is zero, which plays a role in zero adjustment.

Since the information between the sensor module and the wireless transmission module is to adapt to possible changes in the field, the voltage drop from 12V to 5V and the communication distance of RS485 can be adapted to long-distance communication.

The principle of the wireless transmission module is shown in Figure 4. The sensor module sends the collected data to a serial port of the dual-serial MCU in the wireless transmission module through the RS485 protocol. The RS485 to 232 protocol is used in the middle. The main functions of the MCU STC485EESA are The data is received from the serial port 1 (TX1/RX1) and sent to the wireless transmission module through the serial port 2 (TX2/RX2). The clock chip simulates the scl clock line and the sda data line through the P12 and P13 of the single-chip microcomputer, and respectively sends the read data Provide time record, and can complete the function of automatic measurement to the time point. The 18B20 thermometer chip can not only provide the temperature of the wireless transmission module, but also provide a 16-digit unique number for the wireless transmission module, which can prevent human confusion. The single-chip microcomputer can set self-numbering for the sensor module, which is convenient for memorizing the information of the module. The self-numbering information of the sensor module, the time of automatic reading and the online configuration information of the wireless transmission module are all set in the memory chip 24C256, and the communication between the single-chip microcomputer and the memory chip 24C256 The IIC communication protocol is also used. Ports P12 and P13 simulate the scl clock line and the sda data line. The difference between the clock chips depends on their address bits.

In this embodiment, the wireless transmission module adopts SIM300 module of Siemens, which is a tri-band/quad-band GSM/GPRS module with a small size and a board-to-board connector, and can be widely used in wireless public telephones, commercial telephones, WLL applications such as station entry, M2M (machine-to-machine) applications such as vehicle applications, remote meter reading, security monitoring, remote control telemetry, and handheld devices. Before connecting with the computer client, a connection needs to be established. The SIM needs to configure its server address, the IP address or domain name of the terminal to be sent to, and its self-number and network port number for easy identification.

When a connection needs to be established, the MCU sends commands according to the AT commands needed by SIM300. After the connection is established, the data collected by the sensor module can be freely communicated with the collection terminal. Data cannot be communicated without establishing a connection, and the command to establish a connection is resent every 10 minutes until the connection is successful.

The data communication link after the connection is established is as shown in Figure 5. In order to solve the problem that the public network IP of redialing or accessing the Internet is randomly generated, this embodiment adopts the domain name resolution function of peanut shells, and each connection Instead of using the IP address as the destination, the peanut shell software is run on the computer terminal, and the public network IP of the collection terminal to access the Internet can be known on the peanut shell server. After the Internet enters the route, it is mainly based on the port number agreed in advance, and the corresponding port number is mapped to the corresponding IP in the LAN through the route.

Claims (5)

1. remote wireless monitoring system, comprise sensor assembly, wireless transport module and the acquisition terminal that is attached thereto, wherein the signal output part of sensor assembly inserts the signal input part of wireless transport module, it is characterized in that, described sensor assembly comprises foil gauge bridge-type circuit and the single-chip microcomputer that is positioned at tested point, wherein the output terminal of foil gauge bridge-type circuit is by the signal input part of analog to digital converter access single-chip microcomputer, and described single-chip microcomputer is connected with storage chip and chip temperature.

2. according to the described remote wireless monitoring system of claim 1, it is characterized in that what described foil gauge bridge-type circuit adopted is the direct current half-bridge circuit.

3. according to claim 1 or 2 described remote wireless monitoring systems, it is characterized in that described chip temperature is a DS18B20 type thermometer chip.

4. according to claim 1 or 2 described remote wireless monitoring systems, it is characterized in that that described single-chip microcomputer adopts is chip STC89C58RD.

5. according to claim 1 or 2 described remote wireless monitoring systems, it is characterized in that that described wireless transport module adopts is the SIM300 of Siemens.

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