Yun Shi ^1,2，Cangxu Feng²

¹⁾ Agricultural University of Hebei, Baoding city Hebei province 071051

²⁾ Institute of hydrogeology and engineering geology technic, CGS, Baoding city Hebei province 071051

Abstract: The monitoring of groundwater is an important basal commonweal work. It can ensure the economy and society go on development. But the present monitoring methods can’t adapt to the needs of Hydrogeology, Engineering Geology and Environment Geology. The paper simply introduces the advanced technique of sensor and wireless communication, including their characters and the system structure. The system of groundwater dynamic monitoring integrates many-advanced technique. It collects the data of water level and water temperature through multi-sensor. It manages the datathrough embed-chip. It transfers the data wirelessly through the GSM data model-TC35. All this makes up of an aptitude-monitoring network that is used on groundwater.

Key words: groundwater monitoring, advanced sensor technique, wireless communication technique, construction of network, multi-sensor, embed-chip

1 Introduction

Water resource is one of human's valuable wealth. Water is the necessary absoluately in the human'daily life, industry and agricultury production. The quatity of the human'needing water is increasing gradually with the population in the world and the development of the industry and the agriculture. At the same time, the daily life and the production of  industry and agricuture caused the pollution of surface water and groundwater and the deterioration of water quality. This makes the limited water resource more absent.

In order to exploit and utilize the groundwater resource with reason, we must monitor the change of groundwater trends on the basis of strengthening perambulation to prevent the environment of groundwater from deterioration in the utility area and prevent the new developing areas from arizing the simiar question. The trends includ the changes of the quality and quatity of groundwater. We can understand the distributing rule of groundwater from time and space and the dynamic chang rule through monitoring the groundwater dynamic. So we can make the consequent countermeasure to protect the water for daily life and industry and agriculture.

The groundwater monitoring is an important work of foundation and commonweal for ensureing the social economy to develop continuously. On the one side, to strengthen the work of groundwater monitoring can provide basic information for establishing the utilizing and protecting scheme , On the other side, it is also the direct method to verify whether the resource utilized with reason and the measures of protecting geological environment proper.We can find out the extisting problems in the process of developing and utilizing the water through analyzing the long-term monitoring information. As a result, we can present the improving direction and the more protecting measures. So groundwater monitoring is the basic support condition of the country economy and social development, it is also the guaranteeing measures to realize continuable development.

Water conservancy began to monitor the level,  temperature, quality and utilizing quatity of groundwater since 1960.This monitoring information of groundwater did a great contribution for the water resource management and utilization with reason in the past years. But at present the work of groundwater monitoring exists many questions. The whole work is weak. For example,there is few monitoring well for groundwater in the important water source and the big crateriform. The methods of groundwater monitoring is behindhand. The real time and efficiency of information transmission is lagging. All this can't meet the require of water resource management.

2 Modern detection technique

Sensor technique, communication technique and information management technique constitutes the three big foundation of modern detection technique. They finished the information pick-uping,transmission and management to the object measured respectively. They are important marks of modern science and technique development. The application of detection technique has been used in many fields such as industry ,agriculture, national defence and daily life. The detecting object is more complicated. The need of detection precision and reliability is more high than before. The study of modern detection theory and application is an important studying direction to adapt the background.

2.1 Modern sensor technique

Modern sensor technique, computer technique and communication technique are intituled the three big stanchion technique. As the bionic view, computer is thought as the "cerebrum"of managing and identifying the information, the communication system is thought as "nerve systerm"of transfering the information, then the sensor is thought as the "sensor apparatus"of picking up the information.

The sensor technique is about to get hold of the information from national signal source and then managing and identifying the information. It is a cross modern science and engineering technique of referring many subject.It refers the sensor(transducer), information processing and identification's layout designing, development, construction, test, application,estimate and improvement. Getting hold of the information rely on many kinds of sensors including physical signal,chemical signal and biological signal. Gaining the national information has already become the common require of nearly all natural science and engineering technique fields. With the expansion of human activities fields and the deep of exploiting process, sensor technique has been the new fields of basal science study and modern technique introjecting each other. It influxes and contains a lot of results of multi-subject.It becomes the one of the most active parts of human exploiting activities. The trends of modern sensor' development fully represents this characters.

2.2 Data processing technique

Data processing includs data collecting, saving,indexing, matching, transforming and communicating.The basal object of data processing is to extract and educe the most valuable and significative data to some given people from a plenty of datas which may be mussy and unreadable. Data processing is the basic tache of systemic project and automation.Data processing runs through many fields of social production and social life. The extent and deepness of data processing affented greatly the course of human society development. Data processing can't leave the support of soft. The data processing soft includs: all kinds of programme designing language and the compiler; the file system and database system of managing data; all kinds of software package of data processing methods. Different processing methods require differents hardware and software support.Data processing mainly includs four methods:①Online processing methods and offline processing methods based on the structure of processing device. ②batch-processing method, tine-shareing processing method and real time processing method based on the distributing method of data processing time. ③Concentrateing processing method and distributing processing method based on the distributing method of data processing space. ④Single-route work processing method, multi-route work processing method and inter-processing method.

2.3 Communication technique

Data communication is company with the origin of human. The human entered the modern communication period in 19 century. The communication theory began to set up accompanied the information statement put forward. The human began to enter the internet period with the emission of artificial communication satellite. At present the actuality communication technique is coexistence of wireness and wireless. The development of wireless communication technique have the trends to overren the wireness because of the its convenience. The wireless communication net has the GSM net, GPRS net and CDMA net. The GSM net holds the most quotient of market. It is the leading mode and the fact standard of Global mobile communication.

3 Designning of the Groundwater Monitoring System

The essay discussed the designning idea of blocking based on the sensor of water-level and water-temperature. It realizes the foundation of groundwater monitoring net system. This system integrated the embeded-technique,sensor technique and wireless communication technique. It has widely application value in practice.

3.1 Designning of Groundwater Monitoring system's structure

The studied groundwater monitoring system based this essay is composed with sensor module, signal transformed module,data processing module and wireless transmission module. The monitoring system's structure frame is as Fig.1:

 

 

(1) Sensor module. Sensor module is constituted with temperature sensor(PN Junction), pressure sensor, modem circuit and simulation signal switch. The PN Junction and pressure sensor transform the water level signal and water temperature signal to the electronic signal. The two of signal are switched by the simulation signal switch. The two signals common use one chip anplifier and A/D transmission chip. The controlling circuit gives the controlling signal to choose the two simulation signals on or off. The signal is amplified through modulating circuit. The simulated signal is outputted finally.

(2) Signal transmission module. Signal transmission is composed with the A/D transmission chip and its peripheral circuit. It transforms the simulated signal outputted by the simulation module to digital signal and outputs the digital signal to P1 port of SCM.

(3) Data processing module. Data processing module is composed with the SCM module and alarmed module, The SCM module completed the data's processing and transmiting. It controls also the alarmed module, transmission module and the timing work. The alarmed module is composed with the LBD, buzzer audion and the related resistance and capacitance.

(4)Wireless transmission module. The wireless transmission module is composed with the TC35 data module and its peripheral circuit. It is connected with the SCM's serial port. It commute data through serial port. The wireless transmission module can complete the intercommunication. It receives the commanding signal from center node and send the signal to temperature and pressure sensor. It also can send the digital signal coming from sensor to center node.

3.2  The realization of wireless transmission

This system makes the GSM public net as the data transmission net. It is a outstanding excellence of the whole groundwater monitoring system. Adoptting the TC35 wireless transmission module, we can realize the data transmission during sensor's net rapidly and reliably.

TC35 module is composed with some SLSI and radioapparatus, embeded SIEMENS TL35 which is mobile engine circuit module and sustainning the data operation.

The controlling circuit of wire transmission module makes a low-power AT89C51 as the core. The "TC-35 MODEM" is controlled forwardly through the controlling lined. It can complete the GSM module's dial-up calling, the responsion of  in coming telephone and the correct of the error during the system running. The circuit includes 256KD flash memory, MAX3221 of voltage transfering chip and the peripheral controlling circuit. Their function is to save the monitoring programme, telling telephone numbers and 232 chip's voltage conversion. In order to prevent disturbing the node's normal work as the communication system is working. We add a simulate switch in the "GSM module" RS-232 output port of communication system. It is off if there is not valid data calling. The controlling circuit will turn on the simulate swith if there is valid data calling. Then the monitoring device state up and process data communication. The controlling system will turn off the simulate controlling switch after they receive the "NO CNT" command if the communication is completee. The node enters the automatism work's state in order to response the next call or the data's automatism collecting. The module can enter the sleep module automatically when the module don't transmit the data. So it can save the power.

 TC35 module embeded the AT communication protocol. It processes the writting operation to GSM controller through AT command. The module sustains the standard AT command. During real running, we only requires to equip SIM card to the module. The data transmission's process is as follows:

The communication system is in the waitting for calling state in the common days. When the center node calls the general node, the system first judges if the calling number is valid. If it isn't valid, the system don't response the calling. If it is valid, the system judges if the calling is data communication call. The system don't response the calling . If it is valid, the system waits till the diabolo sings three times to ensure the calling is valid. The SCM controlling system send out the command. The node responsed and set up the communication relation.

When the data communication succeeds to link, the SCM controlling system connects the "RS-232" port of general node and enters the communication states. It response the controlling command sent by the center node. At this time the "GSM communication system" becomes a transparence channel. It cann't response the data which is transmitted in communication.

The center node or general node send out the command when the communication ends. It exits the communication state and waits for the next call.

3.3  Function of the system

The main function of Groundwater monitoring system is as follows:

(1) The function of data collecting. The subsystem collects the monitoring data and saves it to the internal memory. The data is timely transmitted to the superior system automatically. The data can be transfered by the superior system with the statement and refreshs the database.

(2) The function of mobile net communication. The application of GSM communication technique make the monitoring data to enter the net of Groundwater monitoring net expediently. It offers the convinence for the extension and maintenance.

4 Conclusion

The foundation of groundwater monitoring net is a commonweal project which benefits the afterword. It is a very diffcult thing because it refers to many kinds of techniques and departments. How to get the exactest data in the shortest time is very important of groundwater monitoring. Optimizing and perfecting the network of groundwater monitoring using the technique of modernization, which is discussed by this essay, makes the monitoring level of our country to get ahead.

 

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