Design of Environmental Monitoring Instrument Based on Single Chip Microcomputer

introduction

With the continuous enhancement of people's environmental awareness and the continuous improvement of the country's attention to environmental protection, the society has put forward new and higher requirements for environmental monitoring, and the task of environmental monitoring has become increasingly arduous. According to incomplete statistics, my country has formulated more than 400 national environmental standards of various types, covering the fields of atmosphere, water quality, soil, noise, radiation, solid waste, pesticides, etc. In addition, environmental quality monitoring, environmental quality weekly, daily, and forecast monitoring have been carried out; pollution source monitoring, pollution accident emergency monitoring, total pollutant control monitoring, pollution source analysis monitoring, environmental pollution control project effect monitoring, etc., and there are hundreds of pollution factors to be monitored. This kind of environmental monitoring situation with many points, wide areas, and heavy tasks urgently needs to improve the automation level of environmental monitoring, reduce the amount of manual work, and improve the effectiveness of environmental monitoring. With the continuous development of large-scale integrated circuit manufacturing technology, it has promoted the development of single-chip microcomputer technology. It provides convenience for real-time environmental monitoring under field conditions. The single-chip microcomputer is characterized by its "small size and strong functions". It has the function of a microcomputer. The application of single-chip microcomputer in environmental monitoring instrument can reduce the volume and weight of environmental monitoring instrument, improve the automation level of environmental monitoring instrument, and enhance the accuracy of environmental monitoring.

1 Analysis of main environmental monitoring instruments

As all sectors of society pay more and more attention to the environment, more and more investment is being made in environmental monitoring at all levels. This has effectively promoted the improvement of environmental monitoring levels. The methods and approaches of environmental monitoring have also shown new characteristics and trends. Environmental monitoring is developing from manual operations to automation and intelligence. From single-item monitoring to three-dimensional comprehensive monitoring, environmental monitoring instruments have become more high-tech.

1.1 Infrared greenhouse gas monitor

Greenhouse gases have a great impact on global temperature, leading to melting of glaciers, rising sea levels, and abnormal deterioration of global climate. Therefore, it is of great significance to strengthen the monitoring of greenhouse gases in the atmosphere. The automatic greenhouse gas monitoring system mainly monitors the concentration changes of greenhouse gases in the atmosphere, assesses the impact of greenhouse gases on environmental changes, and provides support for the country to formulate long-term development plans. Infrared spectroscopy gas monitors are mainly used for air environment analysis, combustion emission detection, incinerator detection, scientific research, and gas purity analysis. It has the characteristics of high sensitivity, high resolution, and a wide range of monitored gases.

1.2 Air environment organic pollutant monitor

The air environment organic pollutant monitor mainly completes the continuous automatic monitoring of organic pollutant emissions in the air. Accurately define the emission configuration of organic pollution sources. Effectively reduce the emission of organic pollutants. Reduce the harm of organic pollutants to the human body. Reduce the degree of air deterioration and improve the monitoring level of regional characteristic organic pollutants. The monitoring analyzer is portable, easy to operate, and has fast and accurate testing. It is mainly used for the organized emission of particulate pollutants. The use of this equipment can effectively reduce the labor intensity of on-site monitoring, greatly improve work efficiency, realize on-site data, and improve the reliability of monitoring data. It can timely reflect the emission concentration and emission rate of the monitored object at the monitoring site, providing a reliable technical means for the formulation and verification of regional total control indicators. It provides a convenient means for the effectiveness of automatic monitoring data of key pollution source enterprises under state control and the supervision of audit work.

1-3 Water Quality Monitor Water quality monitor is mainly used to effectively monitor the discharge of water quality pollutants in water bodies, and is particularly suitable for monitoring heavy metals. Water quality monitor is mainly based on sequential injection analysis platform, combined with photometric colorimetry, anodic voltammetric dissolution and other detection technologies. It realizes the online monitoring of heavy metals in water environment. It meets the current demand for online monitoring of heavy metals in water environment. The equipment can be widely used in drinking water safety early warning, pollution source energy conservation and emission reduction management, water environment status management evaluation and planning, etc.

1.4 Fugitive Ammonia Monitor

The probe of the escape ammonia monitor uses a catalyst to convert ammonia into NOx, and after dust removal and water removal, it passes through a nitrogen oxide converter to convert NO into NO. It is sent to a high-precision measurement unit to measure the NO concentration of the mixed gas. At the same time, another independent channel is sent to the measurement unit after dust removal, water removal, and ammonia removal, and then passes through a nitrogen oxide converter to measure the NOx concentration. The concentration of the measured mixed gas converted to NO minus the concentration of NOx is the concentration of ammonia. At the same time, it is sampled and processed, using spectral analysis technology and analysis methods to achieve high-precision measurement. [page]

2 Design of environmental monitoring instrument based on single chip microcomputer

2.1 Overall system structure

In order to improve the effectiveness of environmental monitoring and reduce the amount of outdoor work, the advantages of small size, low power consumption and strong data processing capability of single-chip microcomputer are brought into play. The author proposes a design scheme for environmental monitoring instrument based on single-chip microcomputer. The overall system of this design includes microprocessor module (16-bit single-chip microcomputer, calendar clock chip, reset circuit and peripheral circuit), sensor measurement module (infrared sensor, temperature and humidity sensor, gas sensitive element, etc.), memory module (Fjash memory), communication module f serial communication, wireless communication), power supply module, etc., which mainly completes the monitoring of air quality, organic pollutants in the air and related gases. The overall structure block diagram is shown in Figure 1. The instrument can monitor the concentration of gas and inhalable particles at the same time. On the same display screen, one instrument can monitor four parameters at the same time. The working mode of the instrument is automatic sampling and automatic analysis. The measured concentration is directly displayed on the display screen. It also automatically calculates the daily average and monthly average, and can store 30 days of monitoring data (including daily average and monthly average). The instrument has USB and RS485 data transfer interfaces. The stored data can be transferred to the computer.

Figure 1 Overall structure diagram

2.2 Sensor Selection

The sensor is the key element that determines the accuracy of the monitor. It must be carefully selected. The selection of sensors in this instrument is mainly based on the outdoor working environment, measurement accuracy, linearity, interchangeability, sensitivity, response speed, stability, power consumption, size and other factors. The various sensors selected for this monitor are: ion-sensitive sensor ISFET, integrated temperature sensor TMP35, integrated humidity sensor HM1500, gas sensor MR51l, etc. These sensors have the above advantages and are also small in size. They are very suitable for the requirements of outdoor environment monitoring equipment.

2.3 Greenhouse gas measurement module

MH-410V/D NDIR infrared gas sensor is used to monitor CO2 gas. MH-410V/D NDIR infrared gas sensor is a universal, intelligent, miniature sensor. The sensor uses the principle of non-dispersive infrared (NDIR) to detect CO2 in the air. It has good selectivity, no oxygen dependence, stable performance and long life. Built-in temperature sensor can be used for temperature compensation; MH-410V/D is a compact infrared gas sensor made by combining mature infrared absorption gas detection technology with micro-machining and sophisticated circuit design.

2.4 Software Design

The software adopts modular design and is written in a mixture of assembly language and C language. It includes the main program and interrupt program, and has initialization module, data acquisition and processing module, display module, interrupt module, system test and alarm module. After the single-chip microcomputer system is powered on, it enters the initialization program to complete the initialization work such as setting up each module in the chip, clearing LCD memory, and setting the terminal VI, and then enters the main program. Turn on the interrupt, set the low power mode in a loop and perform no operation. Initialization is to initialize the external interface, timer and other components; the sensor module completes the data collection: the data acquisition and data processing module completes the analysis and processing of the relevant single measurement results: the display module will monitor the results: the interrupt control module completes the self-diagnosis function of the environmental protection data exceeding the standard alarm or the abnormal alarm.