Soil moisture detection and recording equipment maintenance and maintenance
The monitoring of soil moisture content and its variation is one of the basic tasks for the monitoring of agro-meteorological and ecological environment and hydrological environment. Soil moisture reflects the wet conditions of soil, and it is the basic work for agro-meteorology, ecological environment and hydrological monitoring, and also for agricultural drought. The important basis for information and forecasting, and mastering the laws of soil moisture changes, are important for the monitoring and prediction of agricultural irrigation, soil moisture content and agricultural drought, and related theoretical research. Agricultural weather observation is a basic meteorological observation project. For a long time, China's agricultural meteorological observations are mainly based on artificial visual inspection and simple instrumentation. There is basically no automated observation method and far behind the general surface meteorological elements. At present, the method commonly used at the vast stations is the weighing and drying method. . Therefore, it is of great practical significance to have time-saving, labor-saving, and accurate monitoring of soil moisture in practical work.
The soil moisture recorder is a part of the first phase project of the China Meteorological Administration's Atmospheric Monitoring Automation System Project. Shandong Province Soil moisture recorder is based on the relevant arrangements of the first phase project of the China Meteorological Administration's Atmospheric Monitoring Automation System project, since 2005. Construction of automatic soil moisture monitoring system. Since the automatic soil moisture collection system is used at numerous stations, it simplifies the original method of weighing and drying, and shortens the determination time of soil moisture, reduces the artificial strength, and most importantly achieves the continuous observation of soil moisture at a fixed point. Changes have more adapted to the needs of the current meteorological development.
Most of the agricultural meteorological observation objects are scattered in the natural state, with scattered data sampling points, large cycle differences, difficulty in the supply of mains electricity, high equipment installation and maintenance requirements, and strict requirements for safety precautions, in order to enable automatic observation and manual observation of soil moisture. Comparing and evaluating the requirements for achieving agro-meteorological observing norms, making the automatic observation data of soil moisture more objective and accurate, and connecting with the current general artificial observation data of soil moisture, with continuous line, comparability and applicability of business services, and thus better The application value and socio-economic benefits of the automatic observation of soil moisture are exerted, and the maintenance and repair of agricultural meteorological automatic observation stations are more important. The following uses the DZN1 Automatic Soil Moisture Monitor as an example to introduce the system components, main functions, and problems that need to be paid attention to in routine maintenance and repair of the agricultural automatic observation station.
1 Overview DZN1
The automatic soil moisture monitor is a soil moisture automatic measurement system integrating FDR principle soil moisture measurement sensor and bus data acquisition technology. Its technical specifications are in line with the design requirements of the China Meteorological Bureau soil moisture observation instrument. The system consists of four parts: sensor, collector, communication interface and system power supply. It can be equipped with a microcomputer according to business needs. It can display real-time and whole-point soil relative humidity, volumetric water content, weight water content, water storage and other dynamic changes and automatic Generate standard data files. According to the needs of users, the system can be expanded and the data collector can be expanded to access weather sensors such as wind direction, wind speed, temperature, humidity, pressure, rainfall, and ground temperature.
The instrument can be widely used in the field of meteorology, ecology, agriculture, geological disasters and other areas of detection and research. The instrument can be divided into three types according to the actual installation location: fixed segment type (station type), crop type (field type), auxiliary section (portable).
2 The system consists of an automatic soil moisture monitor consisting of hardware and software.
Hardware includes three parts: sensors, collectors, and peripherals. The software includes two kinds of acquisition software and computer software. Among them: the computer software of the station-type soil moisture observation instrument is installed in the computer of the observation room; the field-type soil moisture observation instrument needs to install the monitoring software of the central station at the central station. The equipment composition is shown in the figure below:
2.1. The soil moisture sensor adopts the world-class frequency domain reflectometer (FDR) soil moisture sensor, which is precise, reliable, durable, and free of radioactive sources. The sensor is made of environmentally friendly materials and is fully sealed. It can be buried for a long time and continuously measured at any depth in the ground.
The SWS-406 Soil Moisture Sensor uses the FDR principle to directly measure volumetric water content in soil.
SWS-406 soil moisture sensor consists of high-frequency transmitters, receivers, micro-processing, probes and other components. The high-frequency transmitter, receiver, and micro-processing seal are in a Ф40mm long, 130mm waterproof room, and four 60mm long stainless steel probes are fixedly connected to it.
Stainless steel probes are inserted directly into the soil. The cable at the end of the sensor is used to power the sensor and output an analog signal.
Its working principle is: Using FDR principle to measure the dielectric constant of soil. The change of the moisture in the soil leads to the change of the dielectric constant, and the volumetric moisture content of the soil has a function relationship with the dielectric constant.
2.2. MDT-30 Meteorological Data Collector MDT-30 Meteorological Data Collector uses a high-speed microprocessor as a CPU. The periphery includes an accurate clock device, a 16-bit A/D conversion device, a 128MB standard CF card, a low-temperature-resistant liquid crystal display and signals. Lightning protection interface. With RS-232/RS-485 two standard communication ports. Stores data for the entire 60 days.
The collector is the core of an automatic soil moisture measurement system. Its main function is to complete the sampling of soil moisture sensors in each layer, control data for the sampling data, data calculation and processing, data quality control, data recording and storage, and realize data communication and transmission. The collector can be equipped with self-check and self-diagnosis functions, including the following: power supply voltage status monitoring; sensor status monitoring; and communication status monitoring.
2.3. Peripheral devices 2.3.1 Power supply The power supply system is mainly divided into two types: the battery is the backup mains supply system and the solar-assisted rechargeable battery supply system. They are used in municipal and non-mainstream environments.
The 12 volt DC voltage is the basic operating voltage of the data collector and the other DC operating voltages in the collector are converted.
2.3.2 A computer, ie a microcomputer, is used as a station-type terminal to realize the monitoring, data processing and storage of the collector, and completes the soil moisture observation service in accordance with the requirements of the "Agricultural Meteorological Observation Standards".
2.3.3 GPRS wireless transmission module is used for wireless data transmission of field type automatic soil moisture monitor.
2.4 Software 2.4.1 Acquisition Software Acquisition software supports the data acquisition, data processing, data storage, and data transmission functions of the collector.
2.4.2 Station Business Software The software software for processing soil moisture observations is an application software installed in a microcomputer connected to a soil moisture analyzer.
2.4.3 GPRS Central Station Software Center Station Software The Provincial Meteorological Observatory or Information Center is used to collect, monitor, manage, and query data from field stations based on GPRS wireless networks.
3 Main functions 3.1 Data acquisition The observer automatically collects soil moisture data in real time and reads the measurement results every 1 minute. The average of every 10 measurement data is used as the observed value for 10 minutes, and every 6 observations for 10 minutes The arithmetic average is taken as the average of the hourly observations.
3.2. Data processing Based on the measured soil moisture volume moisture content, according to the input soil parameters measured in advance, according to the relevant formula to calculate the soil moisture content, relative humidity, effective storage of soil moisture.
3.3. There is a standard CF card (128M) in the data storage. It stores the measurement data and average data for the entire 60-day period so that it can be queried at any time.
3.4. Display and key control The current data can be read directly from the display. The date and clock can be set or modified via the display panel.
3.5. The data communication observation instrument can be connected to the upper terminal through a serial communication port. According to the established communication protocol, the upper computer can read out the measurement data and stored data of the observer; set the parameters required for the observer; set the observer's The time interval between communication and automatic data transmission;
4 Routine maintenance 1. Inspect the equipment after bad weather such as dust storm, strong thunderstorm, strong wind, and heavy rain at the time of 08:00 daily to check whether the power supply of the instrument (equipment and computer) is normal, whether the sensor is working properly and whether the communication is normal.
2. Daily through the automatic soil moisture monitor computer terminal to check whether the data collected the previous day is complete, if there is a lack of timely measurement manual supplement.
3. Regularly check whether the connection between the cable and the sensor and the collector is loose. Check the cable regularly every year for damage and aging.
4. Establish a dedicated diary work diary, fill it out on a daily basis, and carefully record the above inspection and treatment.
5. When it is found that the instrument is faulty, it should be recorded in detail in the diary on duty, and promptly notify the manufacturer of the necessary treatment according to the fault condition.
5 Failure Judgment and Maintenance 5.1 Computer Terminal Failure 5.1.1. Software Failure 1. Phenomenon: The system failed to start up and check the operating system. If the operating system fails, reinstall the operating system.
2. Phenomenon: The crash of the terminal service software First, restart the computer and check whether the terminal service software is normal. If it is abnormal, reinstall the service software.
5.1.2, hardware failure 1. Phenomenon: The power indicator is off after power on.
Check that the power plug is securely connected.
2. Phenomenon: The terminal computer has no data or communication status is abnormal.
Inspection and processing steps:
1) Check whether the terminal computer is dead, check whether the communication module connected to the communication port of the terminal computer is off, and whether the communication cable connected to the communication module is off.
2) Check if the collector time is normal and the soil observation data in each layer is normal through the monitor on the data collector. Check the communication cable on the data collector is connected properly.
3) Check if the communication cable between the terminal computer and the data collector is normal.
4) Replace the communication module connected to the terminal computer communication port.
5) If all of the above are normal, please contact the manufacturer.
5.2 Data Collector Failure Symptom: The data collector display does not display or show data failure.
Inspection and processing steps:
1, check the data collector power supply. Unplug the power input terminal on the data collector and use the multimeter's DC voltage level to measure whether the DC voltage of the power input terminal is normal. The normal voltage range is 10-15 volts. If it is 0, it can be judged that the fault appears in the power supply part, and check the power supply system according to the relevant procedures of 4.4.
2, check the data collector. Turn off the power switch on the data collector and remove all the terminals on the data collector except the power supply. Then turn on the power switch to check whether the data collector recovers. If it is abnormal, you can determine the failure of the data collector and replace it.
3. Damage to other components If the voltage is abnormal, you can unplug the terminals of each sensor terminal and communication cable terminal from the interface board of the data collector one by one. Use a multimeter to monitor the DC power supply voltage to see if the voltage returns to normal. Normally, the external components (sensors, etc.) that were recently unplugged are damaged and need to be replaced.
5.3 Sensor Failure Check (Live Measurement)
1. Find the corresponding sensor on the collector and unscrew the + and - feet of the sensor terminals from the collector terminal.
2. Measure the voltage between cable + terminal and foot with a multimeter DC voltage 2V. The voltage should be between 0 and 1.2 volts. Determine if the sensor is normal according to the environment.
3, check the sensor terminals are loose.
4. If the sensor fails, replace the sensor.
5.4 Power supply system failure Phenomenon: The terminal service software shows that the power supply voltage is too low, less than 9V or no voltage in the data collector.
Inspection and processing steps:
1. Check the air switch. The AC switch of the data collector is closed. If it is closed, open it.
2. Check the AC input. The AC input cable of the data collector is connected properly. If the connection is normal, you can use the multimeter's AC or electric pen to measure whether there is AC input.
3, check the power converter. If the AC input is normal, remove the positive and negative wires of the battery fork, and then use the multimeter DC voltage file to measure the DC input voltage of the data collector. If there is no voltage output, it can be determined that the power converter is faulty and replaced.
4, check the battery. Remove the positive and negative battery wires and forks, and then use the multimeter DC voltage range to measure the DC voltage across the battery, whether it is normal (10V or more). If the voltage is too low, connect the positive and negative wires of the battery fork, use the power converter to charge, charge for more than 10 hours, disconnect the air switch, use the battery to power the data collector, and measure the voltage of the battery positive and negative. If the voltage is lower than 10V, it can be judged that the battery is faulty and replaced.
5, check each sensor. Use a multimeter DC voltage file to measure the DC voltage at the DC input of the datalogger.
If the voltage is abnormal, all sensor terminals on the data collector can be unplugged and measurement can continue. If the voltage is normal, it can be judged that there is a sensor failure. Insert the sensor terminals one by one into the data collector. When the voltage is abnormal, the sensor can be judged to be faulty and replaced.
5.5 GPRS Module Failure 1. Phenomenon: The network status of a single station is disconnected and data cannot be received.
Maintenance: First, check if the station is owed. Then check if the signal of the mobile company in the area where the station is located is normal. Finally, go to the site to check the wireless transmission module indicator.
If it is a steady red light, it indicates that the wireless transmission module is working properly. It may be an instrument failure of the substation.
If it is green and flashing, it indicates that the wireless transmission module is looking for the network. It may be that the wireless network signal is not good. A simple method is to use the mobile phone to check it at the antenna, or change the antenna to a position and then recharge it.
If the indicator is off, check if the input power of the wireless transmission module is normal. The power terminal is a headphone jack type. The inside of the hole is the positive terminal of the power supply, and the outside of the hole is the negative terminal of the power supply. If the power supply is normal, the wireless transmission module may be faulty and the module needs to be replaced.
Special Note: When replacing a new module, be sure to use the phone card in the original module. The SIM card number of the phone card is used for identification of the external station. If the phone card is replaced, you need to change the SIM card of the mobile phone card. The number is notified to the central station administrator and is set by the administrator so that the station can normally transmit data.
2. Symptom: The network status of all stations is disconnected and data cannot be received.
Maintenance: The problem may be at the central station. First, check if the software is normal and restart the central station software. Then, check whether the mobile line is properly connected. Finally, the mobile company is queried for any outstanding fees or other reasons.
5.6 Lightning Strikes, Short Circuits, etc. If there is a major fault such as a lightning strike or a short circuit, it is possible to clearly observe damage to the device or damage to the electric shock. Contact the manufacturer in time and the factory will send someone to solve it on site.
6 Conclusions and discussion At present, the drab drying method is commonly used at many stations. This measurement method is relatively simple. The disadvantages are long measurement time, large labor intensity, and large destruction, and it is not possible to observe the continuous change of soil moisture at fixed points. Many of the land sections are combined with crop observation areas, and their data do not truly reflect the soil moisture status of a region under natural conditions. Obviously, this method can no longer meet the needs of the national economic construction and the current meteorological reform and development. The DZN1 Automatic Soil Moisture Monitor, which is highly automated, was developed to meet the needs of ecological environment monitoring and meteorological business development.
The Agricultural Meteorological Automatic Station is the first phase project of the China Meteorological Administration's Atmospheric Monitoring Automation System Project. Resolving the current problems, taking it seriously, carefully assessing it, and accumulating experience, will surely make the Agricultural Meteorological Automated Station move on to a healthy and stable development. the road. The faults of the DZN1 Automatic Soil Moisture Monitor can be solved by station operators. Some need to be solved by technical professionals. However, regardless of any failures, station personnel must first analyze the failure phenomena, and gradually check and accurately determine the faults. Fault location, using a reasonable method to troubleshoot, can not appear as soon as the equipment failure, please superior professional and technical personnel, but do not dare to manually check, analyze the reasons, troubleshooting. If you can't really judge and troubleshoot, and then ask the professional and technical personnel for help, this method is not only suitable for automatic soil moisture collection system, but also applies to other collection systems. In this way, station business personnel can continuously sum up experience and improve their own technical skills.
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