Water is an important part of natural soil. It not only affects the physical properties of the soil, but also restricts the dissolution and transfer of nutrients in the soil and the activity of microorganisms. It is an important factor in composing soil fertility, and it is the survival of all plants. The basic conditions. Therefore, measuring the soil moisture content is of great significance to the implementation of precision agriculture, water-saving irrigation, and improving agricultural production efficiency. At present, the methods for measuring soil moisture can be summarized into two major categories. One is the variable position sampling measurement (such as drying weighing method, etc.), and the other is the in situ sampling measurement (such as neutron method, γ-ray method, time domain Reflectometer method, frequency domain emitter method, sensor method, etc.). Different methods have their own advantages and disadvantages. The drying and weighing method has a simple principle and high precision, but its operation is cumbersome and cannot be continuously monitored in the field in real time. Although neutron method and gamma ray method can be quickly and accurately monitored outdoors, there are radioactive substances that endanger human health. The time domain reflectometry method and frequency domain transmitter method are relatively expensive, and the sensor method is safe and reliable, and the soil water content can be quickly and directly read. There is no need to sample the soil, the soil structure is not destroyed, and the electric signal can be continuously monitored and output. It is very suitable for Monitoring the dynamic distribution and change of soil moisture in the field, facilitating long-term observations and accumulating field water potential data, etc., are therefore widely used to monitor soil moisture in the field. The soil moisture quickness tester uses a soil moisture sensor to convert the soil moisture content θ (%) to the soil water suction and act on the piezoresistive sensor. The piezoresistive sensor converts the soil water suction into a differential voltage signal output to the double Input single-ended output differential amplifier. The differential amplifier is used here because it has a good effect of suppressing zero drift and anti-interference, and it can convert the double-ended input signal into a single-ended output signal. Since the output and input of the differential amplifier are in opposite phase, the output signal is sent to the inverting amplifier again, and the output is inverted again while the signal is amplified, and the voltage is converted into a voltage signal in phase with the output of the piezoresistive sensor. In order to adjust the amplification of the inverting amplifier as needed, a potentiometer is connected in series in the feedback loop, and the signal is zeroed and corrected. Finally, the output signal of the circuit is sent to the voltmeter to display the final output voltage value. A soil moisture content meter is prepared according to the calibration condition of the test data, and the soil moisture content can be directly read out. It can be seen from the measurement results that the difference between the measured value of the soil moisture meter and the drying weighing method is within 5%, which indicates that the measurement accuracy of the soil moisture meter is relatively high. In particular, the use of soil moisture quick-measuring device to measure soil moisture content speed (measurement takes only a few seconds at a time), numerical display, very intuitive, easy to use, small size, easy to carry, can measure moisture content at any time, very suitable for the field , greenhouses, lawns and other occasions to use. Because the piezoresistive sensor is made of semiconductor materials, the influence of temperature must be considered in the occasion where the measurement accuracy is relatively high. The experiment shows that the piezoresistive sensor exhibits negative temperature characteristics. When the temperature rises, the piezoresistive coefficient becomes smaller, and when the temperature decreases, the piezoresistance coefficient becomes large. In order to reduce the influence of temperature, it is necessary to use a constant current source as much as possible on the one hand. On the other hand, a positive temperature coefficient material is used as a temperature compensation circuit and it should be as close as possible to the piezoresistive sensor so as to achieve a better compensation effect. Oxygen Sensor For Buick,Best Oxygen Sensor,Buick Oxygen Sensor,Buick O2 Sensor RUIAN XIANGTAI AUTOMOTIVE PARTS CO ., LTD , https://www.raxiangtais.com