The soil moisture measuring instrument is a professional instrument for measuring soil moisture. The instrument emits electromagnetic waves of a certain frequency. Electromagnetic waves are transmitted along the probes, return to the bottom, and measure the voltage output from the probe. The change in the dielectric constant of the soil depends on the soil. The water content of the soil can be calculated from the relationship between the output voltage and moisture. In this way, the measured soil moisture can meet a large part of the requirements, but for some standards in scientific research, the accuracy of the soil moisture measured by the probe has yet to be improved. However, we can do some work on the basis of the soil moisture meter so that the results can achieve higher accuracy. Aluminum Bar,Aluminum Round Rod,Aluminium Round Bar,Solid Aluminium Bar GanSu Port Logistics Co.,Ltd , https://www.gskouan.com
When using the probe method to measure soil moisture, it will be affected by the soil environment, and the measurement error in the saline-alkali land is the largest. In order to minimize the occurrence of this error, digital filter technology is added in the soil moisture measuring instrument. To reduce the impact of environmental factors on the determination of soil moisture, commonly used digital filtering algorithms: finite amplitude filtering, median filtering, arithmetic average filtering, weighted average filtering, moving average filtering, low-pass filtering, and composite filtering Laws, etc., there is always one of the most suitable methods for measuring soil moisture:
1) The limiting filter method compares the difference between two adjacent data sets and the maximum allowable error value to obtain the data. It is mainly used to deal with slowly changing data.
2) Median filtering method by measuring N sets of data. N is the cardinal number, which is taken as the result of the soil moisture temperature meter measurement by taking the average value. Only accidental factors can be excluded, and those quickly changing values ​​have no effect.
3) Arithmetic mean filter method, arithmetic average filter method is to take N times sample value continuously and perform arithmetic average, which is suitable for filtering the signal with random interference, which is affected by the data group.
4) The weighted average filter method, this kind of conversion comparison inconvenience, the advanced measurement N group of data multiplies it by the weighting coefficient, carries on the accumulation sum.
5) The moving average filter method, the sliding average filter method is to sample only once, compare this value with the value of the past sampling, and average. When the sampling speed is slow, the real-time performance of the system can be guaranteed.
6) Low-pass filter method, low-pass filter method is to express the differential equation of the analog low-pass filter by difference equation, so that the software filter can be used to simulate the function of hardware filter, and it has certain effect for those slow changes.
7) The composite filtering method and the composite filtering method combine two kinds of digital filters with different filtering functions to form a composite filter, which has a good buffering effect for both fast and slow signals.
By using the above method, and then comparing it with the results measured by a soil moisture temperature meter or a soil moisture monitoring system, it was found that the arithmetic average filtering method and the moving average filter are used as the filtering algorithm of the measuring instrument and can be applied to the environment. The disturbance of each parameter was reduced to a minimum, and the accuracy of the value measured by the soil moisture meter was the highest.