True root mean square value detection-based soil moisture sensor

Abstract

The invention relates to a true root mean square value detection-based soil moisture sensor, which comprises a power supply filter circuit, an active crystal oscillator, a Schmidt trigger, a signal attenuator, a probe and a true root mean square value detector. The Schmidt trigger shapes a high-frequency sine wave or square wave signal output by the active crystal oscillator into a standard waveform square wave signal, the amplitude of the standard waveform square wave signal is reduced by the signal attenuator, a resistor-capacitor (RC) circuit consisting of the signal attenuator and the probe is charged and discharged periodically, a periodic charging and discharging curve waveform is obtained on the probe, and the true root mean square value detector converts a waveform signal on the probe into equivalent direct current voltage serving as a sensor output signal. When soil moisture is different, the equivalent capacitance of the probe is different, the charging and discharging waveforms are different, and the final output signals are different, so that the soil moisture is measured according to the principle. The soil moisture sensor has the characteristics of simple structure, small volume, low power consumption, low cost, high soil adaptability, simple input / output interface and the like, is easy to apply and facilitates the development of secondary instruments.

Description

technical field [0001] The invention relates to the technical field of soil moisture measurement, in particular to a soil moisture sensor based on a dielectric method and high-frequency signal true effective value detection. Background technique [0002] Soil moisture is one of the important factors affecting the growth of crops, and it is closely related to the growth status of crops. In precision agricultural production, long-term monitoring and timely acquisition of moisture content information in the soil are required to achieve precise irrigation, so as to meet the physiological water requirements of crops without wasting water resources. This requires a soil Moisture testing device. [0003] The measurement methods of soil moisture are: drying method, neutron method, resistance method, capacitance method, TDR (time domain reflection method), FDR (frequency domain reflection method) and SWR (standing wave method). The drying method has high measurement accuracy, but s...

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Problems solved by technology

However, at present, most of the various commercial dielectric soil moisture sensors are needle-type structures. This structure has the characteristics of simple geometric structure and convenient manufacture. However, due to the influence of the strength of the probe, the length of the probe cannot be too long, which limits the measurement. The range of the soil depth; in addition, due to the sensor's external dimensions and other reasons, it is inconvenient to bury it in the deep soil for measurement

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