Capacitance-process soil water measurement instrument with ultra-high measurement precision based on phase-locked loop technology

Abstract

The invention relates to a capacitance-process soil water measurement instrument with ultra-high measurement precision based on a phase-locked loop technology, and belongs to a capacitance-process soil water measurement instrument. An output end of a singlechip MCU of the water measurement instrument is connected with an input end of a phase-locked loop circuit PLL; phase-locked voltage PD of the phase-locked loop circuit PLL is simultaneously connected with an input end of a voltage-controlled oscillator VCO, a negative pole of a variable capacitance diode, a switch K1, a switch K2 and an input end of an AD converter; an output end of the AD converter is connected with an input end of the singlechip MCU; a positive pole of the variable capacitance diode is connected with a calibration capacitor and is grounded simultaneously; the other end of the calibration capacitor is connected with the other end of the switch K2; and the other end of the switch K1 is grounded by a fitting capacitor. The capacitance-process soil water measurement instrument with ultra-high measurement precision based on the phase-locked loop technology has the advantages that water of soil or other similar application is measured in a non-invasive, single sensing or stereoscopic multi-layered sensing mode, ultra-high stability of measurement is realized, the resolution ratio, reliability and precision of measurement are greatly improved, and the shortcomings that an existing measuring method is poor in measuring precision and center lines drift severely are overcome fundamentally.

Description

technical field [0001] The invention relates to a capacitance-method soil moisture measuring instrument, in particular to a capacitance-method soil moisture measuring instrument with ultra-high measurement precision based on phase-locked loop technology. Background technique [0002] Moisture is an important part of soil. It not only affects the physical properties of soil, but also is an important factor of soil fertility. It is also the basic condition for the survival of all crops. The understanding and research and development of soil moisture are important in theory and production. Its significance, and its application fields such as: 1. For agricultural activities such as tillage, irrigation and fertilization, this soil moisture meter can be used to measure the water content in the soil in advance, so as to achieve real-time online, intelligent irrigation according to water demand, and maximize Save water for agricultural irrigation. 2. When carrying out some engineer...

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Problems solved by technology

[0003] There are several measurement methods for soil moisture today, including the following: 1. Frequency domain reflection method, 2. Time domain reflection method, 3. Neutron method, 4. Negative pressure method, 5. Resistance method, 6. Capacitance method; In addition to the frequency domain reflection method and the capacitance method, other methods have more or less shortcomings such as the need for intervention, low measurement accuracy, poor stability and repeatability of measurement results, while the neutron method has high measurement accuracy, but there are radiation problems. shortcoming

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