Measuring method for moisture content and conductivity of soilless culture substrate and sensor thereof

Abstract

The invention discloses a measuring method for the moisture content and conductivity of a soilless culture substrate and a sensor thereof. According to the measuring method, a signal collecting and conditioning circuit is used for performing time-sharing measurement on the conductivity and moisture content of a substrate, and a measured value of the moisture content is corrected according to a measuring result of the conductivity. The sensor comprises a power module, a conductivity exciting module, two polar sensor probes, a moisture content signal conditioning circuit, a conductivity signal modulating circuit and a wireless singlechip module, wherein a moisture content and conductivity capacitance sensor is formed by the two polar sensor probes; an exciting signal is generated by the conductivity exciting module under the control of a wireless signalchip; the exciting signal is acted on the polar sensor probes; a conductivity signal conditioning module is used for conditioning the signal, thereby obtaining two paths of voltage signals related to the conductivity of the substrate; a signal processing control unit, namely, the wireless singlechip, is used for collecting and processing a data, thereby obtaining a value of the conductivity; and under a high working frequency, an output signal of the moisture content signal conditioning circuit is processed by the wireless singlechip and is compensated by utilizing the value of the conductivity, thereby obtaining the value of the moisture content. The measuring method and the sensor provided by the invention can be used for accurately measuring the content and conductivity of the substrate and can be widely applied to greenhouse substrate soilless culture.

Description

technical field [0001] The present invention relates to a method for detecting water content and electrical conductivity of a soilless culture substrate and a wireless sensor thereof, in particular to a detection method capable of time-divisionally measuring the water content and electrical conductivity of a substrate based on the dielectric properties of the substrate and the electrical properties of capacitance It and its wireless sensor are mainly used to detect the water content and conductivity of the substrate in the process of soilless cultivation, and can also be used to detect the water content of soil, grain and other granular or powdery substances. Background technique [0002] The moisture and nutrients of the substrate in soilless culture are necessary conditions for plant growth and determine the quality of crops. The water content and conductivity of the matrix can reflect the content of water and nutrients in the matrix, and it is a comprehensive reflection o...

AI Technical Summary

Problems solved by technology

In summary, capacitive sensors have been researched and applied in the measurement of soil moisture content, but the detection results are affected by soil texture, bulk density, temperature, etc., and the measurement accuracy and accuracy are low.

[0006] At present, the more mature detection methods of soil conductivity include "current-voltage" four-electrode method and electromagnetic induction method. The current-voltage four-electrode method is simple to implement, but it is affected by temperature and water content.

A utility model patent for a real-time soil conductivity detector (CN2627503), which is large in size and poor in portability

However, at high conductivity, the TDR method cannot measure soil moisture due to excessive signal attenuation

FD fixed frequency decomposition method: Because the phase angle is too small, the water content and conductivity cannot be accurately obtained

Invention patent A method and sensor for simultaneous measurement of soil water content and electrical conductivity based on dielectric theory and frequency domain method (CN1719245A) A multi-frequency admittance decomposition method for simultaneous measurement of soil water content and electrical conductivity is proposed , to overcome the insufficiency of the FD method measuring soil moisture content being affected by conductivity and conductivity measurement being affected by water content

This method is based on the time domain reflectometer method and the frequency domain reflectometer method to measure water content. The circuit is complicated and expensive, so it is not suitable for popularization and application.

[0008] To sum up, there is currently a lack of on-line detection sensors for substrate water content and conductivity suitable for soilless cultivation; the more mature time-domain reflectometry and frequency-domain reflectometry methods for measuring soil water content have complex circuits, expensive prices, or are affected by the soil. The impact of texture is complex and other issues; ordinary capacitive soil moisture sensors have the advantages of low cost and rapidity, and the commonly used "current-voltage" four-electrode method and electromagnetic induction method to detect soil conductivity are simple to implement, but the measurement results are easy. Affected by the test object and environmental factors, the accuracy is not high; in terms of water content and conductivity composite sensors, the detection range is often limited, the detection circuit is complicated, and the price is expensive, so it is not suitable for promotion

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