Soil moisture - Capacitance-sensors (Volumetric)

Volumetric sensors measure the water content in the soil, providing information on the amount of water currently contained in the soil, including the not plant-available water. When interpreting volumetric readings, the soil type must be considered, and generally applicable optimum ranges are not available. Common units are Vol.% or mm water per liter or m³ of soil.

Advantages

• Soil specific calibration possible
• Information about the amount of water contained in the soil
• very accurate measuring technique
• immediate reaction to changing moisture conditions in the soil.
• maintenance-free and frost-proof sensors

Functionality

We offer sensors and devices based on the measuring techniques TDR (Time Domain Reflectometry) and FDR (Frequency Domain Reflectometry).

Working Principle TDR

TDR (Time Domain Reflectometry) sensors determine the water content in the soil by measuring the dielectric properties of the soil by measuring the travel time of an electromagnetic pulse through conductors located in the soil. The speed at which the electromagnetic pulse propagates in the soil depends on its dielectric properties, and thus its water content. The measured value of the transit time is then automatically converted into volumetric soil water content.

Working Principle FDR

FDR (Frequency Domain Reflectometry) sensors measure the dielectric properties of the soil using typically two electrodes. The readout device "checks" returning electromagnetic waves for deviations in the frequency range and thus ultimately determines the water content in the soil.