TDR Overview

TDR (Time Domain Reflectometry)

Technology Explainer

TDR sensors measure the time it takes for an electromagnetic pulse to travel along a probe and reflect back. The travel time changes with the soil’s dielectric constant, which varies with moisture content.

Accuracy

Together with TDT sensors TDR sensors give the most accurate measurements of volumetric water content.

Price

TDR sensors are the most expensive sensors that practical for in-situ measurements. The high cost of these sensors usually make them not feasible to be used in agricultural operations.

Installation & Maintenance

TDR sensors need to be buried in the ground. This requires that a hole is dug to the depth the sensors should be installed at. Thereafter, the sensors need to be inserted into the side walls of the holes.

Once installed, TDR sensors do not require any maintenance or recalibration.

Soil Types

TDR sensors work in all types of natural soils

Measurements

Besides measuring volumetric water content (VWC) TDR sensors also measure soil temperature and soil salinity (EC).

Summary

High Accuracy: TDR sensors provide precise measurements of soil moisture, making them highly reliable for scientific and commercial agricultural use.

Versatility: They can be used in a variety of soil types and conditions and give measure

Depth Profiling: These sensors can measure soil moisture at various depths, offering a detailed moisture profile.

Cost: High quality TDR sensors are usually the most expensive, which can make them uneconomical for some users especially in agriculture.

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