One of the most sought after items in our portfolio, Soil moisture sensors are the starting point for studies in agriculture, civil engineering, remediation, slope stability and several diverse studies.
Time Domain Reflectometry (TDR)
Time Domain Reflectometry, commonly known as TDR, largely developed as the result of World War II radar research, offered a method to define dielectric relationships.
Beginning in 2001, Acclima developed and patented a means of development of a TDR soil moisture sensor where the waveform generator, the digitizing receiver, and the precision timing circuitry were small enough to be incorporated directly into the probe in a small, low cost package.
TDR methods offer immunity to errors caused by soil conductivity and are independent of amplitude,
current, impedance, or other Gaussian-related methods used to derive water content. Time domain sensors are also immune to errors that can be evident in other sensors when compacting the soil (soil
electrical conductivity is affected by compaction).
With Acclima’s introduction of TDT technology the cost of TDR-type technology was reduced from tens of thousands of dollars to hundreds of dollars. This makes it practical to install the sensor permanently
thus offering stable soil moisture readings with TDR credibility at a small fraction of conventional TDR costs.
The result is that the Acclima sensors are able to provide stable permittivity measurements with an accuracy of ±1% of full scale (relative permittivity from 1 to 80) even over the range of 0 to 4000 μS/cm bulk (in-soil) electrical conductivity.
Options available
TDR-315 
Completely intergrated TDR accurately yields VWC and BEC/PWEC with a high-speed 150 pico-second rise time for a detailed wave form analysis.
TDR-315L
Also a fully integrated TDR, the 315L consumes less power than its sibling, but still maintains a 300 pico-second rise time for superb accuracy.
True TDR-310S
This TDR is from the same family of the other Acclima True TDRs, however its rounded form factor allows it to easily attached to a (sched. 40) 1″ PCV pipe and/or be inserted into an access tube as small as 1.25″ (sched. 40 PVC) to be inserted into the soil at a specified depth.
TDR-310S Soil Moisture Sensor True TDR-310S Data Sheet
DataSnap Data Logger
Portable SDI-12 mini data recorder. Takes over 53,000 5-datapoint scans before it overwrites the oldest data. A/B USB cable included. Battery pack requires 8 AA batteries. AC/DC universal adapter is also included.