About the Current Version of WinTDR

Over the past 10 years WinTDR has constantly been improved and updated. Originally designed to run only under 16-bit Windows, today WinTDR can be run under Windows 9x, ME, NT, 2000, or XP. Analysis accuracy has been improved as newly researched principles have been incorporated to allow lab settings to calculate very accurate Electrical Conductivity, Water Content, and Bulk Dielectric values.

Currently WinTDR has the following features:

Connects to the Tektronix 1502/3 B/C TDR units, via the Tektronix SP232 module
Self calibration of probe length and impedance (cell constant) values
New Graphical Interface to allow the user to quickly view waveform values, multiple waveform viewing (see how a waveform changes over time) and enhanced usability.
Quickly change analysis information and settings.
Dynamic file formatting for saving waveforms and file location specified by the user (even save to a hard drive over a local area network).
Ability to change the third order polynomials coefficients of Topp's (1980) equation with user defined coefficients.
Waveform values are in Reflection Coefficient values (Rho).
Option to calculate Dielectric Constant from the temperature of water.
Ability to use Multiplexers (Campbell SDMX50 8 to 1 and VaZEC 16 to 1)
Automated readings for automatic data capturing and analysis.

Future plans for WinTDR include:

Connectivity with Campbell TDR100 device
Power user options for file structuring and multiple methods of analysis

ABOUT WinTDR

WinTDR is developed by the Soil Physics Group at Utah State University, Logan Utah, USA. This program is designed to measure volumetric water content, electrical conductivity, and permitivity (or dielectric content) of soils / solutions, using Time Domain Reflectometry (TDR) research. (Additional information regarding TDR can be found in "Time Domain Reflectometry (TDR) Measurement Principles and Applications" by Jones S.B, J.M. Wraith, and D. Or.) [pdf]

Since it's conception in 1993, WinTDR has continued to evolve and grow with the research of TDR concepts. The intent of the program has been to create an easy and friendly Windows interface with which to have accurate and efficient analysis under a variety of conditions. The program is in use here at Utah State University and now at a variety of research and management locations throughout the world.

The basic principles used by WinTDR for analysis to determine the bulk dielectric from a TDR waveform are (see the diagram for a visual description of a TDR waveform):

First, the reflected distance an electromagnetic wave travels from the TDR device, through cables of fixed dielectric properties to the head of the probe and back again, is fairly constant, with exception of small variations due to temperature. We call this the first reflection, or "peak" of the waveform. The first peak can be set by the user or determined by the waveform 'analyzer' of WinTDR.
Second, the travel distance (time), back and forth, along the length of the probe is determined by finding the point of the second reflection, which follows the peak, and subtracting the peak from the point of the second reflection.
Finally, the length of the probes prongs, is a known fixed constant. The travel distance along the probe length determines the bulk dielectric which is then converted into the volumetric water content by applying Topp's (1980) equation.

Additional information, including more detail about the analysis process accomplished by WinTDR can be found on the documentation page.