Time-Domain Reflectometer

Detailed Description

The TDR200 generates a short rise time electromagnetic pulse that is applied to a coaxial system that includes a TDR probe for soil water measurements. Then the reflectometer samples and digitizes the resulting reflection waveform for analysis or storage.

The elapsed travel time and pulse reflection amplitude contain information used by the on-board processor to quickly and accurately determine soil volumetric water content, soil bulk electrical conductivity, rock mass deformation, or a user-specific time-domain measurement.

The data logger collects a 250-point waveform and analyzes it in approximately two seconds. Each waveform can have up to 10,112 data points for monitoring long cable lengths used in rock mass deformation or slope stability. Advanced noise filtering and averaging make accurate measurements possible in noisy environments.

A Complete System

A complete TDR200-based system includes the TDR200, SDM8X50 multiplexers, data logger, power supply, enclosures, and probes. PC-TDR version 3 software supports TDR200 and sensor setup, troubleshooting, and program generation.

This software is available, at no charge, from our website.

The SDM8X50 Multiplexer brochureTDR Probes component category brochure, and Time-Domain Reflectometry System brochure provide additional information about the TDR system components.


Pulse Generator Output 250 mV into 50 Ω
Output Impedance 50 Ω ±1%
Time Response of Combined Pulse Generator & Sampling Circuit ≤ 85 ps
Pulse Generator Aberrations
  • ±16% (within first 1 ns)
  • ±1% (after 1 ns)
Pulse Length 25.5 μs
Waveform Averaging 1 to 128
Operating Temperature Range -40° to +85°C
Power Supply Unregulated 12 Vdc (9.6 to 16 Vdc)

150 mA maximum, USB powered (5 Vdc)

Dimensions 21.6 x 5.1 x 10.7 cm (8.5 x 2.0 x 4.2 in.)
Weight 0.79 kg (1.75 lb)
Waveform Sampling
-NOTE- 20 to 10112 waveform values over chosen length

Distance is Vp=1. Time is one-way travel.

  • 0 to 3800 m (distance)
  • 0 to 27.75 μs (time)
  • 1.35 mm (distance)
  • < 4.4 ps (time)
Electrostatic Discharge Protection
Air ±8 kV @ 2 Ω
Contact ±4 kV @ 2 Ω
Surge ±2 kV @ 2 Ω
Current Drain
During Measurement 120 mA
Sleep Mode 1 mA