Time-Domain Reflectometer

OverviewThe TDR200 Time-Domain Reflectometer is the core of the Campbell Scientific time-domain reflectometry (TDR) system. TDR systems accurately determine soil volumetric water content, soil bulk el

  • Product Name:Time-Domain Reflectometer
  • Item No.:TDR200
  • Manufacturers:Campbell
  • Country of Origin:USA

Overview

The TDR200 Time-Domain Reflectometer is the core of the Campbell Scientific time-domain reflectometry (TDR) system. TDR systems accurately determine soil volumetric water content, soil bulk electrical conductivity, rock mass deformation, or a user-specific time-domain measurement. One Campbell Scientific data logger can control multiple TDR200 reflectometers.


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.


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.

Range 

0 to 3800 m (distance)

0 to 27.75 μs (time)

Resolution  

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