Outstanding performance for demanding applications.  
What do you gain when you choose the ThetaProbe? 
Feature Description  Advantage
DC in, DC out 
Requires 5 - 15V dc at 20mA. Provides 0 - 1V dc output. 

Compatible with ThetaMeter Readout Unit and most data loggers 

 

  • Dual purpose:
    - for burial and data logging - for hand-held use 
     
  • Long cable runs possible
  •  Easy to include in large-scale logging set ups
  

100 MHz signal

With frequencies below ~30 MHz, salinity effects can be a problem. With frequencies above ~250 MHz, measuring bound-water in clay soils is a problem.  

100 MHz is an excellent compromise 

  • Performs well in most soil types, including clays
  •  Usable in saline soils - up to 2000 mS.m-1
 
Standing Wave Ratio 

 

Simple, elegant circuit responds precisely to the dielectric properties of soil.
  • ±1% accuracy
  
  • Precision measurements at moderate cost
  4-Rod arrangement 

 
  

 

3 rods are arranged in a circle around a central rod. This creates a cylindrical zone of measurement 60mm long x 26.5mm diameter 

  

 

  • Holds soil closer to central rod when drying and cracking ( 2 and 3 rod arrangements don’t do this)
  
  • Measurements can be made close to the soil surface
  Replaceable rods 

 

 

Made of 3mm diameter, resilient, 304 austenitic stainless steel, with sharpened ends. 

Rods have threaded ends that screw into ThetaProbe body. 

 

  • Withstand repeated insertion in soil. Can be replaced at low cost if bent or damaged
  
  • Highly resistant to corrosion
  
  • Narrow rods with sharp tips minimise errors due to soil compaction as rods are inserted
 
Cylindrical 

shape 

 

The ThetaProbe casing is a 40mm diameter tube, with threaded end.  

Extension tubes (500 and 1000 mm) screw onto this thread.

  • Easy to insert and remove in augered holes 
  
  • Rapid attachment of extension tubes
 
 
  Compact size 

Case is robust and sealed to IP68 standard.   

Overall length of probe is 207mm

  • Handy size for portable use 
   
  • Rugged, waterproof and buriable to 5m
 
 
Delta-T support  
Thousands of ThetaProbes are in use all over the world. The latest ML2x includes improvements suggested by customer feedback
  • World-wide availability
   
  • Reassurance of quality
   
  • Advice on complete systems

Delta-T's new catalogue:   covering:
Soil Water Content: ThetaProbe -   introduction ;   performance ;   theory
Soil Water Potential:
Tensiometer ;   Equitensiometer
Pore water conductivity:
Sigmaprobe     theory
Evapotranspiration:
(Software and weather stations)
Data loggers and readout units ;   Application examples ;
 


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© Bruce Metelerkamp

www.sowacs.com/feature/deltat/ml2X-table.html
last update : 14 August 1999