Soil moisture probes

 
 
 
 
   
 
 
 

 

   

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
 
 
 
 
Most sensor types infer the moisture content from measurements of soil electrical properties but  our choice of sensor method is thermal dissipation .

The principle can be appreciated by placing a hand on dry then wet soil and noting the latter feels cooler due to the greater heat conduction from the hand.


A key advantage of this approach is that measurements are negligibly affected by temperature and solute content, which is particularly  important where nutrient salts are added to the irrigation water. 

We have developed a miniaturised  sensor to reduce power requirement and manufacturing costs.

One version is embedded in  our engineered porous ceramic with known moisture-release characteristics. This enables measurements to be calibrated against water potential and closely relates to plant water availability and is independent of soil type and bulk density.


 

    
 A bare sensor version is calibrated for volumetric moisture, which is suitable for use in  highly porous horticultural substrates used in hydroponic culture and many types of green wall planting systems.
 

All sensor versions also measure temperature

 A modular electronic system developed has been for sensor excitation, signal capture, data processing and communication by a variety of protocol. Currently this consists of one module for RS485/SDI12 cable transmission and another for zigbee wireless networking.

 A GPRS option also exists to transmit data to a web portal for display on a remote computer and to drive irrigation decision-support software.