An accurate knowledge of soil characteristics is essential for all researchers studying pollutant transfers through soils or agricultural management practises (modelling irrigation, fertilization, plant protection).
The WIND method has been specifically designed to simultaneously determine the fundamental hydrodynamic soil properties which govern water transfers in soils :
- The matric potential / water content relationship
- The hydraulic conductivity / water content relationship
The WIND method is a laboratory method. It consists in submitting a cylinder of soil (collected in the field) initially saturated, to a progressive evaporation and to follow:
- The temporal variation of the mass of soil contained in the cylinder m(t), in order to determine the water loss by evaporation and the average water content of the soil sample.
- The matric potential evolution of the soil sample at different depths ψ(z,t).
(National Agronomical Research Institute)
The unit contains six pressure transducers (differential voltage output) and the associated electronic circuit. The six micro tensiometers connected to this unit are introduced into the stainless steel cylinder containing the soil sample. The cylinder is placed on a very precise balance in order to measure its mass variations and determine the water content variations. These data are then related to the soil matric potentials measured with the micro tensiometers over the same period of time. The unit has been designed to eliminate the influence of external disturbing effects (temperatures, pressures, etc.) and ensure very accurate measurements.
Measuring ranges : 0 to -999 HPa
Power supply : 12 volts c.c (9 to18 V possible.).
Output voltage for pressure sensor : 0 to 50 mV. (These values can be different for each sensor. The calibration certificate given with each points the measurement range for each sensors with a great accuracy, and the correspondence hPa (mbar).
Voltage regulator for pressure sensors : 5,00 Volts / 400 mA.
Voltage output : ± 2%.
Line regulation : ± 0,5 % maxi.
Charge regulation : ± 1% maxi. (10-90%).
Residual ripples : (20Mhz pass-band) : 60 mV. typical crest to crest.
Protection against short-circuits : continuous.
Operating temperature : -10°C à +40°C. (WARNING, the centralizing box does not to be at these temperatures.
Temperature of centralizing box : +15°C to + 25°C.
Internal measurement of box temperature : by PT100 class A (3 wire).
Inner resistances network : Welwyn type 15 ppm / 0,1%.
[**] Differential presure sensor :
Offset : 0 ±1,5mV (given by calibration certificate).
Linearity : ± 0,25 (% SPAN).
Repeatability & hysteresis : ±0,20 (% SPAN).
Response time : 1 msec.
Stability over one year : ±0,5 (% SPAN).
Compensated temperature : 0°C to +50°C.
Sensitivity : 6,67mV/psi (0,1mV/mbar).
Overpressure input : + 2,5 bars.
Precision balance : in option