Soil Moisture
   |
Tensiometers
Tensiometers consist of a ceramic cup attached to a tube filled with water. The tube is inserted in the soil. As the soil dries, water is pulled out of the tube through the porous ceramic cup and a negative pressure is created inside the tube. This is measured either by Bourdon type dial or electronically.
Standard "Bourdon" Tensiometer
Accepted as the traditional way of measuring soil potential, the standard "Bourdon" type tensiometer is robust and very good value for money. It is simple to use with low upkeep and easy to read. This type of tensiometer is very well suited to arable or horticultural water potential studies. The 1 bar ceramic has a diameter of 22mm and the measuring range is from 0-99 cbar (kPa). Standard tensiometers are available in lengths from 30cm to 150cm.
Electronic tensiometer -Tensicorder
The measuring technique with the SMS2500S electronic tensimeter consists in piercing through a silicon bung which seals a tensiometric cane, by means of a hypodermic needle, itself connected to a pressure transducer. This type of measurement, is very precise and very economical as one meter can be used on a great number of canes. The measuring principle of this system is both simple and gives very accurate readings. It consists of measuring the air pressure decrease created in an airtight system when water transfers through the porous ceramic.
Tensiometric canes consist of a ceramic cup glued to the bottom of a hollow PVC tube which is inserted into the soil to measure the water potential. The ceramic cups have the same characteristics as the standard tensiometer. Tensiometric canes are available in lengths from 15cm to 150cm.
 |
 |
 |
Standard "bourdon" tensiometer |
Electronic tensiometer - tensicorder |
Tensicorder set |
| Measuring range: | 0 Hpa-999 Hpa |
|---|---|
| Accuracy: | <2% of full scale |
| Pressure sensor: | Differential piezo-resistive sensor |
| Null Offset: | adjustable by user |
| Calibration: | a calibration certificate is given with each device |
| Measure type: | by hypodermic needle fixed in a DELRIN box. |
| Display: | by LCD display. Direct readings of the measured value in Hpa (or mbar). |
| Power: | dry cell 9 Volts 6LR61 or PP23 type |