Maximum Measuring Range And Data Interpretation - UMS T5 User Manual

Useful notes
6.2 Maximum measuring range and data
interpretation
The measuring range of Tensiometers is limited by the boiling point
of water. At a temperature of 20°C the boiling point is at 2,3 kPa over
vacuum. So with 20°C and an atmospheric pressure of 95 kPa the
Tensiometer cannot measure a tension below -92,7 kPa, even if the
soils gets drier than that. The readings remain at a constant value
(fig. 7.1, between day 10 and 16).
Interpretation Messwerte bis über 15 bar nahe der
100000
10000
1000
100
10
1
0
Fig. 7.1: Tensiometer readings with tensions to -2 bar
If the soil will get even drier and reaches -2 bar, the ceramic's bubble
point is reached. The cup water will run out quickly and the reading
of the air filled cup will go to zero (fig. 7.1, day 16-19)
Interpretation of readings to -2 bars
Bodenoberfläche
2 4 6
Bodenwasserspannung
Soil water tension
Tensiometer reading
Tensiometermesswert
8 10 12
Time
Zeit
36/48
14 16 18 2 0