The Ceramic Tip; Analog Output Signals - UMS T5 User Manual

Sensor description
2.1.4

The ceramic tip

To transfer the soil water tension as a negative pressure into the
Tensiometer, a semi-permeable diaphragm is required. This must
have good mechanical stability and water-permeability, but also have
gas impermeability.
The Tensiometer cup consists of porous ceramic Al2O3 sinter
material. The
homogeneous porosity with good water conductivity and very high
firmness. Compared to conventional porous ceramic the cup is much
more durable.
The bubble point of a T5 cup is about 200 kPa, of a T5x about 500
kPa. If the soil gets dryer than this air passes through so the
negative pressure inside the cup decreases and the readings go
down to 0 kPa.
With these characteristics this material has outstanding suitability to
work as the semi permeable diaphragm for Tensiometers.
Ceramic cup: Do not touch the cup with your fingers. Grease,
sweat or soap residues will influence the ceramic's hydrophilic
performance.
Do not allow the T5 ceramic to dry out by leaving it unprotected in
air: By drying out the bubble point might be reached, the reading
will go to 0 kPa and air might enter the cup which requires a
refilling.

2.2 Analog output signals

The pressure transducer offers the soil water tension as a linear
output signal, with 1 mV corresponding to 1 kPa.
As the pressure transducer is a Wheatstone full bridge, it has to be
connected in a certain mode. Please read chapter 3.5.3 and the
manual of your display unit or data-logger before connection.
special manufacturing
13/48
process guarantees