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Service and maintenance
If the soil dries out more than -1500 kPa (-15 bar), the negative
pressure will drop much faster as air will enter the cup.
5.1.2 Refilling in the lab
To reach the optimal measuring range of -90 kPa Tensiometers
should be refilled in the laboratory using the refill kit.
1.
Set up the refilling kit and connect the vacuum pump as shown in
the photo. The pump should achieve at least 0,8 kPa against
vacuum. Use distilled or de-ionized water which necessarily does
not have to be degassed when a pump is used.
2.
Unscrew the cup in clockwise direction and empty it.
Do not touch the ceramic cup with your fingers. Wrap a clean
towel around the cup!
The pressure sensor diaphragm is inside the small hole on the
pressure sensor body. It is very sensitive and may never be
touched! It can be destroyed even by slightest contact!
No contamination should get on the sealing and gasket.
3.
If the cup is dry it should be placed in a beaker filled with distilled
water for several hours or overnight. Initially there should be no
water inside the cup! Place the empty cup into the beaker in an
upright position, with the external water level reaching no higher
than 2/3 of the cup.
If the cup is filled with water and water intrudes from both inside
and outside cavities of air will be enclosed inside the ceramic.
Adaptor for
sensor body
Adaptor for
ceramic cup
Fig. 5.1: UMS laboratory refill kit BKT468
Vacuum gauge
Connection to vacuum
pump
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