T8 Manual - UMS
T8 Manual - UMS
T8 Manual - UMS
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Service and maintenance<br />
5.2 Testing<br />
5.2.1 Calibration<br />
When delivered Tensiometers are calibrated with an offset of 0 kPa<br />
(when in horizontal position) and a linear response. The offset of the<br />
pressure transducer has a minimal drift over the years. Therefore,<br />
we recommend you check sensors once a year and re-calibrate<br />
them every two years.<br />
Return the Tensiometers to us for recalibration, or use the calibration<br />
accessories available from <strong>UMS</strong>.<br />
5.2.2 Check the Offset<br />
With zero pressure difference between inside and outside of the cup<br />
(cup in air) the signal should be 0 kPa.<br />
There are two ways to check the offset.<br />
1. Connect the Tensiometer to a readout device. Place the filled <strong>T8</strong><br />
in a beaker and fill the beaker with distilled or de-ionized water to a<br />
height of 7,5 cm. Wait until the reading is stable. If there are bubbles<br />
inside the cup this might take a while. The reading now should be<br />
0 kPa.<br />
2. To check the zero-point more precisely unscrew the cup. Shake<br />
the pressure sensor to remove water from the pressure transducer<br />
hole. The offset is acceptable when the reading is between -0,5 and<br />
+0,5 kPa.<br />
The pressure sensor diaphragm is inside the small hole on the<br />
pressure sensor body. It is very sensitive and must never be<br />
touched! It can be destroyed even by slightest contact! No<br />
contamination should get on the sealing and gasket.<br />
Before reassembling cup and sensor body carry out the degassing<br />
procedure (see chapter 5.1.2 "Refilling in the lab").<br />
For testing the signal gradient a calibration kit is required.<br />
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