T8 Manual - UMS
T8 Manual - UMS T8 Manual - UMS
Description of the T8 2.1.5 Filling status indicator The filling status indicator indicates the filling status of a T8 in a downwards installation (cup lower than end of the shaft). If the Tensiometer is installed in an upward angle (cup higher than the end of the shaft), the water will still cover the indicator even if air is already inside the cup. Thus, the indicator will react not before the cup is almost completely empty (s. fig. 5.3 on page 38). The filling status is determined by measuring the heat flux with the internal temperature probe. For a probe dipped into water the heat flux rate is lower than in air. If an air bubble appears around the temperature probe, the heat flux rate rises and the insufficient filling status is detected. This method offers a rough but reliable reference for checking the filling and has the advantage of staying stable over the whole lifespan of the Tensiometer. It replaces the previously use IR-photo diode. The measurement of the soil water tension is not influenced. Benefits of the filling status indicator are an optimal service: If for example mounting rails with integrated LEDs are used, the user can check at a glance if all Tensiometers work well or which need to be refilled. Also, for quality assurance, the status of the signal can be logged for later evaluation of the readings. 2.1.6 The ceramic cup 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 T8 cup consists of ceramic Al2O3 sinter material. The special manufacturing process guarantees homogeneous porosity with good water conductivity and very high firmness. Compared to conventional porous ceramic the cup is much more durable. The bubble point is at least 1500 kPa (15 bar). If the soil is dryer than 1500 kPa 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. The cup has a lifetime guarantee against breakage. 12/56
Description of the T8 2.2 Output signals 2.2.1 Analog The T8 version 2005 has an internal microprocessor and offers water tension and temperature as analog output signals plus the refilling status as a digital signal. Water tension and temperature are available as linear voltage signals in a selectable range of 0...1 V, 0...2 V (default setting) or 0...5 V. Thus, the T8 are compatible to almost any data logger or data acquisition system. Furthermore, the measuring range itself can be set for special measuring tasks. Standard is +100 kPa to -100 kPa and -30 to +70°C. The standard setting for the filling status is either switch “open” (0 V) or “closed” (voltage signal equal to power supply voltage). 2.2.2 Digital To change the settings of signal range or use the serial interface of the T8 the tensioLINK ® USB converter with Windows software tensioVIEW ® is available as an accessory. Filling status as a Digital Status If the indicator detects an air bubble the indicator switch closes and the supply voltage is available on the output. If for example a LED with a series resistor is connected, the LED will light up to indicate the necessity of refilling. In addition, or instead, connect the signal to a digital or analogue logger channel to record the filling status for quality control of the matrix potential readings. 2.3 Serial interfaces The T8 has two serial interfaces: the RS485 compatible tensioLINK interface and SDI12. 13/56
- Page 1 and 2: User Manual T8 Long-term Monitoring
- Page 3 and 4: Tensiometer T8 3.5.4 Connecting the
- Page 5 and 6: Tensiometer T8 1.2 Content of deliv
- Page 7 and 8: Tensiometer T8 Soil water and Tensi
- Page 9 and 10: Tensiometer T8 External syringe ref
- Page 11: Description of the T8 2 Description
- Page 15 and 16: Description of the T8 2.4 Software
- Page 17 and 18: Installation • Lightning: cables
- Page 19 and 20: Installation 3.2.1 "Vertical" with
- Page 21 and 22: Installation 4. Connect the Tensiom
- Page 23 and 24: Installation 3.5 Connecting T8 3.5.
- Page 25 and 26: T8 configuration with tensioVIEW®
- Page 27 and 28: T8 configuration with tensioVIEW®
- Page 29 and 30: T8 configuration with tensioVIEW®
- Page 31 and 32: T8 configuration with tensioVIEW®
- Page 33 and 34: T8 configuration with tensioVIEW®
- Page 35 and 36: Service and maintenance If the soil
- Page 37 and 38: Service and maintenance With this m
- Page 39 and 40: Service and maintenance Remove the
- Page 41 and 42: Protecting the measuring site 6 Pro
- Page 43 and 44: Protecting the measuring site Gener
- Page 45 and 46: Useful notes If there will be rain
- Page 47 and 48: Troubleshooting 7.5 Using a T8 as a
- Page 49 and 50: Appendix Optional settings* Output
- Page 51 and 52: Appendix 9.3 Accessories 9.3.1 Conn
- Page 53 and 54: Appendix 9.3.4 Refill kits BKTex Re
- Page 55 and 56: Appendix 55/56
Description of the <strong>T8</strong><br />
2.1.5 Filling status indicator<br />
The filling status indicator indicates the filling status of a <strong>T8</strong> in a<br />
downwards installation (cup lower than end of the shaft).<br />
If the Tensiometer is installed in an upward angle (cup higher than<br />
the end of the shaft), the water will still cover the indicator even if<br />
air is already inside the cup. Thus, the indicator will react not<br />
before the cup is almost completely empty (s. fig. 5.3 on page 38).<br />
The filling status is determined by measuring the heat flux with the<br />
internal temperature probe. For a probe dipped into water the heat<br />
flux rate is lower than in air. If an air bubble appears around the<br />
temperature probe, the heat flux rate rises and the insufficient filling<br />
status is detected. This method offers a rough but reliable reference<br />
for checking the filling and has the advantage of staying stable over<br />
the whole lifespan of the Tensiometer. It replaces the previously use<br />
IR-photo diode. The measurement of the soil water tension is not<br />
influenced.<br />
Benefits of the filling status indicator are an optimal service: If for<br />
example mounting rails with integrated LEDs are used, the user can<br />
check at a glance if all Tensiometers work well or which need to be<br />
refilled.<br />
Also, for quality assurance, the status of the signal can be logged for<br />
later evaluation of the readings.<br />
2.1.6 The ceramic cup<br />
To transfer the soil water tension as a negative pressure into the<br />
Tensiometer, a semi-permeable diaphragm is required. This must<br />
have good mechanical stability and water-permeability, but also have<br />
gas impermeability.<br />
The <strong>T8</strong> cup consists of ceramic Al2O3 sinter material. The special<br />
manufacturing process guarantees homogeneous porosity with good<br />
water conductivity and very high firmness. Compared to conventional<br />
porous ceramic the cup is much more durable.<br />
The bubble point is at least 1500 kPa (15 bar). If the soil is dryer than<br />
1500 kPa the negative pressure inside the cup decreases and the<br />
readings go down to 0 kPa.<br />
With these characteristics this material has outstanding suitability to<br />
work as the semi permeable diaphragm for Tensiometers.<br />
The cup has a lifetime guarantee against breakage.<br />
12/56
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