T8 Manual - UMS

More documents

Recommendations

Info

Useful notes 7.2 Temperature influences If the sensor is not powered continuously the voltage should be switched on 10 seconds before a measurement. In this case, the self heating is negligible. The correlation of water tension to water content is temperature dependent. The influence is low at tensions of 0 to 10 kPa ⇒ 0 … 0,6 kPa/K, but high for tensions over 100 kPa: Ψ = ⎛ ⎜ ⎝ R ⋅T ⎞ ⎛ Ρ ⎞ ⎟⋅ln ⎜ ⎟ M ⎠ ⎝ Ρo ⎠ Ψ = Water tension R = Gas constant (8,31J/mol K) M = Molecular weight p = Vapor pressure p o = Saturation vapor pressure at soil temperature (from Scheffler/Straub, Grigull) 7.3 Vapor pressure influence on pF/WC If the temperature of a soil with a constant water content rises from 20°C to 25°C the soil water tension is reduced for about 0,85 kPa due to the increased vapor pressure which antagonizes the water tension. Temperature in °C 4 10 16 20 25 30 50 70 Pressure change per Kelvin in [kPa] 0,06 0,09 0,12 0,15 0,19 0,25 0,72 1,4 7.4 Osmotic effect The ceramic has a pore size of r = 0,3 µm and therefore cannot block ions. Thus, an influence of osmosis on the measurements is negligible because ion concentration differences are equalized quickly. If the T8 cup is dipped into a saturated NaCl solution the reading will be 1 kPa for a short moment, then it will drop to 0 kPa again. 46/56
Troubleshooting 7.5 Using a T8 as a piezometer The T8 can be used as a piezometer for measuring water over pressure. Calculate the height of the water level with: p p = H2O ⋅ g ⋅ h [hPa] and: h = p p ⋅ g H2O p H2O Density of water at 20°C: 0,998205 kg/dm3, at 4°C: 1,0 kg/dm3. [Pa] = [N]/[qm]; [N] = [kg/m qsec]; [kg] = [Pa qm/m]; [Pa] = kg/[qqm qsec]. A water column of 100 cm causes the following pressure: p [Pa= N/qm] = 998,205 kg/qqm x 9,81 m/qs x 1m p = 9792,39 [N/qm x Pa qs/m /qqm x m/qs x m] = 9,792 kPa. Accordingly 10 kPa at 20°C indicate a water column of 102,15 cm. 8 Troubleshooting Please refer to our webpage where you will find a regularly up-dated list of FAQs: http://www.ums-muc.de/en/support/faq/tensiometer.html 47/56
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 and 12: Description of the T8 2 Description
Page 13 and 14: Description of the T8 2.2 Output si
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 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: Useful notes If there will be rain
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

T8 Manual - UMS

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?