ku-pF apparatus
The ku-pF MP10 is a laboratory instrument for the automatic determination of any saturated hydraulic conductivity ku and the pf curve (water tension curve) in accordance with the condensation method on up to 10 soil ring samples simultaneously. The apparatus is designed for the use of the UGT soil sample rings with 250 cm³ inner volume and 41 cm² cross sectional area. These soil sample rings have bore holes arranged exactly at height intervals of 3 cm for the insertion of the tensiometers. However, they may also be used for obtaining samples separately from the ku-pf apparatus. The filled soil sample rings are set onto filter plates, saturated and sealed basally in the carrier basket for the test run. The gradient resulting from the condensation on the free ground surface is recorded by two tensiometers which record the corresponding water content and the flow rate by periodical weighing respectively. The Tensio 130 tensiometers with particularly small ceramic cup (Ø = 6,5 mm / L = 20 mm) provide exact measurements with a minimum destruction of the soil. Air bubbles are easy to recognise and eliminate through the acrylic head with bleed screw. The arrangement of the samples on the star shaped carrier which rotates at the set test interval permits the examination of 10 samples simultaneously. The sample on the weighing position is lifted from the carrier by lifting the scales so that it is standing free. The weighing data and the tensions here are stored on the internal data logger. Automatic measuring produces continuous measurement series with a minimum of monitoring. The scales are automatically balanced between weighings. Drift effects or any foreign bodies on the scales do not therefore cause any interference. The ku-pf apparatus works independently of a PC due to the integrated data logger and a microcomputer. A connection must be created to the PC only for maintenance, test start and reading out of the data.
The ku-pF apparatus is available as a single measurement station -> ku-pF SP.
Technical Specifications
| Soil sample ring volume: | 250 cm3 |
| Cross section of the soil sample rings: | 41 cm2 |
| Number of samples: | 1 – 10 |
| Cycle time of data acquisition: | 10 – 40 min |
| Resolution of weighing: | 0,01 g |
| Measurement range for ku value: | < 10 cm/d |
| Measurement rangefor tensiometer:: | +100 … -85 kPa |
| Accuracy of tensiometer: | ±0,1 kPa |
Advantages
- Investigation of large samples possible due to large measurement chamber
- No soil sample ring necessary
- No additional devices necessary
Air pyknometer
The air pycnometer is an innovative measurement instrument to determine the pore volume of a substrate sample in the laboratory. It is suitable both for undisturbed soil samples as well as for bulk goods such as sands, gravelsor plant granulate. The measurement chamber is permanently connected to the basic body and is sealed by a lid which is held in place by a bar. A soil sample ring is not essential to conduct the measurement. Due to the large measurement chamber with a volume of 2120 cm³, appropriately large samples may also be examined which increases the accuracy of the measurement and makes a few of the investigations at all possible. .
The design of this instrument is based on the guidelines of the FLL (Forschungsgesellschaft Landschaftsentwicklung und Landschaftsbau). The measurement principle is based on the isothermal gas expansion experiment according to BOYLE-MARIOTTE. An additional volume of a known size is filled with compressed air, connected to the measurement chamber of known size with substrates sample and a pressure equilibrium achieved. The compensating pressure is a measurement of the air filled pore volume because only the solids volume within the measurement chamber serves to push out gas. The pressure values are displayed by a digital manometer in a freely selectable pressure unit. The integrated compressor renders additional devices or gas flasks superfluous as long as air is used as measurement gas. As an option, a different measurement gas may be used via a separate feed lin.
Technical Specifications
| Measurement chamber: | V ≈ 2120 cm³ h =12 cm Ø =15 cm |
| Measurement range for digitalmanometer: | -1 … 3 bar |
| Resolution of digital manometer: | 1 mbar |