|Evaporation method||Evaporation method|
|Undisturbed soil samples||O||Undisturbed soil samples||O|
|Only turned once before saturation for fixing the perforated plate. In an upright position and undisturbed during the entire experiment||+||During the experiment turned in the saturated state. In cohesive soils, greatly decreases their structural stability in the saturated state (flowing samples), which could lead to a rearrangement of internal disturbances or structural changes.||–|
|Measuring range of tensiometers up to 850 hPa (state of the technique)||O||Measuring range of tensiometers up to 850 hPa (state of the technique||O|
|Bumping under ideal conditions possible, already observed up to 1500 (1800) hPa.
– Requirements for bumping (gas- and particle-free liquid)
|O||Product Information: official measuring range up 850 hPa, but increase by bumping up to 2500 hPa
– Requirements for bumping (gas- and particle-free liquid)
– Practically no guarantee that in each Tensiometer and any attempt such a bumping occurs
– There is an exchange of soil water by inevitable entry of solutes and gases through the ceramic membrane, resulting in the water in the tensiometer boiling
– Small vibrations and external disturbances also lead to termination of the delayed boiling
|Ceramic size of the tensiometer|
|5.35cm2 contact area with soil||0.5cm2 contact area with soil|
|More than 10 times larger contact area||+||Very small ceramic tip for contact with soil|
|Installation horizontal||Installation vertical|
|No preferential flow paths in the direction of the flow||+||Potential preferential flow paths in the direction of the flow||–|
|Both tensiometers are exactly above each other, measure direct gradient||+||Both tensiometers are side by side installed from bottom, no direct gradient||–|
|Caused by the horizontal tensiometer installation, soil samples can be kept on a sieve plate with filter paper from the beginning. Unstable soil samples (especially when saturated) can be measured||+||Caused by the vertical tensiometer installation in the soil, it is difficult to measure unstable (especially when saturated) soil samples||–|
Inner diameter: 7.2cm
Inner diameter: 8.0cm
|Lower evaporation from less surface area, longer test time with higher accuracy (especially in warmer surroundings)||+||Higher evaporation from higher surface area, reduces test time and therefore the accuracy of the test and it also reduces the analysable range of the time variation curve||–|
|Available as 1SP ku-pF (single place) or as 10MP ku-pF (multiplace) version||Only single place version available. Hyprop is a “modular system”, one “module” consists of one electronic laboratory balance, one adapter for the soil sample (including the two tensiometers) and one sample ring|
|– 10MP ku-pF device measures up to 10 samples at the same time completely automated
– Depending on the homogeneity 6 to 12 samples are necessary (DIN 19683).
|+||Only one sample can be measured automatically. To measure several samples you have to use several single places or several adapters and sample rings. If you use only one balance you have to switch the samples manually. That means you don’t have automatic continuous measurements for the samples and staff is necessary to take care of the test. Increased influence of measurement inaccuracies by handling the samples.||–|
|10MP ku-pF is a compact device, minimum space in lab necessary||+||To measure 10 samples automatically a 10-fold space is necessary||–|
|Auto-Zero of the balance. While automatically switching the samples on the balance, the ku-pF lifts the current sample from the balance and before placing the next sample on the balance, sets the balance to zero. Therefore no drift effects in the weighing, no effects of dirt/water on the balance||+||No Auto-Zero of the balance. Since the samples stay on the balance continuously for the Hyprop system it is not possible to automatically set the balance to zero. Therefore the weight measurements are influenced by drift effects of the balance (every balance has a drift!).||–|
|No influence on the weighing by cable.
The Tensiometers of the ku-pF have short cables that are connected to the sample basket. This sample basket is completely on the balance for the measurement without any contact to the surrounding. To read the tensiometer data the complete basket is lifted and the contacts on top of the basket meet the contacts of the ku-pF device
|+||Influence on the weighing by cable.
For the Hyprop, the tensiometer cables are directly connected to the balance. Therefore a part of the weight of the cable is also included in the weight measurement. This influence cannot be clearly defined, especially if you switch the samples on your balance: the influence of the cable will always be different since you moved the cable.
|10MP ku-pF only one interface to your PC/Laptop (USB) necessary||+||For 10 samples (automatically measured) you need 10 interfaces, one for each||–|
|PC/laptop doesn’t have to be connected to the ku-pF over the complete test time. Only to start/stop and to read the data. Therefore no additional lab-PC just for that test.||+||PC/laptop must be connected at all times||–|
|The advantages of the ku-pF basically result in better handling and more accurate weight measurements. The weight change caused by water evaporating within 10 minutes is the basic measurement value, therefore the exact weight measurement is very important as this weight change is very small.|
|Hood permeameter according to HARTGE and Soil LT||k-sat|
|Consistency of the measurement systems: hood permeameter and ku-pF (saturated and unsaturated conductivity). Samples can be used directly in saturated state without changes||O||Consistency of the measurement systems: Hyprop and k-Sat||O|
|Extension with Soil LT to determine the surface area and volume change due to shrinking during the drying process of the soil sample using laser triangulation.||+||–|