pF Curves for Determining Soil Water Retention
ecoTech pF systems enable the determination of soil water retention curves over defined suction and pressure ranges. The modular system concept covers lower pF ranges using suction plates and vacuum control as well as higher pF ranges using the membrane apparatus.
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Products at a Glance
pF Laboratory Station
Benchtop system for determining pF curves from pF 1.0 (10 hPa) to approximately pF 2.9 (750 hPa) with precise vacuum control.
- integrated pump and vacuum system
- suction plates ready for use after wetting
- precise vacuum control with 1 hPa resolution
- simultaneous display of system pressure and limit values
- connection for pressure step modules and additional suction plate modules
- in combination with the membrane apparatus, the complete pF range up to pF 4.2 can be covered
pF Suction Plate Module
Module for determining pF curves of soil samples under vacuum. It extends the pF Laboratory Station or pF Pressure Step Module and allows different pressure levels to be operated in parallel.
- up to approximately 40 soil sample rings with a volume of 100 cm³ per plate
- modular expansion of sample capacity and pressure ranges
- includes collection bottle with adjustable level
- precise adjustment of pressure and drainage level
pF Pressure Step Module
Pump-free vacuum control module for use with an existing laboratory vacuum supply or the pF Laboratory Station.
- precise vacuum adjustment with 1 hPa control accuracy
- freely adjustable upper and lower limits
- integrated vacuum buffer reduces pressure fluctuations
- up to three pF Suction Plate Modules can be connected directly
Membrane Apparatus
System for determining soil water retention curves in the higher pF range from pF 3.0 to pF 4.2, corresponding to approximately 1 to 15.5 bar.
- set comprising membrane apparatus, 20-bar compressor, pressure gauge, air filter, membrane filter, filter cloth and soil sample rings
- data quality at least equivalent to ceramic plate systems according to the source documentation
- maximum sample capacity of approximately 15
- in combination with the pF Laboratory Station, the complete pF range up to pF 4.2 can be covered
Selection and Configuration Guide
| Requirement / Range | Typical ecoTech Option | Selection Guidance |
|---|---|---|
| Lower pF / suction range | pF Suction Plate Module or pF Laboratory Station | For controlled drainage of soil sample rings under vacuum. |
| pF 1.0 to approx. pF 2.9 | pF Laboratory Station | Integrated pump and vacuum system with precise vacuum control and 1 hPa resolution. |
| Multiple pressure levels or higher sample capacity | pF Pressure Step Module and Suction Plate Modules | Allows different suction levels to be operated and increases sample capacity. |
| pF 3.0 to pF 4.2 | Membrane Apparatus | For higher pressure ranges from approximately 1 to 15.5 bar; complements the pF Laboratory Station. |
Technical Information
| System | Measurement Range | Capacity / Dimensions | Technology / Features |
|---|---|---|---|
| pF Laboratory Station | approx. 10 to 750 hPa |
Active filter area 480 × 280 mm Dimensions 760 × 580 × 605 mm |
Electronic vacuum control with pressure sensor Connections for pressure step and suction plate modules |
| pF Suction Plate Module | approx. 3 to 750 hPa |
Active filter area 480 × 280 mm up to approx. 40 rings Ø 53 mm up to approx. 30 rings Ø 60 mm up to approx. 15 rings Ø 84 mm |
Expansion module for the pF Laboratory Station |
| pF Pressure Step Module | Control of different suction levels | approx. 7 L buffer volume |
Microprocessor-controlled vacuum regulation Pressure sensor and solenoid valve Display of system pressure and limit values 12 V DC |
| Membrane Apparatus |
pF 3.0 to pF 4.2 approx. 1 to 15.5 bar |
max. 15 samples |
Pressure gauge Connection for an additional membrane apparatus 230 V AC |
FAQ
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Can one system cover the complete pF curve?
Determining a complete pF curve often requires a combination of systems. The pF Laboratory Station covers the lower vacuum range, while the membrane apparatus or pressure extractor is used for higher pF values.
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When should a pF Laboratory Station be used?
It is suitable when a compact system with an integrated pump and precise vacuum control is required for soil sample rings in the lower pF range.
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When is a pF Suction Plate Module useful?
It is useful when additional sample capacity is required or when several suction levels need to be operated in parallel.
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When is the membrane apparatus the better choice?
It is designed for the higher pressure range from pF 3.0 to pF 4.2 and complements the pF Laboratory Station.
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Are pressure extractors still relevant?
Yes. Pressure extractors with ceramic plates remain a widely used standard method for higher pF ranges.
Related Applications
- Drought Stress Monitoring in Viticulture Soil water tension measurements using pF meters and Tensiomark for assessing drought stress in grapevines. View Application
- Soil Water Tension-Controlled Irrigation System Irrigation control based on measured soil water tension. View Application
