The 1920 Pressure/Vacuum Soil Water Sampler consists of a PVC body with a ceramic cup epoxy bonded to one end. The porous ceramic cup has an outside diameter of 1.9" (4.8 cm) and is 2.0" (5.0 cm) in length. The 1920F1 is normally supplied with a 2 bar (200 kPa) ceramic cup, but 0.5 bar (50 kPa) and 1 bar (100 kPa) cups are also available. Nylon compression fittings are threaded into the top cap and are used to attach lengths of Polyethylene tubing to a remote sampling station. A pressure-vacuum hand pump, Model 2006G2, is used for evacuating the sampler and recovering the sample. For situations where specific cleaning operatings are required, the 1920F1K1, which has a removable ceramic cup, is available. Please specify ceramic cup:-B0.5M2 1/2 BAR POROUS CERAMIC CUP or -B02M2 2 BAR POROUS CERAMIC CUP or -B01M3 1 BAR HIGH FLOW POROUS CERAMIC CUP
Weight: 0.38-1.5 lbs (0.17-0.68 kgs)
1920 vacuum samplers Features
The Pressure-Vacuum Soil Water Sampler (Model 1920F1) comes fully assembled. The Pressure-Vacuum Soil Water Sampler (see Figure 3) is constructed of a 1.9 inch O.D. PVC tube (made of FDA-approved material) with a 2 bar porous ceramic cup bonded to one end. The serviceable end of the Sampler is completely sealed and two 1/4-inch tube connectors protrude from the top. The white tube connector indicates the “Pressure/Vacuum” side and is used exclusively for pressurising and evacuating the Sampler. The green tube connector is used to recover the collected sample.
Two 1/4-inch O.D. polyethylene access tubes are used for pressurising and recovering samples which are terminated in neoprene tubing. Clamping rings are used to clamp the neoprene to keep the Sampler under negative pressure.
Soilmoisture’s Soil Water Samplers allow water to be removed from the soil by creating a vacuum (negative pressure or suction) inside the sampler greater than the soil suction holding the water in the capillary spaces. This establishes a hydraulic gradient for the water to flow through the porous ceramic cup and into the sampler. Note: when evaluating soil suction ratings of a ceramic plate or cup, a positive pressure rating is used. Water can be held at tensions far greater than 1 atm (the limit for vacuum-type measurements). Positive pressure can force water out of capillary pores equivalently as negative pressures, and is the practical method for evaluation of soil suction. In practice, a vacuum is drawn in the Soil Water Sampler that exceeds the soil water tension. Then liquid water will flow to the ceramic cup due to the potential gradient (i.e. water will move from less negative potential to more negative potential). The practical limit for water flow in soils is about 65 cb (centibar) (although in some soils, the value can approach 85 cb). When soil moisture tensions exceed 2 bars, the wetted meniscus in the ceramic pores will break and the Soil Water Sampler will appear to be unable to hold vacuum. The ceramic cup will have to be rewetted to hold a vacuum and soil moisture tensions will have to decrease to less than 85 cb before water can again be moved toward the ceramic cup.