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Rapid water flow instrumentation

^a Department of Agronomy and Horticulture, University of Nebraska, Lincoln, NE 68583-0915
^b School of Natural Resource Sciences, University of Nebraska, Lincoln, NE 68583-0915

View larger version (41K): [in a new window]   Fig. 1. Apparatus used to test the flow system (includes measuring system, water supply system, and water delivery system but excludes core) for repeatability. Inclusion of core allows the apparatus to be used for falling head measurements. The measuring system is limited to the pressure transducers and the cylinder to which they are attached. Pressure transducers P1 and P2, mounted on cylinder a distance Hp apart, are used to measure water head in the cylinder. Maximum cylinder fill height was regulated by Mariotte device at H1. Minimum cylinder fill was regulated to H3. Manual valve V2 and automatic valve V1 regulated water flow. Switch SW energizes control relay R. SW simultaneously opens valve V1 and sends a signal to the data logger. H is related to total water flow from cylinder.

View larger version (44K): [in a new window]   Fig. 2. Modified measuring cylinder placed on scale pan. Other labeled components are the same as in Fig. 1. Wires coming from transducer are taped to scale pan to eliminate bias because of changes in wire tension as water level changes. The tubing inside the measuring cylinder allows water to flow without drops forming.

View larger version (25K): [in a new window]   Fig. 3. Output from simultaneous readings of scale and data logger. The inset shows data from the initial 400 s. Output from scale shows an initial lag in response.

View larger version (15K): [in a new window]   Fig. 4. Application of instrumentation to the determination of hydraulic conductivity using the falling head method.