automatic collection and transmission of ... - E-Library - WMO
automatic collection and transmission of ... - E-Library - WMO
automatic collection and transmission of ... - E-Library - WMO
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ReportedinstrumentsReportingcountriesNumberinoperationTl'"~+'~~AnalogueRecordingDigitalmachine formReported costBasic,s-",,,,Telemetered"'".... ..--.~'"~ s-","", o> '""'>,=> "'~'"3 SOIL MOISTURE3.1 Instruments <strong>of</strong> Proven Reliability3.1.1 Neutron ProbeThis method is based on the principle <strong>of</strong> measuring the slowing <strong>of</strong> neutrons emittedinto the soil from a fast-neutron source. The energy loss is much greater inneutron collisions with atoms <strong>of</strong> low atomic weight <strong>and</strong> is proportional to thenumber <strong>of</strong> such atoms present in the soil. Hydrogen, which is the principalelement <strong>of</strong> low atomic weight found in the soil, is largely contained in the molecules<strong>of</strong> the water in the soil. The number <strong>of</strong> slow neutrons detected by a counter tubeafter emission <strong>of</strong> fast neutrons from a radioactive source tube is electronicallyindicated on a scaler <strong>and</strong> indicates the amount <strong>of</strong> water per unit volume <strong>of</strong> soil.Oanbridge/NEA Sweden 6 NoNIC-5 United States --- NoUnited States United States 2 NoWallingford United Kingdom 20 No3.1.2 Bouwer Double TubeMeasures the hydraulic conductivity <strong>of</strong>Bouwer Double Tube United Statessaturated soil above the water table.14 No26 500 OKR n.a.n.a.$3 500. n.a.t: 1 000 n.a.$300.n.a.8+10-205+n.a.>IH():c
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