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Method and apparatus for automatic measurement of evapotranspiration

  • US 5,311,769 A
  • Filed: 03/04/1992
  • Issued: 05/17/1994
  • Est. Priority Date: 03/04/1992
  • Status: Expired due to Term
First Claim
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1. An atmometer comprising:

  • an evaporator, having a fluid inlet, that evaporates a fluid whose evaporation is to be measured;

    a fluid supply that supplies fluid to be evaporated;

    a flow metering reservoir having a service orifice that receives, retains and subsequently supplies retained fluid, through the service orifice;

    a valve, hydraulically coupled to the fluid inlet of the evaporator, to the fluid supply and to the service orifice of the flow metering reservoir, that while in a first state (a) hydraulically couples the fluid inlet of the evaporator to the service orifice of the flow metering reservoir and (b) blocks fluid flow from the supply outlet of the fluid supply, and also that while in a second state (c) blocks fluid flow between the valve and the fluid inlet of the evaporator and also (d) hydraulically couples the supply outlet of the fluid supply to the service orifice of the flow metering reservoir;

    a fluid sensing circuit, disposed proximate the flow metering reservoir, that produces a first signal indicative of when the flow metering reservoir contains an amount of fluid less than or equal to a first selected amount and a second signal indicative of when the flow metering reservoir contains an amount of fluid greater than or equal to a second selected amount that is greater than the first selected amount; and

    a valve control circuit, coupled to the valve and responsive to the first and second signals, that causes the valve to be in the second state upon the presence of the first signal, to then remain in the second state until the presence of the second signal, to return to the first state upon the presence of the second signal, and to subsequently remain in the first state in the absence of both the first and second signals.

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