Abstract: An automatic atmometer includes an evaporating head that is coupled to a metering vial through a three-way valve controlled by fluid sensors disposed proximate inlet and open ends of the metering vial. The three-way valve is ordinarily in a quiescient state that connects the evaporating head to the metering vial. As water evaporates from the evaporating head water is drawn by suction out of the metering vial. When a sensor proximate the inlet of the metering vial indicates that the vial is empty the three-way valve is activated. This refills the metering vial from a fluid reservoir above the metering vial. As soon as one or more sensors proximate the open end of the metering vial indicate that the vial is full the three-way valve is returned to its quiescient condition. An output signal activates a counter or other logging device to record the number of times the metering vial has been emptied and refilled.

Abstract: A covering for an atmometer includes an expanded polytetrafluoroethylene barrier layer that allows the passage of water vapor but not of liquid water. The barrier layer my be covered with a fabric layer, and may be coated on either side with a hydrophilic layer. The covering fits over an evaporating plate that may have either a flat or a convex evaporating surface.

Abstract: An automatic atmometer includes an evaporating head that is coupled to a metering vial through a three-way valve controlled by fluid sensors disposed proximate inlet and open ends of the metering vial. The three-way valve is ordinarily in a quiescient state that connects the evaporating head to the metering vial. As water evaporates from the evaporating head water is drawn by suction out of the metering vial. When a sensor proximate the inlet of the metering vial indicates that the vial is empty the three-way valve is activated. This refills the metering vial from a fluid reservoir above the metering vial. As soon as one or more sensors proximate the open end of the metering vial indicate that the vial is full the three-way valve is returned to its quiescient condition. An output signal activates a counter or other logging device to record the number of times the metering vial has been emptied and refilled.

Abstract: An hour meter is activated by the stray magnetic flux leaking from a piece of equipment to be monitored or surrounding a conductor supplying current to operate that equipment. A tie down rod extends from the housing of the hour meter, and serves the dual function of providing a means to strap the hour meter onto the housing of the equipment and as an antenna to conduct alternating magnetic flux to a coil within the hour meter. There an alternating voltage is induced in the coil, which is rectified by a doubler circuit and applied to a switching transistor, which in turn allows a timer to run from a battery contained within the hour meter. The battery only supplies power to run the timer; the sensing circuit itself is self-powered by the energy induced by inductive coupling to the coil.

Abstract: A digitizer propagates coarse and fine wavelength electric fields across a platen to perform phase delay measurements, the results of which correspond to a displacement of a cursor along a measurement axis. The time interval between propagating the longer wavelength coarse electric field at a high velocity and subsequently establishing and propagating a shorter wavelength fine electric field at a low velocity is minimized by pre-loading at high speed a propagation circuit with the pattern to be propagated as the shorter wavelength fine electric field.

Abstract: A cursor for a digitizer is selectively made to adhere to the digitizing surface by the controlled application of a vacuum to the underside of the cursor. The control can reside either in a manually activated switch on the cursor, or in commands issued to the digitizer by its controlling device.

Abstract: A digitizer shifts long and short wavelength square waves across x and y grids in a platen to perform upon a cursor signal time measurements that represent coarse and fine cursor position data. The periodic staircase cursor signal is filtered before use to permit time measurements that resolve cursor positions to locations between lines in the grids. The contribution of the filter to the coarse and fine time measurements is obtained in a special reference measurement, so that it may be removed. A processor combines these data into Cartesian coordinates, and implements procedures for error reduction. These include averaging of consecutive time measurements, dynamic adjustment of a timing reference to remove ambiguities inherent in measuring very small or very large cyclic quantities, and correction of coordinates for the effects of cursor motion during measurement and for any non-perpendicularity of the x and y grids.

Abstract: The location and shape of a region of capacitive coupling between two conductive surfaces is determined by a grounded shield interposed between the two surfaces. The shield has an aperture which limits and defines the region of capacitive coupling, between the two surfaces, for a signal referenced to the ground. This principle is applied to provide a transparent capacitive aperture pickup for a digitizer by laminating together pieces of glass having transparent conductive coatings.