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Advanced Distributed Sensor Systems

Patrick French

Bradley Delton Veatch

Michael William O'Connor

Leo John Staarmann

David Jansen

Chris Myers

James R Butz

In one embodiment, a first sensor nodeincludes a radio to effect wireless communications; a sensor moduleto sense a selected parameter; and a schedulerthat selects a listen time for the first sensor node, such that, during the listen time, the radio is activated and able to receive wireless signals and, during a time other than the listen time, the radio is deactivated and unable to receive wireless signals, and causes transmission to a second sensor node a first message. The first message includes a time offset from a transmission time of the first message, the time offset indicating a timing of a first listen time for the first sensor node. In response, the nodereceives, from the second sensor node, a second message, with the time selected by the second sensor node to transmit the second message to the first sensor node being based on the time offset.

Long range, low power, mesh networking without concurrent timing

An apparatus and method for measuring the total thermal resistance to heat flow from the air to the evaporative cooler fins of a refrigeration system. The apparatus is a frost sensor that measures the reduction in heat flow due to the added thermal resistance of ice (reduced conduction) as well as the reduction in heat flow due to the blockage of airflow (reduced convection) from excessive ice formation. The sensor triggers a defrost cycle when needed, instead of on a timed interval. The invention is also a method for control of frost in a system that transfers heat from air to a refrigerant along a thermal path. The method involves measuring the thermal conductivity of the thermal path from the air to the refrigerant, recognizing a reduction in thermal conductivity due to the thermal insulation effect of the frost and due to the loss of airflow from excessive ice formation; and controlling the defrosting of the system.

Frost sensor for use in defrost controls for refrigeration

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Littleton, CO, United States of America

Patrick French