Degree Controls, Inc.

David Gagnon

Rajesh M Nair

Roger Holman

Owen R Mann

An air flow sensor including a temperature dependent resistor device, a first circuit and a second circuit. The first circuit applies a voltage to the temperature dependent resistor device until it reaches a first temperature. The first circuit includes a first reference resistance leg, a first variable resistance leg including the temperature dependent resistor device, and a first comparator connected to both legs for determining when the temperature dependent resistor device reaches the first temperature. The second circuit includes a second reference resistance leg, a second variable resistance leg including the temperature dependent resistor device, and a second comparator connected to both legs for determining when the temperature dependent resistor device reaches a second temperature. A processor is connected to both the first and second comparators and programmed to time the period of time it takes the temperature dependent resistor device to change from the first temperature to the second temperature to determine the heat loss rate of the temperature dependent resistor device.

Air flow sensor using measurement of rate of heat loss

A thermal management system for an enclosure housing devices which generate heat inside the enclosure. A fan, whose speed is responsive to an input signal, has a gas flow output in communication with the enclosure. A filter is disposed in the gas flow path of the fan's output. At least one temperature sensor is disposed in the enclosure for measuring the temperature inside the enclosure. A controller adjusts the speed of the fan until the temperature inside the enclosure is within a predetermined range to ensure that the devices inside the enclosure do not overheat. A processor compares the signal input to the fan with the speed of the fan to determine the condition of the fan and, in response to the temperature sensor, determines the condition of the filter.

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Brookline, NH, United States of America

David Gagnon