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Air-Flow Direction Detector System

IP.com Disclosure Number: IPCOM000042630D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Dunn, RM: AUTHOR [+4]

Abstract

An air-flow direction detection system comprises a probe having thermally sensitive resistors on opposite sides of a dielectric plate positioned in a hollow tube located in an air duct. Air is directed to flow over the resistors which are connected in a bridge circuit such that reverse air flow and flow cessation can be detected. As shown in Fig. 1, the probe comprises resistors RX1 and RX2 deposited on opposite sides of plate 10. RX1 and RX2 are made of the same high temperature coefficient of resistance materials. Plate 10 is made of phenolic or other heat-insulating material. RX1 and RX2 have finger sections 11 extending from base 12, as shown in the enlargement in Fig. 2, to provide greater temperature sensitivity. The probe is placed in a tube 13 located within an air duct formed by walls 14 (Fig. 3).

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Air-Flow Direction Detector System

An air-flow direction detection system comprises a probe having thermally sensitive resistors on opposite sides of a dielectric plate positioned in a hollow tube located in an air duct. Air is directed to flow over the resistors which are connected in a bridge circuit such that reverse air flow and flow cessation can be detected. As shown in Fig. 1, the probe comprises resistors RX1 and RX2 deposited on opposite sides of plate 10. RX1 and RX2 are made of the same high temperature coefficient of resistance materials. Plate 10 is made of phenolic or other heat-insulating material. RX1 and RX2 have finger sections 11 extending from base 12, as shown in the enlargement in Fig. 2, to provide greater temperature sensitivity. The probe is placed in a tube 13 located within an air duct formed by walls 14 (Fig. 3). Air flowing in the duct in the direction shown by the arrows enters port 15 and exits from ports 16 after flow past RX2.

In the case of reverse air flow, air enters tube 13 through port 17 and exits from ports 18 after flow past RX1. Resistors RX1 and RX2 are part of a control circuit which operates as follows: RX1 and RX2 together with precision resistors R1 and R2 are connected in a bridge circuit (Fig. 4). Transistor Q1 provides constant current to the bridge to heat resistors RX1 and RX2. If the air supply is cut off (blower malfunction), both sides of the probe are heated equally and the bridge is balanced. The output lev...