Importance

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Abstract

A thermal type flow meter for measuring the mass flow rate of a fluid medium especially that of a gas in a duct, said meter comprising a plurality of thermistors operated electrically in the 'self-heated' mode located on the trailing edge of rigid, rectangular members oriented with the long axis perpendicular to the primary direction of flow. The thermistors are located strategically throughout transverse plan of the duct. Each sensor (thermistor) is located substantially at the center of the downstream end of a right circular cylinder. The voltage drops through all of the thermistors located in a two-dimensional array oriented normal to the flow direction are summed electrically using an operational amplifier. Due to both the geometrical location of the sensors and the characteristics of thermistors in the self-heated mode, the voltage drop across each sensor is linearly proportional to the local mass flow velocity. This allows the summed output from all of the flow dependent sensors to represent a true average of the flow in a duct providing a sufficient number of sensors exist to reveal the overall flow patterns in the duct.

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First Claim