Thermal flow meter
First Claim
1. A thermal flow meter comprising:
- a thermal flow sensor to provide a first electrical signal indicative of a flow rate of a fluid flowing between the fluid inlet and the fluid outlet;
a sensor housing enclosing the thermal flow sensor, the housing having one or more thermal isolation slots extending completely through the housing from front to back, the slots dividing the housing into an upper portion and lower portion by extending laterally partially but not all the way across the housing so that the upper and lower portions of the housing are continuous in the medial portion of the housing; and
a sensor housing base, the housing attached to said base at two or more laterally spaced contact points.
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Accused Products
Abstract
A thermal mass flow controller or mass flow meter having a novel sensor housing that reduces heat conduction from the housing mounting plate or base to the sensor itself. The housing also greatly minimizes the thermal gradient that can result from the uneven application of heat to the housing base. This reduction is accomplished in part by the use of one or more thermal isolation slots to isolate the upper portion of the housing (which holds the sensor) from the lower portion of the housing. Heat transfer to the sensor housing is also minimized by raising the middle portion of the bottom of the housing so that thermal contact is made between the base and the housing only at the two ends of the housing.
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Citations
38 Claims
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1. A thermal flow meter comprising:
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a thermal flow sensor to provide a first electrical signal indicative of a flow rate of a fluid flowing between the fluid inlet and the fluid outlet; a sensor housing enclosing the thermal flow sensor, the housing having one or more thermal isolation slots extending completely through the housing from front to back, the slots dividing the housing into an upper portion and lower portion by extending laterally partially but not all the way across the housing so that the upper and lower portions of the housing are continuous in the medial portion of the housing; and a sensor housing base, the housing attached to said base at two or more laterally spaced contact points. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 23, 24, 25, 26, 27, 28, 31, 36)
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22. A thermal mass flow controller comprising:
a thermal mass flow meter, including; a mass flow sensor including a capillary tube and wire winding to provide a first electrical signal indicative of a mass flow rate of a fluid flowing through the thermal mass flow meter; and a sensor housing enclosing the thermal mass flow sensor, the housing divided into an upper portion and a lower portion by one or more thermal isolation slots, the thermal connection between the upper and lower housing portions being divided into a central region having a high thermal conductivity and side regions having thermal conductivity lower than that of the central region; a sensor housing base supporting the sensor housing; and a valve for controlling a fluid in accordance with signals from the mass flow meter. - View Dependent Claims (29, 30, 35)
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32. A thermal flow meter, comprising:
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a thermal flow sensor to provide a first signal indicative of a flow rate of a fluid flowing through the thermal flow meter; and a sensor housing enclosing the thermal mass flow sensor, the housing divided into an upper portion and a lower portion by one or more thermal isolation slots, the thermal connection between the upper and lower housing portions being divided into a central region having a high thermal conductivity and side regions having thermal conductivity lower than that of the central region. - View Dependent Claims (33, 34)
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37. A method of measuring flow, comprising passing fluid through a capillary tube, the capillary tube being supported in a sensor housing divided into an upper portion and a lower portion by one or more thermal isolation slots, the thermal connection between the upper and lower housing portions being divided into a central region having a high thermal conductivity and side regions having thermal conductivity lower than that of the central region.
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38. A housing for a fluid flow sensor, comprising a thermally conductive block divided into an upper portion and a lower portion by one or more thermal isolation slots, the thermal connection between the upper and lower housing portions being divided into a central region having a high thermal conductivity and side regions having thermal conductivity lower than that of the central region.
Specification