Thermal mass flow sensor
First Claim
1. A thermal mass flow sensor comprising:
- a housing comprising a first sensor region and a second sensor region;
a first thin film temperature sensor is formed at said first sensor region;
a second thin film temperature sensor formed at said second sensor region and mounted at a first angle to said first thin film temperature sensor;
a heating element arranged to heat said first temperature sensor; and
a controller operably connected to said first temperature sensor, said second temperature sensor and said heating element, said controller controlling a power level to said heating element to maintain a temperature difference between said first temperature sensor and said second temperature sensor, wherein said first angle is from about 12 degrees to 70 degrees.
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Accused Products
Abstract
A thermal mass flow sensor is disclosed that includes a housing (16) having a first sensor region and a second sensor region, a first thin film temperature sensor (39) formed at the first sensor region and a second thin film temperature sensor (58) formed at the second sensor region. A heating element (40) is arranged to heat the first temperature sensor (39) and a controller (46) is operably connected to the first temperature sensor (39), the second temperature sensor (58) and the heating element (40), and controls a power level to the heating element (40) to maintaining a temperature difference between the first temperature sensor (39) and the second temperature sensor (58). A thin film temperature sensor and a method of using the thermal mass flow sensor are also disclosed.
53 Citations
36 Claims
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1. A thermal mass flow sensor comprising:
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a housing comprising a first sensor region and a second sensor region; a first thin film temperature sensor is formed at said first sensor region; a second thin film temperature sensor formed at said second sensor region and mounted at a first angle to said first thin film temperature sensor; a heating element arranged to heat said first temperature sensor; and a controller operably connected to said first temperature sensor, said second temperature sensor and said heating element, said controller controlling a power level to said heating element to maintain a temperature difference between said first temperature sensor and said second temperature sensor, wherein said first angle is from about 12 degrees to 70 degrees. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A thermal mass flow sensor comprising:
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a housing comprising a first sensor region and a second sensor region; a first thin film temperature sensor comprising an RTD formed at said first sensor region; a second thin film temperature sensor formed at said second sensor region; a heating element arranged to heat said first temperature sensor; a controller operably connected to said first temperature sensor, said second temperature sensor and said heating element, said controller controlling a power level to said heating element to maintain a temperature difference between said first temperature sensor and said second temperature sensor; and a mast connected to said housing and a mounting plate connected to said mast.
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13. A thermal mass flow sensor comprising:
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a housing comprising a first sensor region and a second sensor region; a first thin film temperature sensor comprising an RTD formed at said first sensor region; a second thin film temperature sensor formed at said second sensor region; a heating element arranged to heat said first temperature sensor; a controller operably connected to said first temperature sensor, said second temperature sensor and said heating element said controller controlling a power level to said heating element to maintain a temperature difference between said first temperature sensor and said second temperature sensor; and a thermal choke between said first temperature sensor and said housing.
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14. A flow sensing element for use in a thermal mass flow sensor comprising:
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a substrate; a planar RTD supported by said substrate and having a periphery; and a planar heating element comprising a strip of resistive material surrounding said RTD. - View Dependent Claims (15, 16)
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17. A method of measuring mass flow comprising the steps of:
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providing a first planar temperature sensor and a second planar temperature sensor; mounting a planar heating element along the first planar temperature sensor; mounting the first planar temperature sensor in a mass flow passageway defining a mass flow direction at a first angle to the mass flow direction; mounting the second planar temperature sensor in the mass flow passageway at a second angle to the mass flow direction such that said first sensor is not parallel to said second sensor; maintaining a predetermined temperature difference between the first temperature sensor and the second temperature sensor; and determining a mass flow from an amount of power required to maintain the predetermined temperature difference. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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25. A thermal mass flow sensor comprising:
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a housing comprising a first support region and a second support region; a first substrate at the first support region and a second substrate at the second support region, said first substrate being mounted at an angle of about 12 to 70 degrees to said second substrate; a first planar temperature sensor formed on said first substrate; a second planar temperature sensor formed on said second substrate; a heating element arranged to heat said first temperature sensor; and a controller operably connected to said first temperature sensor, said second temperature sensor and said heating element, said controller controlling a power level to said heating element to maintain a temperature difference between said first temperature sensor and said second temperature sensor. - View Dependent Claims (26, 27, 28)
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29. A method of measuring mass flow comprising the steps of:
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providing a first thin film RTD and a second thin film RTD; forming a thin film heating element around the first thin film RTD; mounting the first thin film RTD in a mass flow passageway defining a mass flow direction at a first angle to the mass flow direction; mounting the second thin film RTD in the mass flow passageway at a second angle to the mass flow direction; maintaining a predetermined temperature difference between the first RTD and second RTD; and determining a mass flow from an amount of power required to maintain the predetermined temperature difference. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36)
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Specification