Thermal air flowmeter
First Claim
1. A thermal air flowmeter, comprising a temperature-dependent heating resistance element arrangeable in an air flow path, a gauge circuit which includes said heating resistance element configured to provide an output having a nonlinear characteristic from which air flow rate is measurable, and a calculation circuit configured to calculate the difference of a nonlinear target output characteristic and a real output characteristic of said gauge circuit by a polynomial expression higher than a quadratic expression, and to correct the real output-characteristic by the calculated difference.
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Accused Products
Abstract
A thermal type air flowmeter arranges a temperature-dependent heating resistance element in an air flow path and measures the air flow rate from the output of a gauge circuit containing the heating resistance element. A calculation circuit in the flowmeter is provided for correcting the output characteristic by a polynomial expression higher than a quadratic expression. Thereby, high flowmeter measuring accuracy is achieved in lieu of laser trimming and with small-scale circuit composition.
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Citations
9 Claims
- 1. A thermal air flowmeter, comprising a temperature-dependent heating resistance element arrangeable in an air flow path, a gauge circuit which includes said heating resistance element configured to provide an output having a nonlinear characteristic from which air flow rate is measurable, and a calculation circuit configured to calculate the difference of a nonlinear target output characteristic and a real output characteristic of said gauge circuit by a polynomial expression higher than a quadratic expression, and to correct the real output-characteristic by the calculated difference.
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8. A thermal type air flowmeter, comprising a temperature-dependent heating resistance element arrangeable in an air flow path, a gauge circuit including said heating resistance element configured to provide an output from which air flow rate is measurable, map data of an air flow rate—
- output characteristic, wherein a region of the map data is divided and has a low flow rate region of the air flow rate that is more finely divided than a high flow rate region of the air flow rate, and a calculation circuit configured to change an output characteristic correction expression for each air flow rate region and thereby calculate the air flow rate.
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9. A thermal air flowmeter, wherein said polynomial expression is a multidimensional expression of one of a cubic expression to a quintic expression comprising a temperature-dependent heating resistance element arrangeable in an air flow path, a gauge circuit which includes said heating resistance element configured to provide an output from which air flow rate is measurable, and a calculation circuit configured to correct an output characteristic of the gauge circuit by a polynomial expression higher than a quadratic expression.
Specification