Flow sensor with thermocouples
First Claim
1. A device for measuring a flow of a fluid comprising:
- a substrate,a heater arranged on said substrate,at least one first and one second sensing thermopile for measuring a temperature difference between a location upstream and a location downstream of said heater and for generating a sensing signal, said sensing thermopiles being arranged on said substrate, wherein a junction of said sensing thermopiles closest to said heater is arranged at a first distance from said heater,in addition to and distinct from the first and the second sensing thermopile at least a first and a second monitoring thermocouple arranged upstream and downstream from said heater for generating a monitoring signal, said monitoring thermocouples being arranged on said substrate, wherein a junction of said monitoring thermocouples closest to said heater is arranged at a second distance from said heater, wherein said second distance is smaller than said first distance, anda control circuit adapted to measure the flow of the fluid over said heater and said sensing thermopiles from a flow-dependent heating of said sensing thermopiles by said heater,wherein said sensing thermopiles extend parallel to said monitoring thermocouples.
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Abstract
The flow sensor comprises a heater arranged between two sensing thermopiles. In addition, at least one monitoring thermocouple is provided for measuring the temperature of the heater. The signal from the monitoring thermocouple can be used to improve the accuracy of the device in several ways. In particular, the signal from the monitoring thermocouple depends on changes of the Seeback constant and other inherent properties of the thermopiles in the same way as the signal from the sensing thermopiles, which allows a compensation of such effects. The signal from the monitoring thermocouple can also be used as a reference voltage to an A/D converter for converting the signals from the sensing thermopiles.
48 Citations
17 Claims
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1. A device for measuring a flow of a fluid comprising:
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a substrate, a heater arranged on said substrate, at least one first and one second sensing thermopile for measuring a temperature difference between a location upstream and a location downstream of said heater and for generating a sensing signal, said sensing thermopiles being arranged on said substrate, wherein a junction of said sensing thermopiles closest to said heater is arranged at a first distance from said heater, in addition to and distinct from the first and the second sensing thermopile at least a first and a second monitoring thermocouple arranged upstream and downstream from said heater for generating a monitoring signal, said monitoring thermocouples being arranged on said substrate, wherein a junction of said monitoring thermocouples closest to said heater is arranged at a second distance from said heater, wherein said second distance is smaller than said first distance, and a control circuit adapted to measure the flow of the fluid over said heater and said sensing thermopiles from a flow-dependent heating of said sensing thermopiles by said heater, wherein said sensing thermopiles extend parallel to said monitoring thermocouples. - View Dependent Claims (2, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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- 3. The device of claim I wherein said sensing signal is proportional to said temperature difference.
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14. A device for measuring a flow of a fluid comprising
a substrate, wherein said substrate is divided into a measuring region and a regular region, wherein a thermal conductance in said measuring region is lower than a thermal conductance in said regular region, a heater arranged at least partially on said measuring region, at least one sensing thermocouple for generating a sensing signal, said sensing thermocouple being arranged at least partially on said measuring region, wherein a junction of said sensing thermocouple closest to said heater is arranged at a first distance from said heater, a control circuit adapted to measure the flow of the fluid over said heater and said sensing thermocouple from a flow-dependent heating of said sensing thermocouple by said heater, and in addition to and distinct from the sensing thermocouple at least one monitoring thermocouple for generating a monitoring signal, said monitoring thermocouple being arranged completely on said measuring region, wherein a junction of said monitoring thermocouple closest to said heater is arranged at a second distance from said heater, wherein said second distance is smaller than said first distance, wherein said sensing thermocouple extends parallel to said monitoring thermocouple.
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15. A device for measuring a flow of a fluid comprising
a substrate, a heater arranged on said substrate, wherein said heater comprises several conductors with at least one gap between said conductors, at least one sensing thermocouple for generating a sensing signal, said sensing thermocouple being arranged on said substrate, wherein a junction of said sensing thermocouple closest to said heater is arranged at a first distance from said heater, a control circuit adapted to measure the flow of the fluid over said heater and said sensing thermocouple from a flow-dependent heating of said sensing thermocouple by said heater, and in addition to and distinct from the sensing thermocouple a plurality of monitoring thermocouples for generating a monitoring signal, said monitoring thermocouples being arranged in said gap and comprising a first bar of a first material extending from a first end of said heater to a center of said heater and a second bar of a second material connected at said center of said heater to said first bar and extending to a second end of said heater.
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17. A device for measuring a flow of a fluid comprising
a substrate, a heater arranged on said substrate, at least one sensing thermocouple for generating a sensing signal, said sensing thermocouple being arranged on said substrate, wherein a junction of said sensing thermocouple closest to said heater is arranged at a first distance from said heater, a control circuit adapted to measure the flow of the fluid over said heater and said sensing thermocouple from a flow-dependent heating of said sensing thermocouple by said heater, in addition to and distinct from the sensing thermocouple at least one monitoring thermocouple for generating a monitoring signal, wherein said monitoring thermocouple is arranged on said substrate, wherein a junction of said monitoring thermocouple closest to said heater is arranged at a second distance from said heater, wherein said second distance is smaller than said first distance and an analog/digital converter for converting said sensing signal, wherein said analog/digital converter has a reference input and generates a digitized value of said sensing signal normalized by a signal at said reference input, wherein said monitoring signal is applied to said reference input.
Specification