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US 6,681,625 B1Granted
Constant-temperature-difference bidirectional flow sensor
AssigneeLockheed Martin Corporation
InventorsErtugrul Berkcan, Scott Baxter Hoyle
Life of this patent
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Abstract
A bidirectional flow sensor (800) for automated systems includes a heater (18) which is maintained at a constant temperature above the temperature of the fluid flowing past the heater. A pair of temperature sensors (26a,26b) is located to either side of the heater (18). The temperature sensors may be two-terminal constant-current devices, electrically connected in series, so that the current is controlled by the sensor sensing the lower temperature, which is on the upstream side of the heater. In one embodiment, a processor (1010) processes the signals produced by the temperature sensors to produce a flow-direction indicating signal. The bidirectional sensor is adapted for interfacing with a digital network.
Claims26
A bidirectional flow sensor for determining the flow magnitude in a fluid path, said flow sensor comprising:
- a path for the flow of fluid in mutually opposite first and second directions;
- heating means thermally coupled to said path, for transferring heat to said fluid at a first location along said path;
- a first electrically responsive temperature sensor located downstream from said heating means for said first direction of fluid flow, said first temperature sensor having a temperature-dependent electrical characteristic;
- a second electrically responsive temperature sensor located downstream from said heating means for said second direction of fluid flow, said second temperature sensor having a temperature-dependent electrical characteristic;
- control means coupled to said first and second temperature sensors and to said heating means, for controlling the power applied to said heating means in a manner which tends to maintain said heating means at a fixed temperature difference above the temperature of that one of said sensors having said electrical characteristic indicative of the lesser temperature;
- and
- processing means for converting a signal representing said power applied into a quantitative indication of at least one of volumetric and mass fluid flow.
4 more elements
A bidirectional fluid flow sensor, said sensor comprising:
- a path for the flow of fluid in mutually opposite first and second directions;
- heating means thermally coupled to said path, for transferring heat to said fluid at a first location along said path;
- a first electrically responsive temperature sensor located downstream from said heating means for said first direction of fluid flow, said first temperature sensor having a first temperature-dependent constant-electrical-current characteristic;
- a second electrically responsive temperature sensor located downstream from said heating means for said second direction of fluid flow, said second temperature sensor having a second temperature-dependent constant-electrical-current characteristic;
- sensor coupling means electrically coupled to said first and second electrically responsive temperature sensors, for coupling said sensors in electrical series in a manner which results in a electrical combined sensor current which depends only on that one of said sensors providing the lesser constant electrical current;
- control means coupled to said sensor coupling means and to said heating means, for controlling the power applied to said heating means in a manner which tends to maintain said heating means at a fixed temperature difference above the temperature of that one of said sensors providing the lesser constant electrical current;
- and
- processing means for converting a signal representing said power applied into an indication of flow.
5 more elements
A method for determining the flow of a fluid through a region, said method comprising the steps of:
- determining the temperature of a fluid flowing in a path, at first and second spaced-apart locations along said path;
- applying power to a heater thermally coupled to said path at a location lying between said first and second spaced-apart locations, for raising the temperature of said heater by a fixed temperature differential above the lesser of the temperature of the fluid at said first and second locations;
- and
- from a signal representing said power applied to said heater, determining the quantitative value of one of volumetric and mass fluid flow.
1 more element
A bidirectional fluid flow sensor, said sensor comprising:
- a path for the flow of fluid in mutually opposite first and second directions;
- a heater thermally coupled to said path, for transferring heat to said fluid at a first location along said path;
- a first electrically responsive temperature sensor located downstream from said heater for said first direction of fluid flow, said first temperature-sensor having a temperature-dependent constant-electrical-current characteristic;
- a second electrically responsive temperature sensor located downstream from said heater for said second direction of fluid flow, said second temperature sensor having a temperature-dependent constant-electrical-current characteristic which may differ from that of said first electrically responsive temperature sensor;
- an electrical coupler electrically coupled to said first and second electrically responsive temperature sensors, for coupling said sensors in electrical series in a manner which results in a electrical combined sensor current which depends only on that one of said sensors providing the lesser constant electrical current;
- a controller coupled to said electrical coupler and to said heater, for controlling the power applied to said heater in a manner which tends to maintain said heater at a fixed temperature difference above the temperature of that one of said sensors providing the lesser constant electrical current;
- and
- a processor for converting said power applied into an indication of flow.
5 more elements
Dependencies are inferred from the claim text.