# US 5,349,851 A · Active thermal isolation for temperature responsive sensors > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,349,851 A - Document ID: US5349851A - Status: Granted - Kind: A - Application number: 08/181,938 - Filed: 1994-01-18 - Granted: 1994-09-27 - Earliest claimed: 1992-01-02 - Assignees: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration - Inventors: Scott D. Martinson; David L. Gray; Debra L. Carraway; Daniel C. Reda - Web page: https://patentgrep.com/patent/US5349851A ## CPC - G01P 5/12: using variation of resistance of a heated conductor - B64F 5/60: Testing or inspecting aircraft components or systems - G01M 9/065: {dealing with flow} - G01P 1/006: {used for thermal compensation} - G01P: MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT (measuring or recording blood flow A61B5/02, A61B8/06; monitoring speed or deceleration of electrically-propelled vehicles B60L3/00; vehicle lighting systems adapted to indicate speed B60Q1/54; determining position or course in navigation, measuring ground distance in geodesy or surveying G01C; combined measuring devices for measuring two or more variables of movement G01C23/00; measuring velocity of sound G01H; measuring velocity of light G01J7/00; measuring direction or velocity of solid objects by reception or emission of radiowaves or other waves and based on propagation effects, e.g. Doppler effect, propagation time, direction of propagation, G01S; measuring speed of nuclear radiation G01T; measuring acceleration of gravity G01V; {measuring or recording the speed of trains B61L23/00; speed indicators incorporated in motor vehicles B60K35/00; measuring frequency or phase G01R; traffic control G08G}) - B64F: GROUND OR AIRCRAFT-CARRIER-DECK INSTALLATIONS SPECIALLY ADAPTED FOR USE IN CONNECTION WITH AIRCRAFT; DESIGNING, MANUFACTURING, ASSEMBLING, CLEANING, MAINTAINING OR REPAIRING AIRCRAFT, NOT OTHERWISE PROVIDED FOR; HANDLING, TRANSPORTING, TESTING OR INSPECTING AIRCRAFT COMPONENTS, NOT OTHERWISE PROVIDED FOR - G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR ## Abstract A temperature responsive sensor is located in the airflow over the specified surface of a body and is maintained at a constant temperature. An active thermal isolator is located between this temperature responsive sensor and the specified surface of the body. The temperature of this isolator is controlled to reduce conductive heat flow from the temperature responsive sensor to the body. This temperature control includes (1) operating the isolator at the same temperature as the constant temperature of the sensor and (2) establishing a fixed boundary temperature which is either (a) less than or equal to or (b) slightly greater than the sensor constant temperature. ## Claims ### Claim 1 An apparatus for monitoring airflow over a specified surface of a body comprising: a temperature responsive sensor located in the airflow over the specified surface of the body; means for maintaining said temperature responsive sensor at a constant temperature; an active thermal isolator located between said temperature responsive sensor and the specified surface of the body, wherein said active thermal isolator comprises an upper layer facing said temperature responsive sensor and having a relatively high temperature coefficient of resistance and a lower layer having a relatively high electrical resistance; and means for controlling the temperature of said active thermal isolator to reduce conductive heat flow from said temperature responsive sensor to the body, wherein said temperature controlling means controls the temperature of the upper layer of said active thermal isolator. ### Claim 2 (depends on 1) The airflow monitoring apparatus according to claim 1, wherein the upper layer of said active thermal isolator comprises a metal. ### Claim 3 (depends on 1) The airflow monitoring apparatus according to claim 1, wherein the lower layer of said active thermal isolator comprises a polyimide. ### Claim 4 (depends on 1) The airflow monitoring apparatus according to claim 1, wherein said temperature responsive sensor comprises an upper layer facing the airflow and having a relatively high temperature coefficient of resistance and a lower layer located between this upper layer and the upper layer of said active thermal isolator and having a relatively high electrical resistance, wherein said constant temperature maintaining means maintains the temperature of the upper layer of said temperature responsive sensor. ### Claim 5 (depends on 1) The airflow monitoring apparatus according to claim 1, wherein the fixed boundary temperature of said active thermal isolator is equal to the maintained constant temperature of said temperature responsive sensor. ### Claim 6 (depends on 1) The airflow monitoring apparatus according to claim 1, wherein the fixed boundary temperature of said active thermal isolator is less than the maintained constant temperature of said temperature responsive sensor. ### Claim 7 (depends on 1) The airflow monitoring apparatus according to claim 1, wherein the fixed boundary temperature of said active thermal isolator is greater than the maintained constant temperature of said temperature responsive sensor. ### Claim 8 An apparatus for monitoring airflow over a specified surface of a body comprising: a temperature responsive sensor located in the airflow over the specified surface of the body;. means for maintaining said temperature responsive sensor at a constant temperature; an active thermal isolator located between said temperature responsive sensor and the specified surface of the body, wherein said active thermal isolator comprises an upper layer facing said temperature responsive sensor and having a relatively high electrical resistance and a lower layer having a relatively high temperature coefficient of resistance; and means for controlling the temperature of said active thermal isolator to reduce conductive heat flow from said temperature responsive sensor to the body wherein said temperature controlling means controls the temperature of the lower layer of said active thermal isolator. ### Claim 9 (depends on 8) The airfoil monitoring apparatus according to claim 8, wherein the upper layer of said active thermal isolator comprising a polyimide. ### Claim 10 (depends on 8) The airfoil monitoring apparatus according to claim 8, wherein the lower layer of said active thermal isolator comprises a metal. ### Claim 11 (depends on 8) The airflow monitoring apparatus according to claim 8, wherein said temperature responsive sensor comprises an upper layer facing the airflow and having a relatively high temperature coefficient of resistance and a lower layer located between this upper layer and the upper layer of said active thermal isolator and having a relatively high electrical resistance, wherein said constant temperature maintaining means maintains the temperature of the upper layer of said temperature responsive sensor. ### Claim 12 (depends on 8) The airflow monitoring apparatus according to claim 8, wherein the fixed boundary temperature of said active thermal isolator is equal to the maintained constant temperature of said temperature responsive sensor. ### Claim 13 (depends on 8) The airflow monitoring apparatus according to claim 8, wherein the fixed boundary temperature of said active thermal isolator is less than the maintained constant temperature of said temperature responsive sensor. ### Claim 14 (depends on 8) The airflow monitoring apparatus according to claim 8, wherein the fixed boundary temperature of said active thermal isolator is greater than the maintained constant temperature of said temperature responsive sensor. ### Claim 15 An apparatus for monitoring airflow over a specified surface of a body comprising: a temperature responsive sensor located in the airflow over the specified surface of the body, wherein said temperature responsive sensor is a hot wire anemometer comprising a sensing wire connected end-to-end between a support structure and an active thermal isolator comprising first and second wires in communication with said temperature controlling means, the first wire being wrapped around one end of the sensing wire and the second wire being wrapped around an opposite end of the sensing wire; means for maintaining said temperature responsive sensor at a constant temperature; said active thermal isolator located between said temperature responsive sensor and the specified surface of the body; and means for controlling the temperature of said active thermal isolator to reduce conductive heat flow from said temperature responsive sensor to the body. ### Claim 16 (depends on 15) The airflow monitoring apparatus according to claim 15, wherein said temperature controlling means controls the temperature of the first and second wires such that the temperature of the first and second wires is approximately equal to that of the sensing wire. ### Claim 17 (depends on 15) The airflow monitoring apparatus according to claim 15, wherein said temperature controlling means maintains a fixed boundary temperature of the first and second wires between the body and the sensing wire. ### Claim 18 (depends on 17) The airflow monitoring apparatus according to claim 17, wherein the fixed boundary temperature of the first and second wires is less than or equal to the maintained constant temperature of the sensing wire. ### Claim 19 (depends on 17) The airflow monitoring apparatus according to claim 17, wherein the fixed boundary temperature of the first and second wires, is slightly greater than the maintained temperature of the sensing wire. ### Claim 20 (depends on 15) The airflow monitoring apparatus according to claim 15, wherein the fixed boundary temperature of said active thermal isolator is equal to the maintained constant temperature of said temperature responsive sensor. ### Claim 21 (depends on 15) The airflow monitoring apparatus according to claim 15, wherein the fixed boundary temperature of said active thermal isolator is less than the maintained constant temperature of said temperature responsive sensor. ### Claim 22 (depends on 15) The airflow monitoring apparatus according to claim 15, wherein the fixed boundary temperature of said active thermal isolator is greater than the maintained constant temperature of said temperature responsive sensor. ### Claim 23 An apparatus for thermally isolating a temperature responsive sensor having a maintained constant temperature for monitoring airflow over a specific area of a body, the apparatus comprising: an active thermal isolator located between the temperature responsive sensor and the specific area of the body, wherein said active thermal isolator comprises an upper layer facing the temperature responsive sensor and having a relatively high temperature coefficient of resistance and a lower layer having a relatively high electrical resistance located between the upper layer and the body; and means for controlling the temperature of said active thermal isolator to reduce conductive heat flow from the temperature responsive sensor to the body wherein said temperature controlling means controls the temperature of the upper layer of said active thermal isolator. ### Claim 24 (depends on 23) The airflow monitoring apparatus according to claim 23, wherein the fixed boundary temperature of said active thermal isolator is equal to the maintained constant temperature of said temperature responsive sensor. ### Claim 25 (depends on 23) The airflow monitoring apparatus according to claim 23, wherein the fixed boundary temperature of said active thermal isolator is less than the maintained constant temperature of said temperature responsive sensor. ### Claim 26 (depends on 23) The airflow monitoring apparatus according to claim 23, wherein the fixed boundary temperature of said active thermal isolator is greater than the maintained constant temperature of said temperature responsive sensor.