# US 2009/0260431 A1 · Mass flow meter with solder/braze-flow secured spacer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2009/0260431 A1 - Document ID: US20090260431A1 - Status: Published application - Kind: A1 - Application number: 12/106,772 - Filed: 2008-04-21 - Published: 2009-10-22 - Earliest claimed: 2008-04-21 - Assignees: Sierra Insturments, Inc. - Inventors: John G. Olin; John P. Smitherman - Web page: https://patentgrep.com/patent/US20090260431A1 ## CPC - G01F 1/692: Thin-film arrangements - G01F 1/684: Structural arrangements; Mounting of elements, e.g. in relation to fluid flow - G01P 1/026: {for speed measuring devices, e.g. pulse generator} - G01P 5/12: using variation of resistance of a heated conductor - G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME - 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}) ## Abstract A thermal anemometer or mass flow meter typically having temperature and flow velocity sensor elements is provided in which a thin film temperature sensor is used in the heated sensor of the fluid velocity sensor element of the system. At least one thin-film RTD sensor is held within a spacer or interface member and the spacer, optionally, received within a housing. The thermal anemometer is preferably constructed to offer sufficient precision and accuracy in its design to be suitable for sensitive scientific and industrial applications. This goal is achieved while using cost effective parts by employing a construction approach in which the spacer and RTD sensor(s) is secured in place by solder, braze or another compound flowed into place while inserting the spacer and/or sensor(s). ## Claims ### Claim 1 An apparatus for use in a mass flow meter for immersion in a fluid including a velocity sensor element, the velocity sensor element, comprising: an elongate housing shell, a distal portion of the housing shell receiving a solid metal spacer therein, the spacer receiving at least one thin-film Resistance Temperature Detector (RTD) sensor therein, the sensor comprising an active area and electrical leads to carry current to the active area from a proximal end of the shell, and a fill metal, the fill metal having a melting point below a temperature that will damage the at least one RTD and electrical leads, the fill metal interposed between the spacer and the shell, and between the spacer and at least the RTD active area. ### Claim 2 (depends on 1) The apparatus of claim 1, further comprising a temperature sensor separate from the velocity sensor. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the housing shell has a closed distal end. ### Claim 4 (depends on 1) The apparatus of claim 1, further comprising a computer processor. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the spacer comprises stacked pieces. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein the spacer defines a through hole. ### Claim 7 (depends on 6) The apparatus of claim 6, wherein two thin-film RTD sensors are set within the hole in a back-to-back orientation. ### Claim 8 (depends on 7) The apparatus of claim 7, wherein a distal end of the spacer is chamfered to a terminal annulus. ### Claim 9 (depends on 1) The apparatus of claim 1, wherein the spacer comprises at least one powdered metal fabricated piece. ### Claim 10 (depends on 1) The apparatus of claim 1, wherein the spacer is fabricated from at least one piece of bar stock. ### Claim 11 (depends on 1) The apparatus of claim 1, the spacer comprises a material selected from pure metal, metal alloy and high thermal conductivity ceramic. ### Claim 12 (depends on 10) The apparatus of claim 10, wherein the housing shell comprises stainless steel. ### Claim 13 (depends on 1) The apparatus of claim 1, wherein the fill metal is selected from solder and brazing compounds. ### Claim 14 (depends on 13) The apparatus of claim 13, wherein the fill metal is silver solder. ### Claim 15 An apparatus for use as a mass flow meter in a fluid, comprising a metal spacer having cross-section defining a circular diameter and a hole, the hole sized to fit at least one thin-film RTD temperature sensor with a gap up to about 0.020 inches around the at least one sensor, and a fill material at least substantially filling the gap. ### Claim 16 (depends on 15) The apparatus of claim 15, wherein the gap is less than about 0.015 inches. ### Claim 17 (depends on 16) The apparatus of claim 16, wherein the fill material comprises a metal having a melting point below a temperature that will damage the at least one RTD. ### Claim 18 A method of making an apparatus for use as a mass flow meter in a fluid, the method comprising: providing an elongate housing shell with a closed distal end, a metal spacer, at least one thin-film Resistance Temperature Detector (RTD) sensor, and a bolus of fill material within the distal end of the housing shell; setting a portion of the at least one thin-film RTD sensor in the spacer; and inserting the spacer into the housing shell to cause the fill material to flow between the shell and spacer. ### Claim 19 (depends on 18) The method of claim 18, wherein a distal end of the spacer is open and the fill material also flows between the at least one thin-film RTD and the spacer. ### Claim 20 (depends on 18) The method of claim 18, wherein the full material comprises solder or braze and is heated to form the liquid bolus after introducing it in a solid state into the housing shell.