Flow meter with ultrasound transducer directly connected to and fixed to measurement circuit board

Abstract

An ultrasound flow meter unit arranged to measure a fluid flow rate with one or more ultrasound transducers ( 606 ), and a circuit board ( 602 ) with an electronic circuit arranged to operate the ultrasound transducer(s) ( 106, 306 ). The ultrasound transducer ( 606 ), e.g. in the form of a piezo-electric element, is mechanically fixed to the circuit board ( 602 ) by a first electrically conducting fixing means which additionally serve(s) to provide an electrical connection between an electrical terminal of the transducer ( 606 ) and the electronic circuit. Hereby a functional flow measurement unit ( 600 ) is provided which can be tested prior to assembly with a flow meter housing etc. Preferably, a set of ultrasound transducers ( 106, 306 ) are soldered directly onto electrically conducting paths ( 631 ) on a surface of the circuit board ( 602 ) being in electrical connection with the electronic circuit, e.g. in a single SMT mounting process together with mounting of all other electronic components on the circuit board ( 602 ). Through-going openings ( 630, 640 ) of the circuit board ( 602 ) in the vicinity of these conducting paths ( 631 ) serve to provide thermal elasticity. A metal clip soldered to the circuit board ( 602 ) may serve to electrically connect a second electrical terminal of the transducer ( 606 ) to the electronic circuit.

The invention claimed is: 
     
       1. An ultrasound flow meter unit arranged to measure a fluid flow rate, the unit comprising:
 a first ultrasound transducer having a first and a second electrical terminal, and 
 a circuit board with an electronic circuit arranged thereon for operating the first ultrasound transducer, wherein the circuit board comprises a first conducting path electrically connected to the first electrical terminal, and to the electronic circuit, wherein the first ultrasound transducer is includes a monolithic body of piezo-electric material with and has one surface in contact with a surface of the circuit board, and wherein the monolithic body is mechanically fixed to the circuit board by a first electrically conducting fixing means, which provides the electrical connection between the first electrical terminal and the first conducting path 
 wherein the first ultrasound transducer is mounted on top of a through-going hole of the circuit board and surface mounted to the circuit board by fixing the first conducting path arranged at least partially around a periphery of the through-going hole of the circuit board to the first electrical terminal arranged on a periphery of the one surface of the first ultrasound transducer in contact with the circuit board. 
 
     
     
       2. The ultrasound flow meter unit according to  claim 1 , wherein the first fixing means comprises the first conducting path is fixed to the first electrical terminal by using at least one of: solder, or electrically conducting glue, or an electrically conducting clip. 
     
     
       3. The ultrasound flow meter unit according to  claim 1 , wherein the circuit board has one or more through-going openings hole is partly or entirely covered by the first ultrasound transducer when fixed to the circuit board. 
     
     
       4. The ultrasound flow meter unit according to  claim 3 , wherein a part of the first conducting path is arranged in the vicinity of at least one of the through-going opening(s) in the circuit board. 
     
     
       5. The ultrasound flow meter unit according to  claim 1 , wherein the ultrasound transducer is mounted on top of a through-going hole of the circuit board or on top of a non through-going cavity of the circuit board. 
     
     
       6. The ultrasound flow meter unit according to claim  4  1, wherein the monolithic body first ultrasound transducer is fixed to the circuit board by soldering the first conducting path to the first electrical terminal on a periphery of the end part of the ultrasound transducer facing the circuit board. 
     
     
       7. The ultrasound flow meter unit according to claim  5  1, wherein a the through-going opening hole is accompanied by openings positioned outside the area covered by the first ultrasound transducer when fixed to the circuit board. 
     
     
       8. The ultrasound flow meter unit according to  claim 7 , wherein a the through-going opening in the form of hole is a circular hole surrounded by a circular conducting path, and is accompanied by four narrow through-going openings outside the area with the circular conductive path. 
     
     
       9. The ultrasound flow meter unit according to  claim 7 , wherein the first conducting path includes a generally annular conductor with a cut serves for connection to the first terminal of the first ultrasound transducer, and wherein a the through-going opening hole is arranged inside the conductor and a through-going grove groove is arranged outside the conductor. 
     
     
       10. The ultrasound flow meter unit according to  claim 7 , wherein the first conducting path includes an annular conductor serves for connection to the first terminal of the first ultrasound transducer, and wherein a the through-going opening hole is arranged inside the conductor and a through-going grove groove is arranged outside the conductor. 
     
     
       11. The ultrasound flow meter unit according to  claim 1 , wherein a second conducting path on the surface of the circuit board serves to electrically connect the electronic circuit with to the second electrical terminal of the first ultrasound transducer. 
     
     
       12. The ultrasound flow meter unit according to  claim 11 , wherein a metal clip serves to electrically connect the second conducting path to the second electrical terminal of the first ultrasound transducer. 
     
     
       13. The ultrasound flow meter unit according to  claim 11 , wherein the second conducting path is placed within the first conducting path and separated by a through-going opening. 
     
     
       14. The ultrasound flow meter unit according to  claim 1 , wherein the ultrasound flow meter further comprises a second ultrasound transducer, wherein the electronic circuit is further arranged for operating the second ultrasound transducer, wherein the second ultrasound transducer is mechanically fixed to the circuit board by a second electrically conducting fixing means, which additionally serve(s) to provide an electrical connection between at least one electrical terminal of the second ultrasound transducer and the electronic circuit, and wherein both of the first and second ultrasound transducers are mechanically fixed to the same side of the circuit board. 
     
     
       15. The ultrasound flow meter unit according to  claim 14 , comprising a substantially watertight membrane arranged around the circuit board and the first and second ultrasound transducers, and wherein a plug with a plurality of electrical terminals penetrates through the membrane so as to allow external connection to the electronic circuit, wherein at least a part of the membrane is electrically conducting and serves to electrically connect the second electrical terminal of the first ultrasound transducer with a second electrical terminal of the second ultrasound transducer. 
     
     
       16. A flow meter arranged to measure a flow rate of a fluid flowing through a measuring tube, wherein the flow meter comprises:
 a housing with the measuring tube arranged inside, and 
 an ultrasound flow meter unit according to  claim 1  arranged in relation to the housing. 
 
     
     
       17. The flow meter according to  claim 16 , wherein said flow meter is a heat meter, a cooling meter, a water meter, or a gas meter. 
     
     
       18. An ultrasound flow meter unit arranged to measure a fluid flow rate, the unit comprising:
 a first ultrasound transducer including a monolithic body of piezo-electric material and having a first and a second electrical terminal;   a circuit board with an electronic circuit arranged thereon for operating the first ultrasound transducer;   wherein the first ultrasound transducer is electrically and mechanically connected to the circuit board by connecting one of the first and second electric terminal to an at least partially annular conductive path of the circuit board having outside thereof at least one through-going opening or groove to effectively absorb extensions and contractions of the piezo-electric material.   
     
     
       19. The ultrasound flow meter unit of claim 18, wherein the first ultrasound transducer has a cylindrical shape with a first end surface with a first periphery and a second end surface with a second periphery, wherein the first end surface faces the circuit board. 
     
     
       20. The ultrasound flow meter unit of claim 19, wherein the at least partially annular conductive path of the circuit board is at least partially surrounded by a void formed in the circuit board. 
     
     
       21. The ultrasound flow meter unit of claim 20, wherein the void at least partially surrounds the first periphery of the first ultrasound transducer. 
     
     
       22. The ultrasound flow meter unit of claim 18, wherein the ultrasound flow meter unit comprises a second ultrasound transducer. 
     
     
       23. The ultrasound flow meter unit of claim 22, wherein the second ultrasound transducer includes an additional monolithic body of piezo-electric material and having a third and a fourth electrical terminal;
 wherein the electronic circuit is arranged for operating the second ultrasound transducer;   wherein the second ultrasound transducer is electrically connected to the electronic circuit arranged on the circuit board via the third and fourth electrical terminals, and   wherein the second ultrasound transducer is mechanically connected to the electronic circuit arranged on the circuit board by a second at least partially annular conductive path of the circuit board having outside thereof at least one second through-going opening or groove to effectively absorb extensions and contractions of the piezo-electric material of the second ultrasound transducer.   
     
     
       24. The ultrasound flow meter unit of claim 23, wherein the second ultrasound transducer has a cylindrical shape with a third end surface with a third periphery and a fourth end surface with a fourth periphery, the third end surface facing the circuit board, wherein the second ultrasound transducer is mechanically fixed onto a surface of the second at least partially annular conductive path of the circuit board, wherein the second at least partially annular conductive path of the circuit board is arranged along the third periphery of the second ultrasound transducer; and
 wherein the second at least partially annular conductive path of the circuit board is at least partially surrounded by a second void formed in the circuit board.   
     
     
       25. The ultrasound flow meter unit of claim 24, wherein the second void at least partially surrounds the third periphery of the second ultrasound transducer. 
     
     
       26. A flow meter arranged to measure a flow rate of a fluid flowing through a measuring tube, wherein the flow meter comprises:
 a housing with the measuring tube arranged inside, and   an ultrasound flow meter unit according to claim 18 arranged in relation to the housing.   
     
     
       27. The flow meter according to claim 26, wherein said flow meter is a heat meter, a cooling meter, a water meter, or a gas meter.