Ultrasonic sensor assembly and method

Abstract

An ultrasonic point level measurement instrument comprises a measurement circuit and a transducer. The transducer transmits and receives acoustic signals under control of the measurement circuit. An improvement in the transducer comprises a transducer housing including a pair of spaced apart legs to define a gap therebetween. Each leg includes an interior cavity. A pair of crystal assemblies each comprise a crystal mounted to a circuit board. The circuit board includes conduction paths for connection between the crystal and a terminal pad. Each crystal assembly is received in the interior cavity of one of the legs with the circuit board spacing the crystal from walls of the leg. A pair of cables are each connected between the measurement circuit and the terminal pad of one of the crystal assemblies so that the measurement circuit detects presence of a material in the gap.

1 . In an ultrasonic point level measurement instrument comprising a measurement circuit and a transducer, the transducer transmitting and receiving acoustic signals under control of the measurement circuit, the improvement comprising: 
 a transducer housing including a pair of spaced apart legs to define a gap therebetween, each leg including an interior cavity;    a pair of crystal assemblies each comprising a crystal mounted to a circuit board, the circuit board including conduction paths for connection between the crystal and a terminal pad, each crystal assembly being received in the interior cavity of one of the legs with the circuit board spacing the crystal from walls of the leg; and    a pair of cables each connected between the measurement circuit and the terminal pad of one of the crystal assemblies so that the measurement circuit detects presence of a material in the gap.    
   
   
       2 . The improvement of  claim 1  wherein each crystal is generally planar having opposite first and second conductive surfaces and the first conductive surface makes electrical contact with conductive pads on the circuit board.  
   
   
       3 . The improvement of  claim 2  wherein each crystal assembly further comprises a connector electrically connecting the second conductive surface to conduction paths on the circuit board.  
   
   
       4 . The improvement of  claim 1  wherein each circuit board insulates one side of the crystal from the walls of the leg and an insulating spacer insulates another side of the crystal from the walls of the leg.  
   
   
       5 . The improvement of  claim 4  wherein each insulating spacer biases the circuit board against one of the walls of the leg.  
   
   
       6 . The improvement of  claim 1  wherein the interior cavities are encapsulated with a potting compound.  
   
   
       7 . A transducer for an ultrasonic point level measurement instrument comprising a measurement circuit, the transducer transmitting and receiving acoustic signals under control of the measurement circuit, the transducer comprising: 
 a metal housing including a generally cylindrical body with a pair of spaced apart legs extending from the body, the legs being generally semi-cylindrical with facing planar walls to define a gap therebetween, each leg including an interior cavity opening into the body;    a pair of crystal assemblies each comprising a crystal mounted to a circuit board, the circuit board including conduction paths for connection between the crystal and a terminal pad, each crystal assembly being received in the interior cavity of one of the legs with the circuit board against the planar wall and spacing the crystal from the planar wall; and    a pair of cables each connected between the measurement circuit and the terminal pad of one of the crystal assemblies so that the measurement circuit detects presence of a material in the gap.    
   
   
       8 . The transducer of  claim 7  wherein each crystal is generally planar having opposite first and second conductive surfaces and the first conductive surface makes electrical contact with conductive pads on the circuit board.  
   
   
       9 . The transducer of  claim 8  wherein each crystal assembly further comprises a connector electrically connecting the second conductive surface to conduction paths on the circuit board.  
   
   
       10 . The transducer of  claim 7  wherein each circuit board insulates one side of the crystal from the planar wall and an insulating spacer insulates another side of the crystal from other walls of the leg.  
   
   
       11 . The transducer of  claim 10  wherein each insulating spacer biases the circuit board against the planar wall.  
   
   
       12 . The transducer of  claim 7  wherein the interior cavities are encapsulated with a potting compound.  
   
   
       13 . The method of assembling a transducer for an ultrasonic point level measurement instrument comprising a measurement circuit, the transducer for transmitting and receiving acoustic signals under control of the measurement circuit, comprising: 
 providing a metal housing including a generally cylindrical body with a pair of spaced apart legs extending from the body, the legs being generally semi-cylindrical with facing planar walls to define a gap therebetween, each leg including an interior cavity opening into the body;    assembling a plurality of crystal assemblies, for each comprising mounting a crystal to a circuit board, the circuit board including conduction paths for connection between the crystal and a terminal pad;    inserting a crystal assembly in the interior cavity of each of the legs with the circuit board against the planar wall and spacing the crystal from the planar wall; and    electrically connecting a cable between the measurement circuit and the terminal pad of each of the crystal assemblies so that the measurement circuit can detect presence of a material in the gap.    
   
   
       14 . The method of  claim 13  wherein each crystal is generally planar having opposite first and second conductive surfaces and the first conductive surface is soldered to conductive pads on the circuit board.  
   
   
       15 . The method of  claim 14  wherein assembling a plurality of crystal assemblies further comprises electrically connecting connectors between the second conductive surfaces and conduction paths on the circuit boards.  
   
   
       16 . The method of  claim 13  wherein each circuit board insulates one side of the crystal from the planar wall and further comprising inserting an insulating spacer between another side of the crystal and other walls of the leg.  
   
   
       17 . The method of  claim 16  wherein each insulating spacer biases the circuit board against the planar wall.  
   
   
       18 . The method of  claim 13  further comprising encapsulating the interior cavities with a potting compound.