Patent Publication Number: US-2003221492-A1

Title: Assembly structure for pressure sensor, and assembling method thereof

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to a pressure sensor and, more particularly, to an assembly structure for an electrostatic capacity type pressure sensor and a assembling method of the pressure sensor.  
       [0003] 2. Background Art  
       [0004] As the pressure sensor of the background art, electrostatic capacity type pressure sensors have been disclosed in JP-A-11-248579 and JP-A-2000-9572, for example. In the former pressure sensor, a sensor element is temporarily fixed in a housing case  10 , and an output adjustment is done in the state where a pressure occurring at a caulking time is loaded. Then, the sensor element  1  is caulked and fixed in the housing case  10 .  
       [0005] In the latter pressure sensor, on the other hand, before a sensor element  1  is housed in a housing case  10 , there is established a simulated assembly state, which falls under a proper compressibility range capable of keeping the sealing properties of a seal member  13 , and the output of the pressure sensor element  1  is adjusted in the state where the atmospheric pressure is applied to a pressure sensing face  2   a  of the pressure sensor element  1 . And, the pressure sensor element  1  is housed in the housing case  10  and is loaded with the atmospheric pressure. The pressure sensor element  1  is caulked and finally fixed when its output reaches that adjusted value.  
       [0006] In either of the methods, therefore, the output is adjusted by loading the pressure sensor element with a virtual pressure before the components are finally fixed.  
       SUMMARY OF THE INVENTION  
       [0007] However, it is difficult to caulk the pressure sensor element under absolutely the same pressure after the output adjustment as that virtual one, and the caulking pressure easily disperses. Therefore, an assembly error easily occurs so that the detection accuracy seriously disperses among the pressure sensors. In case a trouble is found at the shipping test time after all the components were assembled, on the other hand, it is extremely difficult and troublesome to disassemble and adjust the pressure sensor. As a matter of fact, therefore, the troublesome pressure sensor has to be discarded in its entirety thereby to degrade the production yield. Thus, a problem is encountered by a rise in the production cost.  
       [0008] In view of the aforementioned problem, the invention has an object to provide a pressure sensor assembling structure capable of keeping a homogeneous detection accuracy without any error that might otherwise be caused by a stress at an assembling time, and an assembling method for the assembling structure.  
       [0009] In order to achieve the above-specified object, according to an aspect of the invention, there is provided a pressure sensor assembling structure, which is constructed to comprise: a base having a fluid inlet port on one end side and an opening communicating with the fluid inlet port on the other end side; and a sensor element inserted from the opening of the base and fixed in the base such that a connecting face formed on its one side is exposed from the side of the opening.  
       [0010] According to this aspect of the invention, the connecting face of the sensor element fixed in the base is exposed so that the output adjustment can be performed by connecting output adjusting means with the sensor element. Therefore, the sensor element need neither be fixed in the base after the output adjustment nor has its characteristics varied, so that an assembly structure for a pressure sensor having a homogeneous detection accuracy can be obtained without causing any error.  
       [0011] According to another aspect of the invention, there is provided a pressure sensor assembling structure, which is constructed to comprise: a base having a fluid inlet port on one end side and an opening communicating with the fluid inlet port on the other end side; a sensor element having a connecting face on one side and inserted from the opening of the base; and a cylindrical case forced to contact, when inserted from the opening of the base and fixed in the base, with the outer circumference edge portion of the connecting face of the sensor element and exposing the connecting face of the sensor element from an outside opening.  
       [0012] According to this aspect of the invention, the sensor element is fixed with the base and the cylindrical case before the output adjustment, and the connecting face of the sensor element is exposed. Therefore, the sensor element need neither be fixed in the base after the output adjustment nor has its characteristics varied, so that an assembly structure for a pressure sensor having a homogeneous detection accuracy can be obtained without causing any error.  
       [0013] According to still another aspect of the invention, there is provided a pressure sensor assembling structure, which is constructed to comprise: a base having a fluid inlet port on one end side and an opening communicating with the fluid inlet port on the other end side; a sensor element having a connecting face on one side and inserted from the opening of the base; an element holding ring inserted from the opening and abutting against the outer circumference edge portion of the connecting face of the sensor element; and a cylindrical case forced to contact, when inserted from the opening of the base and fixed in the base, at its inside opening edge portion with the element holding ring and exposing the connecting face of the sensor element from an outside opening.  
       [0014] According to this aspect of the invention, the sensor element is not only fixed through the element holding ring fixed in the base and the cylindrical case but also has its connecting face exposed from the outside opening of the cylindrical case. Therefore, the sensor element need neither be fixed in the base after the output adjustment nor has its characteristics varied, so that an assembly structure for a pressure sensor having a homogeneous detection accuracy can be obtained without causing any error.  
       [0015] According to a further aspect of the invention, there is provided a pressure sensor assembling method, which comprise: inserting a sensor element from an opening formed in the other end side of a base and communicating with a fluid inlet port formed in the one end side of the base; fixing the sensor element in the base such that a connecting face formed on one side of the sensor element is exposed from the side of the opening; connecting output adjusting means mounted in a printed substrate, electrically with the connecting face of the sensor element thereby to adjust the output by activating the output adjusting means; and fixing the printed substrate with a case fixed in the base and a cover.  
       [0016] According to this aspect of the invention, after the sensor element was fixed in the base, the output adjustment is performed by connecting the output adjusting means with the exposed connecting face of the sensor element. Therefore, the sensor element does not have its characteristics varied, so that a pressure sensor having a homogeneous detection accuracy can be obtained.  
       [0017] According to a further aspect of the invention, there is provided a pressure sensor assembling method, which comprise: inserting a sensor element having a connecting face on one side, from an opening formed in the other end side of a base and communicating with a fluid inlet port formed in the one end side of the base; inserting a cylindrical case from the opening of the base and fixing the cylindrical case in the base thereby to force the inside opening edge portion of the cylindrical case to contact with the outer circumference edge portion of the connecting face of the sensor element thereby to expose the connecting face of the sensor element from the outside opening of the cylindrical case; connecting output adjusting means mounted in a printed substrate, electrically with the connecting face of the pressure sensor element thereby to adjust the output by activating the output adjusting means; and fixing the printed substrate with the cylindrical case and a cover.  
       [0018] According to this aspect of the invention, after the sensor element was fixed with the base and the cylindrical case, the output adjustment is performed by connecting the output adjusting means with the exposed connecting face of the sensor element. Therefore, the sensor element does not have its characteristics varied, so that a pressure sensor having a homogeneous detection accuracy can be obtained.  
       [0019] According to a further aspect of the invention, there is provided a pressure sensor assembling method, which comprise: inserting a sensor element having a connecting face on one side, from an opening formed in the other end side of a base and communicating with a fluid inlet port formed in the one end side of the base; inserting an element holding ring to abut against the outer circumference edge portion of the connecting face of the sensor element, from the opening of the base; inserting a cylindrical case from the opening of the base and further fixing the cylindrical case in the base thereby to force the inside opening edge portion of the cylindrical case to contact with the element holding ring thereby to expose the connecting face of the sensor element from the outside opening of the cylindrical case; connecting output adjusting means mounted in a printed substrate, electrically with the connecting face of the sensor element thereby to adjust the output by activating the output adjusting means; and fixing the printed substrate with the cylindrical case and a cover.  
       [0020] According to this aspect of the invention, after the sensor element was fixed with the base, the element holding ring and the cylindrical case, the output adjustment is performed by connecting the output adjusting means with the exposed connecting face of the sensor element. Therefore, the sensor element does not have its characteristics varied, so that a pressure sensor having a homogeneous detection accuracy can be obtained. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0021] Of FIGS. 1A and 1B showing a first embodiment of a pressure sensor assembly structure according to the present invention, FIG. 1A is a perspective view, and FIG. 1B is a sectional perspective view of FIG. 1A;  
     [0022]FIG. 2 is an exploded perspective view of the first embodiment shown in FIGS. 1A and 1B;  
     [0023]FIG. 3 is a sectional front elevation of the first embodiment shown in FIG. 1B;  
     [0024] Of FIGS. 4A and 4B showing a second embodiment of the pressure sensor assembly structure according to the invention, FIG. 4A is a perspective view, and FIG. 4B is a sectional perspective view of FIG. 4A;  
     [0025]FIG. 5 is an exploded perspective view of the second embodiment shown in FIGS. 4A and 4B;  
     [0026]FIG. 6 is a sectional front elevation of the second embodiment shown in FIG. 4B;  
     [0027] Of FIGS. 7A and 7B showing a third embodiment of the pressure sensor assembly structure according to the invention, FIG. 7A is a perspective view, and FIG. 7B is a sectional perspective view of FIG. 7A;  
     [0028]FIG. 8 is an exploded perspective view of the third embodiment shown in FIGS. 7A and 7B;  
     [0029]FIG. 9 is a sectional front elevation of the third embodiment shown in FIG. 7B;  
     [0030]FIG. 10A is a sectional view showing a fourth embodiment of the pressure sensor assembly structure according to the invention;  
     [0031]FIG. 10B is a sectional view showing a fifth embodiment;  
     [0032]FIG. 11A is a sectional view showing a sixth embodiment of the pressure sensor assembly structure according to the invention;  
     [0033]FIG. 11B is a sectional view showing a seventh embodiment;  
     [0034]FIG. 12A is a sectional view showing an eighth embodiment of the pressure sensor assembly structure according to the invention;  
     [0035]FIG. 12B is a sectional view showing a ninth embodiment; and  
     [0036]FIG. 13 is a sectional view showing a tenth embodiment of the pressure sensor assembly structure according to the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0037] Embodiments according to the invention will be described with reference to FIGS. 1A and 1B to FIG. 13.  
     [0038] A first embodiment of the invention is applied to an electrostatic capacity type pressure sensor, as shown in FIGS.  1 A and  1 B to FIG. 3. This pressure sensor is constructed by assembling an O-ring  11 , a sensor element  12 , a case  13 , first and second substrates  14  and  15  and a cover  17  sequentially with a base  10 .  
     [0039] In order to facilitate the assembling works, the base  10  is formed in its outer circumference to have a hexagonal nut shape and is provided with a protrusion  10   b  having a fluid inlet port  10   a  at its one side end face and is largely opened on its remaining side.  
     [0040] The sensor element  12  is exemplified by the electrostatic capacity type pressure sensor, which is formed by joining two ceramic substrates integrally, and a (not-shown) connecting pin terminal is protruded from the side end face opposed to the first substrate  14 .  
     [0041] This first substrate  14  is provided with such a (not-shown) through hole as can be connected with the pin terminal of the sensor element  12 , and is connected to the second substrate  15  through a flexible filmed lead wire  14   a . The second substrate  15  is clamped and fixed by a later-described stepped portion  13   a  of the case  13  and the leading end edge portion of the cover  17 .  
     [0042] The case  13  has such an outer circumference shape as can be inserted from the opening edge portion  10   c  of the base  10 , and is provided on its inner circumference with the stepped portion  13   a  for positioning the second substrate  15 .  
     [0043] The cover  17  has such an outer circumference shape as can be inserted into the case  13 , and is provided therein with such a cylindrical portion  17   a  as is protruded to abut against the surface of the second substrate  15 .  
     [0044] Here will be described how to assemble the pressure sensor which is composed of the aforementioned parts.  
     [0045] At first, the O-ring  11 , the sensor element  12  and the case  13  are introduced from the opening edge portion  10   c  of the base  10 , and the opening edge portion  10   c  is caulked to fix the sensor element  12  in the base  10 . Next, the first substrate  14  is assembled with the base  10  and is electrically connected with the pin terminal of the sensor element  12 . At this stage, the output is adjusted to store the pressure characteristics and the temperature characteristics.  
     [0046] Then, the second substrate  15  connected with the first substrate  14  through the flexible filmed lead wire  14   a  is positioned on the stepped portion  13   a  of the case  13 . Lead wires  16   a ,  16   b  and  16   c  are electrically connected with the second substrate  15 , and the cover  17  having the lead wires  16   a ,  16   b  and  16   c  is assembled and positioned with the case  13 , and the cover  17  sealed and fixed in the case  13  by a not-shown sealing member.  
     [0047] In this embodiment, the sensor element  12  is properly fixed in the base  10 , and the remaining components parts including the first and second substrates  14  and  15 , the lead wires  16   a ,  16   b  and  16   c  and the cover  17  are assembled in the base  10 . When the first and second substrates  14  and  15  and so on are assembled, however, it is not feared in the least that a high pressure is applied to the sensor element  12 . Therefore, it is advantageous that the action characteristics of the pressure sensor element  12  do not change even after completion of the assembly thereby to provide a pressure sensor having a homogeneous detection accuracy.  
     [0048] Here, the first substrate  14  maybe electrically connected in advance with the sensor element  12 , or the lead wires  16   a ,  16   b  and  16   c  may be electrically connected in advance with the second substrate  15 . Moreover, the case  13  may be fastened integrally with the base  12 , or the cover  17  may be fastened or caulked integrally with the cover  13 .  
     [0049] As shown in FIGS. 4A and 4B to FIG. 6, a pressure sensor according to a second embodiment is constructed by assembling an O-ring  11 , a sensor element  12 , an element holding ring  18 , first and second substrates  14  and  15 , a spacer  19 , a case  20 , an O-ring  21  and a cover  22  with a base  10 .  
     [0050] In order to facilitate the assembling works, the base  10  is formed in its outer circumference to have a hexagonal nut shape and is provided with a protrusion  10   b  having a fluid inlet port  10   a  at its one side end face and is largely opened on its remaining side to form a female screw portion (not-shown) to the inner circumstance.  
     [0051] The sensor element  12  is exemplified by the electrostatic capacity type pressure sensor which is formed by joining two ceramic substrates integrally, and a connecting pin terminal  12   a  (FIG. 6) is protruded from the side end face opposed to the first substrate  14 .  
     [0052] The element holding ring  18  has such an internal diameter as can abut against the outer circumference edge or one side end face of the sensor element  12  and is provided at an equal pitch with four lugs capable of abutting against the inner circumference of the base  10 .  
     [0053] The first substrate  14  is provided with such a through hole  14   b  (FIG. 6) as can be connected with the pin terminal  12   a  of the sensor element  12 , and is connected to the second substrate  15  through a flexible filmed lead wire  14   a . Moreover, lead wires  16   a ,  16   b  and  16   c  are electrically connected with the second substrate  15 .  
     [0054] The spacer  19  is a ring having such an internal diameter as can fit the outer circumference of the case  20 , and is clamped by the base  10  and the case  20 .  
     [0055] The case  20  has such an outer circumference shape at its one side portion as can be inserted from the opening of the base  10 , and is provided on the inner circumference of its remaining side portion with such a stepped portion  20   a  for positioning the cover  22  as can be caulked at its opening edge portion  20   b.    
     [0056] The cover  22  has such an outer circumference shape as can be inserted from the opening of the case  20  and can be fitted on the stepped portion  20   a.    
     [0057] Here will be described how to assemble the pressure sensor which is composed of the aforementioned parts.  
     [0058] At first, the O-ring  11 , the sensor element  12  and the element holding ring  18  are introduced from the opening of the base  10 . Next, the case  20  having the spacer  19  fitted therein is inserted into the base  10  and is fastened integrally to fix the sensor element  12  in the base  10 . For convenience of description, here is not shown the portion illustrating the state in which the base  10  and the case  20  are fastened.  
     [0059] Moreover, the first substrate  14  is assembled in the base  10 , and the pin terminal  12   a  of the sensor element  12  is inserted into and electrically connected with a through hole  14   b  of the first substrate  14 . At this stage, the output is adjusted to store the pressure characteristics and the temperature characteristics.  
     [0060] Here in this embodiment, the spacer  19  functions as a thickness gauge at the time when the case  20  is fixed in the base  10 . It is, therefore, unnecessary to meter the caulking force or torque.  
     [0061] And, the second substrate  15  connected with the first substrate  14  through the flexible filmed lead wire  14   a  is positioned in the case  20 . Next, the O-ring  21  and the cover  22  are sequentially introduced and positioned in the case  20 , and the opening edge portion  20   b  of the case  20  is caulked.  
     [0062] In this embodiment, the sensor element  12  is fixed in the base  10  and is connected with the first substrate  14 . After adjustment of the output, another component or the second substrate  15  is assembled with the first substrate  14 . Especially when the cover  22  is caulked in the case  20 , the caulking force is applied to the outer circumference edge portion of the sensor element  12 . Therefore, it is advantageous that the action characteristics of the pressure sensor element  12  do not change even after completion of the assembly thereby to provide a pressure sensor having a homogeneous detection accuracy.  
     [0063] Here, the first substrate  14  maybe electrically connected in advance with the sensor element  12 . Moreover, the case  20  may be caulked in the base  10 , or the cover  22  may be fastened integrally with the case  20 .  
     [0064] As shown in FIGS. 7A and 7B to FIG. 9, a pressure sensor according to a third embodiment is constructed by assembling an O-ring  11 , a sensor element  12 , first and second substrates  14  and  15 , a cover  23  and a case  24  with a base  10 .  
     [0065] In order to facilitate the assembling works, the base  10  is formed in its outer circumference to have a hexagonal nut shape and is provided with a protrusion  10   b  having a fluid inlet port  10   a  at its one side end face and is so largely opened on its remaining side that its opening edge portion  10   c  can be caulked.  
     [0066] The sensor element  12  is exemplified by the electrostatic capacity type pressure sensor which is formed by joining two ceramic substrates integrally, and a (not-shown) connecting pin terminal is protruded from the side end face confronted with the first substrate  14 .  
     [0067] The first substrate  14  is provided with such a (not-shown) through hole as can be connected with the pin terminal of the sensor element  12 , and is connected to the second substrate  15  through a flexible filmed lead wire  14   a , as shown in FIG. 9. The second substrate  15  is clamped and fixed by a stepped portion  24   a  of the case  24  and the leading end edge portion of the cover  23 .  
     [0068] This cover  23  has such an outer circumference shape as can be inserted into the case  24 , and is provided therein with a cylindrical portion  23   a  to abut against the central portion of the surface of the second substrate  15 .  
     [0069] The case  24  is formed into such a cylindrical shape as can be fitted on the outer circumference of one side end portion of the base  10 , and is provided with the stepped portion  24   a  for positioning the second substrate  15  on its inner circumference and such an opening edge portion  24   b  as can be caulked.  
     [0070] Here will be described how to assemble the pressure sensor which is composed of the aforementioned parts.  
     [0071] At first, the O-ring  11  and the sensor element  12  are introduced from the opening edge portion  10   c  of the base  10 . After this, the opening edge portion  10   c  of the base  10  is caulked to fix the sensor element  12  in the base  10 . Next, the case  24  is fitted and fixed on the outer circumference of the caulked side end portion of the base  10 . Moreover, the pin terminal of the sensor element  12  is electrically connected with the first substrate  14 . At this stage, the output is adjusted to store the pressure characteristics and the temperature characteristics.  
     [0072] And, the second substrate  15  connected with the first substrate  14  through the flexible filmed lead wire  14   a  is positioned on the stepped portion  24   a  of the case  24 . Then, the cover  23  is assembled and positioned with the case  24  by inserting the lead wires  16   a ,  16   b  and  16   c  connected with the second substrate  15 , and is fixed by caulking the opening edge portion  24   b  of the case  24 .  
     [0073] In this embodiment, the sensor element  12  is fixed in the base  10 , and the first substrate  14  is electrically connected to adjust the output. After this, the remaining components including the second substrate  15  are assembled. Even in case the cover  23  is caulked in the case  24 , however, no high pressure is applied to the sensor element  12 . Therefore, it is advantageous that the action characteristics of the pressure sensor element  12  do not change even after completion of the assembly thereby to provide a pressure sensor having a homogeneous detection accuracy.  
     [0074] Here, the first substrate  14  maybe electrically connected in advance with the sensor element  12 . Alternatively, the case  24  may be fastened integrally with the base  12 , or may be adhered integrally through a sealing member. Moreover, the cover  23  may be fastened or adhered integrally with the case  24 .  
     [0075] In a fourth embodiment according to the invention, as shown in FIG. 10A, the O-ring  11  and the sensor element  12  are housed and positioned in the base  10 , and the opening edge portion  10   c  of the base  10  is then caulked. And, an O-ring  25  is arranged on the outer circumference of the opening edge portion  10   c  caulked, and a flanged portion  26   a  of a case  26  is fitted on one side end portion of the base  10  and is fastened on the same by means of screws. Next, the first substrate  14  housed in the case  26  is electrically connected with the sensor element  12  through a lead wire. In this state, the output is adjusted for the pressure characteristics or the like. Moreover, the first substrate  14  is positioned on ribs  26   b  of the case  26 , and the second substrate  15  electrically connected is put on the first substrate  14 . And, a cover  27  is inserted into the case  26 , and an opening edge portion  26   c  of the case  26  is caulked and fixed through an O-ring  28 .  
     [0076] According to the fourth embodiment, the ribs  26   b  of the case  26  receive the caulking pressure. Therefore, no pressure is applied to the sensor element  12  so that the output-adjusted action characteristics do not change.  
     [0077] In a fifth embodiment according to the invention, as shown in FIG. 10B, the O-ring  11  and the sensor element  12  are housed and positioned in the base  10 , and the opening edge portion  10   c  of the base  10  is then caulked. And, an O-ring  25  is arranged on the outer circumference of the opening edge portion  10   c  caulked, and a flanged portion  26   a  of a case  26  is fitted on one side end portion of the base  10  and is fastened on the same by means of screws. Next, the first substrate  14  housed in the case  26  is electrically connected with the sensor element  12  through a lead wire. In this state, the output is adjusted for the pressure characteristics or the like. Moreover, the second substrate  15  electrically connected is put on the first substrate  14 . And, a cover  27  is inserted into the case  26 , and an opening edge portion  26   c  of the case  26  is caulked and fixed through an O-ring  28 .  
     [0078] According to the fifth embodiment, the first substrate  14  is held in direct abutment against the sensor element  12 . It is, therefore, advantageous that the outside dimension can be reduced.  
     [0079] As shown in FIG. 11A, a sixth embodiment according to the invention is similar to the foregoing fourth embodiment but is different in the shape of the sensor element  12 .  
     [0080] Specifically, the sensor element  12  is formed by joining a thick, diametrically larger base  12   a  and a diaphragm or a diametrically smaller substrate  12   b  integrally. The O-ring  11  is pressure-welded on the outer circumference edge portion of the base  12   a . Therefore, the stress to be generated when the base  10  is caulked is wholly loaded on the base  12   a . It is advantageous that the stress will hardly affect the action characteristics of the sensor element  12 .  
     [0081] As shown in FIG. 11B, a seventh embodiment according to the invention is similar to the foregoing fifth embodiment but is different in that the sensor element  12  is formed by joining a thick, diametrically larger base  12   a  and a diaphragm or a diametrically smaller substrate  12   b  integrally. Like the foregoing fifth embodiment, therefore, it is advantageous to provide a pressure sensor having action characteristics hardly varied by the caulking force of the base  10 .  
     [0082] In an eighth embodiment according to the invention, as shown in FIG. 12A, not only the O-ring  11  and the sensor element  12  but also a case  29  is housed in the base  10 . Next, an O-ring  30  is inserted into and positioned in the case  29 , and this case  29  is then fixed by caulking the opening edge portion  10   c  of the base  10 . And, the first substrate  14  is inserted from the opening edge portion  29   a  of the case  29  and is electrically connected with the sensor element  12 . In this state, the output is adjusted for the pressure characteristics or the like. Moreover, the second substrate  15  electrically connected with the first substrate  14  is inserted into the case  29 , and A cover  31  having a generally T-shaped section is housed. Moreover, an O-ring  32  is fitted and positioned on the cover  31 , and the cover  31  is then fixed through the O-ring  32  by caulking the opening edge portion  29   a  of the case  29 .  
     [0083] As shown in FIG. 12B, a ninth embodiment according to the invention is substantially similar to the foregoing eighth embodiment and is constructed such that the sensor element  12  is formed by joining a thick, diametrically larger base  12   a  and a diaphragm or a diametrically smaller substrate  12   b  integrally. Therefore, it is advantageous to provide a pressure sensor having action characteristics hardly varied by the caulking force.  
     [0084] In a tenth embodiment according to the invention, as shown in FIG. 13, the O-ring  11  and the sensor element  12  are housed and positioned at first in the base  10 . And, the sensor element  12  is fixed by positioning and fastening a flanged portion  33   a  of a case  33  on the base  10  by means of screws. At this time, the pin terminal (not-shown) of the sensor element  12  is inserted into and electrically connected with the through hole of the first substrate  14 . The two substrates  14  and  34  housed in the case  33  are inserted and positioned from the insertion hole (not-shown) so that they are completely electrically insulated from each other. Moreover, the substrate  14  is held in abutment against the sensor element  12  through a cushioning member  35 .  
     [0085] Next, an O-ring  37  and a sensor element  39  are inserted into and positioned in another base  36 , and a flanged portion  33   b  of the case  33  is assembled and fastened by means of screws. At this time, the pin terminal of the sensor element  38  is inserted into and electrically connected with the through hole of the substrate  34  through a cushioning member  39 .  
     [0086] According to this embodiment, it is advantageous that two kinds of measurements can be done with the single pressure sensor by arranging the two sensor elements  12  and  38 .  
     [0087] In all the foregoing embodiments, the sensor element  12  is not integrally adhered to the component parts such as the first substrate  14 . Therefore, it is advantageous that the pressure sensor can be easily disassembled, repaired and replaced.  
     [0088] According to the invention, the sensor element fixed in the base has its connected face exposed so that the output can be adjusted by connecting the output adjusting means with the sensor element. Therefore, the sensor element need neither be fixed in the base after the output was adjusted nor has its characteristics varied. Therefore, the invention has an effect that it can provide an assembly structure for a pressure sensor having a homogeneous detection accuracy without causing any error.