Abstract:
The invention relates to a module for measuring purposes comprising an electrical or electronic circuit, which has at least one power supply connection and at least one data line connection for connecting, in the manner of a bus, to at least one other module of the same type that is also used for measuring purposes. According to the invention, the electronic circuit ( 80 ) is arranged inside a housing, the housing has a first contact surface ( 90 ) and a second contact surface ( 91 ), and the first contact surface ( 90 ) is joined to the second contact surface ( 91 ) of the other module ( 22, 32, 42 ) in a manner that permits it to be mechanically detached. The at least one power supply connection has a power supply contact ( 84   a   , 85   a ) in the first contact surface ( 90 ) and has a corresponding power supply contact ( 84   b   , 85   b ) in the second contact surface ( 91 ). The at least one data line connection has a data line contact ( 86   a   , 87   a ) in the first contact surface ( 90 ) and has a corresponding data line contact ( 86   b   , 87   b ) in the second contact surface ( 91 ). When the first contact surface ( 90 ) is joined to the second contact surface ( 91 ) of the other module ( 22, 32, 42 ), the power supply contact ( 84   a   , 85   a ) in the first contact surface ( 90 ) is connected in an electrically conductive manner to the corresponding power supply contact ( 84   b   , 85   b ) in the second contact surface ( 91 ) of the other module ( 22, 32, 42 ), and the data line contact ( 86   a   , 87   a ) in the first contact surface ( 90 ) is connected in an electrically conductive manner to the corresponding data line contact ( 86   b   , 87   b ) in the second contact surface ( 91 ) of the other module ( 22, 32, 42 ).

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is a national stage of PCT/EP01/14031 filed Nov. 30, 2001, and based upon DE 100 61 854.5 filed Dec. 12, 2000 under the International Convention. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention concerns a module for measuring purposes according to the main clause of claim  1 . 
   2. Description of the Related Art 
   Housings or racks are known from the state of the art into which a limited number of so-called slide-in cards can be inserted. Among those working in this field, these are known by the name 19″-rack or the like. 
   Such modularly built slide-in cards, preferably boards carrying an electrical or electronic circuit, usually have one or more power supply connections and one or more data line connections, which are inserted into the plug arrangements located at the back of the corresponding rack, by inserting the slide-in cards into one of the racks described above. 
   As a rule, all the plug arrangements provided on the back side of a rack are of similar design and the corresponding contacts of the individual slots are connected together via an electrical connection. In this way, it is achieved that the slide-in cards inserted into the rack are connected together in the manner of a bus. 
   Although such systems were found to be useful, an inherent disadvantage is that the rack can hold only a limited number of slide-in cards. Therefore, such a system is not freely scalable, but is always limited by the size of the corresponding rack. In addition, because of this predetermined constructional size, such a system has limited usefulness for the so-called portable measuring technique. 
   SUMMARY OF THE INVENTION 
   Thus, the task of the invention is to provide a system which no longer has the disadvantages mentioned above. Especially, a system should be provided which is freely scalable in any arbitrary manner and is not limited by the size of the rack. In addition, use at almost any arbitrary location should be possible. Finally, it should be useable both for very simple as well as complicated measuring purposes. 
   This task is solved by a module for measuring purposes according to the invention having the characteristics of the characterizing part of claim  1 . 
   Advantageous embodiments and further developments of the invention are given in the subclaims. 
   The essential idea of the invention consists in the fact that the electronic circuit is arranged in a housing which has a first contact surface and a second contact surface. According to the invention, it is provided that the first contact surface can be connected to the second contact surface of another module of like design, so that it can be joined in a manner that permits it to be mechanically detached, that is, it can be in slidingly coupled, interlocked, snapped together or the like. It is provided that at least one power supply connection has a power supply contact in the first contact surface and a corresponding power supply contact in the second contact surface and that the at least one data line connection always has a data line contact in the first contact surface and a corresponding data line contact in the second contact surface. Specifically, this means that the corresponding power supply contacts or data line contacts are in cooperative engagement from the first contact surface to the second contact surface. 
   Moreover, it is provided that, in the connected state, that is, when the second contact surface of the additional module is joined to the first contact surface in the manner described above, the power supply contact in the first contact surface be in an electrical connection with the corresponding power supply contact in the second contact surface of the other module and, correspondingly, the data line contact in the first contact surface is an electrical connection with the corresponding data line contact in the second contact surface of the other module. 
   Forming connections between the individual modules (corresponding to the slide-in cards in the system according to the state of the art) is done directly by contacting the contacts arranged in the particular housing of the module and not with the aid of additional connections like in the system of the state of the art, which are, for example, components of a rack or optionally are to be produced with the aid of separate cables or lines. 
   In this way, it is made possible that, for example, with the aid of a single module, simple measurement tasks can be performed and, depending on the requirements, other modules can be joined together to a larger measuring unit according to the Lego principle. Furthermore, as a result, it is made possible to combine modules from a module assortment for almost any arbitrary measuring tasks. In this way, the measuring system can be assembled and disassembled again rapidly at almost any arbitrary location. Transportation of individual modules is possible as well as transportation of a larger connected total system. Furthermore, the danger of destruction or contamination of the actual electrical or electronic circuits is clearly reduced in comparison to the system according to the state of the art mentioned above. 
   A preferred embodiment of the invention provides that the joining of the module with the other module be done with the aid of a bayonet-like lock. The advantage of such a bayonet-like lock consists in the fact that, first of all, joining and separation of the connection can be done rapidly, but on the other hand, it can be done simply. Such bayonet-like lock has been found to be useful in many ways. 
   In an especially advantageous variant, it is provided that the first and second contact surfaces be essentially opposing housing surfaces arranged parallel to one another. A measurement unit is obtained by stacking several or a large number of such modules on top of one another. Thus, an especially compact measuring arrangement is obtained. 
   Hereby, it is especially advantageous when the first and second contact surfaces are the bottom and covering surfaces, so that the base necessary for the positioning of such a system is not increased by increasing the number of individual modules used. 
   An especially advantageous variant provides that the housing be essentially rectangular, a housing form which excels by its low space requirement. 
   According to the invention it is provided that, on the first contact surface, at least two guide rails are arranged which run essentially parallel to one another; on the side, which is away from the contact surface, engagement elements in the form of tabs or bars are formed which run essentially parallel to the contact surface, and on the second contact surface guide rails are arranged which are essentially parallel to one another and correspond to the guide rails of the first contact surface; on the side of these, which is away from the contact surface, engagement elements are formed which correspond to the engagement elements of the guide rails of the first contact surface and are essentially parallel to the contact surface, so that the engagement elements can be brought into overlapping contact with the corresponding engagement elements of another module and the modules held together in this way. First of all, an advantage of such an arrangement is that it can be produced with simple means, for example, with the aid of an injection molding method and, on the other hand, it makes it possible to produce safe and rapid connection between the individual modules, which can then be separated again, rapidly and safely. An embodiment of this variation provides that the engagement elements and the corresponding engagement elements are at such a distance that, in order to join the first contact surface to the second contact surface of the other module, the engagement elements can be engaged in the interval of the corresponding engagement elements of the second contact surface of the other module and, vice versa, the corresponding engagement elements of the second contact surface of the other module can be engaged in the interval of the engagement elements and, in this position, by shifting the particular modules against one another, the engagement elements can be joined to the corresponding engagement elements of the other module to form a joint which holds the module together. 
   In a further embodiment of this variant or in an individual embodiment independent of this variant of the module according to the invention, it is provided that a rocker lever be supported on a side surface of a rocker bearing arranged on the housing, so that it is tiltable. A lever arm of the rocker lever is supported against the force of a spring on the side surface of the module housing. The other lever arm of the rocking lever has a latch which can be engaged in a groove of the housing of the other module and can be locked with it. Such a rocker lever thus locks two attached modules to one another so they cannot be separated from one another unintentionally. 
   The locking and interlocking mechanism of the rocker lever can be realized in a simple manner by the fact that the latch engages in a groove formed from the guide rails and the engagement element. Accordingly, additional measures are not necessary in this variant. 
   Furthermore, according to the invention, it is provided that at least one contact of the first contact surface be a contact head with a contact surface inserted into a recess of the first contact surface. 
   Corresponding to this, the corresponding contact of the second contact surface is a contact tappet which is arranged so it can be shifted perpendicularly to the contact surface against the force of a spring. In this way, an electrically conducting joint between two attached and optionally locked modules can be produced simply and rapidly. The fact that the contact tappet can be shifted against a spring has the advantage that a reliable electrical contact can be produced even after frequent attachment processes, especially even when the corresponding contact side had been worn due to frequent use, or even contaminated or corroded. 
   An especially advantageous variant of the invention provides that, for producing the electrical contact between the contact head and the contact tappet, a spring plate be provided within the housing of a module, one end of which is supported by spring force against a contact tip of the contact head directed toward the inside of the housing and, on the end, it is supported against a contact surface of the contact tappet directed toward the inside of the housing. Such a spring contact has the advantage, first of all, in comparison to a rigid contact that, in the case of shocks, breaking off of the electrical contact is largely avoided and, on the other hand, it has the advantage of simple mounting of a module without time-intensive soldering or attachment processes. 
   Furthermore, according to the invention, it is provided that the circuit be arranged on a board and that the spring plate be joined to the board mechanically, rigidly and in an electrically conducting manner. This variation of the embodiment of the invention has the advantage that no additional holder is required for the spring plate, since an attachment in the board within the housing of the module is required anyway. Thus, the board holds the spring plate securely, so that, for example, the cover or bottom plates forming the contact surfaces merely have to be put in place during manufacture or assembly. 
   Another variant of the invention provides that the contact tappet be guided so it can be shifted in a guide element. A sealing element is placed into this guide element, surrounding the contact tappet in the manner described above, so that it can be shifted; the inside has a sealing lip surrounding the contact tappet on its periphery for sealing. In this way, entry of water or other fluids inside the housing and destruction of the electrical or electronic circuits or individual electric or electronic circuit elements is prevented. 
   Another preferred variation of the embodiment provides that the contact surface of the contact head be enclosed by two bars aligned essentially parallel to the guide rails, extending above the contact surface of the contact head in such a way that touching it by a standardized measuring finger is impossible. Such a design of the invention serves as a safety device against electrostatic discharges. 
   In a corresponding manner, it is provided that the contact tip of the contact tappet, designed on the base of a groove formed in the contact surface, running essentially parallel to the guide rail and that the width of the groove be chosen so that touching the contact tip of the contact tappet by a standardized measuring finger is impossible. These two latter variants thus ensure that the electrical or electronic circuits or individual circuit elements, arranged in the module, will not harm the operators due to accumulated electric charge. 
   Modules with the following functions are provided:
     a) Measured value recording module   b) Power supply module   c) Radio connection module to provide radio connection between measuring systems and measuring units built from one or several modules   d) Analog-digital converter module or digital-analog converter module   e) Modules with operating and display functions   f) Modules with printing functions   g) Smoke reporting modules   

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A practical example of the invention is shown in the drawing and will be described in more detail below. 
     The following are shown:
           FIG. 1  is a measuring unit consisting of an operating, measuring, display and printing module according to the invention and two measuring modules according to the invention   perspective view from above     FIG. 2  is a measuring unit consisting of a radio module and two measuring modules according to the invention   perspective view from above     FIG. 3  is a measuring module according to the invention according to FIG.  1  and  FIG. 2     perspective view from underneath     FIG. 4  is the measuring unit according to  FIG. 2 , consisting of the radio module according to the invention and two measuring modules according to the invention   cross-sectional representation along plane A—A     FIG. 5  is the measuring unit according to FIG.  2  and  FIG. 4     detailed view in a longitudinal section along B—B   a) Radio module according to the invention and measuring module according to the invention, in the combined but not locked state.   b) Radio module according to the invention and measuring module according to the invention according to  FIG. 5   a ) in the locked state.     FIG. 6  is the measuring unit according to FIG.  2  and  FIG. 4  with protective device against electrostatic discharges   detail view Z from  FIG. 4       FIG. 7  is the measuring unit according to FIG.  2  and FIG.  4 : locking mechanism with the latch of a rocker lever engaged in a guide rail of a measuring module according to the invention   detail view Y from FIG.  4         

   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a measuring unit  1  a consisting of several individual modules  2 ,  22 ,  32  according to the invention. Specifically, the measuring unit  1   a , shown in  FIG. 1 , has a combined operating, measuring, display and printing module  2 , a measuring module  22  connected with this and another measuring module  32  connecting to the latter. 
   The operating, measuring, display and printing module  2 , as it is obvious from the name, has a keyboard  7  for data input and thus for operation of module  2 , a measuring channel connection  5  to connect it with a measuring cell, a measured value recorder, a sensor or similar. Furthermore, a display  8  is provided in order to display the measured value introduced to measurement channel connection  5  and as well as a small printer  9 , for example, to produce a measuring or data protocol. Furthermore, the operating, measuring, display and printing module  2  has a sending element  3  and a receiving element  4 , through which data communication, for example, via radio, infrared or similar, with another module, can be provided. Finally, the operating measuring display and printing module has a power supply connection  6  on its front side  12  in order to be able to supply module  2  with power from the outside. In the present example, the power supply is provided via a power plug to a conventional low voltage power connection, but it is also conceivable to make module  2  self-sufficient with regard to power or to operate it through an integrated accumulator, batteries or similar. 
   The two other measurement modules,  22  and  32 , shown in  FIG. 1 , have a largely identical form. Both have four measuring channel connections  23 ,  24 ,  25  and  26  as well as  33 ,  34 ,  35  and  36  on their front side  12  in front surfaces  94 . These measuring channel connections  23 ,  24 ,  25 ,  26  and  33 ,  34 ,  35 ,  36 , respectively, are designed in the manner of measuring channel connection  5  of the operating, measuring, display and printing module  2 . Thus, they represent merely an extension for the connection of other eight measuring value recorder, sensors or similar. 
   According to the invention, it is provided that the operation, parametrization and control of the other measuring channel connections  23 ,  24 ,  25  and  26  of the measuring module  22 , as well as the measuring channel connections  33 ,  34 ,  35  and  36  of measuring module  32  occur through the operating, measuring, display and printing module  2 . The evaluation, data acquisition, protocolling, etc., also occurs via the operating, measuring, display and printing module  2 , which, as will be described below, is connected mechanically as well as electrically to the individual modules  22  and  32 . 
   In order to demonstrate how such a mechanical and electrical connection between the individual modules according to the invention is realized,  FIGS. 2  to  7  show details of the mechanical locking and interlocking mechanism as well as that for producing an electrical connection between the corresponding contact elements necessary for the individual modules. 
     FIG. 2 , first of all, shows a measuring unit  1   b  according to the invention, consisting of two measurement modules  22  and  32  according to the invention of the type described above, as well as instead of the operating, measuring, display and printing module  2  shown in  FIG. 1 , it has a radio module  42  according to the invention, namely shown in perspective view from the top onto the top side  10  of radio module  42 . Corresponding to this,  FIG. 3  shows, as an example, the measuring module  32  according to the invention according to  FIGS. 1 and 2 , also in a perspective view from underneath looking at the bottom side  11 . 
   The housing of the modules  22 ,  32 ,  42  has an essentially rectangular shape. Consequently, it consists of six individual surfaces, which are designated below as side surfaces  92  and  93 , front surface  94 , back surface  95  as well as first contact surface  90  and second contact surface  91 . The first and second contact surfaces  90 ,  91  are the oppositely arranged base and cover surfaces. The particular front surfaces (and optionally also the back surface  95 ) have, as described above, measuring channel connections  23 ,  24 ,  25 ,  26  or  33 ,  34 ,  35 ,  36 , respectively, as well as sending elements  43  and  44 . 
   The first contact surface  90  of a module  22 ,  32 ,  42  can be locked to the second contact surface  91  of another module  22 ,  32 ,  42 . The locking mechanism is designed in the example in the manner of a bayonet lock. Specifically, two guide rails  50  and  50 ′, running essentially parallel to one another, are arranged on the first contact surface  90 ; on the side away from contact surface  90 , engagement elements  49   a ,  49   b ,  49   c ,  49   d ,  49   a ′,  49   b ′,  49   c ′,  49   d ′ are formed essentially parallel to contact surface  90 . On the second contact surface  79 , guide rails  40 ,  40 ′ are arranged, again running parallel to one another, and essentially corresponding to the guide rails  50 ,  50 ′ of the first contact surface  90 . On these guide rails  40 , 40 ′, on their side away from contact surface  91 , engagement elements  38   a ,  38   b ,  38   c ,  38   d ,  38   a ′,  38   b ′,  38   c ′,  38   d ′ are formed corresponding to the engagement elements  49   a ,  49   b ,  49   c ,  49   d ,  49   a ′,  49   b ′,  49   c ′,  49   d ′ of guide rails  50 ,  50 ′ of the first contact surface  90 . While in the first case, the engagement elements  49   a ,  49   b ,  49   c ,  49   d ,  49   a ′,  49   b ′,  49   c ′,  49   d ′ tend toward the inside against one another, in the second case, the engagement elements  38   a ,  38   b ,  38   c ,  38   d ,  38   a ′,  38   b ′,  38   c ′,  38   d ′ run directed toward the outside, so that the engagement elements  49   a ,  49   b ,  49   c ,  49   d ,  49   a ′,  49   b ′,  49   c ′,  49   d ′ can be brought into overlapping connection with the corresponding engagement elements  38   a ,  38   b ,  38   c ,  38   d ,  38   a ′,  38   b ′,  38   c ′,  38   d ′ of the other module and, in this way, two neighboring modules  42  and  22  or  22  and  32 , respectively, are being held together. 
   In the present example, the engagement elements  49   a ,  49   b ,  49   c ,  49   d ,  49   a ′,  49   b ′,  49   c ′,  49   d ′ and the corresponding engagement elements  38   a ,  38   b ,  38   c ,  38   d ,  38   a ′,  38   b ′,  38   c ′,  38   d ′ are spaced in such a way that, for assembling the first contact surface  90  of a module  22 ,  42  with the second contact surface  91  of the neighboring module  32 ,  22 , the engagement elements  49   a ,  49   b ,  49   c ,  49   d ,  49   a ′,  49   b ′,  49   c ′,  49   d ′ can engage in the intervals  41   a ,  41   b ,  41   c ,  41   a ′,  41   b ′,  41   c ′ of the corresponding engagement elements  38   a ,  38   b ,  38   c ,  38   d ,  38   a ′,  38   b ′,  38   c ′,  38   d ′ of the second contact surface  91  of the neighboring module. In an analogous manner, the corresponding engagement elements  38   a ,  38   b ,  38   c ,  38   d ,  38   a ′,  38   b ′,  38   c ′,  38   d ′ of the second contact surface  91  of the other module can engage in the intervals  51   a ,  51   b ,  51   c ,  51   a ′,  51   b ′,  51   c ′ of engagement elements  49   a ,  49   b ,  49   c ,  49   d ,  49   a ′,  49   b ′,  49   c ′,  49   d ′. The particular modules  22 ,  32 ,  42  are brought into the fixed position, that is, in the position where the two neighboring modules  42 ,  22  or  22 ,  32 , respectively, are held together, by being shifted in the position described above, so that the engagement elements  49   a ,  49   b ,  49   c ,  49   d ,  49   a ′,  49   b ′,  49   c ′,  49   d ′ engage with the corresponding engagement elements  38   a ,  38   b ,  38   c ,  38   d ,  38   a ′,  38   b ′,  38   c ′,  38   d ′ of the neighboring module  22 ,  32 ,  42 . 
   Furthermore, according to the invention, it is provided that two neighboring modules  42  and  22  or  22  and  32 , respectively, can be locked with the aid of a rocker lever  27 ,  37 ,  47 . The special design according to the invention of such an interlocking mechanism can be seen in detail in  FIG. 4 , which shows the measurement unit according to  FIG. 2 , consisting of the radio module  42  according to the invention and two measurement modules  22  and  32  according to the invention in a cross-sectional representation along plane A—A shown in FIG.  2  and in the detail view Y from  FIG. 4 , which is shown in FIG.  7 . 
   As can be seen from the drawings, the rocker lever  27 ,  37 ,  47  is supported tiltably on a rocker bearing  52  arranged on the side surface  92  of the particular housing. A lever arm  48   b  of rocker lever  27 ,  37 ,  47  is supported against the force of a spring  53  on the side surface  92  of the particular housing. In the drawing, the spring  53  is designed in the manner of a spring plate, but a spring, for example, with the aid of a spiral spring or similar, can also be considered. 
   The other lever arm  48   a  of the rocker lever  27 ,  37 ,  47  has a latch  54 , which can be engaged in a groove  55  of the housing of the neighboring module and can be locked with it. 
   In the present case, the groove is formed by the guide rails  40  and the engagement element  38   b.    
   As it was already presented in detail in the introductory part of the Specification, the individual modules  22 ,  32 ,  42  are joined together in a contacting manner through electrical contact locations which come into contact in the switched state. Especially, in the present case, two power supply contacts  84   a ,  85   a  are provided, which are arranged in the first contact surface  90  of a module  22 ,  32 ,  42  and can be brought into contact with the corresponding power supply contact  84   b ,  85   b  in the second contact surface  91  of the other neighboring module  22 ,  32 ,  42 . Furthermore, data line contacts  86   a ,  87   a  are provided in the first contact surface  90  of a module  22 ,  32 ,  42 , which can be brought into contact with the corresponding data line contacts  86   b ,  87   b  in the second contact surface  91  of the other neighboring module  22 ,  32 ,  42 . 
   The concrete design of contacts  84   a ,  85   a ,  86   a ,  87   a  in the first contact surface  90  and of the corresponding contacts  84   a ′,  85   a ′,  86   a ′,  87   a ′ of the second contact surface  91  can be seen in the drawings according to  FIG. 2 ,  FIG. 3 , FIG.  4  and FIG.  6 . The electrical and mechanical bond between contacts  84   a ,  85   a ,  86   a  and  87   a  in the first contact surface  90  and the corresponding contacts  84   a ′,  85   a ′,  86   a ′,  87   a ′ of the second contact surface  91  within a module can be seen especially in  FIGS. 4 ,  5   a  and  5   b.    
   Specifically, as it can be seen in  FIG. 5 , the contacts  84   a ,  85   a ,  86   a ,  87   a  of the first contact surface  90  always consist of a contact head  70 , which is placed in a recess  75  of the first contact surface  90 , and has a contact surface  72 . The corresponding contacts  84   a ′,  85   a ′,  86   a ′,  87   a ′ of the second contact surface  91  are essentially perpendicular to contact surface  91  against a contact tappet  60 , guided against the force of a spring  81  so that it can be shifted. 
   The contact surfaces  72  of the particular contact heads  70  are always enclosed by two bars  76   a  and  76   b , aligned essentially parallel to guide rails  50 ,  50 ′. These stand above contact surfaces  72  of the particular contact head  70 , so that, especially as can be seen in  FIG. 6 , touching of it by a standardized measuring finger M is impossible. In the present case, the distance between the tip of the standardized measuring finger M with a tip radius of 4 mm and a contact surface  72  is designated with the aid of reference d 2 . 
   In principle, the other contacts  84   b ,  85   b ,  86   b ,  87   b  with contact tappet  60  are designed similarly. As shown in  FIG. 6 , the particular contact tappets  60  are led from the base of grooves  31   a ,  31   b ,  31   c ,  31   d  running essentially parallel to the guide rails  40 ,  40 ′ and formed in contact surface  91 , where the width of the corresponding grooves  31   a ,  31   b ,  31   c ,  31   d  is chosen so that touching the particular contact tips  61  of contact tappet  60  by the standardized measuring finger M with a tip radius of 4 mm is impossible. The distance between the contact tip  61  of a contact tappet  60  and a standardized measuring finger M is shown with reference d 1  in the drawing. 
   As can be seen especially from the drawings according to FIG.  4  and  FIGS. 5   a  and  5   b , the bars  76   a ,  76   b , which enclose the contact surfaces  72  of the particular contact heads  70 , are designed specifically so that when sets of two modules  22 ,  32 ,  42  are joined together, they engage exactly in the particular grooves  31   a ,  31   b ,  31   c ,  31   d  from the base of which the particular contact tappets  60  are guided out. The electrical connection is now produced by the fact that, in the shifting process V described above, the corresponding contacts  84   a ,  85   a ,  86   a ,  87   a  are brought into connection with the corresponding contacts  84   a ′,  85   a ′,  86   a ′,  87   a ′. In this case, the contact tip  61  of the contact tappet  60  is guided against the force of spring  81  above the recess  75  and the contact head  70  with contact surface  72  placed in it, where the bars  76   a  and  76   b  serve as guide rails for the contact tip  61  of contact tappet  60 . 
   The guidance of the contact tappet  60  so it can be shifted under the action of a spring and the formation of the electrical connection between the particular contacts  84   a ,  84   b ,  85   a ,  86   a ,  86   b ,  87   a ,  87   b  within a housing is realized with the aid of a spring plate  81 , as described below. Thus, a spring plate  81  is arranged between the contact head  70  and contact tappet  60  in such a way that, at its one end, it is supported against the contact tip  71  of contact head  70  directed toward the inside of the housing, and on the other end it is supported against contact surface  62  of contact tappet  60  directed inside the housing. A mechanical attachment of the spring plate  81  is realized by the fact that it is connected mechanically, rigidly and electrically conducting to the board  80  carrying the circuit. 
   Reference List 
   
       
         1   a  measuring unit 
         1   b  measuring unit 
         2  operating, measuring, display and printing module 
         3  sending element 
         4  receiving element 
         5  measuring channel connection 
         6  power supply connection 
         7  keyboard 
         8  display 
         9  printer 
         10  top side 
         11  bottom side 
         12  front side 
         13  back side 
         22  measuring module 
         23  measuring channel connection 
         24  measuring channel connection 
         25  measuring channel connection 
         26  measuring channel connection 
         27  rocker lever 
         31   a  groove 
         31   b  groove 
         31   c  groove 
         31   d  groove 
         32  measuring module 
         33  measuring channel connection 
         34  measuring channel connection 
         35  measuring channel connection 
         36  measuring channel connection 
         37  rocker lever 
         38   a  engagement element 
         38   b  engagement element 
         38   c  engagement element 
         38   d  engagement element 
         38   a ′ engagement element 
         38   b ′ engagement element 
         38   c ′ engagement element 
         38   d ′ engagement element 
         40  guide rails 
         40 ′ guide rails 
         41   a  interval 
         41   b  interval 
         41   c  interval 
         42  radio module 
         43  sending element 
         44  receiving element 
         47  rocker lever 
         48   a  lever arm 
         48   b  lever arm 
         49   a  engagement element 
         49   b  engagement element 
         49   c  engagement element 
         49   d  engagement element 
         49   a ′ engagement element 
         49   b ′ engagement element 
         49   c ′ engagement element 
         49   d ′ engagement element 
         50  guide rails 
         50 ′ guide rails 
         51   a  interval 
         51   b  interval 
         51   c  interval 
         52  rocker bearing 
         53  spring 
         54  latch 
         55  groove 
         60  contact tappet 
         61  contact tip 
         62  contact surface 
         63  sealing element 
         64  sealing lip 
         65  guide element 
         70  contact head 
         71  contact tip 
         72  contact surface 
         75  recess 
         76   a  bar 
         76   b  bar 
         80  board 
         81  spring plate 
         84   a  contact 
         84   b  contact 
         85   a  contact 
         85   b  contact 
         86   a  contact 
         86   b  contact 
         87   a  contact 
         87   b  contact 
         90  first contact surface 
         91  second contact surface 
         92  side surface 
         93  side surface 
         94  front surface 
         95  back surface 
       V shifting direction 
       d 1  distance 
       d 2  distance 
       M standardized measuring finger