Abstract:
Field devices for measuring a pressure or a fill level are connected with an external energy supply through a cable connector. An energy supply unit for a field device is provided, which has a housing and a solar module integrated therein. The housing is hereby used for receiving the measurement electronics of the field device and the solar module of the energy supply. An external energy supply is thus not necessary anymore. For energy buffering, furthermore, a respective energy storage may be provided.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of the filing date of U.S. Provisional Application Ser. No. 60/830,228 filed on Jul. 12, 2006 and German Patent Application Serial No. 10 2006 032 250.9 filed on Jul. 12, 2006, the disclosures of both applications are hereby incorporated by reference. 
     
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the energy supply of field devices. The present invention particularly relates to an energy supply unit for a field device for measuring a pressure or a filling level, a field device with such energy supply unit, the use of an energy supply unit for a field device, and a process for the energy supply of such field device. 
       TECHNOLOGICAL BACKGROUND 
       [0003]    Filling level sensors and pressure sensors are supplied with external power via a respective connection. Such energy supply may e.g. be performed through a 2-conductor system, through which also data exchange is performed. Furthermore, energy storages may be provided within the field device, in order to make the field device independent from an external energy supply. However, these energy storages then have to be exchanged in regular, relatively small time intervals, or have to be charged externally. 
         [0004]    An external energy supply may require respective connections at the field device, and an external supply station, which is connected to the field device. Hereby, the area of application of the field device may be restricted. 
         [0005]    Therefore, it is the object of the invention to provide an improved energy supply for a field device. 
       SUMMARY OF THE INVENTION 
       [0006]    According to an exemplary embodiment of the present invention, an energy supply unit for a field device for measuring a pressure or a filling level is provided, the energy supply unit comprising a solar module for generating electrical energy for the field device and a housing for receiving the measuring electronics of the field device, wherein the solar module is integrated in the housing. 
         [0007]    Through providing a solar module, independence of the field device from an external energy supply may be achieved to a large extent. The solar module is hereby integrated in the housing, so that no internal installation of the solar module is required. To the contrary, the solar module and the housing form a cohesive unit, into which the respective measuring electronics of the measuring device (field device) may be installed. Additional installation effort may not be necessary. 
         [0008]    According to a further exemplary embodiment of the present invention, the housing has a cavity, wherein the solar module is provided so that it may be integrated into the cavity. 
         [0009]    If the cavity is adapted to the shape of the solar module to be integrated, additional mounting means may be dispensed with. The solar module is simply inserted into the cavity and is clamped there. 
         [0010]    According to a further exemplary embodiment of the present invention, the housing is at least partially made from light permeable material, wherein the solar module is disposed in the interior of the housing. 
         [0011]    Thus the solar module may be protected from external damages through the housing wall. These may be e.g. simple mechanical damages, or also chemical or temperature related damages, which are avoided by the protective housing wall. Through at least partially providing the housing light permeable, it may be assured that sufficient sunlight may always reach the solar module. 
         [0012]    According to another exemplary embodiment of the present invention, the energy supply unit further comprises a field device display module for displaying measurement values, wherein the field device display module is provided as a liquid crystal display, and wherein the solar module is located on the backside of the field device display module. 
         [0013]    A field device display module may use a LC-display (Liquid Crystal Display). Such display may be provided as a monitor, in which special liquid crystals are being used, which may influence the polarization of light, in order to be able to deflect light in certain angles. Through punctiform control of the liquid crystals, a pixel may be made visible at the controlled locations. From many of these pixels e.g. a numerical value for a measurement value may be displayed. 
         [0014]    In such a measurement value display, typically approximately 60% of the pixels are light colored, and thus the display is at least 60% transparent. This way, it is assured that enough sunlight may always reach the solar module. 
         [0015]    Through mounting the solar module directly behind the field device display module, a compact assembly is provided, which may be integrated into the housing in a simple manner. 
         [0016]    According to another exemplary embodiment of the present invention, the solar module comprises a plurality of solar cells, wherein the housing is formed by the solar cells. 
         [0017]    In other words, that many solar cells are integrated into the housing, so that the housing is actually substantially only made up of the particular solar cells. This way, the energy generation rate of the energy supply unit may be maximized. 
         [0018]    According to another exemplary embodiment of the present invention, the solar module is provided as an encased part. 
         [0019]    The solar module may be encased in a resin or in a plastic material as a component. The encasing may provide a predeterminable outside contour to the component, and may make the component robust against mechanical impact. 
         [0020]    According to a further exemplary embodiment of the present invention, the solar module is encased in the housing. 
         [0021]    The solar module and the housing thus form an integral component, which may be configured by the manufacturer according to the respective requirements (e.g. the energy requirement of the field device or the dimensions of the field device). 
         [0022]    Furthermore, the housing may have a housing cover, into which the solar module is encased, or to which the solar module is bolted or mounted otherwise. 
         [0023]    According to a further exemplary embodiment of the present invention, the energy supply unit also comprises an energy storage for buffering the electric energy generated by the solar module. 
         [0024]    It may happen e.g. that the field device does not operate continuously, or that the energy required by the field device is less than the amount of energy provided by the solar module. The field device may also be connected to an external energy supply (e.g. to a 4 to 20 mA 2-conductor loop). When controlling a 4 to 20 mA signal, an additional current may be provided, which is not used for the measurement task by the measurement circuit of the field device. This current may then be used for the charging the energy storage. 
         [0025]    An energy storage with a respective charging control system, or a respective energy management may allow to store energy at a moment, in which superfluous energy is available, and to supply the stored energy for the operation of the field device at a later point in time. Thus the capacity of the energy storage may be adapted to the power required by the field device. 
         [0026]    According to a further exemplary embodiment of the present invention, the solar module is provided for providing the total amount of energy required by the field device, so that no additional power supply is necessary. 
         [0027]    Hereby, an autonomous, independent operation of the field device is assured. 
         [0028]    According to a further exemplary embodiment of the present invention, the energy supply unit further comprises a measurement bus conductor system, which is comprised of a 2-conductor HART® bus system, a 4-conductor HART® bus system, a SDI-12, a Profibus bus system, or a Fieldbus Foundation bus system. 
         [0029]    The energy supply unit may consequently draw additional power via a separate conductor system, whereby it may be assured that sufficient power for the operation of the field device is always available. A possible system in which a separation of the power supply and the measurement signals may occur, may be the 4-conductor HART® bus system. 
         [0030]    The energy supply unit hereby serves as support of the energy supply of the field device, e.g. via one of the above mentioned measurement bus conductor systems. Thereby, the power capability of the field device may be increased, e.g. by increasing the measurement rate. 
         [0031]    The additional energy of the energy supply unit may also be stored in a preliminary manner, and may be called up during periods of higher energy requirements. 
         [0032]    In other words, thus a permanent or time limited increase of the power capacity of the field device may be possible. 
         [0033]    According to a further exemplary embodiment of the present invention, the solar module has a glue side, wherein the glue side is provided, so that the solar module may be mounted to the housing via the glue side. 
         [0034]    This way, a simple and secure mounting of the solar module to the housing is possible. 
         [0035]    Furthermore, the shape of the solar module may be adapted to the shape of the field device display module, so that the solar module may be coupled to the field device display module in a precisely fitting and tight manner. Through the tight contact between field device display module and solar module, light losses through diffusion at the transition area between display and solar module may be minimized. 
         [0036]    According to an exemplary embodiment of the present invention, the energy supply unit further comprises a control- or regulating unit for controlling or regulating an externally supplied amount of energy. 
         [0037]    Furthermore, the control- or regulating unit may be provided for controlling or regulating the energy requirements of the field device. 
         [0038]    For example the measurement rate of the field device may be set according to the available amount of energy. 
         [0039]    In particular in combination with an internal energy storage, thus effective energy management is possible, which allows an autonomous operation of the field device without having to supply electrical energy through an external connection. 
         [0040]    According to another exemplary embodiment of the present invention, a field device is provided comprising an energy supply unit as described above. 
         [0041]    This may e.g. be a fill level measurement device or a pressure measurement device. Such fill measurement device may be provided, e.g. as radar fill measurement device, TDR-fill measurement device, ultrasound fill measurement device, microwave fill measurement device, a pressure measurement device, a capacitive level measurement device, or a vibration level measurement device. 
         [0042]    Furthermore, the use of an above mentioned energy supply unit for a field device is provided for measuring a pressure or a fill level. 
         [0043]    According to a further exemplary embodiment of the present invention, a process for the energy supply of a field device for measuring a pressure or a fill level is provided, in which electrical energy for the field device is provided through a solar module, which is integrated in a housing of the field device. 
         [0044]    An external supply with electrical energy may thus not be required anymore. 
         [0045]    Further exemplary embodiments of the invention may be derived from the dependent claims. 
         [0046]    Subsequently exemplary embodiments of the present invention are described with reference to the figures. 
     
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0047]      FIG. 1  shows a schematic illustration of an energy supply unit according to an exemplary embodiment of the present invention. 
           [0048]      FIG. 2  shows an illustration of a field device with energy supply unit according to an exemplary embodiment of the present invention. 
           [0049]      FIG. 3  shows a schematic illustration of fill level radar with energy supply unit according to an exemplary embodiment of the present invention. 
           [0050]      FIG. 4  shows a field device according to a further exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0051]    The illustrations in the figures are schematic and not to scale. 
         [0052]    In the following description of the figures, the same reference numerals are being used for the same or similar elements. 
         [0053]      FIG. 1  shows a schematic illustration of an energy supply unit according to an exemplary embodiment of the present invention. The energy supply unit comprises a solar module  101 , which is connected to a measuring unit display module  105  through a mounting surface  106 . The connection may e.g. be performed as glue joint in this location. It is also possible that the solar module  101  and the display  105  are encased or glued together in the housing (not shown in  FIG. 1 ) of the energy supply unit. 
         [0054]    A heat foil  115  is mounted on the backside of the solar module  101 , which may bring the solar module and/or the display  105  to operating temperature. The heat foil  115  may also be provided, so that it protects the display  105  and/or the solar module  101  from icing, or avoids fogging of the display  105 . 
         [0055]    For this purpose the heat foil  115  may be activated according to the requirements, e.g. through a hand switch, or automatically through respective control electronics  107  (see  FIG. 3 ). 
         [0056]    The display  105 , the solar module  101 , and the heat foil  115  may be provided as an entire module and may then be integrated into a respective housing, in order to form the energy supply unit. 
         [0057]    This way, the energy supply of a fill level or pressure measurement sensor is supplemented or even replaced. 
         [0058]    Through the installation of the solar module  101  behind the liquid crystal display  105 , the solar module is protected towards the outside on the one hand, and on the other hand does not require an installation surface of its own on the top side of the housing. Hereby, eventually space is being saved on the housing surface. 
         [0059]      FIG. 2  shows a fill level measurement apparatus with a housing  102  and an antenna  110 . The antenna  110  is provided as a parabolic antenna in the exemplary embodiment of  FIG. 2 . Also other antenna shapes are possible. The housing  102  of the fill level sensor hereby has a housing cover  117 , into which a first solar module  103 , shaped as a single solar cell, is integrated. The solar module  103  may e.g. be encased in the sensor cover  117  or screwed into it. 
         [0060]    An additional solar module  104 , also shaped as a single solar cell is integrated into the housing wall. In an extreme case, that many solar cells may be embedded in the housing  102 , so that the housing is substantially only made up from these solar cells (which may then be joined into an entire module). Each particular solar cell  103 ,  104  may e.g. be provided as an encased component. The encased components may then be joined to form a respective housing. 
         [0061]      FIG. 3  shows a further exemplary embodiment of the present invention in the form of a fill level radar. The fill level radar hereby has a housing  102 , which receives the transmission- and receiving electronics. Furthermore, an antenna  110  is provided, which is provided for transmitting a transmission signal  110  and for receiving a reception signal  112 , which is reflected at a filling material surface  113 . 
         [0062]    A display  105  and a solar cell  103  are integrated in the cover  117  of the housing  102 . Furthermore, a second solar cell  104  is integrated in the housing wall. Both solar cells  103 ,  104  are connected through respective conductors to an electronic control unit  107 , which controls or regulates e.g. the energy requirements of the filling level sensor. 
         [0063]    Furthermore, a 2-conductor connection  108  is provided, through which the fill level sensor may be connected to a 2-conductor loop. Via this 2-conductor loop measurement- or control signals are transferable. Furthermore, an external energy supply may be provided via the 2-conductor loop. 
         [0064]    The electrical control unit  107  may hereby adjust the energy requirements of the fill level sensor, so that a sufficient energy supply is always assured. For example, the smay rate may be changed for this purpose. Furthermore, the electronic control unit  107  is capable of balancing peaks in the energy requirement of the fill level sensor, e.g. by connecting the energy storage  109  or e.g. by drawing energy from the outside (via the 2-conductor loop). 
         [0065]    However, such an external energy supply is not necessary, when the energy supply unit according to the invention is sized accordingly, thus when a sufficient number of solar cells is available and/or when the energy storage  109 , which is being used as an energy buffer, has sufficient storage capacity. The energy storage  109  may e.g. be an accumulator, or another suitable storage. 
         [0066]      FIG. 4  shows a schematic illustration of a measurement apparatus according to an additional exemplary embodiment of the present invention, in which the housing is substantially comprised of the solar cells  103 ,  104 ,  116  (and additional rearward solar cells, which are not visible in  FIG. 4 ). Furthermore, a display  105  is provided. Electronics are located in the interior of the housing. 
         [0067]    Additionally it should be mentioned, that “comprising” does not exclude other elements or steps and “a” does not exclude a plurality. Furthermore, it should be mentioned that features or steps, which have been described with reference to one of the above exemplary embodiments, may also be used in combination with other features or steps of other exemplary embodiments described above. Reference numerals in the claims are not to be considered as restrictions.