Abstract:
An instrument ( 210 ) for gravimetrically determining moisture content has a housing ( 220 ), with a weighing device ( 40 ) arranged inside. The weighing device ( 40 ) has a load receiver ( 260 ) onto which a sample ( 62 ) is placed. The housing has stationary and movable housing parts ( 221,222 ), the movable housing part moving between a measuring position and a servicing position. In the measuring position, the respective housing parts form an essentially enclosed testing compartment ( 30 ) surrounding a load receiver ( 260 ) in which a sample heater ( 270 ) heats a sample. In the servicing position, the respective housing parts are spaced apart from each other, allowing the sample heater to be accessed for servicing. A glass shield ( 272 ), protects the sample heater while in the measuring position. The glass shield is arranged on the movable housing part and can be taken out without using tools when in the servicing position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is entitled to benefit of a right of priority under 35 USC §119 from European patent application 11183598.9, filed 30 Sep. 2011, the content of which is incorporated by reference as if fully recited herein. 
       TECHNICAL FIELD 
       [0002]    The disclosed embodiments relate to a measuring instrument for the gravimetric determination of moisture content, particularly an instrument in which a glass shield protects a sample heating means. 
       BACKGROUND 
       [0003]    The moisture content of a sample is determined by drying the sample and by manually determining its weight before and after the drying process. Due to the laborious procedures involved, this method is very expensive and error-prone. 
         [0004]    Under certain conditions, the weight loss can also be determined during the drying process. For a given sample, the measured value for the weight decreases as a function of the temperature, the elapsed drying time, and the parameters of the testing compartment, according to a weight/time graph which asymptotically approaches the dry weight of the sample. The graph for the sample under examination can be determined through comparison experiments and expressed mathematically in the form of an approximation formula. Based on the available electronic capabilities, an appropriately equipped measuring instrument for the gravimetric determination of moisture content is able to calculate the moisture content of a sample from the measured parameters of the graph and the drying time and to indicate the moisture content on a display unit. With this method, it is no longer necessary for the material under test to be completely dried out, because sufficient information is obtained by determining the coordinates of two measurement points in the weight/time diagram. 
         [0005]    As mentioned above, the change in the weight of a sample is essentially a function of the temperature, the elapsed drying time, and the parameters of the testing compartment. The instruments that are commercially available at this time are limited in their accuracy primarily because of the demanding requirements which have to be met by the testing compartment. 
         [0006]    Normally, the sample is spread in a thin layer onto a flat sample receiver, for example a sample tray. The tray is arranged inside the gravimetric moisture determination instrument, extending preferably in a horizontal plane and parallel to the plane of the sample-heating means, in order to achieve a uniform heating of the sample. 
         [0007]    Devices that are used as sample-heating means include a variety of radiation sources such as radiant heaters, microwave generators, halogen- and quartz lamps. As could be established by experiments, one of the main causes for the inaccuracy in the determination of measurement values in existing gravimetric moisture-determination instruments lies in the nature of the radiation sources being used and in their arrangement in the testing compartment. 
         [0008]    A measuring instrument of the aforementioned kind for the gravimetric determination of moisture content is described in the European Patent EP 0 611 956 B1. In this instrument, the loading of the weighing pan occurs outside of the gravimetric moisture-determination instrument. To load and unload the sample, the balance which is arranged on a drawer-like carriage is slid out of the instrument housing. As a radiation source, a ring-shaped halogen lamp is being used which, in the operating state of the apparatus, is arranged above the sample receiver. Examples of further design configurations are published in EP 1850 110 A1. For example, a measuring instrument is disclosed which is opened up for loading through a horizontal swivel movement of a part of the housing. In a further embodiment, a part of the housing is swiveled in the vertical direction. Likewise, the measuring instruments disclosed in U.S. Pat. No. 7,851,712 B2 are opened for loading by vertically swiveling a part of the housing. 
         [0009]    To protect the heating means, a glass shield can be arranged between the sample and the sample-heating means. This glass shield tends to get dirty. In the measuring instruments of the known state of the art, the glass shield can be accessed only with difficulty and is therefore rarely cleaned, which can cause errors in the results of the measurements. 
         [0010]    It is therefore an object to provide a measuring instrument for gravimetric moisture determination which can be cleaned easily. 
       SUMMARY 
       [0011]    This task is solved by an embodiment of the measuring instrument for gravimetric moisture determination as defined in the appended claims. 
         [0012]    The measuring instrument for gravimetric moisture determination comprises a housing and a weighing device arranged inside the housing. The weighing device has a load receiver onto which a sample can be placed. The housing has a stationary housing part and a movable housing part. The movable housing part can occupy positions for measuring and for servicing, respectively, wherein in the measuring position, the stationary housing part and the movable housing part form an essentially enclosed testing compartment around the load receiver, and wherein in said testing compartment a heating means is arranged for the heating of a sample that can be placed on the load receiver. In the servicing position, the stationary housing part and the movable housing part are spaced apart from each other in such a way that the heating means is accessible for servicing. In the measuring position, a glass shield is arranged between the sample-heating means and the sample. The glass shield is arranged on the movable housing part and removable without the use of tools. Thus, the glass shield can easily be taken out and cleaned. The user or the service technician will need less time for this process and will therefore perform it more frequently. 
         [0013]    The term “testing compartment” means a space which is enclosed by the housing of the measuring instrument and which can be opened and closed in order to bring in or take out a sample. Arranged inside the testing compartment are a sample receiver and a means for heating the sample. The sample receiver is connected to a gravimetric measuring instrument. 
         [0014]    The term “housing part” in the present context is meant to include the elements of the instrument that are attached to it. Typically, the sample-heating means is arranged in the movable housing part while the weighing device, the sample receiver and the electronic module are arranged in the stationary housing part. 
         [0015]    The measuring instrument can occupy a loading position where the stationary housing part and the movable housing part are spaced apart from each other in such a way that a sample can be put on the load receiver. By means of a position-shifting device, the movable housing part can be brought from the measuring position into the loading position. In the measuring position as well as in the loading position or in the servicing position, the movable housing part is located above the stationary housing part. 
         [0016]    Advantageously, in the servicing position, the heating means and consequently also the glass shield are oriented essentially in a vertical position. As a result, the heating means is facing towards the user and is more easily accessible. 
         [0017]    In one embodiment, the glass shield is connected to the movable housing part by means of a connection that can be released without tools. For servicing, the glass shield can simply be pulled out of the movable housing part. 
         [0018]    In a further possible embodiment, the glass shield is connected to the movable housing part by means of components that can likewise be released without tools. These components can, for example, hold the glass shield clamped in a predefined position. It is also possible that the glass shield and the components are connected to each other by way of a spring and groove connection. The spring and groove connection can be released manually without the use of tools. 
         [0019]    It is also possible to use holders. The holders can also serve to hold the glass shield in a defined position. In a possible embodiment, the glass shield can be held in a defined position between an upper holder and a lower holder, wherein at least one of the holders can be removed without tools. In this configuration, the upper holder is arranged on the side facing towards the sample-heating means. The lower holder is arranged on the side facing towards the sample receiver. The glass shield is held in place between the upper and the lower holder. Either the upper or the lower holder is removable without the use of tools. To uninstall the glass shield, the holder that is removable without a tool needs to be taken out. Subsequently, the glass shield can be removed without the need for a tool. 
         [0020]    The glass shield as well as the upper and the lower holder can be slid into the movable housing part and positioned and held in their place by means of guide tracks that are arranged on the movable housing part. In the measuring position and/or loading position the guide tracks have an essentially horizontal orientation. In the servicing position, the guide tracks are oriented essentially in a vertical direction. 
         [0021]    The holder that is removable without tools and/or the glass shield can be pulled in a controlled direction out of the movable housing part by means of at least one guide track. The guide track makes it easier for the user to remove or to install the glass shield and/or the holder that is removable without tools. 
         [0022]    In the servicing position the guide track is oriented vertically. This makes it possible for the user to remove the glass shield and/or the holder that is removable without tools from the movable housing part through an upward-directed movement. Furthermore, the user has the holder, the glass shield and the sample-heating means directly in his view. This arrangement makes it easier for the user to take out the glass shield. 
         [0023]    The removal of the glass shield and the holder is additionally facilitated by a service opening in the movable housing part. The service opening allows the glass shield and/or a holder to be taken out. Ideally, the service opening is arranged in the extension of the path of the guide track. This arrangement makes it possible to pull the glass shield and/or the holder out of the movable housing part through the service opening in a track-guided move. 
         [0024]    The service opening is open in the servicing position, but closed in the measuring position and the loading position. In the measuring position and the loading position, the service opening is closed by a portion of the movable housing part. Accordingly, the opening does not exist when measuring or loading takes place. Thus, no contaminants can enter through the service opening into the measuring instrument during measuring and loading. 
         [0025]    In a preferred embodiment, at least a part of an interior draft shield is arranged around the sample-heating means and the glass shield. A part of the interior draft shield serves as the upper holder for holding the glass shield in place. Thus, no additional holder is necessary for the glass shield. The interior draft shield is arranged on the movable housing part. 
         [0026]    The measuring instrument further includes a light-screening barrier by means of which the direction of the heat radiation falling on the sample can be influenced. This light-screening barrier can serve simultaneously as the lower holder of the glass shield. The light-screening barrier is arranged on the movable housing part and can be taken out without using tools. 
         [0027]    The sample-heating means can include for example a heater plate, a heating foil, a broadband light source, a monochromatic light source, a heat radiator, a heating coil, a Peltier element, or a microwave generator. 
         [0028]    In an advantageous embodiment, the measuring instrument includes an electrical contact means with a first part and a second part. The first part of the electrical contact means is connected to the stationary housing part, and the second part of the electrical contact means is connected to the movable housing part. In the measurement position, an electrical connection exists by way of the first and the second part of the electrical contact means. In the loading position, the electrical connection between the first and the second part of the electrical contact means is interrupted. 
         [0029]    Ideally, only the stationary housing part is directly connected to the electric grid, while the movable part is supplied with electricity only through the electrical contact means. This arrangement serves to ensure that the movable housing part receives electricity only while the instrument is in measuring position. In the loading position and in the servicing position, there is no voltage applied to the movable housing part. Consequently, the sample-heating means is not supplied with current during loading and servicing, and the danger of burn injuries to the user is reduced. 
         [0030]    Ideally, the weighing device is arranged in the stationary housing part. In a preferred embodiment, the weighing device is arranged in a weighing compartment. The weighing compartment and the testing compartment are separated from each other by at least one vertical separating wall, wherein the latter has at least one passage opening through which a connecting member extends which serves to connect the weighing device to the sample receiver that is arranged in the testing compartment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    Details of the disclosed embodiments of the measuring instrument may be learned from the description of the embodiment illustrated in the drawings, wherein 
           [0032]      FIG. 1 , in a sectional view, shows a schematic representation of a measuring instrument in measuring position; 
           [0033]      FIG. 2 , in a sectional view, shows a schematic representation of the measuring instrument of  FIG. 1  in loading position; 
           [0034]      FIG. 3   a  is a schematic representation of a further measuring instrument with a temperature sensor, wherein the latter is in measuring position; 
           [0035]      FIG. 3   b  is a schematic representation of the measuring instrument of  FIG. 3   a , wherein the temperature sensor is in the loading position; 
           [0036]      FIG. 4  shows a perspective view of the measuring instrument in measuring position; 
           [0037]      FIG. 5  shows the measuring instrument of  FIG. 4  in loading position; 
           [0038]      FIG. 6  shows the measuring instrument of  FIG. 4  in servicing position; 
           [0039]      FIG. 7  shows the measuring instrument of  FIG. 6  in servicing position with partially removed glass shield and draft protector; and 
           [0040]      FIG. 8  shows the movable housing part of the measuring instrument of  FIG. 7  in servicing position without glass shield. 
       
    
    
     DETAILED DESCRIPTION 
       [0041]      FIGS. 1 and 2  represent schematic, sectional views of a measuring instrument  10  in measuring position ( FIG. 1 ) and in loading position ( FIG. 2 ). The measuring instrument  10  has a housing  20  in which a testing compartment  30  is arranged. The housing  20  is subdivided into a movable housing part  22  and a stationary housing part  21 . When the instrument is in use, the stationary housing part  21  is standing on a solid support surface. The movable housing part  22  is attached to the stationary housing part. To the rear, i.e. on the side of the testing compartment  30  that faces away from the user, a weighing device  40  is arranged in the stationary housing part  21 . The movable housing part  22  is constrained on the stationary housing part  22  by means of a translatory-motion guide  24 . The translatory-motion guide  24  is configured so that the movable housing part  22  maintains an essentially constant orientation during its movement from the measuring position into the loading position. In other words, during its movement the movable housing part  22  remains essentially parallel to the stationary housing part  21 . The stationary housing part  21 , which is configured as a hollow body, contains a weighing cell  43  and at least one electronic module  90  which are connected to each other by transfer means  52 . The electronic module  90  includes at least one signal-processing module (not shown in detail) and in some cases also a controller- and/or regulator module. The weighing cell  43  has at least one stationary portion  41  and a load-receiving portion  42 . State-of-the-art types of weighing cells include for example elastic deformation bodies carrying strain gauges, weighing cells that operate according to the principle of electromagnetic force compensation, weighing cells with oscillating strings, capacitative weighing sensors and the like. The stationary portion  41  of the weighing cell  43  is solidly connected to the stationary housing part  21 . Arranged on the load-receiving portion  42  is a connecting member  47  through which a sample receiver  60  is connected to the load receiving portion  42  of the weighing cell  43 . As shown in the drawing, a sample tray  61  with a sample  62  can be set on the sample receiver  60 . If the sample receiver  60  is suitably configured, the sample  62  can of course also be put directly on the sample receiver  60 . 
         [0042]    The measuring instrument  10  as shown in  FIG. 1  is in measuring position which means that the sample receiver  60  and the sample tray  61  sitting on it are inside the testing compartment  30 . The stationary housing part  21  and the movable housing part  22  form an essentially enclosed testing compartment  30  surrounding the sample receiver  60 . A heating means  70  is arranged essentially parallel to the plane of the sample receiver  60 , so as to obtain as homogeneous a heat distribution as possible at least on the surface of the sample  62 . It is also possible to arrange an additional heating means in the testing compartment  30  below the sample receiver  60  in order to expose the underside of the sample  62  to radiation. However, it is not absolutely necessary to arrange the heating means  70  parallel to the plane of the sample receiver  60 . Depending on the sample  62  and on the measurement that is to be performed, it may also be advantageous to arrange the heating means  70  at an oblique angle to the sample receiver  60 . 
         [0043]    To allow the moisture given off by the sample  62  to escape from the testing department  30 , the housing  20  has outlet vents  27  arranged at an appropriate location of the movable housing part  22 , preferably above the heating means  70 . To generate sufficient air circulation inside the testing compartment  30 , there should further be air vent openings provided at appropriate locations. 
         [0044]    The measuring instrument  10  in  FIG. 1  is shown in measuring position. The stationary housing part  21  and the movable housing part  22  form an essentially enclosed testing compartment  30 . The latter is essentially delimited at the top by the movable housing part  22  and at the bottom by the stationary housing part  21 . The heating means  70  is arranged in the movable housing part  22 . Ideally, the heating means  70  is mechanically connected to the movable housing part  22  through releasable plug-in connections. Thus, the heating means  70  can be uninstalled without much effort for cleaning or repair. Furthermore, with the use of plug-in connections the user of the measuring instrument  10  is able to select from different heating means with different functional characteristics. This enables the user to match the conditions inside the testing compartment to a specific sample  62 . 
         [0045]    The measuring instrument  10  includes an electronic module  90  which is arranged in the stationary housing part  21 . The electronic module  90  has a variety of controller/regulator devices. Among others, the electronic module  90  also includes a controller/regulator device for the control and regulation of the heating means  70 . A temperature sensor  80  which is illustrated schematically in the drawing serves to measure the temperature of the sample  62  and to deliver to the controller/regulator device  35  the information required for the regulation of the heating means  70 . The controller/regulator device  35  is further connected to the weighing device  40 , specifically to the electronic module  90 , by means of at least one transfer means  52 . The transfer means  52  serves for the transmission of electrical and/or electronic signals. As a result, the controller/regulator device  35  can receive signals from the electronic module  90 . The measuring instrument  10  is supplied with power by means of an electrical connection  88 . The electrical power connection  88  is arranged on the stationary housing part  21 . Preferably, the electrical current is delivered only by way of the stationary housing part  21 . Thus, the user or the service technician is not subjected to the risk of receiving an electric shock in the course of a servicing operation. 
         [0046]    The controller/regulator device  35  and the temperature sensor  80  are connected to each other through a transfer means  51 . Furthermore, the controller/regulator device  35  and the sample-heating means  70  are connected to each other through a further transfer means  53 . The transfer means  51 ,  53  serve to transmit electrical and electronic signals between the respective apparatus components. During the measurement process, the temperature in the testing compartment  30  is measured by means of the temperature sensor  80 . The temperature signal generated by means of the temperature sensor  80  is transmitted by way of the transfer means  51  to the controller/regulator device  35 . For the controller/regulator device  35  the temperature signal is an input signal based on which the sample-heating means  70  is controlled. In the measurement position, the temperature sensor  80  is located between the sample receiver  60  and the sample-heating means  70 . This arrangement makes it possible to obtain the temperature value that is relevant for the measurement. The temperature sensor could also be placed at a different location. However, the temperature values that are thereby obtained are less accurate in representing the heat level in the testing compartment. The temperature sensor  80  is arranged on a rod  81  which is fastened to the stationary housing part  21 . The rod  81  is essentially rigid, with a first end and a second end. Arranged at the first end is the temperature sensor  80 , while the second end is connected to the stationary housing part  21 . Due to the fact that the second end is connected to the stationary housing part  21 , the operation of the temperature sensor  80  does not require an electrical and/or electronic connection from the stationary housing part  21  to the movable housing part  22 . 
         [0047]    The transfer means  51  is arranged at or inside the rod  81 . The rod  81  can be swivel on a fulcrum pivot  82 . The fulcrum pivot  82  is at the second end of the rod  81  and has a substantially horizontal pivot axis  83 . 
         [0048]    The rod  81  and the fulcrum pivot  83  are arranged so that during the change from the measuring position to the loading position, the temperature sensor  80  moves along a circular path in a vertical plane. Arrangements are also possible where the circular path lies in a different, i.e. non-vertical plane. For example, the axis of the fulcrum pivot can be given an essentially vertical orientation, so that the temperature sensor  80  is constrained to a circular path in a horizontal plane during the change from the measuring position to the loading position. 
         [0049]    In the measuring position, the rod  81  is force-biased by the spring tension of a spring element  84 . When the movable housing part  22  is brought from the measuring position into the loading position, the rod  81  moves away from the sample receiver  60  under the elastic force of the pre-tensioned spring element  84 . In the loading position, the temperature sensor  80  and the rod  81  are therefore not obstructing the access to the sample receiver  60 , which facilitates the loading of the measuring instrument. Ideally, the spring element  84  is constituted by a torsion spring wherein the torque axis coincides with the axis of the fulcrum pivot  83 . Of course, other spring elements could also be used, such as for example compression spring elements. In any case, the spring element needs to be arranged so that it is elastically biased in the measuring position while being unstressed or less biased in the loading position. 
         [0050]    As the sample-heating means  70  is arranged in the movable housing part  22  and the controller- and regulator device  35  is arranged in the stationary housing part  21 , the transfer means  53  has to transmit electrical and/or electronic signals from the stationary housing part  22  to the movable housing part  21 . This can be accomplished for example with a flexible cable. However, due to the position shifts of the movable housing part  21 , this cable would be subjected to bending cycles and therefore susceptible to wear. 
         [0051]    This problem can be circumvented by using an electrical contact means with a first part  86  and a second part  87 , wherein the first part  86  is connected to the movable housing part  22  and the second part  87  is connected to the stationary housing part  21 . Under this concept, the first and the second part of the electrical contact means  86 ,  87  are arranged so that in the measuring position the first and second part  86 ,  87  form an electrical connection, and that in the loading position the electrical connection is interrupted. It is a significant advantage of this arrangement that in the loading position the sample-heating means  70  is not supplied with electricity. Ideally, the electronics for the control are arranged exclusively in the stationary housing part  22 . The control of the sample-heating means  70  takes place only by way of the first and second electrical contact means  86 ,  87 . Therefore, no connection is needed for the transmission of control signals to the movable housing part  21 . This is a further reason for arranging the temperature sensor  80  on the stationary housing part  21 . If the temperature sensor  80  were arranged on the movable housing part  22 , it would be necessary to transmit signals between the stationary housing part  21  and the movable housing part  22 . As a further advantage of the measuring instrument  10 , the temperature can also be measured and registered in the loading position by means of the temperature sensor  80 . Thus, it is for example possible to measure the ambient temperature during the loading process. 
         [0052]    The electrical contact means  86 ,  87  include a plug-in connection where one of the two parts of the electrical contact means  86  is configured as a plug and the other part as a socket that cooperates with the plug. The direction of insertion of the plug connection is essentially vertical. 
         [0053]    In  FIG. 2  the measuring instrument  10  of  FIG. 1  is shown in loading position. By means of a translatory-motion guide  24 , the movable housing part  22  can be moved away from the stationary housing part  21 , whereby the measuring instrument  10  is brought from the measuring position into the loading position. In this change of position, the movable housing part  22  undergoes in essence a purely translatory displacement. In the loading position the movable housing part  22  is located above the stationary housing part  21  and above the weighing device  40 . The sample-heating means  70  in this position is located between the movable housing part  22  and the stationary housing part  21 . This prevents accidental touching of the sample-heating means  70  which may be very hot. 
         [0054]    In the change to the loading position, the temperature sensor  80  is moved upward and laterally away from the sample receiver  60 . Thus, the temperature sensor  80  will not interfere with the loading of the sample receiver  60 . 
         [0055]    In the loading position, the electrical contact means  86 ,  87  is interrupted. There is no electricity flowing from the stationary housing part  21  to the movable housing part  22 . Since the movable housing part  22  does not have a power connection of its own, no electric current is entering the movable housing part  22  in the loading position. 
         [0056]      FIGS. 3   a  and  3   b  illustrate a further measuring instrument  110  in a schematic representation.  FIG. 3   a  shows the measuring instrument  110  in the measuring position, and  FIG. 3   b  shows the same measuring instrument  110  in the loading position. 
         [0057]    The measuring instrument  110  has a housing  120  with a stationary housing part  121  and a movable housing part  122 . 
         [0058]    When the instrument is in measuring position, the stationary housing part  121  and the movable housing part  122  together form an essentially enclosed testing compartment  130 , in which the sample receiver  160  is located. Arranged above the sample receiver  160  is a sample-heating means  170 . The sample-heating means  170  is solidly connected to the movable housing part  122 . A temperature sensor  180  is arranged on a rod  181 . The rod  181  has a first and a second end. Attached to the first end is the temperature sensor  180 , while the second end is pivotally connected to the stationary housing part  121 . In the measuring position of the instrument, the temperature sensor  180  is located above the load receiver  160  and underneath the sample-heating means  170 . In loading position, the temperature sensor  180  is located essentially off to the side of the load receiver  160 . This is accomplished with a design where the rod  181  is rigid and is connected to the stationary housing part  121  by means of a fulcrum pivot  182 . Ideally, the axis  183  of the fulcrum pivot  182  is oriented horizontally. In measuring position, the rod  181  can be spring-biased by the elastic force of a spring element. When the movable part  122  is moved from the measuring position into the loading position, the rod  181  moves upwards and laterally in a circular arc under the biasing force of the spring element. In the measurement position, the spring element is preferably held in a pre-tensioned state by the movable housing part  122 . 
         [0059]    To obtain the most stable measurement results possible, there can be an interior draft shield arranged inside the testing compartment (see  FIGS. 6-8 ). This interior draft shield is arranged so that it surrounds the sample receiver  160  and the sample-heating means  170 , delimiting a nearly enclosed section of space. The interior draft shield can include an upper part  174  and a lower part  165 . The upper part  174  is arranged on the movable housing part  122 . The upper part  174  of the interior draft shield forms a cylindrical interior space which is open towards the sample receiver. Arranged inside this cylindrical interior space is the sample-heating means. The upper part of the interior draft shield can consist of a cylindrical circumference wall alone. However, it is advantageous if the cylinder has an upper end wall which is horizontally oriented in the measuring and in the loading position of the instrument. This end wall is preferably arranged above the sample-heating means  170 . Ideally, the side of the end wall that faces towards the sample-heating means  170  is heat-reflecting. Consequently, a part of the heat that is being generated is reflected by the interior draft shield and used to heat the sample which is located on the sample receiver  160 . The lower part  165  of the interior draft shield is arranged on the stationary housing part  121 . The lower part  165  of the interior draft shield forms a cylindrical interior space which is open towards the sample-heating means  170 . Arranged in this cylindrical interior space is the sample receiver  160 . In measuring position, the interior space of the upper part  174  of the interior draft shield and the interior space of the lower part  165  of the interior draft shield form a chamber in which the sample-heating means  170  and the sample receiver  160  are located. The upper as well as the lower part of the interior draft shield  165 ,  174  can be made of one piece of material or assembled from several sections. 
         [0060]      FIGS. 4 ,  5 ,  6 ,  7  and  8  illustrate an embodiment of the measuring instrument  210  in different positions. The measuring instrument  210  has all of the components that have already been covered in the description of the schematic drawings of  FIGS. 1 and 2 . 
         [0061]      FIG. 4  shows the measuring instrument  210  in measuring position. As the housing  220  is closed in the measuring position, most of the components cannot be seen. The housing  220  has a stationary housing part  221  and a movable housing part  222 . In measuring position, the stationary housing part  221  and the movable housing part  222  form an essentially enclosed testing compartment. The movable housing part  222  has outlet vent openings  227  which allow gases to escape from the testing compartment inside the housing  220  into the ambient atmosphere. Advantageously, in the measurement position of the instrument the outlet vent openings  227  are located on the topside of the movable housing part  222 . Especially advantageous is an arrangement of the outlet vent openings  227  above the sample-heating means  170  which is likewise arranged inside the housing  220 . 
         [0062]      FIG. 5  shows the measuring instrument  210  of  FIG. 4  in loading position. The movable housing part  222  has been brought from the measuring position into the loading position by a translatory movement. To enable this translatory movement, the movable housing part  222  is connected to the stationary housing part  221  by a translatory-motion guide  224 . The translatory-motion guide  224  has two essentially parallel pivoting legs whose orientation defines the direction of the translatory movement of the movable housing part  222 . 
         [0063]    The stationary housing part  221  is of an elongated shape. The weighing device is largely enclosed by the stationary housing part  221 . Only a sample receiver  260  which is connected to the weighing device protrudes laterally from the stationary housing part  221 . Containers of various shapes such as sample trays, crucibles and the like can be put on the sample receiver  260 . The stationary housing part  221  includes a portion that is located to the side of the sample receiver  260  that faces away from the user. Advantageously, in this portion the weighing device is arranged. In loading position, the movable housing part  222  is located above the stationary housing part  221 , ideally above the portion that is located to the side of the sample receiver  260 . 
         [0064]    The movable temperature sensor  280  is arranged on a pivotally mounted rod  281 . As described in the schematic representation of  FIGS. 3   a  and  3   b , the rod  281  is connected to the stationary housing part by means of a fulcrum pivot. The axis of the fulcrum pivot is likewise oriented horizontally, and the rod  281  is likewise elastically biased in the measuring position by means of a spring force. In the measuring position, the temperature sensor  280  is located between the sample-heating means  270  and the sample receiver  260 . In the loading position, the temperature sensor  280  and the rod  281  are removed sideways and upward from the sample receiver  260 . This makes it possible to load a sample on the measuring instrument  210  without the temperature sensor  280  standing in the way of the user. 
         [0065]    The sample-heating means  270  is arranged in the movable housing part  222 . During the measurement, the sample-heating means  270  becomes hot and thereby heats the sample which is arranged below the heating means on the sample receiver  260 . An electric current is required for the heating. The stationary housing part  221  is therefore equipped with a power connector  288  which is arranged on the backside of the measuring instrument  210 . The movable housing part does not have a power connection of its own. The electric current therefore has to be transmitted from the stationary housing part  221  to the movable housing part  222 . This is accomplished with an electrical contact means which has a first part  286  and a second part  287 . The first part  286  of the electrical contact means is connected to the stationary housing part  221 , while the second part of the electrical contact means is connected to the movable housing part  222 . The two parts  286 ,  287  of the electrical contact means are arranged so that in measuring position an electrical contact exists from one to the other and the sample-heating means  270  is supplied with electrical current. In the loading position, there is no contact through the electrical contact means  286 ,  287 . The electrical contact is established automatically by the movement of the movable housing part  222 . A pivotable, concentric plug connection of the kind used in water heaters has proven particularly suitable as electrical contact means. The pivotable, concentric plug connection is particularly robust and reliable in closing and opening an electrical contact. However, other configurations are likewise conceivable. Particularly suitable are plug/socket connections. 
         [0066]    With this arrangement, an electrical connection exists in the measuring position by way of the first and second part of the electrical contact means  286 ,  287 , while the connection between the first and second part of the electrical contact means  286 ,  287  is interrupted in the loading position. In the loading position, the heating means is therefore not under power and the risk of injury is therefore reduced. The second part of the electrical contact means  286  is covered up in  FIG. 5  by the movable housing part  222  and is therefore not visible. 
         [0067]    To reduce air turbulence in the testing compartment, an interior draft shield  265 ,  274  which surrounds the sample receiver  260  can be arranged inside the testing compartment. This draft shield  265 ,  274  is preferably designed so that it conforms to the outside contour of the sample tray and/or the outside contour of the sample-heating means  270 . As the sample trays being used are normally round, it suggests itself to use an interior draft shield  265 ,  274  with a round contour shape. The interior draft shield can include an upper part  274  and a lower part  265 . The upper part  274  is arranged on the movable housing part  222 . The upper part  274  of the interior draft shield encloses a cylindrical interior space which is open towards the sample receiver. Arranged inside this cylindrical interior space is the sample-heating means  270 . The upper part of the interior draft shield can consist of a cylindrical circumference wall. It is advantageous if the cylinder also has at least a partial boundary surface above the sample receiver, preferably a cylinder end wall. This surface is arranged preferably above the sample-heating means  270 . Ideally, the side of the end wall that faces towards the sample-heating means  270  is heat-reflecting. Consequently, a part of the heat that is being generated is reflected by the interior draft shield and used to heat the sample which is located on the sample receiver  260 . In addition, the end wall can have openings, so that gases can escape into the outside atmosphere from the testing compartment through the openings in the end wall and outlet vent openings  227  in the housing  220 . However, it is also possible that the end surface has no openings. 
         [0068]    The lower part  265  of the interior draft shield is arranged on the stationary housing part  221 . The lower part  265  of the interior draft shield forms a cylindrical interior space which is open towards the sample-heating means  270 . Arranged in this cylindrical interior space is the sample receiver  260 . In measuring position, the interior space of the upper part  274  of the interior draft shield and the interior space of the lower part  265  of the interior draft shield form a chamber in which the sample-heating means  270  and the sample receiver  260  are located. The upper as well as the lower part of the interior draft shield  265 ,  274  can be made of one piece of material or assembled from several sections. 
         [0069]    To set a sample tray in place in the testing compartment, it is possible to use a sample tray holder  266 . The sample tray holder  266  has a handle  267  and seating surfaces  268  for the sample tray. During the transfer of the sample tray, the rim of the latter rests on the seating surfaces  268 . During the measurement, the sample tray rests only on the sample receiver  260  and the sample tray holder  266  does not touch the sample tray. In particular, the weight of the sample tray holder  266  is not received by the weighing device. 
         [0070]    In  FIG. 6  the inventive measuring instrument  210  of  FIGS. 4 and 5  is shown in servicing position. To arrive at the servicing position, a portion of the movable housing part  222  has been swiveled about an essentially horizontal pivot axis  225  from the loading position into the servicing position. The sample-heating means  270  is arranged in the pivoting portion of the movable housing part  222  and is swiveled together with the pivoting portion of the movable housing part  222  during the change into the servicing position. As a result, the components in the movable housing part  222  are easily accessible for servicing. Arranged in the upper housing part  222  is the sample-heating means  270 . During the measurement process, the sample-heating means  270  is protected by a glass shield  272 . Surrounding the sample-heating means  270  is the upper part  274  of the interior draft shield. 
         [0071]    To give a clearer view of the position and configuration of the sample-heating means  270 , of the glass shield  272  and of the interior draft shield  274 , the measuring instrument  220  is shown in  FIG. 7  with the upper part  274  of the interior draft shield partially removed, and in  FIG. 8  the movable housing part  222  is shown without glass shield  272 . 
         [0072]    Arranged on the cylinder end surface of the interior draft shield  274  is a reflecting surface which serves to reflect the heat radiation generated by the sample-heating means  270 . The reflection can also be achieved with a suitable reflective material of the cylinder end surface or a reflective coating of the cylinder end surface. An essentially circular light-screening barrier  273  serves to concentrate the heat rays generated by the sample-heating means  270 . 
         [0073]    In servicing position, the sample-heating means  270  is oriented vertically. At least a portion of the upper part  274  of the interior draft shield is attached to the movable housing part  222  by means of a plug-in connection, wherein the plug-in direction is essentially vertical in the servicing position. The glass shield  272  is clamped between the light-screening barrier  273  and a portion of the upper part  274  of the interior draft shield  274 . To remove the glass shield, only a part of the interior draft shield  274  needs to be pulled out of the plug-in connection. Subsequently, the glass shield can be removed simply by pulling it out, without using a tool. The easy removal of the glass shield  272  is of particular advantage, because it facilitates the taking-out and cleaning of the glass shield  272  which is prone to get dirty. 
         [0074]    The glass shield  272  and/or a portion of the upper part  274  of the interior draft shield can be pulled out of the movable housing part in a controlled direction by means of a guide track  275 . In the servicing position, the guide track  275  has an essentially vertical orientation. 
         [0075]    The removal of the glass shield  272  is additionally facilitated by a service opening  223 . The service opening  223  is an access opening in the movable housing part  222  which is open only in the servicing position but not in the measuring position or in the loading position. An inadvertent touching of the sample-heating means is thereby prevented, which reduces the risk of burn injuries. The service opening is realized with a two-part configuration of the movable housing part. According to this concept, the two parts of the movable housing part are designed so that in the move to the servicing position a portion of the movable housing part does not participate in the swivel movement. This non-swiveled portion clears the access to the service opening in the swiveled portion of the movable housing part. 
         [0076]    The width of the service opening  223  is advantageously equal to or larger than the width of the glass shield  272 . This allows the glass shield to be removed easily. The service opening  223  is arranged at a right angle to the plug-in direction of the upper part of the interior draft shield  274  and in the extension of the path of the guide track  275 . As a result of this arrangement, the glass shield  272  can easily be pulled out of the service opening  223 . 
         [0077]    The upper part of the interior draft shield  274  can be composed of several components. Advantageously, the portion that faces towards the service opening  223  can be removed without tools. This requires the service opening  223  to be wider than the upper part of the interior draft shield  274 . 
         [0078]    The sample-heating means  270  can be attached to the movable housing part  222  in a variety of ways. For example, the sample-heating means  270  could be fastened to the movable housing part  222  by means of screws or with a plug-in connector. If a plug-in connector is used, the sample-heating means  270  can easily be pulled out for servicing. Ideally, this plug-in connection could be designed so that the plug insertion is directed essentially perpendicular to the plane of the service opening  223 . 
         [0079]    The sample-heating means  270 , the light-screening barrier  273 , the glass shield  272  and the upper part of the interior draft shield  274  have openings which, together with the outlet vent openings  227  allow the vapors and/or volatile substances escaping from a sample to be vented into the outside atmosphere. The openings are therefore arranged so as to ensure the direct venting of gases that escape from the sample. It is of advantage if these openings provide a direct line of vision to the sample that is located on the sample receiver  260 , whereby a visual inspection of the measurement process is made possible. 
         [0080]    In place of the interior draft shield  274  and the light-screening barrier  273 , one could use other suitable attachment devices to hold the glass shield  272  in place. 
         [0081]    Since the glass shield  272  is easy to take out, it can be cleaned more easily and quickly by the user or the service technician. Ideally, the glass shield  272  is made so that it can be cleaned in a conventional washing machine without damage. 
         [0082]    The embodiments presented herein show, partially in schematic form, measuring instruments for the gravimetric determination of moisture content with different properties and features. For clarity&#39;s sake, the different properties and features have been presented in different examples of embodiments, but it is also possible to realize some, several, or all of the described features and properties in one and the same measuring instrument.