AU2013270509B2 - Multiple-force-measuring device, force-measuring module, and method for status monitoring - Google Patents

Abstract

Abstract The invention relates to a multiple force-measuring device, in 5 particular a multiple weighing device, with at least two force measuring modules, each of which includes a force-measuring cell and a power delivery means, and with a power supply unit. The power delivery means of at least one force-measuring module in this arrangement is connected directly or through a junction 10 element to a control cable that is connected to the power supply unit, and the at least two force-measuring modules are connected directly to each other by means of a module-connection cable which serves to transfer electrical power between the force measuring modules. C) C)C C7)) CP-C C;C U)f

Description

MULTIPLE FORCE-MEASURING DEVICE, FORCE-MEASURING MODULE, AND METHOD FOR MONITORING A CONDITION OF THE MULTIPLE FORCE-MEASURING DEVICE ~ The present invention relates to a muitie force-measuring device, in particular a multiple weight-measuring device, and to a force-measuring module, as well as a method of operating the force-measuring device. 10 A multiple force-measuri ng device generally comprises at least two force-measuring modules and an inCicator device. The force measuring module, in turn, typically comprises an electromechanical force-measuring cell serving to determine a force, which functions as a measurement converter in that it 15 converts the inpu quantity, which is a mechanical force, into an electrical outout signal. A special type of multiple force measuring device exists in the form of a weighing scale with a plurality of weighing devices, so-called weighbing modules. The rc-cmeas ur i ng cell is configured in this case as a weighing 20 cell and serves for the mechanical-to-electrical conversion whereby the weight force exerted by a weighing object is converted into an elect.rical signal. Accord",iny, a force measuring module or a weighing module as the term is understood here means, respectively, a force-measuring device or a weighing 25 scale without an incrcator device. A multiple force-measuring device is typically a force-measuring device in which the force to be measured is distributed by means of a mechanical device, in particular a measuring plate or a 30 container, onto a plurality of force-measuring moduleS. Each fc-mesuring module in this arrangement includes a force measuring cell, -by means of which - 1 the portion of the force that is imparted to the respective module can be individually determined. The results from the individual force-measuring cells are then passed on to a common output device, where they are combined into an overall result. 5 Multiple force-measuring devices are used for example in industrial installations for the weighing of the contents of basins, tanks, reactor vessels and the like. Typically in these kinds of applications the weighing modules are configured as 10 high-capacity weighing modules, as so-called tank weighing cells or reactor vessel weighing cells. For each container to be weighed, a plurality of weighing modules are arranged between the feet of the container and the foundation. Thus, each foot of the container rests on a force-measuring module. In order to 15 determine the weight of the container and/or of its contents, the measurement values determined by the force-measuring modules need to be added, as each measurement value represents a part of the mass. This calculation is in most cases performed in a processor device and/or controller device set up in an adjacent 20 location. High-capacity force-measuring cells also find application as weighing modules in weighing scales for trucks. Truck scales typically have several measuring plates or weighing plates, each 25 of which rests on a plurality of force-measuring modules. Accordingly, each force-measuring module measures a partial weight of the truck and/or of one or more trailers. The measuring results of the individual force-measuring modules are transmitted to a common processor device that is located at some 30 distance from the measuring plates and from the force-measuring modules, for example in a controller device located as much as several hundred meters away. - 2- According to US 2004/0245026, the processor device is implemented as an external device in the form of a so-called weighing terminal. By way of an indicator device that belongs 5 to the weighing terminal, the results of the multiple force measuring device can be released. In addition, a device for supplying the multiple force-measuring device with power is arranged in the processor device. Accordingly, the individual force-measuring modules are supplied with electrical energy 10 through this central power supply. To transmit the measurement results and the supply current, the force-measuring modules are connected through cables to the processor device. Typically in such an arrangement, the supply 15 current as well as the transmission of the measurement value are carried by the same cables, but by separate conductors in the cable. Furthermore, as a means to simplify the cable arrangement, the individual force-measuring modules are connected by shorter distributor lines to a distribution device, 20 and only the latter has a direct connection through an individual cable, the so-called "home-run" cable, directly to the controller device. The power supply and the transmission of the measurement values are thus merged in the distribution device in order to avoid multiple parallel cables over the 25 distance between the measuring plates and the controller building. As shown in EP 0 467 562, if there are four force-measuring modules, the distribution device can be arranged so that it is 30 located at the center of a rectangle formed by the four force measuring modules. As a result, a short cable length is achieved between the force-measuring modules and the - 3 distribution device, which in consequence reduces electrical disturbances and mechanical stresses and also lowers the cost of cabling. 5 Particularly in larger installations, for example in weighing installations for trucks, there are often many measuring plates and force-measuring modules involved, for example four measuring plates with a total of sixteen force-measuring modules. As a result, one arrives at a multi-layered, cascaded or hierarchic 10 network of distribution devices in order to achieve the desired merging of the connections. In the case of sixteen force measuring modules, one ends up for example with a first level of four distribution devices, a second lever of two distribution devices, and one third-level distribution device, thus a total 15 of seven distribution devices. However, the distribution devices are expensive and susceptible to interference. The probability of errors in the installation process as well as during operation and maintenance increases 20 with the rising number of components. It is therefore desirable to assemble a force-measuring device with the smallest possible number of distribution devices. In the weighing device according to US 2004/0245026 Al, eight 25 weighing modules are connected to a central distribution device. Thus, the use of intermediate hierarchic levels of distribution devices can be dispensed with. The central distribution device serves a common juncture for the power supply as well as for the communication leads and offers the advantage of a simple 30 arrangement of the conductor lines. Nevertheless, in most cases this arrangement involves longer distribution leads and a larger -4 overall length of the distribution leads, thus an increased susceptibility to interference and higher costs. To avoid these drawbacks, the cabling of the weighing modules is 5 replaced in US 2004/0026135 by a radio transmission and individual independent power supplies of the individual weighing modules. The distribution device functions in this case as a radio relay for the transmission of the signals from the weighing modules to the processor device. Furthermore, the 10 distribution device, too, is equipped with an independent power supply in order to eliminate all cabling. Batteries are used for the individual independent power supplies of the weighing modules and the distribution device. However, this solution has the disadvantage that the charge level of the batteries has to 15 be checked at regular intervals, and that insufficiently charged batteries have to be recharged or exchanged. Besides, typically the performance of the batteries depends strongly on extraneous influence factors of the environment, in particular the ambient temperature. Expensive checking and monitoring activities are 20 therefore required in order to ensure a stable, reliable operation of the weighing modules, particularly in outdoor applications. in accordance with a first aspect, the present invention 25 provides, a force-measuring module for a force-measuring device having a terminal connected to a plurality of the force measuring modules through a plurality of connection cables, each of which has a conduit to transmit communications bidirectionally between the terminal and the force-measuring 30 modules and a conduit to transmit power uni-directionally from a power supply to the force-measuring modules, each force measuring module comprising: , 59 a housing; a first and a second plug connector, arranged on the housing, each of the plug connectors configured on the exterior of the housing for connection to one of the 5 connection cables and configured on the interior of the housing to electrically communicate the respective conduits of the connection cables; a force-measuring cell, arranged in the housing to receive force imposed on the housing; 0 a communication means, arranged in the housing, for receiving a measurement signal from the force-measuring cell and communicating with the terminal through the communications conduit of the connection cable; and a power delivery means, arranged in the housing, 5 for receiving through the power conduit of the connection cables and distributing the received power within the housing. The housing may be attached to the force-measuring cell by .0 welding such that deformation of the housing by a load results in elastic compression of both the housing and the force measuring cell. The housing may be tightly sealed against the ambient environment of the force-measuring device. 25 In an embodiment, the communication means comprises a CAN bus system interface. The module may further comprise a device for monitoring or terminating a communication with the terminal. The module may also comprise a device for monitoring one or more voltages of the power supply through one or more connection 30 cables. The one or more voltages of the power supply may comprise (VLC1). In addition, the device for monitoring one or - 6 more voltages of the power supply may be arranged to alter the one or more voltages of the power supply. -6a- The term "power delivery means" encompasses all devices that serve to supply the force-measuring module with electric power, such as supply cables, distribution cables, voltage converter, 5 current converters, stabilizers, smoothing elements or filter elements. Also included are the voltage supplies for communication leads, for example the CAN power supply of a CAN bus communication system. 10 The term "cable" includes all kinds of electrical conductor lines such as single-lead or multi-lead cables, stranded conductors, or wires, as well as the delivery of electrical current through fixed devices such as ground rails, housings and connecting rods. The junction element can be realized in the 15 most different ways, for example as a simple T-element, as a housing with connector terminals, as a forked cable or as a cable breakout. In a further embodiment of the invention, at least three force 20 measuring modules are connected in chain-like manner to each other by means of the module-connection cable, with the first force-measuring module and the last force-measuring module in the chain each being connected directly or through the junction element to the control cable. With this arrangement of 25 supplying current through more than one in-feed connection, one achieves a clear reduction in the voltage drop at the force measuring modules, particularly at those force-measuring modules that are supplied with current or with electrical energy by way of a large number of other force-measuring modules arranged in 30 between in the chain. Furthermore, the junction element in this embodiment can be of a particularly simple configuration, as only two force-measuring modules have to be connected to the - 7 control cable. With this arrangement, a particularly simple and cost-effective design is achieved for the multiple force measuring device. 5 In a special embodiment of the invention, no more than one force-measuring module is connected to the control cable. Thus, the junction element can be omitted, whereby the number of required components is reduced and thus the fail-safety is improved. 10 Further, in a preferred embodiment all force-measuring modules are connected to each other in a chain-like manner by means of a module-connection cable. In this way, one achieves a particularly simple, clear and cost-effective arrangement. 15 In a further embodiment according to the invention, each of the force-measuring modules includes a means of communication, and through the module-connection cable it is in addition possible to transmit communication signals between these means of 20 communication. This transmission can be realized in particular by means of a bus system, in appropriate cases by means of a CAN bus system. This concept avoids the need to arrange an additional communication setup. Besides, a bus topology can be combined in a particularly advantageous way with the chain-like 25 arrangement of the force-measuring modules. The communication signals can in this case be directed through separate leads independent of the power supply line in the module-connection cable, as well as together with the power supply line through common leads in the module-connection cable. 30 In the same manner as in the module-connection cable, the communication, likewise, can be transmitted through the control - 8 cable, for example through separate leads, or together with the power supply through common leads. The term "communication means" encompasses all elements that 5 serve for the transmission of data, in particular sender- and receiver elements, processing elements for analog and/or digital data, transponders, impedance converters, transmitters, conductor terminals, plug connecters or couplings. The communication signals can be of analog or digital nature in the 10 form of measurement values, pre-processed measurement values, intermediate values or final measurement results, computed results, time records of events, in particular times when threshold values were exceeded. Furthermore, additional data and measurement parameters can be transmitted, for example 15 identification data of the force-measuring modules, data regarding the time and location of measurements, or information about the operating states of the force-measuring modules. Furthermore, data such as control information, operating parameters, control programs, or calibration data can be 20 transmitted to the force-measuring modules. Preferably, the communication signals of the force-measuring modules are transmitted to a terminal or from a terminal. The terminal can in this case be configured as a lead computer, as a 25 system controller, a process control system, but also as a simple output instrument, for example as a display screen and/or as a printer. Particularly in smaller installations, the functions of power supply, processing of the measurements, control of the force-measuring device, and display can be 30 combined in one device, for example in an office computer. - 9 - In a further embodiment of the invention, each of the force measuring modules has a device for determining and/or monitoring the electrical voltage of the power delivery means. The device can in particular serve to determine and/or monitor the positive 5 voltage and/or the negative voltage, wherein the voltages can be determined and/or monitored, if applicable in reference to a common potential, in particular the ground potential. Valuable information can thereby be gained regarding the operating condition of the power supply of the force-measuring modules as 10 well as regarding the condition of the module-connection cable. In a preferred embodiment, the monitoring of the voltage is accomplished by examining whether the measured values are within threshold values, and if the threshold values were found to be 15 exceeded, actions are triggered such as transmitting messages and/or recalibrating or switching off the respective force measuring module. This makes it possible on the one hand that failures in the force-measuring modules and/or the module connection cables are recognized early and on the other hand 20 that the location of these errors can be pinpointed more easily. With this concept, the monitoring can be active during the installation and/or calibration as well as during operation of the force-measuring device. 25 Furthermore, by determining the voltage of the power delivery device and/or the time profile of said voltage, one obtains essential information about the current condition and anticipated future operating experience of the force-measuring module. Thus, these data can provide information in regard to 30 anticipated future servicing needs, the advancement of the aging process, the change of the ambient conditions, or the anticipated remaining operating life of the force-measuring - 10 modules. For example a strong rate of change of the voltage in a cell can indicate a corrosion-related damage in the coupling device of a force-measuring module. This monitoring surveillance is particularly advantageous in large installations 5 with a multitude of force-measuring modules. The threshold values can be determined through theoretical calculations, taking into account in particular the characteristic quantities of the module-connection cable such as 10 the length and cross-section of the conductor lines and/or the internal resistance values of the force-measuring module, and/or through reference measurements. The reference measurement values can be obtained preferably from measurements in a newly installed and/or newly calibrated force-measuring device and 15 stored in a memory unit. The reference values and/or threshold values can also be taken from manuals and operating instructions. In addition, they can also be specified by the manufacturer or transmitted to the installation from the manufacturer as needed. It is particularly advantageous to 20 store the reference values and/or the threshold values in the individual force-measuring modules, whereby a modular interchangeability of the modules can be achieved. In a further embodiment of the invention, all module-connection 25 cables have a largely identical conductor resistance, in particular largely identical lengths, materials and conductor cross-sections. In this case, the threshold values are particularly easy to determine through calculations of voltage divider circuits. 30 In a further embodiment, the junction element and/or the force measuring modules include a device for the monitoring of the - 11 termination of the communication connection and/or for effecting the termination. Since the lack of a termination can cause problems in the transmission of the communication signals, this concept allows the problems to be detected and reported or even 5 to be automatically corrected by the force-measuring device. In a further embodiment, the force-measuring module or the module-connection cable includes a device for interrupting the continuity in the power supply circuit. This provides the 10 possibility to ensure that the delivery of power is limited to a certain maximum number of force-measuring modules. Thereby it can be assured for example that the supply current can be transmitted between a maximum of four power delivery means. This allows the maximum power being transmitted through the 15 power supply, in particular the maximum current, to be kept below a certain maximum value. This limitation of the current is particularly important in hazardous environments where an explosion danger exists and 20 where special regulatory requirements have to be met in regard to the maximum current consumption of the force-measuring modules and/or the force-measuring device. Furthermore, this interruption allows the force-measuring device to be subdivided into different, independently supplied subsystems. This 25 separation can be achieved for example by means of manual or electromagnetic switches or by means of a special module connection cable. In the case of the special module-connection cable it is possible for example that the communication leads have contact connectors providing a continuous conductive path, 30 while the leads for the power supply have no contacting connectors, so that the conductive path is interrupted. The conformance to the regulations on current limitation can also be - 12 monitored by the terminal, and a reconfiguration of the force measuring device can be effected through appropriate control commands from the terminal to the force-measuring modules. 5 In a further preferred embodiment, the force-measuring module also includes at least one plug connector, in particular two plug connectors where the module-connection cable and/or the control cable can be connected. This provides an efficient way of setting up, testing and servicing the force-measuring device. 10 In a further embodiment of the invention, force-measuring module includes a plug connector which is encapsulated against environmental influences, in particular dirt, liquids or gases and/or whose at least one electrical contact surface is designed 15 to be corrosion-resistant. With this measure, a fail-safe operation of the installation is also achieved in particular in harsh ambient conditions. Details of the force-measuring device according to the 20 invention, the force-measuring module according to the invention, and the method according to the invention will become evident from the description of the examples of embodiments represented in the drawings, wherein: 25 Figure 1 schematically illustrates in a sectional view a multiple force-measuring device according to the invention with two force-measuring modules, each of which includes a force-measuring cell, a power delivery means, and a communication means, which are connected 30 to a controller device by way of module-connection cables and a control cable; - 13 - Figure 2 illustrates a multiple force-measuring device according to the state of the art in the form of a truck-weighing installation with two measuring plates, each of which is supported by four force-measuring modules; 5 Figure 3 shows a configuration of a multiple force-measuring device according to the invention, which is similar to the device of Figure 2 but wherein the force-measuring modules are connected directly to each other in a 10 chain-like arrangement through a module-connection cable, and wherein the first and the last force measuring module of the chain is connected through a forked cable with a junction element to the control cable. 15 Figure 4 represents a multiple force-measuring device according to Figure 3, but with two force-measuring modules, each of which measures the weight contributions from two measuring plates; 20 Figure 5 represents a multiple force-measuring device according to Figure 3, but with a direct connection of an individual force-measuring module to the control cable; 25 Figure 6 shows the simplified circuit schematic of the multiple force-measuring device according to the invention with a power supply unit, 1 to n force-measuring modules, conductor resistances, electrical voltages and a common ground connection. 30 Figure 1 shows a multiple force-measuring device 200 in the form of a tank-load weighing device. For the weighing of a - 14 container, a plurality of force-measuring modules 244 are arranged between the feet of the container 230 and the foundation 231, so that each foot of the container 230 rests on a force-measuring module 244. In order to determine the weight 5 of the container and/or of its contents, the measurement values determined by the force-measuring modules 244 need to be added, as each measurement value represents a part of the mass. To perform the addition, the measurement values of the individual force-measuring modules 244 are transmitted to a terminal 206, 10 where they are processed and presented on the display 207. The terminal 206 is arranged in a remotely located controller device 280. The force-measuring module 244 includes a force-measuring cell 15 210 which is enclosed in a housing 220. Typically, the housing 220 is welded to the force-measuring cell 210 and tightly sealed against the ambient environment of the force-measuring device 200. In performing a measurement, the force-measuring cell 210 as well as the housing 220 are elastically compressed. The 20 deformation of the force-measuring cell 210 is measured by means of the force-measuring cell 210 and directed to a communication means 248. The power supply of the force-measuring module 244, in 25 particular of the associated electronic circuit, the force measuring cell 210 and the communication means 248 is made possible by a power delivery means 246 which, in turn, is supplied by the power supply PS. This power supply unit 270 of the multiple force-measuring device 200 is arranged in the 30 controller device 280 and incorporated in the terminal 206. - 15 - The force-measuring modules 244 are connected directly to each other by means of a module-connection cable 250. This module connection cable 250 can transmit the supply current PS as well as the communication C between the force-measuring modules 244. 5 The module-connection cable 250 therefore connects the power delivery means 246 and the communication means 248 of the individual force-measuring modules 244 to each other. Further, a force-measuring module 244 is connected through a control cable 205 to the controller device 280. The control cable 205, 10 the so-called home-run cable bridges the often major distance between the segment coupler 204 and the controller device 280 and thus establishes the immediate connection to the controller device 280. 15 This power supply unit 270 of the multiple force-measuring device 200 is arranged in the controller device 280 and incorporated in the terminal 206. The distribution of the power supply PS occurs through the control cable 205 and the module connection cable 250 to the power delivery means 246 of the 20 individual force-measuring modules 244. In the same way, the communication means 248 of the force measuring modules are connected to the terminal 206 in order to transmit the signals of the communication C, in particular the 25 measurement values, the processed results and the control commands. This communication C is transmitted bidirectionally from the communication means 248 to the terminal 206, i.e. from the communication means 248 through the module-connection cable 250 and the control cable 205 to the terminal 206 in the 30 controller device 280. - 16 - To illustrate the existing state of the art, Figure 2 schematically represents a multiple force-measuring device 100 in the form of a truck scale. The latter has two independent measuring plates 140, each of which is supported by four force 5 measuring modules 144. For the weighing, the trucks are put on the measuring plates, and the resultant forces are measured by means of the force-measuring modules 144. The processing of the measurement results occurs in the terminal 106. 10 Each force-measuring module 144 is connected through a distribution line 101 to a distribution device 102. The distribution device 102, in turn, is connected through a segment cable to a segment coupler 104. The segment coupler 104, finally, is connected through a control cable 105 to the 15 controller device 180. The segment coupler 104 couples two independent, physically separated segments of the multiple force-measuring device 100 together. A segment is in each case formed by a measuring plate 140, the associated force-measuring modules 144, the distribution lines 101, the distribution device 20 102, and the segment cable 103. The power supply unit 170 is incorporated in the terminal 106 which includes a display 107 and which is arranged in the controller device 180. The distribution of the power supply PS 25 occurs through the control cable 105, the segment coupler 104, the segment cable 103 and the distribution device 102, and finally through the distribution line 101 to the individual force-measuring modules 144. In the opposite direction the measurement values of the force-measuring modules are 30 transmitted to the terminal 106, i.e. from the force-measuring module 144 through the distribution line 101, the distribution - 17 device 102, the segment cable 103, the segment coupler 104, and the control cable 105 to the terminal 106. Figure 3 shows a configuration of the multiple force-measuring 5 device 300 according to the invention. The force-measuring modules 344 are connected to each other directly as a chain through module-connection cables 350. These module-connection cables 350 can transmit the power supply PS as well as the communication C between the force-measuring modules 344. The 10 module-connection cable 350 therefore connects the power delivery means 246 and the communication means 248 of the individual force-measuring modules 344 to each other. The communication C can for example consist of the transmission 15 of measurement values and their processed results in one direction and of control commands in the opposite direction. This bidirectional communication C can be transmitted through separate cable connections independent of the power supply PS and/or together with the power supply conductors in separate 20 leads within the same cable and/or in the power supply leads, preferably as a modulated signal. The module-connection cable 350 is at both ends connected to force-measuring modules 344 by means of plug connectors 352. 25 Accordingly, each force-measuring module 344 has two plug connectors 352, through which the two neighboring modules in the chain can be respectively connected. However, in the case of the first and the last force-measuring module 344, only one neighboring module of the chain is connected. 30 Furthermore, the first and the last force-measuring module 344 in the chain are each connected through a forked cable 354 and a - 18 junction element 356 to the control cable 305. The fork junction element is in this case configured as a simple T junction and serves to split the power supply PS and the communication C into respective branches leading to the first 5 and the last force-measuring module 344 of the chain. Accordingly, the distribution lines 101, distribution devices 102, segment cables 103 and segment couplers 104 are absent in this arrangement. 10 Finally, the power supply PS provided by the power supply unit 370 to the force-measuring modules 344 as well as the communication C between the terminal 306 and the force-measuring modules 344 are transmitted through the control cable 305. Besides, in this embodiment the force-measuring modules 344 are 15 supplied with power or with electrical energy not by the terminal 306 but by a separate power supply unit 370. The power supply unit 370 together with the terminal 306 and the display 307 is located in the controller device 380. 20 A further embodiment of the multiple force-measuring device 300 according to the invention is illustrated in Figure 4. This embodiment is analogous to the embodiment of Figure 3, except that two of the force-measuring modules 344 are used so that each of them measures the weight contributions from both 25 measuring plates 340. This double force introduction can be achieved for example with a flexibly supported mechanical device. As a result of this arrangement the number of force measuring modules 344 required is reduced from eight to six. 30 A further embodiment of the multiple force-measuring device according to the invention is represented in Figure 5. This arrangement is analogous to Figure 3, except that in this case - 19 only one force-measuring module 344 is connected to the control cable 305. Thus, the forked cable 354 and the junction element 356 are not needed, which makes this arrangement particularly cost-effective and stable. 5 Furthermore, the module-connection cables 350 are connected at one end to a plug connector 352 and at the other end directly to the force-measuring module 344. The direct connection can be realized for example as a clamped connection, a screw 10 connection, a fixed wiring connection or a soldered connection. With this arrangement, a further cost savings can be achieved as well as an increase in stability. Figure 6 shows a simplified block schematic of the multiple 15 force-measuring device 200 according to the invention with a power supply unit 270, 1 to n force-measuring modules 244 (1) ... 244(n), conductor resistances RHR, R 1 C, electrical voltages VLC1+, - - - , VLCn+, - - - , L - - -, VLCn-, and a common ground connection GND. 20 The conductor resistances RHR, R 1 c represent the respective resistance values RHR of the control cable 205 and R 1 c of the module-connection cable 250. Accordingly, a positive voltage VLC±+ and a negative voltage VLCi of the power supply relative to 25 the common ground potential can be measured at each force measuring module 244(i), 1 < i n. These voltages are characteristic for each individual force-measuring module 244(1) ... 244(n). The ground potential is set by the cable screen and/or by the housings of the force-measuring modules 244(1) ... 30 244 (n) and in particular by connecting the entire force measuring device 200 to ground. - 20 - Preferably, the measured voltages VLC1+, - - - , LCn+r VLC1-r ... VLCn are compared to the expected values or to threshold values and/or tolerance values. When these values are exceeded, this is communicated to the terminal through specific signals. The 5 terminal can trigger actions accordingly, such as alerting, informing or warning the user, or correcting the measurement values, or calibrating or adjusting the measuring device. In this embodiment of the invention, the conductor resistances 10 R 1 C of the module-connection cables 250 are largely identical. This can be achieved through a suitable choice of the length, materials and conductive cross-section of the individual conductor lines in the module-connection cable 250. In this way, the values to be expected and the corresponding threshold 15 values for the voltage VLC1+, - - - rLCn+r, VLC1-, - - - VLCn- can be found through a simple calculation. In like manner, largely identical conductor resistance values RHR of the control cable 205 are achieved through a suitable choice of the leads of the control cable 205. However, a calculation of the values to be 20 expected and of the threshold values can also be performed without a problem for conductor resistances of arbitrary magnitude. In the embodiments according to the invention the communication 25 means 248 can, depending on the configuration of the multiple force-measuring device 200 and the terminal 206, automatically transmit pertinent information to the terminal 206 either continuously or periodically and/or at random or after a change has occurred. Of course it is also possible that the terminal 30 206 interrogates the communication means 248 for information such as measurement values or measurement results either - 21 continuously or periodically and/or according to the principle of randomization. The method according to the invention can be performed by means 5 of centralized and/or decentralized parts of a controller device of an installation, for example with the terminal 206 and/or the force-measuring module 244, which are for this purpose equipped with the appropriate operating programs. However, it is also possible to divide the tasks between different levels of the 10 process control. Through appropriate measures, the method according to the invention can thus be implemented on any single-level or multi-level installations at little cost. The terminal 206 and/or the junction element 256 can also be installed in a mobile instrument which can, through radio 15 connections, call for individual measurement values and/or measurement results. For the radio communication, the individual force-measuring modules 244 can be given an identification code, as is known and being practiced in state of-the-art solutions for many applications. - 22 - List of Reference Symbols 100, 200, 300 multiple force-measuring device 101 distribution line 5 102 distribution device 103 segment cable 104 segment coupler 105, 205, 305 control cable 106, 206, 306 terminal 10 107, 207, 307 display 210 force-measuring cell 220 housing 230 container foot 231 foundation 15 140, 240, 340 measuring plate 144, 244, 344 force-measuring module 246 power delivery means 248 communication means 250, 350 module-connection cable 20 352 plug connector 354 forked cable 356 junction element 170, 270, 370 power supply unit 180, 280, 380 controller device 25 C communication PS current supply or power supply - 23 -

Claims (7)

1. A force-measuring module for a force-measuring device having a terminal connected to a plurality of the force-measuring 5 modules through a plurality of connection cables, each of which has a conduit to transmit communications bi-directionally between the terminal and the force-measuring modules and a conduit to transmit power uni-directionally from a power supply to the force-measuring modules, each force-measuring module LO comprising: a housing; a first and a second plug connector, arranged on the housing, each of the plug connectors configured on the exterior of the housing for connection to one of the connection cables L5 and configured on the interior of the housing to electrically communicate the respective conduits of the connection cables; a force-measuring cell, arranged in the housing to receive force imposed on the housing; a communication means, arranged in the housing, for O receiving a measurement signal from the force-measuring cell and communicating with the terminal through the communications conduit of the connection cable; and a power delivery means, arranged in the housing, for receiving through the power conduit of the connection cables and 25 distributing the received power within the housing.

2. The module of claim 1, wherein the housing is attached to the force-measuring cell by welding such that deformation of the housing by a load results in elastic compression of both the 30 housing and the force-measuring cell. - 24 -

3. The module of claim 1 or 2, wherein the housing is tightly sealed against the ambient environment of the force-measuring device. 5

4. The module of any one of the preceding claims wherein the communication means comprises a CAN bus system interface.

5. The module of any one of the preceding claims wherein the module further comprises a device for monitoring or terminating LO a communication with the terminal.

6. The module of any one of the preceding claims wherein the module further comprises a device for monitoring one or more voltages of the power supply through one or more connection L5 cables.

7. The module of claim 6 wherein the one or more voltages of the power supply comprise (VLC1). O B. The module of claim 6 or 7 wherein the device for monitoring one or more voltages of the power supply is arranged to alter the one or more voltages of the power supply. - 25 -