DE102008021241B4 - Measured value display, in particular in the driver's cab of a rail vehicle - Google Patents

Abstract

A method for displaying a measured value of a measured variable or for displaying measured values of the measured variable, in particular in the driver's cab of a rail vehicle, wherein a first signal and a second signal are generated from the measured value and the first signal and the second signal are different or from a first Measured value of the measured variable is a first signal and from a second measured value of the measured variable, a second signal is generated, - are controlled by the first signal and the second signal independent elements (81a, 81b) of a display device (9), and- if one of the first Signal corresponding first value of the measured variable according to a predefined criterion of a second signal corresponding to the second value of the measured variable, a corresponding to the first signal analog representation of the measured value on the display device (9) completely or partially invisible, hidden and / or hidden and / / or in a faultless display ezustand corresponding analog representation of the elements (81a, 81b) is changed.

Description

The invention relates to a method for displaying a measured value of a measured variable or for displaying measured values of the measured variable, in particular in the driver's cab of a rail vehicle for a driver of the rail vehicle. The invention further relates to a display system, in particular in the cab of a rail vehicle. Rail vehicles are understood in this description also track-bound vehicles that do not drive on two rails, z. B. on-lane track-bound vehicles as they are operated on some lines of the Paris Metro.

Increasingly, screens are used in the driver's cabs of rail vehicles, e.g. LCD (Liquid Crystal Display) or TFT (Thin Film Transistor) Display. Together with input means, e.g. so-called soft keys or detectors for the detection of a touch of the screen (eg in so-called touch screens) and one or more microprocessors for data processing and control and for reading the input means of the display device, the screens form a so-called HMI (Human Machine Interface), also called MMI (Man Machine Interface). The invention particularly relates to such HMI that are installed in the cab. In this case, for reasons of redundancy and to present a multiplicity of different information, not just one HMI in the driver's cab can be arranged, but a plurality of HMIs.

The data processors of HMIs can be more or less complex. For example, the data processors or microprocessors may only bring the information transmitted to the HMI in a predefined manner for display on the screen and output the information provided by the input means to connected devices (eg via a data bus). However, the microprocessors can also perform complex test algorithms to check the data available to them. For example, it is possible for the microprocessors to use different data to check for plausibility. For example, it is from the EP 1 655 583 A2 It is known that the same measured value is transmitted in different data formats to an HMI and each value is represented by the position of a pointer segment in an analog representation. Furthermore, it is known from the document to read back the position of the pointer segments and to compare them with the measured value of at least one data format. It is now conceivable that this task is performed by the microprocessor of the HMI.

The operation of the microprocessors of the HMI is usually controlled by software. Now it is important for the operation of rail vehicles that especially safety-relevant values are displayed reliably and correctly, so that the driver can rely on the values. Furthermore, the information entered by the driver via the input means should be reliable to other devices of the rail vehicle, e.g. be transferred to a central control computer. A central computer is understood to be a computer that performs control functions of various systems of the rail vehicle. Incorrect indications can, for example, lead the driver to actions which jeopardize the safe operation of the rail vehicle, for example when the driving speed is displayed too low.

Methods have been defined which secure software in combination with certain hardware engineering measures for the operation of facilities. However, the expense associated with programming the software and designing the hardware system is high. It is also possible in the interaction of different secure systems and devices (eg an HMI and several central control computers, which are connected to one another via a data bus) that the combination causes states which do not take into account in the design of the individual devices as secure devices were.

Furthermore, the data transmission between the central computer and the HMI represents another source of error. The transmission may be disturbed or even communication routines for the control of the data transmission may be configured incorrectly. Also, the interfaces between the data transmission system and the connected devices can be configured incorrectly. It is possible that the errors only occur in special situations or only have an effect in these situations.

In the already mentioned EP 1 655 583 A2 Speed values are displayed even if they differ greatly. However, if the driver only looks at the upper area of the display and, for example, there is currently the outer pointer segment, he may not immediately recognize the deviation of the two pointer segments. Such cases can occur in particular when the driver concentrates on the route and the display is only at the edge of his field of vision. Although it is also proposed in the document that a comparator in the HMI converts the measured values present in the various formats into a third data format and checks for conformity and generates a fault message in the event of an error. For this is however, it again requires the HMI to meet stringent security requirements. In the case of using a standard HMI with standard software, which is not specially adapted to safety-critical applications, the comparison function can not be guaranteed as error-free.

It is therefore an object of the present invention to provide a method for displaying a measured value of a measured variable or for displaying measured values of the measured variable, in particular in the driver's cab of a rail vehicle, even when using display devices that are not specially adapted to high safety standards Errors in the processing and display of the measured value or the measured values can be detected quickly and reliably. Furthermore, it is an object of the present invention to provide a corresponding display system which is particularly adapted to the use in the rail vehicle.

In particular, the invention relates to display systems in which the display device satisfies less stringent safety requirements than a central computer which has the measured value or the measured values of the measured variable and transmits it to the display device.

The central computer is therefore, in particular, a computer which satisfies prescribed security requirements with regard to reliability in the reception, processing and output of information. In this case, the specified security requirements relate in particular to software of the computer. In this sense, the central computer can therefore be referred to as a "secure" computer. Due to the proposed method (see below), it is possible to use a display device that does not have the same high security requirements (in particular software) for receiving, processing, displaying information as well as detecting inputs from the driver, processing the signals and outputting corresponding signals Information is enough. The invention therefore comprises in particular an embodiment in which the display device is "not safe" in this sense. The mentioned predetermined safety requirement may in particular be the so-called "functional safety" (SIL) stage 1 or 2.

The specified safety requirements may be, for example, the "Guide to the Application of EN 50128 on Rail Vehicles" dated 31.08.2005, published by the Federal Railway Authority, PO Box 28 61, 53018 Bonn, Germany in conjunction with the European standard EN 50128.

More generally, the invention relates to arrangements with the central computer, a display device, and a communication link between the central computer and the display device, wherein the functional security level of the display device is lower than the functional security level of the central computer.

Due to the proposed solution, it is possible to relieve the display device of security requirements. This makes it easier, for. B. in terms of their operation complex HMI easier and cheaper to produce. The solution has the additional advantage that not only the functioning of the display device is checked, but also the entire arrangement of central computer, data transmission connection and display device. If the central computer therefore meets the specified security requirements, it can be assumed after successful verification that the entire arrangement also functions reliably.

An important parameter that can be reliably displayed to the driver during the operation of rail vehicles is the driving speed. The invention therefore relates in particular to the measured variable driving speed. However, the invention is also applicable to other parameters that are to be displayed in particular when operating rail vehicles.

• - aus dem Messwert ein erstes Signal und ein zweites Signal erzeugt wird und das erste Signal und das zweite Signal verschieden sind oder wobei aus einem ersten Messwert der Messgröße ein erstes Signal und aus einem zweiten Messwert der Messgröße ein zweites Signal erzeugt wird,
• - durch das erste Signal und das zweite Signal voneinander unabhängige Elemente einer Anzeigevorrichtung angesteuert werden, und
• - wenn ein dem ersten Signal entsprechender erster Wert der Messgröße gemäß einem vordefinierten Kriterium von einem dem zweiten Signal entsprechenden zweiten Wert der Messgröße abweicht, eine dem ersten Signal entsprechende analoge Darstellung des Messwertes oder der Messwerte auf der Anzeigevorrichtung ganz oder teilweise unsichtbar, verdeckt und/oder ausgeblendet wird und/oder eine einem fehlerfreien Anzeigezustand entsprechende analoge Darstellung der Elemente verändert wird.

A method for displaying a measured value of a measured variable or for displaying measured values of the measured variable, in particular in the driver's cab of a rail vehicle, is proposed

• a first signal and a second signal are generated from the measured value and the first signal and the second signal are different or wherein a first signal is generated from a first measured value of the measured variable and a second signal is generated from a second measured value of the measured variable,
• - Controlled by the first signal and the second signal independent elements of a display device, and
• if a first value of the measured variable corresponding to the first signal deviates from a second value of the measured variable corresponding to the second signal, an analog representation of the measured value or of the measured values on the display device corresponding to the first signal invisible, hidden or concealed and / or hidden and / or an analog display of the elements corresponding to a faultless display state is changed.

A signal is understood to include the information about the reading and can be received and processed by the display. In particular, the first signal and the second signal are generated by the central computer and the signals are transmitted to the display device. The signal can also have other features in addition to the information about the measured value. In principle, it is also conceivable for the signal to be an analog signal, e.g. a tension, is. However, it is preferred that the signal be transmitted over a data transmission link for transmission of digital data, e.g. via a data bus, is transmitted to the display device.

The first signal and the second signal are different. The difference may e.g. are alone in a value that corresponds to the measured value. For example, the value may differ only by its data format from the value in the other signal. Alternatively or additionally, however, the value may also have a different meaning than the value in the other signal. For example, it is possible to transmit the measured value or the measured values during the generation of the first signal and the second signal on the one hand in the usual physical units of the measured variable and on the other hand (with the other signal) already referring to the representation for displaying the measured value or the measured values in the display device, ie already converted (approximately in a degree of the angular position of an analog pointer of the display device). If we speak here of an analogue pointer or an analogue representation, this includes the case that a classical, e.g. electromechanically operating display instrument, is used for display. Preferably, however, the display is displayed on a display of a digital display device, e.g. also has a data processor for direct control of the display. Furthermore, at least one image data memory can be coupled to the display in a manner known per se, in which the image data to be displayed on the display is stored and continuously updated.

Alternatively or in addition to the differences of the two signals already mentioned, the difference or the differences may be that different channels of a signal transmission system (eg different time slots and / or frequencies and / or codings of a multiplex transmission system) and / or different transmission paths for the different Signals are used. In a packet-oriented transmission system in which data packets are transmitted, e.g. the first signal and the second signal are basically transmitted in different data packets. Preferably, a plurality of said differences between the first signal and the second signal exist simultaneously. In particular, it is preferred that the values transmitted with the various signals refer to a different scale of values as mentioned and, moreover, that the different signals are not transmitted in the same data packet.

Optionally, further security measures for the reliable transmission of the measured value to the display device are taken, which will be discussed in more detail.

In order to make the deviation of a first value of the measured variable, which is transmitted with the first signal, from the second value of the measured variable, which is transmitted with the second signal, clearly visible to the vehicle driver, the analog representation of the measured value or the measured values is displayed the display device in fulfillment of the predefined criterion completely or partially invisible, hidden and / or hidden. The term "deviation" refers to the measured variable, not to certain scales, such as. For example, the speed or degree scale of an analog pointer.

It is preferred that with increasing deviation of the first value from the second value or vice versa, the analog representation of the measured value or the measured values is increasingly less visible, is obscured to a greater extent and / or other parts of the analog representation are hidden. In this case, the predefined criterion does not necessarily constitute a fixed limit, where the deviation of the values is so great that the measures mentioned begin. Rather, the analog representation can no longer be "perfect" even with the slightest deviation, ie. e.g. no longer as good, sharp or complete, as would be the case with exactly the same values.

Preferably, a limit value for the difference between the first value and the second value is predetermined, wherein the limit value can be defined on a scale other than the speed scale. If the magnitude of the difference reaches the limit, or if the magnitude of the difference is greater than the limit, the representation of the elements driven by the first value and the second value can be completely masked out; H. the elements are not shown. Optionally, other objects of an image display on the display device can be hidden at the same time, for. B. a digital representation of the speed. The limit is z. B. 5 km / h.

In any case, however, larger deviations of the values lead to the analog representation of the measured value or measured values becoming worse in the above-mentioned sense and the driver no longer being able to recognize the representation on the edge of his field of vision so well. Therefore, if he focuses on the display on the display device, he will immediately recognize that the two values are different and there is a fault in the display system. For example, the driver then performs prescribed actions, such as switching off the display, whereby the driving speed and / or the respective other measured variable is displayed on a second display or a second display device. In this case, since a display device is less available, the overall amount of information presented to the driver can be reduced. For example, then less important information is no longer or no longer as detailed as previously presented. The representation of the measured value or the measured values on the second display device can also be carried out according to one of the embodiments of the present invention. If this representation is also faulty, it may be prescribed that the vehicle driver has to carry out further measures, since then the measurement and / or display of the measured variable must be considered to be altogether faulty. For example, it is then necessary to significantly reduce the driving speed or to stop the rail vehicle at the next opportunity.

A comparison device of the display device may be provided, which compares the first value and the second value. In this case, the comparison, eg similar to in the EP 1 655 583 A2 described after conversion of the transmitted with the first signal and the second signal to the display device values are performed in a further data format. But it is also possible to convert only one of the values for the comparison. If the comparison device determines that the predefined criterion has been met, it preferably decides that the analog representation corresponding to the first signal is completely or partially invisibly hidden and / or hidden on the display device. The comparing means may output a corresponding control signal which causes the display device or another means, as mentioned, to change the representation.

The comparison can also be carried out in particular in that an image (in particular a digital image) represented or to be displayed by the display device, which was formed using the first value and the second value, is evaluated. For example, an image area may be defined whose position and / or orientation in the image depends on the second value. For example, this image area may be defined such that the peak of an arrow headed by the first value or a defined part of another analogue display element lies in the image area when the first value and the second value match. This can be stated. If the tip or the defined part is not in the image area, it is decided that there is an error, i. E. the first value and second value are too far apart. The limit of the deviation at which this method leads to the detection of an error can be adjusted by changing the size and / or shape of the image area.

However, preferred is an embodiment that may or may not include the aforementioned comparison. In this embodiment, a second element of the display device is controlled by the second signal, which automatically covers a partially controlled by the first signal first element of the display device fulfilling the predefined criterion, without comparing the first and the second value, and / or or overrides.

Under an element of the display device, which is driven by a signal, it is understood that an object is defined, which can be visibly displayed on the display device. Depending on the driving signal, the shape, orientation, position and / or size of the object, i. of the element, on the display device changes. Preferably, the shape and size of the object is fixed and the element would be driven by the associated signal only in such a way that the signal controls the position and / or orientation on the visible area of the display device. The subjunctive "would" has been used because it is different from the other element, i. can depend indirectly on the other signal, whether the first element is actually displayed in full size and unchanged. On embodiments will be discussed in more detail. In summary, therefore, it should be noted that in this embodiment, each signal drives one element of the display device, wherein in the control of the respective element, the respective other signal has no influence. As a result, the display device can be designed in a simple manner and, in particular in the case of an HMI, can be controlled by relatively uncomplicated software. Therefore, a standard display device can be used, which is not specifically adapted for use in rail vehicles and / or does not meet specific safety requirements for use in rail vehicles.

Because the two elements that are driven separately from the two signals, but can interact with each other, wherein the interaction is dependent on the design of the display device, it may nevertheless occur upon fulfillment of the predefined criterion that at least parts of the elements are not shown, hide each other and / or hidden. This can be done automatically, without the need for special logic or software. However, in some embodiments, a simple logic is used, which relates in particular to the writing of the image data storage, which are constantly updated and read.

In a first embodiment, a first display object visible to a viewer of the display device, whose position and orientation on the display device are controlled by the first signal, and a second display object visible to the viewer of the display device, whose position and orientation on the display device form the second Signal is controlled, together a display of the measured variable. The display is recognizable to the viewer as a unit if the first value and the second value do not differ. On the other hand, if the values deviate from one another, at least partial areas of the first display object and / or of the second display object no longer form a unit or are no longer recognizable as partial areas of the first display object and / or of the second display object. Embodiments will be discussed in the description of the figures.

In particular, in this embodiment, the first representation object can have at least one gap which is completely closed by a partial area of the second representation object if the first value and the second value of the measured variable do not differ from one another. However, if the first and second values deviate from one another, the gap is not or not completely closed by the subarea of the second presentation object. The driver therefore recognizes the error based on the at least one gap.

In a further embodiment, a second element controlled by the second signal has a higher priority with respect to the display on the display device than a first element controlled by the first signal, such that at locations in a visible display area of the display device at which pixels according to the first signal of the first element and at which, according to the second signal, pixels of the second element are to be displayed, only the pixels of the second element are displayed. For example, For example, these second pixels may be displayed in the color of the background of the display area, so that, as a result, nothing appears at the location.

Embodiments will also be discussed in the description of the figures.

The display device may comprise an image data memory in a manner known per se. A memory content of the image data memory is read out and defines a current overall image on the display device. In this case, the overall image may be an image that can only be displayed in a partial region of the display device. For example, a plurality of image data memories may be provided for different subregions of the display device. The overall picture is therefore understood to mean that information from the first and second signals is taken into account. The first signal and the second signal respectively control the writing of the image data in the image data memory.

It is now proposed that, under the control of the second signal, image data written by the first signal be overwritten so that an element of the display device controlled by the first signal is at least partially overwritten if the first value and the second value of the measured variable differ from each other. Preferably, an increasingly larger part of the image data written by the first signal is overwritten by the second signal, the more the first value and the second value of the measured variable deviate from one another.

In a further refinement, the first element controlled by the first signal and the second element controlled by the second signal are logically linked together prior to writing or writing the image data, so that image data respectively correspond to a specific location in a visible display region of the display device be written or not written depending on the first signal as well as depending on the second signal. For example, For example, the logical link may be a "and" link such that e.g. for a given location in the display area, image data is written only if both a portion of the first element and a portion of the second element are located at the location. When referring to elements in this description, they need not be objects that, when displayed on the display device, cover a contiguous area. Rather, an element is also understood to mean an arrangement of a plurality of surfaces or partial surfaces.

However, the logical link can also be a different link.

As it is already for the mentioned application, namely the representation of Measured values, the values transmitted with the first signal and the second signal are usually time-dependent. Therefore, it is common to repeatedly transmit signals to the display device and repeatedly, ie repeatedly, to update the display. In particular, the first signal and / or the second signal is repeatedly transmitted from the central computer via a data transmission connection to the display device, wherein the first signal and / or the second signal each contain an updated measured value of the measured variable.

According to one embodiment, a time signal is transmitted jointly from the central computer to the display device with the first and / or the second signal. In particular, a time value can also be transmitted in a data packet with which the first value is transmitted. The same applies alternatively or additionally for the second signal. The time signal results in a repeatedly updated display of a third element of the display device for displaying the time on the display device. For example, For example, a colon that spatially separates the digitally displayed hours and the digitally displayed minutes, or other elements of the clock display, may be faded in and out rhythmically (eg, every second) while continuously timing signals together with the first signal and / or in common with the first received second signal from the display device and / or processed. If, on the other hand, no time signal is received once or alternatively several times or the same time value is received several times in succession, the third element is either no longer or permanently displayed in the same way on the display device. In the example of the colon, colon is either no longer displayed or it is no longer hidden rhythmically, but permanently displayed. More generally, the third element is no longer or permanently displayed when no new time signals are received from the display device via the data transmission connection and / or when no new time signals are being processed by the display device. In this case, this condition also includes the case that only a part of the expected time signals is not received and / or not processed and / or the same time value is successively received and / or processed in succession. If there is an error in the signal transmission, e.g. in that a data packet having the same content (i.e., the same measured value of the measured value and the same time value) is repeatedly transmitted to the display device but no corresponding updated values are transmitted, this is noticed and presented to the driver by the mentioned change in the time of day display.

The joint transmission of the time signals and measured values therefore increases the security of the representation.

• - zumindest einen zentralen Rechner des Schienenfahrzeugs, der ausgestaltet ist, den Betrieb des Schienenfahrzeugs zu steuern,
• - eine Anzeigevorrichtung für einen Führerstand des Schienenfahrzeugs, die über eine Datenübertragungsverbindung mit dem zentralen Rechner verbunden ist,

wobei der zentrale Rechner ausgestaltet ist, aus dem Messwert ein erstes Signal und ein zweites Signal zu erzeugen oder aus einem ersten Messwert der Messgröße ein erstes Signal und aus einem zweiten Messwert der Messgröße ein zweites Signal zu erzeugen, wobei das erste Signal und das zweite Signal verschieden sind, wobei die Anzeigevorrichtung so ausgestaltet ist, dass durch das erste Signal und das zweite Signal voneinander unabhängige Elemente der Anzeigevorrichtung angesteuert werden, und wobei die Anzeigevorrichtung so ausgestaltet ist, dass eine dem ersten Signal entsprechende analoge Darstellung des Messwertes oder der Messwerte auf der Anzeigevorrichtung ganz oder teilweise unsichtbar, verdeckt und/oder ausgeblendet wird, wenn ein dem ersten Signal entsprechender erster Wert der Messgröße gemäß einem vordefinierten Kriterium von einem dem zweiten Signal entsprechenden zweiten Wert der Messgröße abweicht.The invention further relates to a display system of a rail vehicle, the system comprising:

• at least one central computer of the rail vehicle, which is designed to control the operation of the rail vehicle,
• a display device for a driver's cab of the rail vehicle, which is connected to the central computer via a data transmission connection,

wherein the central computer is configured to generate a first signal and a second signal from the measured value or to generate a first signal from a first measured value of the measured variable and a second signal from a second measured value of the measured variable, wherein the first signal and the second signal are different, wherein the display device is configured such that are controlled by the first signal and the second signal independent elements of the display device, and wherein the display device is configured such that a corresponding to the first signal analog representation of the measured value or the measured values on the Display device completely or partially invisible, hidden and / or hidden when a first signal corresponding to the first signal value according to a predefined criterion of a second signal corresponding to the second value of the measured variable deviates.

With regard to the description of embodiments of the display system, reference is made to the description of the method.

In the following important features and individual embodiments of the invention will be briefly highlighted or explained in more detail.

As mentioned, the measured variable is, in particular, the travel speed of a rail vehicle. The speed is e.g. calculated by evaluation of a pulse generator on a wheel of the rail vehicle from a computer. If the measuring signal of the sensor is not available, the speed may be e.g. be determined from the control of the drive system of the rail vehicle.

A central computer displays the measured value or the measured values recognizably on a display device for the driver. If the display device fails or an error of the display device is detected, the measured value or the measured values are displayed on a second display device.

Although the value to be displayed is preferably transmitted from the central computer via the same data transmission connection, e.g. Ethernet data bus with IP, transmitted to the display device. As mentioned, the measured value can be transmitted in at least two different data formats. It is also possible to transmit different measured values of the same measured variable in different data formats to the display device. Various data formats may e.g. be realized in that the value to be transmitted is present in a first format in the central computer and the value is converted into a different value for at least one of the two data formats used for the transmission and only then transmitted in this converted format. For example, For example, a speed value in a first transmission format could be immediately followed by a speed scale e.g. in units of km / h and in a second data format are already converted prior to transmission from the central computer to the display device in units corresponding to the display mode on a display of the display device (e.g., the angular position of a pointer to indicate the measured value). However, the conversion of the value to be displayed prior to transmission from the central computer to the display device may also be e.g. be made from binary number format to a hexadecimal number format. Alternatively or in addition to the conversion of the value to be displayed but also different methods of actual data transmission between the central computer and the display device can be applied. Thus, e.g. the value is transmitted in accordance with different protocols, protocol layers and / or according to different protocol options that use a different representation of the payload to be transmitted via the same data transmission connection

In a preferred embodiment, the first value drives a pointer on the display device. However, the second value drives an opaque area covering the pointer or the area overlying the pointer if the pointer does not coincide with the orientation of the recess. For example, the covering surface has a slot in which the pointer is recognizable when the first and second values match. In this case, not only in the case of the slot, a tolerance between the first and the second value may be possible, which even with differences between the two values still allows detection of the pointer in the recess or at least partial detection of the pointer in the recess. Depending on the width of the slot, the pointer within the tolerance u. U. still be fully recognized. In prior art solutions, however, in which z. If, for example, each of the signals has its own pointer elements or its own pointer, you will see an offset of the pointer segments or two pointers even with small deviations. The previously known solutions have no tolerance.

Preferably, the display device is configured such that, when a predetermined limit of the difference between the first value and the second value is exceeded, none of the values recognizable to the vehicle driver is displayed on the display device or one of the values is no longer recognizable to the vehicle driver in the illustration which is recognizable if the values agree. Alternatively, the representation of the two values or the representation of one of the values can become increasingly less recognizable as the difference between the values increases. For example, In the embodiment with the covering surface and the recess of the pointer, which represents the first value, can be increasingly covered by the covering surface.

In another embodiment, the display device may have a comparison device and compare the values to be displayed in the two different data formats. If the difference of the two values exceeds a predetermined limit value, the display device adjusts the representation of at least one of the two values, preferably of both values. Although the comparison device of the display device does not have to comply with high safety standards, the overall system of display device, data transmission line and central computer can nevertheless fulfill required safety standards, since the non-representation of at least one of the values to be displayed is the result of incorrect operation of the comparison device. Although it may happen that there is actually no error in the transmission of the values and for the driver nevertheless an error is recognizable. However, this then leads to the detection of the error of the comparator or the display device.

The transmission of the signals from the central computer to the display device is preferably secured by checksums against corruption of the transmitted data. Alternatively or additionally, each of the transmission signals is preferably provided with a sender identification that is unique for the central computer so that the signals can be unambiguously recognized by the display device as being sent by the central computer.

• 1 ein Beispiel für ein Steuerungs- und Anzeigesystem,
• 2 die für den Fahrzeugführer sichtbaren Teile eines HMI mit Anzeigeflächen und Eingabemitteln,
• 3 eine analoge Darstellung eines Messwertes auf einer Anzeigevorrichtung, wobei der Messwert auf verschiedene Weise zu der Anzeigevorrichtung übertragen wurde und dabei oder bei der Verarbeitung der empfangenen Werte durch die Anzeigevorrichtung Unterschiede entstanden sind, die durch die Darstellung erkennbar sind, und/oder wobei ein erster Messwert der Messgröße und ein zweiter Messwert der Messgröße z. B. von verschiedenen Messwertgeber erzeugt wurden und deshalb Unterschiede in den Messwerten bestehen,
• 4 zwei Elemente, die von separaten Signalen angesteuert werden und einander teilweise überlappen,
• 5 ein Element, das von einem Signal angesteuert wird und in der Art eines Schachbretts aus verschiedenen Teilflächen besteht, die über Eck aneinander angrenzen,
• 6 das in 5 dargestellte Element. Ein zweites, komplementäres Element, wobei die beiden Elemente unterschiedlich ausgerichtet sind und um einen Winkel von 4° gegeneinander verdreht sind,
• 7 die Elemente gemäß 6, die doch um einen Winkel von ca. 20° gegeneinander verdreht sind,
• 8 eine Darstellung mit einem ersten, zeigerartigen Element und einem zweiten Element, das einen ausgesparten Bereich aufweist, in dem sich der Zeiger befindet,
• 9 eine Darstellung der Elemente gemäß 8, wobei jedoch das zweite Element gegen die Längsachse des Zeigers verdreht ausgerichtet ist und daher einen Teil des Zeigers verdeckt,
• 10 die Darstellung eines Datenformates zur Übertragung von Signalen zwischen einem zentralen Rechner und einer Anzeigevorrichtung,
• 11 ein Anzeigesystem mit einem zentralen Rechner und einer Anzeigevorrichtung und
• 12 eine Darstellung einer speziellen Ausgestaltung eines Details der Anzeigevorrichtung gemäß 11.

Embodiments of the invention will now be with reference to the accompanying drawings described. The individual figures of the drawing show:

• 1 an example of a control and display system,
• 2 the parts of an HMI visible to the driver, with display areas and input means,
• 3 an analog representation of a measured value on a display device, wherein the measured value has been transmitted to the display device in different ways and thereby or during the processing of the received values by the display device differences have arisen, which are recognizable by the representation, and / or wherein a first measured value the measured variable and a second measured value of the measured variable z. B. were generated by different sensors and therefore differences in the measured values,
• 4 two elements which are driven by separate signals and partly overlap each other,
• 5 an element that is controlled by a signal and in the manner of a chess board consists of different sub-surfaces which adjoin one another at a corner,
• 6 this in 5 represented element. A second, complementary element, wherein the two elements are oriented differently and are rotated by an angle of 4 ° to each other,
• 7 the elements according to 6 , which are twisted by an angle of about 20 °,
• 8th a representation with a first, pointer-like element and a second element having a recessed area in which the pointer is located,
• 9 a representation of the elements according to 8th but wherein the second element is oriented twisted against the longitudinal axis of the pointer and therefore covers a part of the pointer,
• 10 the representation of a data format for the transmission of signals between a central computer and a display device,
• 11 a display system with a central computer and a display device and
• 12 an illustration of a specific embodiment of a detail of the display device according to 11 ,

1 shows an embodiment of an arrangement in a rail vehicle. A signal source 1 is via a data transfer connection 2 with a first computer 3 connected. At the signal source 1 it may, for example, be a speed sensor for measuring the traveling speed of the rail vehicle. However, these may also be a plurality of transducers and / or a transducers of another type. Via the data transmission line 2 or a plurality of such lines, the measurement signals to a first computer 3 transmitted. Instead, measured values from different sensors can be transmitted to different computers. The following applies analogously.

The first computer 3 is via a data transmission line, in particular a first data bus 4 , which may be a MVB of the rail vehicle, for example, with a second computer, the central computer 5 , connected. The first computer 3 transmits the determined from the measurement signals driving speed continuously updated via the data transmission line to the central computer 5 ,

The second computer 5 is over another data transfer connection 7 with a display device 9 connected. In the exemplary embodiment, the data transmission connection 7 an Ethernet data bus, the data being transmitted in accordance with the Internet Protocol. Part of the data bus system is also the in 1 illustrated switch 8th which is still connected to other transmission lines of the data bus 7 can be connected.

In the exemplary embodiment, the second computer transmits 5 over the data bus 7 first and second signals to the display device 9 with which the information about first and second values representing the same value of the vehicle speed, to the display device 9 be transmitted.

In 2 represents the rectangular frame 91 schematically the outlines of the display device 9 Visible areas of the display device are visible to the driver 9 , Inside a rectangular frame 22 Information can be presented to the driver. This area 22 can be eg an LCD display.

For example, in the subareas 24 . 25 Symbols, numbers, numbers, bar graphs etc. are displayed. In the left part of the display area you can see a pitch circle, which is open at the bottom and serves to display speed values in a representation that is a classic tachometer representation 23 like.

Outside the viewport 22 are located on three sides, namely top, right and bottom, input means, eg so-called soft keys. For example, the ten below the range 22 Input means shown can be the digits "1" to "9" and Correspond to "0". As an example, the leftmost input means 21 the number "1". The right of the area 22 and above the range 22 arranged input means may for example be functional means for immediate triggering of functions to be performed.

The display device 9 may be an HMI (Human Machine Interface), which has at least one interface for connection to a data transmission line and a processor for processing the data in addition to the visible elements for the driver and components. Optionally, a data memory may also be provided.

3 shows two pointers 31a . 31b an analog speed display, eg a display of the tachometer display 23 according to 2 , Depending on the current speed value, the pointers will become 31 shown with different orientations on the display, with its end facing away from the arrowhead is always aligned with a center located in the center of the circle 33 located. The two pointers 31a . 31b therefore represent different speed values. This indicates in the present case, an error in the display system, since it is expected that the pointers are almost exactly on top of each other. Each of the pointers 31 is controlled independently of the other pointer by a signal which in each case contains a measured value of the same measured variable, in this case the travel speed of the rail vehicle.

In another than the one in 3 shown state of the display, in which the two pointers include a greater angle to each other, both hands are hidden, that is no longer shown, and will also be in the circle 33 digitally displayed speed value also no longer shown. For example, a comparator of the display device determines that the two pointers enclose an angle α between them that is greater than a predetermined threshold. Thus, a predetermined criterion is met and the pointers are no longer displayed.

The representation in 3 is merely an illustration of an example. In practice, the limit would be chosen so that already at the in 3 illustrated deviation of the orientation of the hands 31 no pointers are displayed anymore.

A variant of the pointer representation is in 4 shown. The pointers are elongated rectangles in this example 41a . 41b , where the in 4 shown outlines of the rectangles in practice can not be displayed. In any case, however, the area is shown on the visible display area of the display device in which the two pointers 41a . 41b overlap. This area is in 4 with the reference number 43 and is in the shape of an equilateral triangle. Would the two pointers 41a . 41b completely overlap, ie superimposed, the overlapping surface would therefore be rectangular and would have the shape of the pointer 41 ,

4 1 illustrates an embodiment in which a first element, which is controlled by a first signal, and a second element, which is driven by a second signal, are represented as a continuous area only in their overlapping area. This is achieved, for example, by the fact that the two signals "or" are combined when the image data memory of the display device is written. Alternatively, in a first step, the area of the first pointer could 41a however, in a second step, the written data is modified so that only the overlapping area of the pointers is written 41a . 41 b is written. Optionally, as in 4 represented, in each case the outline of both hands 41 written, ie presented. When the outlines are displayed thinly, the driver can see how far the pointers are 41 assigned values of the measured variable differ and still at the overlap area 43 Immediately recognize that there is an error.

4 is merely an example. Other forms of elements may be substituted for those in the art 4 illustrated elements 41a . 41b be used for the display. Also in this case, preferably only the overlapping area is displayed.

An embodiment which manages without logical linking of the first signal and the second signal or without logical association of the elements according to their position and orientation is shown in FIG 5 to 7 shown. 5 shows a first element 51a , whose position and orientation is controlled by a first signal. The element 51a has a checkerboard pattern of faces 52 , which are actually displayed on the display device and, for example, correspond to the black fields of a chess board, and transparent or in an inconspicuous, preferably corresponding to the background color faces 53 , which correspond eg to the white fields of a chessboard. Here is the element 51a preferably elongated, ie it does not have the same number of rows and columns unlike the chessboard. Variants of in 5 shown arrangement of partial surfaces are possible in which the individual sub-areas are not square, not adjacent to each other edge and / or have a different shape and / or arrangement.

However, there is preferably a second element complementary to the first element, which is driven by the second, other signal, so that the two elements form an overall image in the desired shape, eg pointer shape, when combined with the first signal and the second signal the display device supplied values and processed correctly. A match is understood to correspond to exactly the same measured value of the measurand and have been calculated correctly. Since the values are calculated, for example, with respect to different value scales, the number representations of the values or other representations of the values may differ significantly from one another, although they represent exactly the same measured value.

6 shows a representation of the first element 51a according to 5 and a complementary second element 51b that do not completely complement each other to the desired overall object, since the values transmitted with the two signals differ. However, the difference is still relatively small, so the elements 51a . 51b only enclose an angle α of about 4 ° between their longitudinal axes. The course of the longitudinal axes is indicated by upward-pointing arrows.

7 shows a state in which the tolerated with the two signals and / or the calculated therefrom by the display device orientations differ by a larger amount. The angle between the longitudinal axes is 24 °. Because of the checkerboard pattern, therefore, no clear orientation of the resulting overall image is more recognizable, so that the driver recognizes the error immediately.

The example of 5 to 7 shows how without comparison of the measured value supplied to the first signal and the second signal of the display device, the analog representation corresponding to the error-free display state (in the exemplary embodiment an elongated rectangle) is automatically changed if the elements controlled by the signals are not present same location are positioned and not aligned the same. In general terms, this can be achieved by using elements which, as described above, have complementary arrangements of partial surfaces which complement one another in the faultless display state. This overall image is preferably designed to allow an easily recognizable analogue display. For example, the overall image may be a pointer representation. In the embodiment of 5 to 7 In addition, for example, an arrowhead could be formed by the elements, for example, in turn, a part of the arrowhead is formed by the one element and the other part of the arrowhead of the other element.

The change in the analog representation of the elements, which corresponds to the error-free display state, thus consists in particular in the fact that the two elements complement each other in a non-fault-free state to a different overall image, which preferably has gaps which are not present in the fault-free display state.

8th shows a preferred embodiment in which a first element 81a is driven by the first signal and represents the actual analog display. In the embodiment, this element 81a an arrow. The second element 81b is a continuous surface 82 with a recess 83 , which is formed in the embodiment as a slot. The continuous area is in 8th plotted to make them recognizable. In practical embodiments, this continuous surface may indeed be visible. However, it is preferred that this continuous surface is not or at most slightly visible to the first element 81a easy to recognize.

The continuous area 81 However, b is configured or the display device is designed such that the continuous surface 81 b areas of the first element 81a covers or deletes that would be displayed in the same location of the ad if they were not covered or deleted.

9 shows a display state in which the second element 81b opposite to the state in 8th is shown rotated by an angle of about 10 °. Therefore, the continuous surface obscures 82 Parts of the tip of the pointer, ie the radially outer end of the first element 81a , In 9 is the continuous area 82 not shown in a checkered pattern. Only the outlines of the surface are shown. In practice, the contours of the continuous surface and the edges of the recess 83 be invisible. In this case, one only recognizes on the display device that parts of the first element are invisible. Is the continuous area 82 Still recognizable, the viewer takes this as a cover of parts of the first element 81a true.

In practice, the recess is preferably designed such that, even with minor deviations of the orientation of the elements, it leads to a covering of the first element or makes parts of the first element invisible. For example, the slot is narrower than in 8th and 9 shown executed.

At the radially outermost end of the slot 83 is in 9 an area 85 represented, which is preferably not visible in the visible display. This area will depend on the orientation of the second element 81 b is positioned and / or becomes dependent on the position and / or orientation of the second element 81b determined. In the error-free display state, this area is at the end of the first element 81a , On the other hand, they soften the elements 81a . 81b corresponding values of the measured variable from each other (as in 9 represented) no area of the first element 81a within the range 85 ,

It is therefore proposed that it be determined whether an area of the first element in the surveillance area 85 lies. This proposal does not just apply to the here specifically by means of 9 described embodiment. Rather, the concept of the monitoring area can also be applied to other designs of a first element, with the first element displaying a measured value received with a first signal.

If this is not the case, optionally an error signal can be generated by the display device and output. For example, The central computer, which outputs the signals for driving the elements to the display device, receives the error signal. The central computer recognizes that the display on the display device is faulty and can take appropriate action, e.g. generate an entry in an error data memory, output a message to a diagnostic device and / or switch off the display device, and e.g. Switch the representation of the measured values of the measured variable to another display device.

Detecting if a subset of the first element 81a in the surveillance area 85 can be realized, for example, that the first element 81a a color is associated with the representation on the display device and this color for the first element 81a in any case in all sorts of places where the surveillance area 85 can be unique. Will in the surveillance area 85 If a display object with this color is detected, the operation is error-free. Otherwise there is an error.

If in the preceding paragraphs of the surveillance area 85 and the first element 81a or the second element 81b This is also applicable to other forms, in particular other forms of elements and surveillance.

10 shows a data packet that is transmitted for example via a data bus between the central computer and the display device, for example via the data transmission connection 7 according to 1 , The data package 100 corresponds to the first signal or the second signal for transmission of a single value of the measured variable.

The data package 100 is designed in a manner known per se. For example, it contains a data header 101 including the destination address of the display device. In a second data field 102 of the data packet 100 For example, the value of the measurand to be transferred is included. In a third data field 103 For example, a time value is included which, for example, corresponds in the manner of a time stamp to the time or system time to which the data packet belongs 100 was sent from the central computer.

Preferably, the display device is configured such that it represents the time updated each time until no more recent time stamps are received in the data packets received by the display device more than previously. In this case, a tolerance time can be defined. If no time stamp corresponding to a later time is received within the tolerance time since the last time a new time stamp was received, the clock display continues. Only after the tolerance time has passed must data packets with newer time stamps be received. Otherwise, the clock will be changed so that it becomes recognizable to the driver.

In further data fields, eg the data field 105 of the data packet 100 , a checksum of the data packet or parts of the data packet may be included to verify the data packet 100 to be able to detect change during transmission.

11 shows a central computer 118 , for example, the calculator 8th according to 1 can be. By two arrows pointing to the right 119 . 120 the transmission of the two different signals that transmit values of the measured variable is indicated. The arrows 119 . 120 ends within the display device 129 at a data processing device 130 , The arrows 119 . 120 cross a block 132 , which indicates that the display device 129 a receiving unit 132 can receive, which receives the signals and, for example, extracts the transmitted values of the measured variable with the signals. The receiving unit can take on additional tasks, such as evaluate the mentioned checksum. As a result, the data processing device is located 130 the values transmitted with the signals.

In a simple embodiment, the data processing device arranges 130 the values, depending on whether they were received with a signal of the first type ("first signal") or a signal of the second type ("second signal"), a first element or a second element on the visible display surface the display device can be displayed. After allocation, the device determines 130 from the value, for example, the position and orientation of the associated element and writes corresponding data in an image data memory 134 the display device. As not shown in detail, this image data memory 134 read out regularly and so the image is updated on the visible display area. It may also be provided, for example, two image data storage, which are written alternately. In each case, then the memory that is currently not written, read out and the display image updated accordingly.

For example, in a first step, when the process of writing the image data memory 134 begins, first written the background of the display. For example, the background consists of an area of light color and dark picture objects, such as the one in 2 shown graduated circle, scaling bars and the like picture objects, which are repeatedly displayed in the same way.

In a second step of the description, the data processing device then processes 130 the image data corresponding to the first element is written. In this case, the current time state of the first signal or of the first element is taken into account, which corresponds to the last received first value. If the image data memory were read out in this state, only the background and the first element would be recognizable.

In a following step, the second element is written in a corresponding manner, taking into account the current information about the second value received with the second signal. Depending on the design of the display device, already written data corresponding to the first element can be deleted, overwritten and / or linked with data of the second element. This refers in each case to a spatially resolved data structure in the image data memory. In other words, for each location of the image area to be displayed, image data is described in the manner described above.

Is the second element eg as based on 8th and 9 As described above, at a location where the second element covers the first element, the already written image values of the first element are overwritten, for example, by the corresponding image values (eg background color) of the second element. After writing the second element, still further picture elements can be written over the second element, e.g. B. an alphanumeric representation of the measured variable.

12 shows a variant of the embodiment according to 11 in which the data processing device 130 includes " and " logic 138 by which when writing the image data memory 134 data to be written is generated by "and" linking the image values resulting from the first element and the second element. For example, an image value is only written to a location of the image area if both an image value of the first element and an image value of the second element for that location are defined, which is different from the background color. With this configuration, for example, the representations can be achieved, based on 4 have been described.

In particular, different colors may be assigned as image values to the first element on the one hand and to the second element on the other hand. In the case of the example of 3 This leads to the fact that, for example, the lighter color and thus the brighter element are not recognizable when the elements 31 completely and congruently on top of each other. For example, the second element may be displayed in a distinctive color, such as orange or red, and the first element may be displayed in black. In the fault-free case, therefore, one recognizes only the black first element on the display device. In case of error, however, the second element appears in orange or red color recognizable.

Claims (22)

Method for displaying a measured value of a measured variable or for displaying measured values of the measured variable, in particular in the driver's cab of a rail vehicle, wherein a first signal and a second signal are generated from the measured value and the first signal and the second signal are different or wherein a first signal is generated from a first measured value of the measured variable and a second signal is generated from a second measured value of the measured variable, - Controlled by the first signal and the second signal independent elements (81a, 81b) of a display device (9), and if a first value of the measured variable corresponding to the first signal differs from a second value of the measured variable corresponding to the second signal, an analog representation of the measured value on the display device (9) corresponding to the first signal is completely or partially invisible, concealed and / or or is hidden and / or in an error-free display state corresponding analog representation of the elements (81a, 81b) is changed. Method according to the preceding claim, wherein a comparator of the display device (9) compares the first value and the second value and checks whether the predefined criterion is met, and it is decided upon fulfillment of the predefined criterion that the analog representation corresponding to the first signal is completely or partially invisible, hidden and / or hidden on the display device (9) and / or in an error-free display state corresponding analog representation of the elements (81a, 81b) is changed. Method according to Claim 1 , wherein by the second signal, a second element (81b) of the display device is driven, the one controlled by the first signal first element (81a) of the display device (9) on fulfillment of the predefined criterion automatically, without comparing the first and the second value completely or partially covers, erases and / or overwrites and / or alters the analog representation of the elements (81a, 81b) corresponding to the error-free display state. Method according to one of the preceding claims, wherein a first display object (51a) which is visible to a viewer of the display device (9), whose position and orientation on the display device is controlled by the first signal, and a second display device visible to the viewer of the display device (9) Display object (51b), whose position and orientation on the display device is controlled by the second signal, together form an indication of the measured value or of the measured values, which is recognizably a unit for the viewer, if the first value and the second value do not differ from one another, and in the case of a deviation of the first value from the second value or vice versa, at least partial areas of the first display object (51a) and / or of the second display object (51b) no longer form a unit or partial areas of the first display object (81a) and / or the second display object are no longer recognizable. Method according to the preceding claim, wherein the first display object (51a) has at least one gap which is completely closed by a partial surface of the second display object (51b) if the first value and the second value of the measured variable do not differ, but not is completely closed by the partial area of the second display object (51b) when the first value and the second value deviate from each other. Method according to one of the preceding claims, wherein a second element (81b) controlled by the second signal has a higher priority with respect to the display on the display device (9) than a first element (81a) controlled by the first signal, such that at locations in one visible display area of the display device, where according to the first signal pixels of the first element (81a) and at which according to the second signal pixels of the second element (81b) are to be displayed, only the pixels of the second element (81b) are displayed. Method according to one of the preceding claims, image data being written to an image data memory of the display device (9) both under control of the first signal and under control of the second signal, a resulting memory content of the image data memory subsequently being read out and an instantaneous overall image being displayed on the display device (9). 9). A method according to the preceding claim, wherein under the control of the second signal, image data written by the first signal is written over so that an element of the display device (9) driven by the first signal is at least partially overwritten if the first value and the second one Value of the measured variable differ from each other. Method according to Claim 7 or 8th wherein the first element driven by the first signal and the second element driven by the second signal are logically linked together prior to writing or writing the image data such that image data each corresponding to a particular location in a visible display region of the display device both become dependent are written or not written by the first signal as well as by the second signal. Method according to one of the preceding claims, wherein the first signal and / or the second signal are repeatedly transmitted from a central computer (5) via a data transmission connection (7) to the display device (9), wherein the first signal and / or the second signal each contain an updated measurement of the measurand. Method according to the preceding claim, wherein a time signal is repeatedly transmitted together with the first and / or together with the second signal from the central computer (5) to the display device (9), wherein the time signal in a repeatedly updated display of a third element of Display device (9) for displaying the time on the display device (9) results and wherein the third element is either no longer or permanently displayed in the same manner on the display device when the display device (9) via the data transmission connection (7) no new Time signals more are received and / or if no new time signals are processed by the display device (9). A display system (5, 7, 9) of a rail vehicle, the system (5, 7, 9) comprising: at least one central computer (5) of the rail vehicle, which is designed to control the operation of the rail vehicle, - A display device (9) for a driver's cab of the rail vehicle, which is connected via a data transmission connection (7) to the central computer (5), wherein the central computer (5) or the central computer is / are configured, from the measured value a first To generate signal and a second signal or to generate a first signal from a first measured value of the measured variable and a second signal from a second measured value of the measured variable, wherein the first signal and the second signal are different, wherein the display device (9) is configured in that independent elements (81a, 81b) of the display device (9) are actuated by the first signal and the second signal, and wherein the display device is configured such that an analog representation of the measured value or the measured values on the Display device (9) completely or partially invisible, hidden and / or hidden and / or in a feh Lerfreien display state corresponding analog representation of the elements (81a, 81b) is changed when a first signal corresponding to the first signal value according to a predefined criterion of a second signal corresponding to the second value of the measured variable deviates. System after Claim 12 in that the display device (9) has a comparison device which compares the first value and the second value and checks whether the predefined criterion is satisfied, and wherein the comparison device decides, upon fulfillment of the predefined criterion, that the analog representation corresponding to the first signal the display device (9) completely or partially invisible, hidden and / or hidden. System after Claim 12 , wherein the display device (9) is designed such that by the second signal, a second element (81b) of the display device is controlled, the one controlled by the first signal first element (81a) of the display device (9) automatically upon fulfillment of the predefined criterion completely or partially covers, deletes and / or overrides and / or changes the analog representation of the elements (81a, 81b) corresponding to the error-free display state without comparison of the first and the second value. System according to one of the preceding claims, wherein the display device (9) is configured such that a first display object (51a) visible to a viewer of the display device (9), whose position and orientation on the display device is controlled by the first signal, and second display object (51b) visible to the viewer of the display device (9b), whose position and orientation on the display device is controlled by the second signal, together form an indication of the measurement or measurements which is recognizable to the viewer as a unit first value and the second value do not differ from each other, and that at a deviation of the first value from the second value or vice versa, at least partial areas of the first display object (51a) and / or the second display object (51b) no longer form a unit or partial areas of the first Presentation object (51a) and / or the second representation (51b) are no longer recognizable. A system according to the preceding claim, wherein the display device (9) is configured such that the first display object (51a) has at least one gap completely closed by a partial surface of the second display object (51b) when the first value and the second value of the measured quantity do not deviate from each other, and that of the partial area of the second display object (51b) is not completely closed when the first value and the second value deviate from each other. System according to one of the preceding claims, wherein the display device (9) is designed so that a second element (81b) controlled by the second signal has a higher priority with respect to the display on the display device (9) than a first element controlled by the first signal (81a) has such that at locations in a visible display area of the display device at which pixels of the first element (81a) and pixels of the second element (81b) are to be displayed according to the first signal, only the pixels of the display device second element (81b). A system according to any one of the preceding claims, wherein the display device (9) comprises an image data memory in which image data is written both under control of the first signal and under control of the second signal, subsequently reading out a resultant memory content of the image data memory and an instantaneous overall image the display device (9) defined. A system according to the preceding claim, wherein the display device (9) is configured such that image data is controlled by the second signal be overwritten, which were written controlled by the first signal, so that an element (81a) driven by the first signal of the display device (9) is at least partially overwritten when the first value and the second value of the measured variable differ from each other. System after Claim 18 or 19 wherein the first element driven by the first signal and the second element driven by the second signal are logically linked together prior to writing or writing the image data such that image data each corresponding to a particular location in a visible display region of the display device both become dependent are written or not written by the first signal as well as by the second signal. System according to one of the preceding claims, wherein the system is configured such that the first signal and / or the second signal are repeatedly transmitted from a central computer (5) via a data transmission connection (7) to the display device (9), the first Signal and / or the second signal each contain an updated measurement of the measured variable. System according to the preceding claim, wherein the system is designed so that a time signal is repeatedly transmitted together with the first and / or together with the second signal from the central computer (5) to the display device (9), wherein the time signal in a repeatedly updated display of a third element of the display device (9) results in the display of the time on the display device (9) and wherein the third element is either no longer or permanently displayed in the same manner on the display device when from the display device (9) via the data transmission connection (7) no longer receive new time signals and / or if no new time signals are processed by the display device (9).

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