DE102022107106A1 - Method for operating a field measuring device for process measurement technology with an analogue power interface and a similar field measuring device - Google Patents

Abstract

A method (1) for operating a field measuring device (2) for process measurement technology is shown and described, wherein the field measuring device (2) has a measuring device (3) for determining a measured value (y) and an analog current interface (4) for transmitting the measured value (y ) to a communication partner (5), wherein in the error-free measurement state (x_m), the determined measured value (y) is transmitted by setting an interface current (i (y)) of the current interface (4) within a measurement signal range (7) of the current interface (4). , and wherein by detecting and evaluating at least one state variable of the field measuring device (2) by the field measuring device (2), an error state (x_err) of the field measuring device (2) or the process (8) connected to the field measuring device is recognized and the error state (x_err) is determined by Setting an interface current (i(x_err)) of the power interface (4) is transmitted outside the measurement signal range (7) of the power interface (4) and within a failure information range (9) of the power interface (4). The risk of a process intervention caused by a reported error condition becomes at least reduced in that an unclear operating state (x_warn) of the field measuring device (2) or the process (8) connected to the field measuring device (2) is recognized by the field measuring device (2) and the recognized unclear operating state (x_warn) by setting an interface current ( i(x_warn)) of the power interface (4) is transmitted in a warning signal area (10) of the power interface (4) outside the measurement signal area (7) of the power interface (4) and outside the failure information area (9) of the power interface (4).

Description

The invention relates to a method for operating a field measuring device for process measurement technology, wherein the field measuring device has a measuring device for determining a measured value and an analog current interface for transmitting the measured value to a communication partner with a corresponding current interface, wherein in the error-free measuring state, the measured value determined by setting an interface current Current interface of the field measuring device is transmitted within a measurement signal range of the current interface of the field measuring device, and wherein by detecting and evaluating at least one state variable of the field measuring device by the field measuring device, an error state of the field measuring device or the process connected to the field measuring device is recognized and the error state is detected by setting an interface current of the current interface of the Field measuring device is transmitted outside the measurement signal range of the power interface of the field measuring device and within a failure information area of the power interface of the field measuring device. The invention further relates to a field measuring device with a power interface, which is designed so that it can carry out the aforementioned method. The invention also relates to a communication partner for the field measuring device with a corresponding power interface, which is designed in such a way that, together with the field device, it is able to carry out the method described during operation.

Methods for operating field measuring devices with a power interface and corresponding field measuring devices have been known in process technology for decades. Field measuring devices of this type are mostly used to record measured values in industrial processes. The field measuring devices measure process variables using their sensors, process the raw measurement data into a measured value to be transmitted using an evaluation unit and transmit this measured value to other communication partners, which can also be field devices or field measuring devices or even a higher-level process control system. The field measuring devices work “in the field”, they are usually designed to be very robust and immune to interference because they are exposed to all the adversities of the industrial process. In some cases they are used outdoors, so there are usually no “laboratory conditions”.

The power interface used to transmit the measured values is particularly secure against the coupling of interference signals and has therefore been one of the established field measuring device interfaces for many years. Because their reliability has been proven, power interfaces have an exceptionally long lifespan in the process industry. The analog current interface is often designed as a so-called 4 mA to 20 mA interface, in which the measured value range of the field measuring device is mapped to the interface current in the range of 4 mA to 20 mA.

The field measuring device can be in an error state for a variety of reasons, with possible error states also depending on the type of field measuring device, i.e. H. for example, depend on the type of measurement method implemented. However, what is typical for an error state is that it is defined and can be determined by evaluating at least one state variable of the field measuring device.

For example, electrical resistances between measuring line connections can be determined and conclusions can be drawn about interrupted contacts or short circuits. With an ultrasonic flowmeter, the fill level of the medium in the measuring tube can be determined and an incompletely filled measuring tube can be detected, which is an error condition for the measuring principle, depending on the arrangement of the ultrasonic transmitters. By detecting and evaluating a state variable of the field measuring device, an error state of the process connected to the field measuring device can also be detected. As an example, a vortex flowmeter can be used whose pressure sensor (“pickup”) records pressures of a level or type that cannot have been caused by typical vortex streets according to the measuring principle. These medium pressures must therefore have been impressed into the medium by unusual events in the process, so that an error in the process connected to the field measuring device can be concluded, especially if normal flow pressure fluctuations are also detected. The list of examples could be continued almost indefinitely.

In any case, it is known to transmit such a detected error state by setting an interface current of the power interface outside the measurement signal range of the power interface and within a failure information range of the power interface and thus to signal it to the external communication partner of the field measuring device. Error messages often result in parts of the system being shut down. This measure is problematic and usually requires a great deal of technical and personnel effort to implement and may also involve considerable costs, so this approach is of course only acceptable in exceptional situations.

The object of the present invention is to design the initially mentioned method for operating a field measuring device for process measurement technology and the same field measuring device in such a way that the risk of a process intervention caused by a reported error condition is at least reduced.

According to the invention, it was first recognized that, in addition to the error-free measurement state and a recognized error state, there are also unclear operating states of the field measuring device, which cannot be clearly assigned to an error state, but which nevertheless suggest that the field measuring device or the connected process are not undisturbed. The idea on which the invention is based is to identify and report such unclear operating states of the field measuring device, in a way that can be distinguished from an error state of the field measuring device.

The previously derived task is initially solved in the initially described method for operating a field measuring device and the related field measuring device in that an unclear operating state of the field measuring device or the process connected to the field measuring device is recognized by the field measuring device and the recognized unclear operating state by setting an interface current of the Current interface of the field measuring device is transmitted in a warning signal area of the current interface outside the measurement signal area of the current interface of the field measuring device and outside the failure information area of the current interface of the field measuring device. This method step makes an unclear operating state technically distinguishable from the error-free measurement state and an error state of the field measuring device. The recipient of the signaled unclear operating state of the field measuring device is thus given the opportunity to react differently than when an error state of the field measuring device is reported, which is clearly associated with significant advantages for the operation of the field measuring device and the process associated with the field measuring device.

In a preferred embodiment of the method it is provided that the field measuring device recognizes the unclear operating state by detecting and evaluating at least one state variable of the field measuring device by specifying a definition for the presence or absence of the unclear operating state depending on the state variable and the definition of the unclear operating state is evaluated using the recorded state variable. The definition for the presence or absence of the unclear operating state is specified in such a way that it can be checked automatically by the field measuring device, so it will typically be formulated mathematically or algorithmically so that it can be determined using programmatic means by an evaluation unit of the field measuring device, for example in the form a processor, a microcontroller, a digital signal processor or even by an appropriately set up field programmable gate array (FPGA).

An alternative embodiment of the method is characterized in that the field measuring device recognizes the unclear operating state by specifying a definition for the presence or absence of the error-free measurement state depending on at least one state variable, the state variable is recorded and the definition of the error-free measurement state Using the recorded state variable is evaluated. If the error-free measurement state is not present and at the same time the error state is not present, it is concluded that the unclear operating state exists and a corresponding interface current is set. This variant of the method works according to the exclusion principle; a definition of the unclear operating state itself is not necessary.

In a preferred embodiment of the method, the current interface is a 4 mA to 20 mA current interface, in particular where the measurement signal range of the current interface corresponds to the range of valid measurement information according to NAMUR recommendation 43, in particular where the failure information range of the current interface corresponds to the range of failure information according to NAMUR recommendation NE 43 (NAMUR = Interest Group for Automation Technology of the Process Industry e.V.), so that a first possible warning signal area for signaling the unclear operating state lies between a low-value failure information area and the measurement signal area. Alternatively or additionally, a second possible warning signal area lies between the area of valid measurement information and a higher-value failure information area. The Namur Recommendation NE 43 is currently available in the July 26, 2021 edition.

A further development of the aforementioned method provides that the first possible warning signal range for signaling the unclear operating state is between 3.6 mA and 3.8 mA. Alternatively or additionally, the second possible warning signal range for signaling the unclear operating state is between 20.5 mA and 21 mA. Due to this distance from the classic 4 mA to 20 mA range for valid measurement signals or a slight extension of the range for valid measurement signals, it is possible, on the one hand, to slightly exceed the range and Overflows of the measurement signal can be handled; on the other hand, interface currents in the measurement signal area and in the warning signal area can be distinguished from one another with greater certainty.

In a further development of the method, it is further provided that in order to recognize the signaled unclear operating state, a safety distance in accordance with NAMUR recommendation NE 43 is taken into account, so that the unclear operating state is recognized in the first possible warning signal range between 3.7 mA and 3.8 mA, and/ or that the unclear operating state is detected in the second possible warning signal range between 20.5 mA and 20.8 mA. This creates an additional distance from the low-value failure information area and the higher-value failure information area, so that confusion of interface signals in the failure information area and in the warning signal area is less likely.

In a specific embodiment, the method is used in a field measuring device designed as a vortex flowmeter, whereby the recorded state variable for determining the existence of the unclear operating state is the medium pressure recorded by a pressure sensor of the vortex flowmeter intended for flow measurement or the flow measurement value derived therefrom. The unclear operating state occurs when the recorded medium pressure no longer shows any change or the flow measurement value derived from it is determined to be zero. When there is an actual zero flow, the vortex flowmeter no longer creates any vortex streets in the medium, so the vortex frequency is determined to be zero. However, this could also be due to the pressure sensor being defective or a downstream signal processing system. The operating state is therefore unclear as to what triggers the message according to the invention.

According to a further specific embodiment of the method, the field measuring device is an ultrasonic flow measuring device, wherein the detected state variable for determining the presence of the unclear operating state is the signal level of an ultrasonic signal detected by an ultrasonic receiver of the ultrasonic flow measuring device, the unclear operating state being present when the signal level of the detected ultrasonic signal is below a signal level limit. The operating status is unclear because the ultrasonic transmitter could be defective, the ultrasonic receiver or downstream signal processing could be defective, but the medium level in the measuring tube of the ultrasonic flowmeter could also have dropped to such an extent that transmission of ultrasonic signals is no longer possible or strong is damped.

For the sake of completeness, it is mentioned that the derived task is also solved in a field measuring device of process measurement technology, the field measuring device having a measuring device for determining a measured value and an analog current interface for transmitting the measured value to a communication partner with a corresponding current interface, whereby in the error-free measuring state determined measured value is transmitted by setting an interface current of the current interface of the field measuring device within a measurement signal range of the current interface, and wherein by detecting and evaluating at least one state variable of the field measuring device by the field measuring device, an error state of the field measuring device or the process connected to the field measuring device is recognized and the error state is detected by setting an interface current of the current interface of the field measuring device is transmitted outside the measurement signal range of the current interface of the field measuring device and within a failure information area of the current interface of the field measuring device.

The task mentioned at the beginning is achieved in the field measuring device in that an unclear operating state of the field measuring device or the process connected to the field measuring device is recognized by the field measuring device and the recognized unclear operating state by setting an interface current of the current interface of the field measuring device in a warning signal range of the current interface outside the measurement signal range the power interface of the field measuring device and outside the failure information area of the power interface of the field measuring device.

The field measuring device is further designed so that in the operating state it carries out the previously described method for operating a field measuring device. This is implemented by an evaluation unit of the field measuring device that is programmed accordingly. For this purpose, the evaluation unit preferably comprises a processor, a microcontroller, a digital signal processor or a correspondingly programmed field programmable gate array (FPGA).

In connection with the previously described field measuring device, the stated task is also solved by a communication partner for the field measuring device of process measurement technology, the communication partner having a power interface, the field measuring device having a power interface, the field measuring device and the communication partner also being in the operating state are connected via a current loop via their current interfaces and the field measuring device also determines the interface current of the communication partner's current interface by setting the interface current of its current interface.

In order to understand what properties the communication partner of the field measuring device has, it must first be explained how the field measuring device uses its current interface: In an error-free measuring state, the field measuring device transmits a determined measured value by setting the interface current of its current interface within a measuring signal range. Furthermore, in an error state, the field measuring device transmits the error state by setting the interface current of its power interface outside the measurement signal range of the power interface and within a failure information range of the power interface. Furthermore, in an unclear operating state, the field measuring device transmits the unclear operating state by setting its interface current of the power interface in a warning signal range of the power interface outside the measurement signal range of its power interface and outside the failure information range of its power interface.

In any case, information about the measurement signal area, the failure information area and the warning signal area is stored in the communication partner. The communication partner determines the interface current of its power interface and from the determined interface current, the communication partner determines whether the connected field measuring device is in the error-free measuring state, in an error state or in an unclear operating state. Depending on the determined operating state, the communication partner of the field measuring device can then react with follow-up actions, such as displaying the measured value, displaying an error condition or displaying an unclear operating condition.

In preferred embodiments, the communication partner is additionally characterized by the fact that the stored information about the measurement signal area, the failure information area and the warning signal area is designed in such a way that it describes the previously presented behavior of the power interface of the field measuring device, so that the behavior of the field measuring device is consistently recognized by the communication partner can be.

• 1 schematisch ein Feldmessgerät mit einer Stromschnittstelle und ein Verfahren zum Betreiben des Feldmessgerätes,
• 2 schematisch ein Verfahren zur Signalisierung eines Messwertes in einem Messsignalbereich in einem fehlerfreien Messzustand und eines Fehlerzustandes in einem Ausfallinformationsbereich der Stromschnittstelle,
• 3 schematisch das Verfahren nach 2 mit der zusätzlichen Signalisierung eines unklaren Betriebszustandes in einem Warnsignalbereich,
• 4a schematisch ein Ausführungsbeispiel des Verfahrens unter Verwendung einer Definition eines unklaren Betriebszustandes,
• 4b schematisch ein Ausführungsbeispiel des Verfahrens unter Verwendung eines Ausschlussprinzips zur Ermittlung des unklaren Betriebszustandes,
• 5 schematisch ein Ausführungsbeispiel des Verfahrens unter Angabe konkreter Grenzen für einen Warnsignalbereich und
• 6 schematisch ein weiteres Ausführungsbeispiel des Verfahrens unter Angabe konkreter Grenzen für den Warnsignalbereich.

In detail, there are now a variety of options for designing and developing the method according to the invention, the field measuring device according to the invention and the communication partner according to the invention. Reference is made, on the one hand, to the patent claims subordinate to the independent patent claims, and, on the other hand, to the following description of exemplary embodiments in conjunction with the drawing. Show in the drawing

• 1 schematically a field measuring device with a power interface and a method for operating the field measuring device,
• 2 schematically a method for signaling a measured value in a measurement signal area in an error-free measurement state and an error state in a failure information area of the power interface,
• 3 schematically the procedure 2 with the additional signaling of an unclear operating status in a warning signal area,
• 4a schematically an exemplary embodiment of the method using a definition of an unclear operating state,
• 4b schematically an exemplary embodiment of the method using an exclusion principle to determine the unclear operating state,
• 5 schematically an exemplary embodiment of the method, specifying concrete limits for a warning signal area and
• 6 schematically a further exemplary embodiment of the method, specifying specific limits for the warning signal range.

The figures show a method 1 for operating a field measuring device 2 of process measurement technology and partly a corresponding field measuring device 2 and a communication partner 5 of the field measuring device.

In 1 a field measuring device 2 is shown with a measuring device 3, a communication partner 5 connected to the field measuring device 2 and partly the method 1 carried out with the field measuring device 2 - and thus partly also with the communication partner 5. The measuring device 3 is used to determine a measured value y. The measuring device 3 includes a sensor 3a, which is in operative connection with an external process 8, which in 1 is symbolized by a line connection. In fact, this active connection is only rarely implemented; it consists in the physical principle of operation, for example in the case of a temperature measurement in the detection of a heat transfer, in the vortex flow measurement in the recording of a pressure signal, etc. The raw measurement data recorded by the sensor 3a are then stored in a Evaluation unit 3b further processes the signal so that a measured value y is finally available in a processable form.

The field measuring device 2 also includes an analog power interface 4a for transmitting the measured value y to a communication partner 5, which here is a higher-level control room. The communication partner 5 also includes a power interface 4b. The field measuring device 2 and the communication partner 5 are connected via their current interfaces 4a, 4b by means of a current loop 6. In the exemplary embodiment shown, the current loop 6 between the field measuring device 2 and the external communication partner 5 is implemented via a two-wire connection. The field measuring device 2 is here supplied with energy via the external communication partner 5 to operate the field measuring device 2; However, this is not important in detail. The communication partner 5 does not belong to the field measuring device 2, the only important thing is that the field measuring device 2 has the option of transmitting information externally, i.e. to the communication partner 5, by means of the power interface 4a.

It is important that if there is an error-free measurement state x_m, the determined measured value y is transmitted to the communication partner 5 by setting an interface current i(y) of the current interface 4a within a measurement signal range 7 of the current interface 4.

The method 1 and the field measuring device 2 are further designed such that by detecting and evaluating at least one state variable of the field measuring device 2 by the field measuring device 2, an error state x_err of the field measuring device 2 or the process 8 connected to the field measuring device 2 is recognized. Which state variable is used to determine an error condition x_err depends on which error condition x_err is to be detected. For example, if it is to be recognized whether the field measuring device 2 is operating in an impermissible temperature range, a suitable temperature of the field measuring device 2 is recorded as a state variable. If it is to be determined whether a measuring line is defective, the ohmic resistance at the connection of the measuring line could be determined as the state variable of the field measuring device 2, which would allow testing for an interrupted line (practically infinitely high connection resistance) or for a short circuit (connection resistance towards zero). The error state x_err is then transmitted by setting an interface current i(x_err) of the power interface 4a outside the measurement signal area 7 of the power interface 4a and within a failure information area 9 of the power interface 4a and thus brought to the attention of the communication partner 5 via its power interface 4b. The interface current i depends on the error state x_err, so different error states x err could also be signaled and differentiated by the communication partner 5.

It has been recognized that the field measuring device 2 or the process 8 connected to the field measuring device 2 can not only be in an error-free measuring state x_m or in a defined error state, but rather that there are also operating states that are unclear, for example ambiguous .

In the 3 The idea presented is to also signal such unclear operating states x_warn to the outside using the power interface 4a, in a way that can be distinguished from the other operating states. For this purpose, in method 1 it is provided that the unclear operating state x_warn of the field measuring device 2 or the process 8 connected to the field measuring device 2 is recognized by the field measuring device 2 and the recognized unclear operating state x_warn by setting an interface current i (x_warn) of the current interface 4a of the field measuring device 2 is transmitted in a warning signal area 10 of the power interface 4a outside the measurement signal area 7 of the power interface 4a and outside the failure information area 9 of the power interface 4a. The level of the interface current i(x_warn) set on the basis of the unclear operating state x_warn depends in turn on the unclear operating state x_warn, so that various unclear operating states x_warn can also be distinguished by the communication partner 5 based on the level of the interface current i.

4 shows two variants of method 1 for determining the presence of an unclear operating state x_warn. The procedure 1 according to 4a is characterized in that the field measuring device 2 recognizes the unclear operating state x_warn by detecting and evaluating at least one state variable, referred to here as x, of the field measuring device 2, using a definition Def(x_warn(x)) for the presence (alternatively for the absence) of the unclear operating state x_warn is specified depending on the state variable x and the definition Def(x_warn(x)) of the unclear operating state x_warn is evaluated using the recorded state variable x. For these procedures, a definition Def(x_warn) of the unclear operating state x_warn is required.

The procedure 1 according to 4b is alternatively characterized by the fact that the field measuring device 2 recognizes the unclear operating state x_warn by providing a definition Def(x_m) for the presence (alternatively for the absence) of the error-free measurement state x_m depending on at least one state variable, referred to here as x1, is specified, the state variable x1 is recorded and the definition Def(x_m(x1)) of the error-free measurement state x_m is evaluated using the recorded state variable x1. If the error-free measurement state x_m is not present and at the same time the error state x_err is not present, the existence of the unclear operating state x_warn is concluded and a corresponding interface current i is set. The check for the existence of the error state x err is carried out as required by detecting a state variable, here referred to as x2, and by evaluating the state variable x2, in the present case by a definition Def(x_err) of the error state x_err. An exclusion principle is therefore applied to draw a conclusion about the unclear operating state x_warn.

The definitions are formulated in such a way that they can be easily applied and evaluated by the evaluation unit 3b, so they are in mathematical or algorithmic form. As examples for the concrete application of such definitions, it can be stated that the field measuring device 2 is a vortex flow measuring device, whereby the detected state variable x for determining the presence of the unclear operating state x_warn is the medium pressure detected by a pressure sensor intended for flow measurement or the flow measurement value derived therefrom , whereby the unclear operating state x_warn occurs when the detected medium pressure no longer shows any change or the flow measurement value is determined to be zero. As another exemplary embodiment, it can be stated that the field measuring device 2 is an ultrasonic flow measuring device, the detected state variable x for determining the presence of the unclear operating state x_warn being the signal level of an ultrasonic signal detected by an ultrasound receiver, the unclear operating state x_warn being present when the Signal level of the detected ultrasonic signal is below a signal level limit. The definitions mentioned can obviously be formulated using elementary mathematical operators (“less than”, “equal to”).

The 5 and 6 show exemplary embodiments for divisions of the working area of the power interface 4 into the measurement signal area 7, the failure information area 9 and the warning signal area 10.

The method 1 and the power interface 4a of the field measuring device 2 are in the exemplary embodiment 5 characterized in that the current interface 4a is a 4 mA to 20 mA interface, wherein the measurement signal range 7 of the current interface 4a corresponds to the range of valid measurement information according to NAMUR recommendation 43, and wherein the failure information range 9 of the power interface 4a corresponds to the range of failure information according to NAMUR Complies with recommendation NE 43. This means that a first possible warning signal area 10a for signaling the unclear operating state x_warn lies between a low-value failure information area 9a and the measurement signal area 7, and a second possible warning signal area 10b lies between the measurement signal area 7 and a higher-value failure information area 9b. Expressed in concrete current values using NE 43 of July 26, 2021, this means that the first possible warning signal range 10a for signaling the unclear operating state x_warn is between 3.6 mA and 3.8 mA, and that the second possible warning signal range 10b for signaling of the unclear operating state x_warn is between 20.5 mA and 21 mA.

At the in 6 In the exemplary embodiment shown, it is provided that in order to detect the signaled unclear operating state x_warn, a safety distance in accordance with the NAMUR recommendation is taken into account, so that the unclear operating state x_warn, taking into account NE 43 of July 26, 2021, in the first possible warning signal range 10a between 3.7 mA and 3. 8 mA is detected, and / or that the unclear operating state x warn is detected in the second possible warning signal range 10b between 20.5 mA and 20.8 mA. This particularly affects the perspective of the communication partner 5.

The method 1 and the field measuring device 2 have so far been explained in particular based on the properties of the power interface 4a of the field measuring device 2. It is obvious that the communication partner 5, which is connected to the field measuring device via the current loop 6, must have knowledge of the different areas of the interface current so that it can consistently recognize different operating states of the field measuring device 2 and, if necessary, react to them.

For the sake of completeness, it should be noted that the communication partner 5 for the field measuring device 2 is characterized by the fact that it has a power interface 4b, with the field measuring device 2, as is known, having the power interface 4a. In the operating state, the field measuring device 2 and the communication partner 5 are connected via the current loop 6 by means of their current interfaces 4a, 4b. By setting the interface current of its current interface 4a, the field measuring device 2 also determines the interface current of the current interface 4b of the communication partner 5.

In its error-free measuring state x_m, the field measuring device 2 transmits the determined measured value y by setting the interface current i(y) of its current interface 4a within a measuring signal range 7. The field measuring device 2 transmits in an error state by setting the interface current i(x_err) of its current interface 4a outside the measuring signal range 7 of the power interface 4a and within the failure information area 9 of the power interface 4a the error state x_err. The field measuring device 2 further transmits the unclear operating state x_warn in an unclear operating state x_warn by setting its interface current i(x_warn) of the current interface 4a in the warning signal area 10 of the current interface 4a outside the measurement signal area 7 of its current interface 4a and outside the failure information area 9 of its current interface 4a.

Information about the measurement signal area 7, the failure information area 9 and the warning signal area 10 is stored in the communication partner 5. The communication partner 5 determines the interface current i of its power interface 4b and from the determined interface current i of its power interface 4b the communication partner 5 concludes whether the connected field measuring device 2 is in the error-free measuring state x_m, in an error state or in an unclear operating state x_warn.

The in 1 Communication partner 5 shown is further characterized in that the stored information about the measurement signal area 7, the failure information area 9 and the warning signal area 10 are designed in such a way that they describe the behavior of the power interface 4a according to one of claims 4 to 6 and the communication partner 5 so reliably detects the operating state of the field measuring device 2 even in these variants.

Reference symbols

1

Proceedings

2

Field measuring device

3

Measuring device

3a

sensor

3b

Evaluation device

4a

Power interface of the field measuring device

4b

Power interface of the communication partner

5

Communication partner

6

current loop

7

Measuring signal range

8th

connected process

9

Failure information area

9a

low-value failure information area

9b

higher quality failure information area

10

Warning signal area

10a

first possible warning signal area

10b

second possible warning signal area

y

Measured value

x_m

Error-free measurement condition Error condition

x_warn

unclear operating status

i(y)

Interface current for measured value in the measurement signal range

i(x_err)

Interface stream in the failure information area

i(x_warn)

Interface current in the warning signal area

Def(x_warn)

Definition of the unclear operating status

Def(x_m)

Definition of the error-free measurement condition

Def(x_err)

Definition of the error condition

Claims (12)

Method (1) for operating a field measuring device (2) of process measurement technology, wherein the field measuring device (2) has a measuring device (3) for determining a measured value (y) and an analog current interface (4a) for transmitting the measured value (y) to a communication partner (5) with a corresponding current interface (4b), wherein in the error-free measuring state (x_m), the measured value (y) determined by setting an interface current (i (y)) of the current interface (4a) of the field measuring device (2) within a measuring signal range (7) the power interface (4a), and wherein an error state (x_err) of the field measuring device (2) or the process (8) connected to the field measuring device is detected by detecting and evaluating at least one state variable of the field measuring device (2) by the field measuring device (2). and the error state (x_err) by setting an interface current (i(x_err)) of the current interface (4a) of the field measuring device (2) outside the measurement signal range (7) the power interface (4a) of the field measuring device (2) and within a failure information area (9) of the power interface (4a) of the field measuring device (2), characterized in that an unclear operating state (x warn) of the field measuring device (2) or the one connected to it Process (8) connected to the field measuring device (2) is recognized by the field measuring device (2) and the detected unclear operating state (x_warn) by setting an interface current (i(x_warn)) of the current interface (4a) of the field measuring device (2) in a warning signal range (10 ) the current interface (4a) of the field measuring device (2) is transmitted outside the measurement signal range (7) of the current interface (4a) of the field measuring device (2) and outside the failure information area (9) of the current interface (4a) of the field measuring device (2). Procedure (1) according to Claim 1 , characterized in that the field measuring device (2) recognizes the unclear operating state (x_warn) by detecting and evaluating at least one state variable of the field measuring device (2) by providing a definition (Def(x_warn)) for the presence or absence of the unclear operating state (x_warn) is specified depending on the state variable and the definition (Def(x_warn)) of the unclear operating state (x warn) is evaluated using the recorded state variable. Procedure (1) according to Claim 1 , characterized in that the field measuring device (2) recognizes the unclear operating state (x warn) by specifying a definition (Def(x _m)) for the presence or absence of the error-free measurement state (x_m) depending on at least one state variable, the state variable is recorded and the definition (Def(x _m)) of the error-free measurement state (x_m) is evaluated using the recorded state variable, and that if the error-free measurement state (x_m) is not present and at the same time the error state (x err) is not present, the existence is determined the unclear operating status (x warn) is closed. Method (1) according to one of the Claims 1 until 3 , characterized in that the current interface (4a) of the field measuring device (2) is a 4 mA to 20 mA interface, in particular wherein the measuring signal range (7) of the current interface (4a) of the field measuring device (2) corresponds to the range of valid measurement information according to the Namur recommendation 43 corresponds, in particular wherein the failure information area (9) of the power interface (4a) of the field measuring device (2) corresponds to the area of failure information according to NAMUR recommendation NE 43, so that a first possible warning signal area (10a) for signaling the unclear operating state (x warn) between a low-value failure information area (9a) and the measurement signal area (7) and / or a second possible warning signal area (10b) lies between the measurement signal area (7) and a higher-value failure information area (9b). Procedure (1) according to Claim 4 , characterized in that the first possible warning signal range (10a) for signaling the unclear operating state (x warn) is between 3.6 mA and 3.8 mA, and / or that the second possible warning signal range (10b) for signaling the unclear operating state ( x warn) is between 20.5 mA and 21 mA. Procedure (1) according to Claim 4 or 5 , characterized in that to detect the signaled unclear operating state (x warn), a safety distance in accordance with NAMUR recommendation NE 43 is taken into account, so that the unclear operating state (x warn) is in the first possible warning signal range (10a) between 3.7 mA and 3.8 mA is detected, and / or that the unclear operating state (x_warn) is detected in the second possible warning signal range (10b) between 20.5 mA and 20.8 mA. Method (1) according to one of the Claims 1 until 6 , characterized in that the field measuring device (2) is a vortex flow measuring device, the detected state variable (x) for determining the presence of the unclear operating state (x_warn) being the medium pressure detected by a pressure sensor intended for flow measurement or the flow measurement value derived therefrom, where The unclear operating state (x_warn) exists when the recorded medium pressure no longer shows any change or the flow measurement value is determined to be zero. Method (1) according to one of the Claims 1 until 6 , characterized in that the field measuring device (2) is an ultrasonic flow measuring device, the detected state variable (x) for determining the presence of the unclear operating state (x_warn) being the signal level of an ultrasonic signal detected by an ultrasonic receiver, the unclear operating state (x_warn) occurs when the signal level of the detected ultrasonic signal is below a signal level limit. Field measuring device (2) of process measurement technology, wherein the field measuring device (2) has a measuring device (3) for determining a measured value (y) and an analog current interface (4a) for transmitting the measured value (y) to a communication partner (5) with a corresponding current interface ( 4b), whereby in the error-free measurement state (x_m), the measured value (y) determined by setting an interface current (i(y)) of the current interface (4a) of the field measuring device (2) is transmitted within a measurement signal range (7) of the current interface (4), and wherein at least one state variable of the field measuring device (2) is detected and evaluated by the field measuring device ( 2) an error state (x_err) of the field measuring device (2) or the process (8) connected to the field measuring device (2) is detected and the error state (x_err) by setting an interface current (i (x_err)) of the current interface (4a) of the field measuring device (2) is transmitted outside the measurement signal range (7) of the power interface (4a) of the field measuring device (2) and within a failure information area (9) of the power interface (4a) of the field measuring device (2), characterized in that an unclear operating state (x warn) of the field measuring device (2) or the process (8) connected to the field measuring device (2) is recognized by the field measuring device (2) and the recognized unclear operating state (x warn) by setting an interface current (i (x_warn)) of the current interface (4a) of the field measuring device (2) in a warning signal area (10) of the power interface (4) outside the measuring signal area (7) of the power interface (4a) of the field measuring device (2) and outside the failure information area (9) of the power interface (4a) of the field measuring device (2). becomes. Field measuring device (2). Claim 9 , characterized in that the field measuring device (2) is designed so that in the operating state it carries out the method (1) according to the characterizing part of at least one claim Claims 2 until 8th carries out. Communication partner (5) for a field measuring device (2) of process measurement technology, the communication partner (5) having a power interface (4b), the field measuring device (2) having a power interface (4a), wherein in the operating state the field measuring device (2) and the communication partner (5) are connected via a current loop (6) by means of their current interfaces (4a, 4b) and the field measuring device (2) also determines the interface current of the current interface (4b) of the communication partner (5) by adjusting the interface current of its current interface (4a), wherein the field measuring device (2) transmits a determined measured value (y) in an error-free measuring state (x_m) by adjusting the interface current (i (y)) of its current interface (4a) within a measurement signal range (7), the field measuring device (2) in one Error state (x_err) transmits the error state (x_err) by setting the interface current (i (x_err)) of its current interface (4a) outside the measurement signal range (7) of the current interface (4a) and within a failure information area (9) of the current interface (4a) and where the field measuring device (2) in an unclear operating state (x_warn) by setting its interface current (i(x_warn)) of the current interface (4a) in a warning signal range (10) of the current interface (4) outside the measurement signal range (7) of its current interface (4a) and transmits the unclear operating state (x_warn) outside the failure information area (9) of its power interface (4a), information about the measurement signal area (7), the failure information area (9) and the warning signal area (10) being stored in the communication partner (5), the communication partner (5) determines the interface current (i) of its current interface (4b) and determines from the determined interface current (i) of its current interface (4b) whether the connected field measuring device (2) is in the error-free measuring state (x_m), in an error state (x_err) or is in an unclear operating state (x warning). communication partner (5). Claim 11 , characterized in that the stored information about the measurement signal area (7), the failure information area (9) and the warning signal area (10) are designed in such a way that they determine the behavior of the power interface (4b) according to one of the claims Claims 4 until 6 describe.

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