EP2622422A1

EP2622422A1 - Measuring transducer having a plurality of field bus addresses and method for retrieving measuring values from such a measuring transducer

Info

Publication number: EP2622422A1
Application number: EP11761303.4A
Authority: EP
Inventors: Michael Konrad; Stephan Konrad; Michael Korn
Original assignee: Endress and Hauser Wetzer GmbH and Co KG
Current assignee: Endress and Hauser Wetzer GmbH and Co KG
Priority date: 2010-10-01
Filing date: 2011-08-25
Publication date: 2013-08-07
Also published as: RU2013120294A; CN103221890A; RU2541145C2; DE102010041866A1; US20130187790A1; WO2012041616A1

Abstract

The invention relates to a measuring transducer (M) comprising an interface for transmitting measuring values via a field bus (2L), wherein the communication via the field bus (2L) is carried out according to a field bus protocol; the number of measuring values provided by the measuring transducer (M) exceeds the measuring values that can be retrieved by means of a basic command of the field bus protocol; the measuring transducer (M) comprises a plurality of field bus addresses (#1... #n); a logic unit is used to distribute the measuring values between the plurality of field bus addresses (#1... #n) of the measuring transducer (M); and the measuring values can be retrieved via the plurality of field bus addresses (#1... #n) of the measuring transducer (M) by means of the basic command.

Description

Transmitter with multiple fieldbus addresses and procedures for retrieving readings from such a transmitter

The invention relates to a transmitter with an interface for transmitting measured values via a fieldbus, the communication taking place via the fieldbus in accordance with a fieldbus protocol, the number of measured values provided by the transmitter being the number of times using a basic command of the fieldbus. Protocols available.

Furthermore, the invention relates to a method for retrieving measured values, wherein the measured values are provided by a transmitter which is connected to a field bus and has a plurality of field bus addresses, wherein the communication takes place via the field bus according to a fieldbus protocol, and wherein the number of measured values provided by the transmitter exceeds the number of measurements retrievable by means of a basic command of the fieldbus protocol.

In systems of process automation technology, field devices are often used today which control and / or regulate the processes taking place in the system. Such field devices consist, for example, of a

Transmitter to the least one sensor, which serves to accommodate a chemical and / or physical measurand is connected. In addition, these field devices, or more precisely the transducers, are often connected to one another today via a field bus. This allows the

Transmitter with each other and / or with a control unit that controls the process, information such as readings in the form of data exchange. For data transmission via the field bus, various so-called fieldbus protocols have become known from the state of the art.

For example, in the HART protocol, there are several groups of commands. The universal commands, also called basic commands, for example, allow the identification of one to the fieldbus

connected HART device. It can be used, for example, manufacturers, Read out measuring point identifier, serial number etc. In addition, these basic commands can also be used to read up to four measured values with a physical unit digitally from one transmitter. The basic commands are supported by all HART slave devices.

Common practice commands, in turn, are used for basic settings of HART devices. This makes it possible, for example, to control and operate very simple field devices. On the other hand, to

Commissioning of more complex field devices Device-specific commands Commands can be used. These are specified by the manufacturer of the devices and therefore also called manufacturer-specific commands. A master connected to a fieldbus must know these commands and therefore be programmed accordingly. It must be ensured that the same command is clearly defined and does not trigger different functions, for example, with different devices connected to the fieldbus, in particular the transmitters.

The same applies to Profibus protocol, in which it also

Basic commands are given, the identification etc. of the fieldbus

connected device, in particular a transmitter allow. Depending on the application profile used, Profibus offers various functions, such as parameter and / or measured value queries. For example, in the PROFIdrive profile, approx. 30 parameter queries are specified as standard, while the remaining measured values or

Parameters (in the case of complex devices it can be more than 1000) can be called up by manufacturer-specific commands.

From the prior art, DE 102007039529 A1 has disclosed a method for operating a field device with at least two measuring channels. The field device there has several

Communication controller to which different field bus addresses are assigned. As a result, the field device appears on the fieldbus as a plurality of logically independent field devices and each of the logically independent

Field devices can be operated by means of a separate device description. Now one of the communication controllers detects that one in one Fieldbus telegram contained address matches its own field bus address, so this communication controller sends user data in the form of response telegrams on the fieldbus. In the case of the device proposed in DE 102007039529 A1, there is also the problem that in the case that a field device provides, for example, more than by means of a (single) basic command retrievable measured values, these measured values only via a general command (common practice command ) or a manufacturer-specific command (device specific command) can be retrieved. These commands must then be introduced and defined for this specific purpose. As a result, however, the devices connected to the fieldbus are under

No longer compatible with all HART-Master devices. For example, it may happen that the same vendor-specific commands are used in different systems to call different functions.

The object of the invention is to enable the retrieval of all measured values provided by a transmitter by means of a command which is available to all field devices compatible with a given fieldbus protocol.

The object is achieved by a transmitter and a method.

With regard to the transmitter, the object is achieved in that the transmitter has multiple field bus addresses, and that a

Logic unit is provided, which distributes the measured values to the plurality of fieldbus addresses of the transmitter so that the measured values can be retrieved via the plurality of fieldbus addresses of the transmitter by means of the basic command.

The interface of the transmitter may be a

Communication interface, especially with only one Act communication controller. The communication controller is used to (pre) process or prepare data originating from the fieldbus and received via the (communication) interface. The interface can, for example, be a wired interface that is used for communication, ie for sending and / or receiving data, for example in the form of

Telegrams via the fieldbus is used. The fieldbus is preferably a wired fieldbus. The protocol may, for example, be the HART protocol or the Profibus protocol. But it is also possible to use in the context of other protocols, in particular fieldbus protocols. These protocols have so-called basic commands available to all devices compatible with the protocol. This ensures that all measured values that are provided by a field device or the transmitter can be retrieved. In particular, if the transmitter provides more measured values than can be queried by means of a (single) basic command, can

be provided to distribute the measured values to the plurality of field bus addresses so that at least a portion of the measured values can be retrieved from one of the field bus addresses of the transmitter by means of the basic commands. In this case, for example, always the same basic command can be used. The different measured values provided by the transmitter can therefore be called up via the different fieldbus addresses of the transmitter. This is advantageous in particular when the number of measured values provided by a transmitter exceeds the number of measured values which can be called up by means of a single basic command. This may, for example, be the case if a plurality of sensors are connected to a transmitter and / or if the sensor in addition to a primary measurement and other measures, such as the temperature of the

Operating electronics or derived measured values provides. Thus, for example, from the measured flow rate of the

Volume flow, total flow, etc., and other readings can be determined and retrieved by the transmitter. On the one hand, it can happen that several sensors are connected to the

Transmitter can be connected, and that the sensor then the measurement signals of these different sensors to readings processed and provided as described. In addition, a plurality of measured values can also be determined and made available by the transmitter from a (single) measuring signal of a measuring sensor or a variable derived therefrom.

It may be sufficient to provide a single (communication) interface and a single communication controller on the transmitter. In one embodiment of the transmitter, the measured values can be called up by the transmitter without the use of manufacturer-specific commands or general-practice commands. It can be completely based on the use of

manufacturer-specific commands or general commands are dispensed with, and the measured values provided by the transmitter can only be retrieved by using a basic command, in particular a single basic command. Instead of the different ones

Commands for getting different readings from one

Transmitter, so different fieldbus addresses can be used.

In a further embodiment of the transmitter, the basic command is therefore a command, which command all devices compatible with the fieldbus protocol used have. An advantage of this

Embodiment is that a corresponding programming of the field device with respect to the general commands and the manufacturer-specific

Commands are omitted.

In a further embodiment of the transmitter, retrieval of the measured values provided by the transmitter takes place via the fieldbus by means of telegrams, which telegrams are addressed to the different fieldbus addresses of the transmitter and the same basic command

include. Thus, telegrams can be sent via the fieldbus, in particular by a so-called master, which has different ones Fieldbus addresses and the same command, ie basic command, to retrieve the readings provided by the transmitter. If the proposed transmitter connected to the fieldbus determines that one of these fieldbus addresses matches one of its fieldbus addresses, it sends the corresponding measured values assigned to the fieldbus address via the fieldbus as

Response telegram. In this answer telegram, the sender address which can be used, for example, is the fieldbus address which was contained in the request telegram and from which the measured values of the transmitter were retrieved.

In a further embodiment of the transmitter base readings of the associated fieldbus address can be retrieved by means of the basic commands. By the basic command are usually, for example, in the HART protocol, the so-called basic readings, i. the primary, secondary, tertiary and quaternary variables are available. Due to the fact that several field bus addresses are provided for a transmitter, those of the

Transmitters provided by the measured values by means of

Basic commands as those associated with the fieldbus address

Basic measured values are retrieved and transmitted via the fieldbus.

In a further embodiment of the transmitter, the logic unit also serves to provide the measurement values provided by the transmitter, the data transmitted via the various fieldbus addresses of the transmitter

Assign the basic command to retrievable basic measured values. In particular, the logic unit of the transmitter can be used to

With regard to the method, the object is achieved by distributing the measured values to the plurality of fieldbus addresses of the transmitter, and by calling up the measured values via the various fieldbus addresses of the transmitter by means of the basic command. As a result, as already explained in connection with the proposed transmitter, more measured values can be retrieved from the transmitter by means of the basic command than by those of the prior art Technique known method. The measured values provided by the transmitter can be retrieved from the transmitter for this purpose by means of different fieldbus addresses. In this case, it may be necessary to program the sender who queries measured values from the transmitter as well as the transmitter itself accordingly.

In one embodiment of the method, no manufacturer-specific or general (so-called common-practice) commands are used to retrieve the measurement values of the transmitter.

In a further embodiment of the method, those of the

Transmitters provided via the fieldbus by means of telegrams, which telegrams are addressed to the different fieldbus addresses of the transmitter and include, in particular the same, basic command.

In a further embodiment of the method, the from

Measured values provided to the transmitter are assigned to the base readings that can be retrieved via the various fieldbus addresses of the transmitter with the basic command.

Furthermore, the object may be achieved by a computer program product

Program code means are solved, which program code means are loadable into a memory of a computing unit and when executed execute the method according to one of the previous embodiments.

The invention will be explained in more detail with reference to the following drawings. 1 shows a schematic representation of an arrangement of field devices from the prior art, Fig. 2: shows a schematic representation of an embodiment of

1 shows a schematic representation of transducers M1 ... Mn, which are operated in HART multidrop mode. Each of the transducers M1 ... Mn has its own fieldbus address # 1 .. # n, via which it can be addressed exclusively via the fieldbus, i. is responsive. The fieldbus consists essentially of a two-wire current loop 2L. The

Two-wire current loop 2L, to which the transducers M1 ... Mn are connected, is supplied with the required electrical energy by a transducer power supply MUS. According to the HART specification version 7, up to 15 sensors can be connected in parallel to such a 2-wire current loop 2L and transmit their measured values digitally via the HART protocol. Thus it is possible the signals of several sensors

evaluate.

Since multiple transducers are required for HART multidrop mode and each transmitter can send a maximum of four readings per the HART protocol standard, the number of transmittable readings is limited. Should more than the four measured values of one of the

Transmitters M1 ... Mn must be special commands, i. the manufacturer-specific commands mentioned above are introduced. As a result, the transducers M1 ... Mn may no longer be compatible with all HART master devices. In addition, the transmitter power supply MUS limits the number of maximum possible

Sensor, as each sensor also requires energy itself in order to make and / or process a measurement. FIG. 2 schematically shows an embodiment of a measuring transducer M according to the invention. The transmitter M has several

Fieldbus addresses, ie in this case the fieldbus addresses # 1 ... # n. Via these field bus addresses # 1 ... # n, the measuring transducer M is also connected to other devices in which are connected to the fieldbus, not shown. approachable. In the exemplary embodiment according to FIG. 2, the field bus also comprises a two-wire current loop 2L which, in addition to the data transmission, also serves to supply the measuring transducer M with energy. The other devices connected to the fieldbus 2L may also be, for example

Transmitter or act also to a control unit. In which

Transmitter M may be a so-called slave and the control unit, not shown, may be a so-called master. The master can, for example, send queries in the form of telegrams via the fieldbus to a slave. The slave then responds to this request with a response telegram.

For addressing, the field bus subscribers, for example, according to the

Embodiment of Figure 1, corresponding field bus addresses, so that telegrams can be exchanged between the field bus participants by means of these addresses.

If a telegram addressed to one of the addresses # 1 ... # n of the transmitter M is sent via the fieldbus and received by the transmitter M, which telegram additionally contains a measured value query by means of a basic command, the transmitter M sends the fieldbus address assigned measured values in the form of a response telegram back over the fieldbus. By using multiple fieldbus addresses # 1 ... # n for a single transmitter M, the definition or

Use of general commands or device-specific

Commands are waived.

In this case, the measuring transducer M is connected via an interface, not shown, to the field bus, which in FIG. 2 consists of the two-wire current loop 2L.

connected. The interface is used for communication via the fieldbus.

Instead of the plurality of transducers Ml .Mn of Figure 1, so according to an embodiment of the present invention, now a single transducer M as shown in Figure 2, which over several

Fieldbus addresses # 1 ... # n has to be used. This transmitter M For example, it also has a large number of measuring inputs to which

Sensor can be connected and can transmit the measured values obtained from the corresponding measurement signals via the fieldbus using, for example, the HART protocol. The transmitter M can thus simulate several transducers.

The maximum number of transmissible by the transmitter M

Measured values only depend on the possible number of addresses and the number of measured values that can be transmitted via a (single) telegram of the fieldbus protocol used. The fieldbus will show the

Transmitter M then, for example, like a multidrop network consisting of several measuring transducers Ml.Mn. This makes the M transmitter compatible with all multidrop masters. As already mentioned, the number of sensors, for example, to a HART fieldbus, i. a fieldbus of the HART fieldbus protocol

used, can be connected, limited by the available energy, but for example. Measurements such as temperature, pressure and / or flow can also be measured passively and thus energy-saving. For example, if the transmitter M is connected to a 4-20 mA 2L 2L current loop, the transmitter M can output up to 20 mA

Provide a current loop for the measurement (s).

The proposed invention appears to be particularly advantageous with respect to a so-called multipoint temperature measurement. In doing so, it is detected by sensors distributed in the process, i. Temperature sensors, a temperature profile

added. These sensors can now be connected to an existing fieldbus via the proposed transmitter M. For example, the transmitter M can transmit the measured values recorded by the connected sensors via several fieldbus addresses # 1 ... # n.

In particular, the sensor M can have a plurality of analog and / or digital inputs via which the different sensors can be connected. Also, the transmitter M can measure several, in particular different physical and / or chemical parameters. In addition, the transmitter M can have an on-site display unit, via which the measured values and / or derived mean values, minimum and / or maximum values are displayed. Furthermore, the

Transmitter M have a microcontroller, which is used to process the transmitted signal from the various connectable sensors. Furthermore, a memory unit for storing the recorded measured values or other process-relevant data provided in the transmitter can also be provided.

LIST OF REFERENCE NUMBERS

MUS transmitter feed

2L two-wire current loop

M transmitter

M1 first transmitter

M2 second transmitter

M3 third transmitter

M4 fourth transmitter

Mn nth transmitter

# 1 first fieldbus address

# 2 second fieldbus address

# 3 third fieldbus address

# 4 fourth fieldbus address

#n nth fieldbus address

Claims

claims

1 . Transmitter (M) with an interface for transmitting measured values via a fieldbus (2L),

wherein the communication takes place via the fieldbus (2L) according to a fieldbus protocol,

the number of measured values provided by the transmitter (M) exceeds the number of measured values which can be called up by means of a basic command of the fieldbus protocol,

characterized,

the transmitter (M) has several field bus addresses (# 1 ... # n), and

a logic unit is provided which is used to distribute the measured values to the several fieldbus addresses (# 1 ... # n) of the transmitter (M) in such a way that the measured values are transmitted over the several fieldbus addresses (# 1 ... # n) of

Transmitter (M) by means of the basic commands are available.

2. Transmitter (M) according to claim 1,

characterized,

the measured values can be called up by the transmitter (M) without the use of manufacturer-specific or general commands.

3. Transmitter (M) according to claim 1 or 2,

characterized,

that the basic command is a command over which command all devices conforming to the fieldbus protocol used have.

4. Transmitter (M) according to the preceding claim,

characterized,

a retrieval of the measured values provided by the transmitter (M) via the fieldbus (2L) takes place by means of telegrams, which telegrams are addressed to the different fieldbus addresses (# 1 ... # n) of the transmitter (M) and contain the same basic command.

5. Transmitter (M) according to the previous claim,

characterized,

that base measurements can be retrieved from the associated fieldbus address (# 1 ... # n) by means of the basic command.

6. Transmitter (M) according to one of the preceding claims,

characterized,

that the logic unit is also used to assign the measured values provided by the transmitter (M) to the basic measured values which can be called up via the various fieldbus addresses (# 1 ... # n) of the transmitter (M) with the basic command.

7. Method for retrieving measured values

the measured values being provided by a transmitter (M) connected to a fieldbus (2L) and having several fieldbus addresses (# 1 ... # n),

and wherein the number of measurement values provided by the transmitter (M) exceeds the number of measurements retrievable by means of a basic command of the fieldbus protocol,

characterized,

that the measured values on the several fieldbus addresses (# 1 ... # n) of the

Transmitter (M) are distributed, and

the measured values are called up via the various fieldbus addresses (# 1 ... # n) of the transmitter (M) by means of the basic command.

8. Method according to the preceding claim,

characterized,

that no manufacturer-specific or general commands are used to retrieve the transmitter's measured values (M).

9. The method according to any one of claims 7 or 8,

characterized, that the measured values provided by the measuring transducer (M) are retrieved via the fieldbus (2L) by means of telegrams, which telegrams are addressed to the different fieldbus addresses (# 1 ... # n) of the measuring transducer (M) and contain the same basic command.

10. The method according to any one of claims 7 to 9,

characterized,

that the measured values provided by the transmitter (M) are assigned to the basic measured values which can be called up via the various fieldbus addresses (# 1 ... # n) of the transmitter (M) with the basic command.