EP0792501B1 - Device for adapting hart actuators or sensors to a local area network, and method for using same - Google Patents

Description

Technical area

The present invention relates to a device for adapting "HART" type sensors or actuators (registered trademark) with a network industrial premises, for example of the "FIP" type or of the "PROFIBUS" type, and a method of implementing this device.

State of the art

For many years the sensors used in automation use a 4-20 mA output to transmit their measurement. The current of 4 mA corresponds to the minimum measured value and 20 mA to the value maximum.

Sensors and actuators are now "intelligent". It is possible to communicate with them to implement advanced functions such as change of range, unit, testing possibilities, calibration, etc. The output information is digitized, which implies a notion of coding. Unfortunately there are many codings different, which creates an incompatibility between them.

To connect the automation devices (sensors, actuators, programmable logic controllers, computers, etc.) we use today preferably a field network, for example "HART" from Rosemount, or "FIP".

The "HART" network is described in an article entitled "The "HART®" Communication protocol (published in bulletin F 2695, Rev O-11/91, "The Smart Family", Rosemount). This protocol is also described in the article entitled "HART PROTOCOL" by Romilly Bowden (June 1991, available at Rosemount).

A "HART" modem is described in an article entitled "HART ' MODEM, ultra low power modem chip "(NCR 20C12, NCR" handbook ").

"HART" (Highway Addressable Remote Transducer) is the name given by Rosemount to its communication protocol for transmitters "intelligent".

"HART" uses the BELL 202 communication standard which based on frequency modulation signal transmission with 2 specific frequencies. The communication speed is 1200 baud.

• Il permet à la fois une communication analogique et numérique. L'accès aux données numériques peut se faire tout en utilisant le signal analogique pour la régulation ou la mesure.
• Le même jeu de cartes électroniques permet d'établir une liaison numérique avec des transmetteurs "2 fils" ou une communication numérique totale. Les instrumentistes peuvent commencer d'utiliser les transmetteurs "intelligents" avec les systèmes analogiques actuels, puis passer progressivement à des systèmes intégralement numériques sans avoir besoin de remplacer ou modifier les appareils de site.
• Plusieurs dispositifs de communication (par exemple RS3 ou l'interface de communication portative 268) peuvent communiquer simultanément.
• La possibilité d'adressage des transmetteurs permet de connecter jusqu'à 15 appareils sur la même paire de fils torsadés.
• Tous les transmetteurs de la "Famille Intelligente" utilisent une structure de message commune.

The main features of the "HART" are as follows:

• It allows both analog and digital communication. Access to digital data can be done while using the analog signal for regulation or measurement.
• The same set of electronic cards makes it possible to establish a digital link with "2-wire" transmitters or a total digital communication. Instructors can begin using "smart" transmitters with current analog systems, and then gradually transition to fully digital systems without the need to replace or modify site devices.
• Several communication devices (for example RS3 or the portable communication interface 268) can communicate simultaneously.
• The possibility of addressing the transmitters allows up to 15 devices to be connected on the same pair of twisted wires.
• All transmitters of the "Intelligent Family" use a common message structure.

This allows interfacing devices to communicate same way with future or current products.

The "FIP" network is standardized in France by the Technical Union of electricity or U.T.E. and the documents relating to this standard bear the references C46-601, PrC46-602, PrC46-603, PrC46-604, C46-605, PrC46-606, C46-607, C46-637, and C46-645.

The standardized industrial local network "FIP" is much more fast and complete than the "HART" network and above all it is standardized. However Rosemount smart sensors are very efficient and the fleet installed considerable.

On the other hand, the sensors compatible with the "FIP" network are still too few. The problem to be resolved therefore consists in carrying out a adapter which allows the use of "HART" sensors on the "FIP" network.

There is currently no such adapter. The the most common solution is to use the standard 4-20 mA output of "HART" sensors by connecting it to the input of an analog-digital converter itself connected to the network. The implementation of functions "intelligent" is impossible from a distance. The user must move with a configuration tool (the portable communication interface 268) to act on these functions: calibration, range change, etc. ..

The local network can also be a network of the type “PROFIBUS” as described in the article entitled “Kommunikation auf der Instrumentierungsebene ”by Walter Borst (Elektronik, vol. 40, number 20, 1st October 1991, pages 82-86, XP 000265899).

The solution envisioned by the creators of the "HART" protocol is obviously different. There is a local industrial network "HART" likely to implement all the functionalities of the sensors and actuators compatible.

• il est lent (1200 bits) par rapport au réseau "FIP" (1Mbit/s) ;
• c'est un réseau "propriétaire" donc non normalisé avec les inconvénients bien connus de ce genre de réseaux : concurrence limitée donc prix élevés, catalogues également limités, pas de garantie de pérennité, etc.

This "HART" network is little used because it has the following drawbacks:

• it is slow (1200 bits) compared to the "FIP" network (1Mbit / s);
• it is a "proprietary" network, therefore not standardized, with the well-known drawbacks of this type of network: limited competition, therefore high prices, catalogs also limited, no guarantee of durability, etc.

An aid entitled "The digitization of field instruments" by Wilhem Van der Bijl (Journal A, volume 32, number 3, October 1, 1991, Antwerp) describes a transmitter called "SMART". This is separated into two parts: the the first being a sensor module, and the second an electronic module. The first module includes a sensor, a digital-analog converter corresponding, and a signal processing means. The second module includes a data processing means and a communication part which produces an appropriate analog, digital or a combination of of them. This article then refers to the "HART" protocol which is a protocol of digital communication specially adapted to allow capacities 4-20 mA simultaneous digital and analog communications. This article declares then that the advantage of a configuration using separate modules is that in the event of a fault, the sensor module can be replaced without recalibration or reprogramming. In addition, this article considers the possibility of exchanging the communication part, when you want to use another communication protocol communication, for example "Fieldbus".

The object of the invention is to establish communication between the "FIP" network and "FIP" sensors and actuators as well as with sensors and "HART" actuators.

Statement of the invention

The present invention relates to a device for adapting "HART" type sensors or actuators with an industrial local network, characterized in that it comprises a first stage of galvanic isolation, a filter amplifier, a formatting discriminator, a modem restoring the coded digital information, a microcontroller programmed to translate messages in local network language, an interface circuit and a second galvanic isolation stage, connected in series, the first galvanic isolation stage being connected to the sensor and the second galvanic isolation stage being connected to the local network.

Advantageously, the local network can be a "FIP" network or a "PROFIBUS" network.

• initialisation de la liaison série à 1200 Bauds ;
• chargement du programme du circuit interface ;
• lecture des informations fixes du capteur ;
• lecture des commandes arrivant par le réseau local ;
• décodage des commandes arrivées par le réseau local, traduction et émission d'une trame "HART" ;
• lecture des variables du capteur.

The present invention also relates to a method of implementing this device, comprising the following steps:

• initialization of the serial link at 1200 Bauds;
• loading the interface circuit program;
• reading fixed information from the sensor;
• reading of orders arriving via the local network;
• decoding of orders received by the local network, translation and transmission of a "HART"frame;
• reading of sensor variables.

• émission d'une trame après calculs de parité et compactage ;
• réception d'une trame ;
• lecture et analyse de la trame reçue après décompactage.

Advantageously, the steps for reading sensor data include the following sub-steps:

• transmission of a frame after parity calculations and compaction;
• reception of a frame;
• reading and analysis of the frame received after unpacking.

Thanks to the presence of the inventive adapter devices who act as interpreters, sensors and actuators are "seen" the same way by the network user. The implementation of all the sensors and actuators compatible with the "HART" protocol become possible. All the digital information produced by a sensor passes through the local network. The exploitation of all the intelligent functions can be done from anywhere on the network.

Brief description of the drawings

• Figure 1 illustrates the subject of the invention;
• FIGS. 2A and 2B illustrate the operation of the "FIP" network;
• Figure 3 illustrates the operation of a "HART" sensor;
• Figures 4 and 5 illustrate the principle of coding the "HART" information;
• Figures 6 and 7 illustrate the device for adapting the invention;
• Figures 8 to 10 show flowcharts of operation of the device illustrated in Figure 6;
• FIG. 11 illustrates an example of application of the the invention.

Detailed description of embodiments

In the following description, we will consider as an example a local network of the "FIP" type.

As shown in Figure 1, the device of the invention must make it possible to establish communication between a local industrial network "FIP" 10 and "FIP" sensors 11 and "FIP" actuator 12, as well as with sensors "HART" 13 and actuator "HART '14.

Thanks to the presence of adapter devices 15 and 16 according to the invention, which serve as interpreters, these sensors and actuators are "seen" from the same way by the network user. The implementation of all sensors and actuators compatible with "HART" protocol become possible. All the digital information produced by a sensor passes through the "FIP" network. All intelligent functions can be operated at from any point on the network.

The local industrial network "FIP" makes it possible to connect the automation components by a single cable which adopts a bus structure. The first goal is to save on wiring compared to wire to wire links to a multiple input acquisition system. The media used are the shielded two-wire pair or optical fiber.

The digital coding of information improves the measurement accuracy. On the other hand, this coding is necessary to establish the two-way dialogue with "intelligent" sensors and actuators.

The network access mode is managed as illustrated in FIGS. 2A and 2B, on which are represented a bus arbiter AB and ST1 stations .... STn.

The bus arbiter manages the communication. He knows the stations transmitters of data and the frequency of each data. For example, as shown in Figure 2A, give the right to speak at the station ST2. All stations listen. ST1 and ST3 stations are interested here by the message sent by the station ST2, not the others.

As shown in FIG. 2B, the station ST2 transmits its message, stations ST1 and ST3 receive it simultaneously. Bus referee go to the next call in due time.

The functionalities of the "FIP" network are very numerous and it it is not possible to describe them here. As described above, this network is standardized in France by the Technical Union of Electricity.

Figure 3 illustrates a "HART" sensor.

• un capteur de température 20 ;
• un convertisseur du signal analogique en signal numérique 21;
• une mémoire du module détecteur 22 avec ses coefficients et ses caractéristiques ;
• un microprocesseur 23 permettant
  • linéarisation du capteur,
  • réétalonnage de l'échelle,
  • amortissement,
  • diagnostic,
  • utilisation d'unités physiques,
  • communication ;
• une mémoire 24 du module électronique avec ses points d'échelle réglés et la configuration du transmetteur ;
• un module 25 de réglages locaux du zéro et de l'échelle ;
• un convertisseur du signal numérique en signal analogique 26 ;
• un module de communication numérique 27, par exemple de type Bell 202 ;

l'entrée 28 étant une entrée de pression différentielle.This figure shows the following elements:

• a temperature sensor 20;
• an analog signal to digital signal converter 21;
• a memory of the detector module 22 with its coefficients and its characteristics;
• a microprocessor 23 allowing
  • linearization of the sensor,
  • recalibration of the scale,
  • amortization,
  • diagnostic,
  • use of physical units,
  • communication;
• a memory 24 of the electronic module with its set scale points and the configuration of the transmitter;
• a module 25 for local zero and scale adjustments;
• a converter from the digital signal to the analog signal 26;
• a digital communication module 27, for example of the Bell 202 type;

the input 28 being a differential pressure input.

The microprocessor 23, incorporated into the sensor, constitutes "intelligence" which brings new functions: linearization of the curve, change of scale, etc.

The non-volatile memories 22, 24 retain the settings, the coefficients and characteristics of the module.

The output 29 of the pressure information is presented under analog form thanks to the digital-analog converter 26 which delivers a current varying from 4 to 20 mA. All digital information remains accessible digitally and in both directions via the digital communication module 27 which superimposes "1" and "0" on the output current.

Figures 4 and 5 illustrate the coding principle of "HART" information, with adapter 32 to the "FIP" network 33.

The sensor or actuator 30 is powered by a power supply continuous 31 (usually 24 Volts). Depending on the value of the quantity physics measured by the sensor, a current having a value of 4 to 20 mA circulates in resistors R1 and R2. A weak sinusoidal signal I is superimposed on this current. As shown in Figure 5, a logical "1" is consisting of a sinusoid period at 1200 Hz, a logical "0" is formed a sinusoid at 2200 Hz of identical duration. Reference 34 corresponds to access to other users.

The current output is not disturbed by these sinusoids because their average value is zero. These frequencies corresponding to the Bell standard 202 used in the United States to transmit logic signals over the network telephone. Bell 202 modem circuits exist and allow to transform these frequencies in logic signals "0" or "1".

The sequence of bits forms bytes which are coded in ASCII. A series of characters forms a message. The "HART" protocol provides for number of standardized messages that make up the questions and answers necessary for dialogue with the whole range of sensor-actuators.

The adapter device of the invention is illustrated in FIG. 6, the references considered in FIG. 4 being preserved. This device includes a first galvanic isolation stage 35, a filter amplifier 36, a formatting discriminator 37, a modem 38 restoring the information digital coded, a microcontroller 39 programmed to translate the messages in “FIP” language, a known “FIP circuit” 40 serving as an interface with the "FIP" network, and a second stage of galvanic isolation 41.

This adapter device collects a voltage across the terminals of R1 proportional to the current 4-20 mA, as well as the sinusoidal voltage previously described. The first stage of galvanic isolation 35 allows transmit the alternating current without letting the DC pass. These signals are very low because the value of resistance R1 must be chosen the lowest possible. It is therefore necessary to amplify them. Amplifier 36 forms a filter bandpass to improve the signal to noise ratio.

The sinusoids V1 represented in FIG. 7A, are transformed into slots V2, represented in FIG. 7B, by the discriminator 37 then presented at the input of modem 38. This reconstitutes the "1" and the "0" logic and directs them to the serial input of microcontroller 39.

This microcontroller can reconstruct the "HART" messages, by decipher the content and translate it to make it available to the "FIP" network 33.

The dialogue also works the other way. That is to say from the microcontroller 39 to the modem 38, then from the modem 38 to the insulation galvanic 35. The message is then injected into the current loop and received by the sensor or actuator 30.

The microcontroller 39 can exchange data with the "FIP" network 33 thanks to one of the integrated circuits specially designed for this network (for example the Fullfip circuits designed by Cegelec, Fipiu by Telemechanics). Galvanic isolation 41, on the "FIP" side, is usually made with a transformer or an optical fiber.

The software implanted in the microcontroller works in the way illustrated in Figures 8, 9 and 10.

• initialisation de la liaison série à 1200 Bauds (module 50) ;
• chargement du programme du circuit "FIP" (module 51) ;
• lecture des informations fixes du capteur (module 52) ;
• lecture des commandes arrivant par le réseau "FIP" (module 53) ;
• décodage des commandes arrivées par le réseau "FIP", traduction et émission d'une trame "HART" (module 54) ;
• lecture des variables du capteur (module 55).

FIG. 8 illustrates the flowchart of operation of the program of the microcontroller, which comprises the following steps:

• initialization of the serial link at 1200 Bauds (module 50);
• loading the program of the "FIP" circuit (module 51);
• reading of fixed information from the sensor (module 52);
• reading of orders arriving via the "FIP" network (module 53);
• decoding of orders received by the "FIP" network, translation and transmission of a "HART" frame (module 54);
• reading of the sensor variables (module 55).

• émission d'une trame après calculs de parité et compactage (module 56) ;
• réception d'une trame (module 57) ;
• lecture et analyse de la trame reçue après décompactage (module 58) ;

le compactage correspondant au passage du code ASCII 8 bits à un code compacté 6 bits, le décompactage correspondant au passage du code compacté 6 bits au code ASCII 8 bits.FIG. 9 illustrates the flowchart of operation of a subroutine for reading the sensor data used for the modules 52 and 55. It comprises the following steps:

• transmission of a frame after parity calculations and compaction (module 56);
• reception of a frame (module 57);
• reading and analysis of the frame received after unpacking (module 58);

the compaction corresponding to the transition from the 8-bit ASCII code to a compacted 6-bit code, the decompaction corresponding to the transition from the compacted 6-bit code to the 8-bit ASCII code.

Figure 10 illustrates the Analyze-Command flowchart (module 54). The action considered corresponds to a letter R, M, A, F, U ...... AT each letter (tests 60 to 65) corresponds to an associated treatment (modules 66 to 71).

• la lecture de la demande transmise par le réseau "FIP" ;
• l'envoi de la commande correspondante vers le capteur ou l'actionneur en langage "HART";
• la lecture de la réponse ;
• la traduction de la réponse et mise à disposition de la donnée vers le réseau "FIP" qui se charge de la transmettre automatiquement.

This software therefore allows:

• reading the request transmitted by the "FIP"network;
• sending the corresponding command to the sensor or actuator in "HART"language;
• reading the response;
• translating the response and making the data available to the "FIP" network, which is responsible for automatically transmitting it.

Application example

All common applications in automation can be envisaged (acquisition of measurements, regulation, supervision, maintenance of sensors, etc.).

Figure 11 shows an example of using adapters in the field of maintenance. In this figure are represented a microcomputer 75, adapters 76, 77, 78 respectively connected to sensors 79, 80 and 81.

• les mesures et l'enregistrement des grandeurs mesurées par les capteurs avec l'unité physique, la constante de temps, le pourcentage de la gamme, choisis à distance par l'utilisateur ;
• les opérations de maintenance par lecture des indications mémorisées à cet effet dans le capteur ;
• les opérations de test des capteurs (périodiques ou déclenchées par l'opérateur) ;
• l'édition d'un journal avec l'heure des incidents, leur nature, la cause, le remède apporté ;
• les opérations de réglage et d'étalonnage à distance deviennent possibles en utilisant des "manifolds" (ce sont des vannes télécommandables). Le réseau se charge de transmettre les ordres de commande. Il renseigne également les autres utilisateurs de l'indisponibilité de ce capteur durant toute l'opération.

From the microcomputer, it is possible to carry out:

• the measurements and recording of the quantities measured by the sensors with the physical unit, the time constant, the percentage of the range, chosen remotely by the user;
• maintenance operations by reading the indications stored for this purpose in the sensor;
• sensor test operations (periodic or triggered by the operator);
• the edition of a newspaper with the time of the incidents, their nature, the cause, the remedy brought;
• remote adjustment and calibration operations become possible using "manifolds" (these are remotely controllable valves). The network is responsible for transmitting control orders. It also informs other users of the unavailability of this sensor during the entire operation.

Claims (3)

1. Device for adapting sensors or actuators of the "HART" type with a local industrial network of the "FIP" or Profibus type, characterized in that it comprises a first isolation stage (35), a filter amplifier (36), a shaping discriminator (37), a modem (38) restoring coded digital informations, a microcontroller (39) programmed for translating the messages into the language of the local network, an interface circuit (40) and a second isolation stage (41), connected in series, the first isolation stage (35) being connected to the sensor (30) and the second isolation stage (41) to the local network (33).
2. Method for using the device according to claim 1, characterized in that the microcontroller (39) of said device dialogues with the local network (33) and the sensor (30), according to the following stages:

   initialization of the 1200 Bauds series link (module 50),

   loading the interface circuit program (module 51),

   reading fixed informations of the sensor (module 52),

   reading controls arriving with the local network (module 53),

   decoding controls which have arrived through the "FIP" or Profibus network,

   translation and emission of a "HART" frame (module 54),

   reading sensor variables (module 55).
3. Method according to claim 2, characterized in that the sensor data reading stages (modules 52 and 55) comprise the following substages:

   emission of a frame following parity and compacting calculations (module 56),

   reception of a frame (module 57),

   reading and analysis of the frame received after decompacting (module 58).

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