Classifications

• • G—PHYSICS
  • G08—SIGNALLING
  • G08C—TRANSMISSION SYSTEMS FOR MEASURED VALUES, CONTROL OR SIMILAR SIGNALS
  • G08C19/00—Electric signal transmission systems
  • G08C19/02—Electric signal transmission systems in which the signal transmitted is magnitude of current or voltage

Definitions

• the present invention relates to a device for adapting sensors or actuators of the "HART" type (registered trademark) with an industrial locar network, for example of the "FIP” type or of the “PROFIBUS” type, and a method of setting up work of this device.
• HART 'from Rosemount or
• FIP field network
• HART ' is described in an article entitled “The HART® Communication Protocol” (published in bulletin F 2695, Rev 0-11 / 91, “The Smart Family”, Rosemount). This protocol is also described in the article entitled “HART PROTOCOL” by Romilly Bowden (June 1991, available from Rosemount).
• a “HART” modem is described in an article entitled “HART 'MODEM, ultra low power modem chip” (NCR 20C12, NCR “handbook”).
• HART uses the BELL 202 communication standard which is based on frequency modulation signal transmission with 2 specific frequencies.
• the communication speed is 1200 baud.
• 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 "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 local network can also be a "PROFIBUS" type network as described in the article entitled “Kommunikation auf der Instrumentierungsebene” by Walter Borst (Elektronik, vol. 40, number 20, October 1, 1991, pages 82-86, XP 000265899).
• the object of the invention is to establish communication between a local network for example "FIP” or “PROFIBUS” and the sensors and actuators for example “FIP” or “PROFIBUS” as well as with the sensors and actuators " HART.
• the present invention relates to a device for adapting sensors or actuators of the "HART 'type with an industrial local area 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 the messages into the language of the local network, an interface circuit and a second stage of galvanic isolation
• the local network can be a "FIP” network or a "PROFIBUS" network .
• the present invention also relates to a method for implementing this device, comprising the following steps:
• the steps for reading sensor data include the following sub-steps:
• the sensors and actuators are “seen” in the same way by the network user.
• the implementation of all sensors and actuators compatible with the "HART" protocol becomes possible. All the digital information produced by a sensor passes through the local network. All intelligent functions can be operated from any point on the network.
• a local network of the "FIP" type will be considered by way of example.
• the device of the invention must make it possible to establish communication between an industrial local network "FIP” 10 and “FIP” sensors 11 and “FIP” actuator 12, as well as with sensors “HART 13 and actuator” HART 14.
• the local industrial network "FIP" makes it possible to connect the automation components to each other 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 the information makes it possible to improve the accuracy of the measurements. On the other hand, this coding is necessary to establish the two-way dialogue with the "intelligent" sensors and actuators.
• the mode of access to the network is managed in the manner illustrated in FIGS. 2A and 2B, on which are represented a bus arbiter AB and stations ST1 .... STn.
• the bus arbiter manages the communication. He knows the data transmitting stations and the frequency of each data. It can for example, as shown in FIG. 2A, give the right to speak to the station ST2. All stations listen. The stations ST1 and ST3 are here interested in the message sent by the station ST2, not the others.
• the station ST2 transmits its message, the stations ST1 and ST3 receive it simultaneously.
• the bus arbiter proceeds to the next call in due course.
• the functionalities of the "FIP" network are very numerous and it is not possible to describe them here. As described above, this network is standardized in France by the Technical Union of Electricity.
• FIG. 3 illustrates a "HART" sensor.
• 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 of the digital signal into 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
• the non-volatile memories 22, 24 store the settings, the coefficients and the characteristics of the module.
• the output 29 of the pressure information is in analog form thanks to the digital-analog converter 26 which delivers a current varying from 4 to 20 mA. All of the digital information remains accessible in digital form and in both directions via the digital communication module 27 which supe suposes "1" and "0" on the output current.
• FIGS. 4 and 5 illustrate the principle of coding the "HART" information, with the adapter 32 to the "FIP” network 33.
• the sensor or actuator 30 is supplied by a continuous supply 31 (usually 24 Volts).
• a current having a value of 4 to 20 mA flows through the resistors R1 and R2.
• a weak sinusoidal signal i is supe ⁇ osed to this current.
• a logic "1” consists of a sinusoid period at 1200 Hz
• a logical "0" consists of a sinusoid at 2200 Hz of identical duration.
• Reference 34 corresponds to the accesses to other users.
• the sequence of bits forms bytes which are coded in ASCII.
• the adapter device of the invention is illustrated in Figure 6, the references considered in Figure 4 being retained.
• This device includes a first galvanic isolation stage 35, a filter amplifier 36, a formatting discriminator 37, a modem 38 restoring the coded digital information, 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 galvanic isolation stage 41.
• This adapter device collects at the terminals of R1 a voltage proportional to the current 4-20 mA, as well as the sinusoidal voltage previously described.
• the first galvanic isolation stage 35 allows the alternating current to be transmitted without allowing the DC to pass. These signals are very weak because the value of the resistance R1 must be chosen as low as possible. It is therefore necessary to amplify them.
• the amplifier 36 forms a bandpass filter in order 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 the modem 38.
• the latter reconstitutes the logical "1" and "0" and directs them to the serial input of the microcontroller 39.
• This microcontroller can reconstruct the "HART" messages, 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 galvanic isolation 35. The message is then injected into the current loop and received by the sensor or the 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
• the galvanic isolation 41 on the "FIP" side, is usually carried out with a transformer or an optical fiber.
• FIG. 8 illustrates the flowchart of operation of the program of the microcontroller, which comprises the following steps:
• 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
• FIG. 10 illustrates the flowchart analyze-command (module 54).
• the action considered corresponds to a letter R, M, A, F, U
• Each letter (tests 60 to 65) corresponds to an associated processing (modules 66 to 71).
• FIG. 11 illustrates an example of use of the adapters in the field of maintenance.
• a microcomputer 75 adapters 76, 77, 78 connected respectively to sensors 79, 80 and 81. From the microcomputer, it is possible to carry out:

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Arrangements For Transmission Of Measured Signals (AREA)
• Control By Computers (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=9468941

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• 1994
  • 1994-11-18 FR FR9413844A patent/FR2727230B1/fr not_active Expired - Fee Related
• 1995
  • 1995-11-16 WO PCT/FR1995/001508 patent/WO1996016384A1/fr active IP Right Grant
  • 1995-11-16 JP JP8516619A patent/JPH10509261A/ja active Pending
  • 1995-11-16 EP EP95940321A patent/EP0792501B1/de not_active Expired - Lifetime
  • 1995-11-16 DE DE69508424T patent/DE69508424T2/de not_active Expired - Fee Related

Non-Patent Citations (1)

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