WO2013117820A1

WO2013117820A1 - Fieldbus communicator

Info

Publication number: WO2013117820A1
Application number: PCT/FI2013/050141
Authority: WO
Inventors: Kari Autio; Heikki Laurila; Marko Stenbacka
Original assignee: Beamex Oy Ab
Priority date: 2012-02-08
Filing date: 2013-02-08
Publication date: 2013-08-15
Also published as: FI20125683L

Abstract

In the invention, a fieldbus communicator (400) is formed, where several fieldbus protocols are supported. This has been achieved by providing the fieldbus communicator with a pair of fieldbus connecting terminals (401) for measuring of the fieldbus signal. The fieldbus communicator comprises a processor (416) and the pair of fieldbus connecting terminals comprises a signal terminal and a ground terminal. The fieldbus communicator further comprises at least two parallel fieldbus protocol units (404, 405, 406) between the processor and the signal terminal of the pair of fieldbus connecting terminals. Each fieldbus protocol unit is assigned to its respective fieldbus protocol. Further, the fieldbus communicator comprises a selection unit (403) for selecting a fieldbus protocol unit and a voltage unit between the terminals of said pair of fieldbus connecting terminals, which voltage unit is arranged to adjust the voltage and the impedance according to the selected fieldbus protocol unit. The selecting unit is controlled manually through the user interface. The user interface is realized by a touch screen or a combination of a touch screen and keyboard or only by a keyboard.

Description

Fieldbus communicator

The invention relates to a fieldbus communicator with a processor and one pair of fieldbus connection terminals with a signal terminal and an earth terminal. PRIOR ART

In industry, the same process and phase can include several process instruments. These are devices or converters that measure a variable and convert the measured value into another, usually electronic, form. Examples of such is a pressure transducer which measures pressure and converts the measured value into one of the following forms: measure, current signal, voltage signal, display, digital signal or something else. Also different controllers related to the process are process instruments.

Devices related to the process may be connected via a fieldbus. By a fieldbus such a usually digital communications solution is meant, whereby several fieldbus instruments are joined in the same fieldbus segment. A fieldbus instrument is a process instrument, which measures continuously or at some frequency a variable and converts the measured value into a form according to the fieldbus protocol. As an example serves a pressure transducer, if a pressure of 1 ,0000 bar is connected to its input, the output according to the fieldbus protocol of the sender needs to tell, that the input is ,0000 bar.

Figure 1 shows a fieldbus 102 related to an industrial process 101 , with three fieldbus instruments: the first fieldbus instrument 103a, the second fieldbus instrument 03b and the third fieldbus instrument 103c.

Fieldbus instruments can include for example frequency converters, switches, valves and measuring devices. The basic idea in a fieldbus is digital data transmission, by which information can be exchanged bidirectionally between the control system of the process and the fieldbus instruments. By means of a fieldbus processes are measured and controlled and they can be automated. Advantages in use of fieldbuses are for example decreasing of wiring and connections, bidi- rectional data transmission and decreasing of maintenance costs. On the other hand, fieldbuses require special skills and management of large entireties from their operator. There are several different standards of fieldbuses, and they use their own fieldbus protocols respectively. A fieldbus communicator is used to communicate with the fieldbus instruments of a fieldbus. Therewith for example different settings of fieldbus instruments can be checked and changed. The fieldbus communicator has to support the fieldbus protocol of the used fieldbus. Generally a fieldbus communicator is manufactured to support one fieldbus proto- col. Publication US7117122 discloses a device for diagnosis of a fieldbus with features of a fieldbus communicator. The device can be operated with two different fieldbus protocols by changing terminals. This slows down the measurements and may cause incorrect measurements or failure of measuring if wrong terminals are used. Usually, process instruments need to be calibrated or checked regularly for proper operation and proper and accurate conversion of signal. Thereby an accurate signal of correct variable is fed into the input, and at the output of the device the signal is read which is indicated by the transmitter as the input. By comparing these two it can be confirmed whether the transmitter is working correctly, that is, whether it converts the output correctly into input. For that reason process calibrators are used that are measuring devices that are accurate enough, so that they can be used for calibrating process instruments. Usually, process calibrators support such variables that are used by the most typical process instruments, that is, for example, pressure, voltage, current, temperature, frequency and the like. Figure 2 shows an example of calibration of fieldbus instruments of the fieldbus 102 shown in Figure 1. The figure shows the third fieldbus instrument 103c being calibrated. The calibration is performed with a process calibrator 201. The process calibrator feeds a known signal to the third fieldbus instrument with the signal unit 203 and reads an analogical signal with output unit 202. Fieldbus instru- ments according to the HART fieldbus protocol comprise an analogical current output which varies between 4-20 mA. A HART fieldbus protocol further includes digital communication. HART fieldbus protocol is the most common fieldbus protocol used in industry. If some other fieldbus protocol is used, such as FOUNDATION Fieldbus or Profibus protocols, where communication is only digi- tal, the output of the fieldbus is to be read from the fieldbus. Thereby the process calibrator feeds a known signal to the fieldbus instrument, and the output of the fieldbus instrument is read by the fieldbus communicator 204.

Generally, the fieldbus communicator is able to communicate with only one fieldbus protocol. This may be problematic, if several different fieldbus protocols are used in the same factory complex or if the operator of the devices moves with the devices from place to place. Thereby the measurer needs several devices. Measurements are not successful with a wrong fieldbus communicator or incorrect measurements may be produced or, in the worst case, this may lead to faults or breakage of components.

SUMMARY The object of the invention is a solution, by which the disadvantages and drawbacks of the prior art can be diminished. Especially, the object of the invention is a solution, by which the use of a fieldbus communicator may be simplified and at the same time its features may be diversified.

The objects according to the invention are achieved by a fieldbus communicator, characterized in what is disclosed in the independent claim. Some preferred embodiments of the invention are disclosed in the dependent claims.

The leading idea of the invention is to form a fieldbus communicator which supports several fieldbus protocols and is arranged such that it does not hamper the use of a fieldbus communicator. This has been achieved by providing the fieldbus communicator with one pair of connecting terminals, to which one or more parallel fieldbus protocol units are connected by means of the selecting unit. By means of the selecting unit one can select the fieldbus protocol unit, i.e. fieldbus protocol, to be used. The fieldbus communicator further comprises a voltage unit between the terminals of said pair of fieldbus connecting terminals, which voltage unit is ar- ranged to adjust the voltage and the impedance according to the selected fieldbus protocol unit.

A fieldbus communicator according to an embodiment of the invention comprises a processor and one pair of fieldbus connection terminals with a signal terminal and a ground terminal. The fieldbus communicator is connected to the fieldbus through the pair of fieldbus connecting terminals. According to a preferred embodiment of the invention the fieldbus communicator comprises at least two parallel fieldbus protocol units between the processor and the signal terminal of the pair of fieldbus connecting terminals. Each fieldbus protocol unit is assigned to its respective fieldbus protocol. Further, the fieldbus communicator comprises a selec- tion unit for selecting a fieldbus protocol unit and a voltage unit between the terminals of said pair of fieldbus connecting terminals, which voltage unit is arranged to adjust the voltage and the impedance according to the selected fieldbus protocol unit. In an embodiment of the process calibrator according to the invention the fieldbus communicator comprises at least one communication unit for communicating with the fieldbus instruments of the fieldbus. In another embodiment of the fieldbus communicator according to the invention, the communication unit is a part of the fieldbus protocol unit.

In a third embodiment of the fieldbus communicator according to the invention the fieldbus communicator comprises input means for controlling the fieldbus communicator. In a fourth embodiment of the fieldbus communicator according to the invention, the input means is a touch screen. In a fifth embodiment of the fieldbus communicator according to the invention, the touch screen is arranged to show the user interface.

In a sixth embodiment of the fieldbus communicator according to the invention, the voltage unit is arranged to adjust the impedance with a regulating resistor. The regulating resistor may, for example, be an arrangement, where the neces- sary resistor is selected or otherwise the value of the resistor is changed into what is necessary.

In a seventh embodiment of the fieldbus communicator according to the invention, the fieldbus communicator is portable. In an eighth embodiment of the fieldbus communicator according to the invention, the fieldbus communicator is fixedly mountable.

In a ninth embodiment of the fieldbus communicator according to the invention, the components and connections of the fieldbus communicator are adapted to potentially explosive atmospheres, i.e. the connections are arranged such that they are applicable in possibly explosive atmospheres. This is realized by choos- ing components and connections such that the device does not produce sparking even in case of a failure.

In a tenth embodiment of the fieldbus communicator according to the invention, the selecting unit for selecting the fieldbus protocol unit is arranged to be used manually. Thereby the operator of the fieldbus communicator calibrator selects by means of the user interface the fieldbus protocol unit to be used. The selecting unit sees to it that only the selected fieldbus protocol unit is active. The selecting unit is thus arranged to manually switch the fieldbus protocol unit according to the selected fieldbus protocol to be active. In an eleventh embodiment of the fieldbus communicator according to the invention, there are two fieldbus protocol units, and the fieldbus protocols supported by them are some of the following: HART, FOUNDATION Fieldbus and Profibus. In a twelfth embodiment of the fieldbus communicator according to the invention, there are three fieldbus protocol units, and the fieldbus protocols supported by them are: HART, FOUNDATION Fieldbus and Profibus.

In a thirteenth embodiment of the fieldbus communicator according to the invention, the fieldbus communicator comprises a memory, and device description files of fieldbus instruments can be stored in the memory. An advantage of the invention is that by means of it a fieldbus communicator is provided, by means of which the communication with the devices of the fieldbus becomes easier, since the amount of devices needed decreases. Thereby the calibration also is accelerated and performing it becomes clearer, whereby the amount of mistakes decreases. An advantage of the invention is further that it decreases the possibility of errors. Further, the general convenience of use is improved.

The invention also enables the use of a fieldbus communicator in several types of fieldbuses.

DESCRIPTION OF THE FIGURES In the following, the invention will be described in detail. In the description, reference is made to the enclosed drawings, in which

Figure 1 shows by way of example a fieldbus,

Figure 2 shows by way of example a fieldbus and a process instrument in a fieldbus, to which fieldbus further a fieldbus communicator is connect- ed,

Figure 3 shows by way of example a fieldbus and a fieldbus communicator according to the invention,

Figure 4 shows an example of a fieldbus communicator according to the invention shown as functional blocks and Figure 5 shows another example of the fieldbus communicator according to the invention.

DETAILED DESCRIPTION OF FIGURES

Figures 1 and 2 are shown in connection of the prior art. Figure 3 shows an example of the use of the fieldbus communicator 302 according to the invention in communication with the fieldbus instruments. The fieldbus communicator according to the invention comprises a first unit 303 and a second unit 301 for communication with the fieldbus 102. The first unit represents the signal terminal and the second unit represents the ground terminal. The fieldbus communicator reads the output of the second fieldbus instrument 103b in the fieldbus. When necessary, the settings of the second fieldbus instrument can also be changed. Thereby the fieldbus communicator is arranged to transmit a message, an instruction or similar to the fieldbus instrument in question. The output of the fieldbus instrument may be the result of the measuring of the fieldbus instru- ment or the feedback of the fieldbus instrument to a calibration signal or a reply to the afore-mentioned message or similar, where for example the fieldbus instrument confirms the new settings received by it.

Figure 4 shows an example of a fieldbus communicator 400 according to the invention shown as functional blocks. The fieldbus communicator 400 according to the example comprises a pair of connecting terminals 401 with a signal terminal and a ground terminal. Said pair of connecting terminals is a pair of fieldbus connecting terminals for measuring the signal of the fieldbus and for communication with the fieldbus instruments.

The fieldbus communicator 400 comprises a control logic 403 for functioning as a selecting unit. The control logic controls the functioning of the pair of fieldbus connecting terminals.

The fieldbus communicator 400 according to the example comprises three fieldbus protocol units: the first fieldbus protocol unit 404, the second fieldbus protocol unit 405 and the third fieldbus protocol unit 406. Each fieldbus protocol unit is assigned to its respective fieldbus protocol. Control logic 403 selects which one of the fieldbus protocol units is active, i.e. which fieldbus protocol is used by the fieldbus communicator. The control logic is controlled manually by the user interface. Since the fieldbus protocols are different, a communication unit (not shown in the figure) is needed for the communication with the fieldbus and the fieldbus instruments therein, which communication unit sees to it that the communication corresponds to the protocol used. There may be several communication units, i.e. one for each protocol, and each communication unit is in a respective fieldbus protocol unit or in connection with it.

The fieldbus communicator 400 comprises a voltage supply 408, by which a desired supply voltage can be provided between the terminals of the pair of connection terminals 401 , which supply voltage corresponds to the fieldbus protocol.

The fieldbus protocols require a suitable impedance for the supply voltage, in or- der to enable the communication. This impedance is regulated by the impedance selector 407. The impedance selector may be a regulating resistor or a similar arrangement.

Said voltage supply 408 and impedance selector 407 are controlled by the control logic 403. The voltage supply and the impedance selector form together a voltage unit. The supply voltage travels through the impedance selector 407, where the desired impedance is selected for the supply voltage under the control of the user interface. The selecting logic selects whether the supply voltage is connected and with which impedance, or without impedance, i.e. with a low impedance.

The fieldbus communicator 400 comprises a processor 416 which controls the operation of the fieldbus communicator. Signals coming to the processor travel via the signal processing arrangement 411. Hereby the signals are converted to a form understood by the processor. The fieldbus communicator further comprises a touch screen 412 and a keyboard 413 which function as input means. The fieldbus communicator may also be realized with a regular display or with a touch screen without the keyboard. The user interface of the fieldbus communicator is shown on a touch screen.

The fieldbus communicator comprises a driving power arrangement 414 which provides the driving power of the fieldbus communicator. The driving power arrangement may comprise an accumulator 415, but also other energy sources can be used, such as batteries or fuel cells. The fieldbus communicator can also be connected to an external source of energy, such as, for example, to mains current. This can be done, for example, if the fieldbus communicator is mounted in a fixed manner. The fieldbus communicator may comprise connectors for transmitting data. In a case according to the example, the fieldbus communicator comprises a first 417 and a second USB connector 418 and an Ethernet network connector 419. Naturally, there may be other connectors as well and the amount of them may vary. The fieldbus communicator of Figure 4 comprises a ROM memory 420, a RAM memory 421 and an add-on storage 422. The instructions and information needed by the fieldbus communicator for its functioning are stored permanently in the ROM memory 420. The RAM memory 421 is used to store for example temporary files such as measuring results and similar. The add-on storage may be fixedly mountable, for example at the factory or the distributor, and it contains files that determine functioning of the fieldbus communicator. These files may comprise device description files. To communicate with the fieldbus instrument, usually a device description file is needed, by means of which the fieldbus communicator supports different fieldbus instruments. New or updated device description files can be added to the add-on storage via the data transmission connectors described above. The add-on storage may also be replaceable.

Figure 5 shows in more detail the fieldbus communicator according to the invention.

A fieldbus communicator according to the example comprises a signal terminal 501 and an earth terminal 502, which form a pair of fieldbus connecting terminals that is connectable to the fieldbus. The pair of fieldbus connecting terminals exists for reading of the fieldbus signal. Via the pair of fieldbus connection terminals also communication with the fieldbus instruments in the fieldbus can be arranged.

The fieldbus communicator comprises a control logic 503, which controls the func- tioning of the pair of fieldbus connecting terminals, i.e. it functions as a selecting unit. The control logic is connected at least to the signal terminal 501. The fieldbus communicator comprises a processor 51 . Signals coming to the processor travel via the signal processing arrangement 510. Hereby the signals are converted to a form understood by the processor. Furthermore, the signal processing arrangement can function as a safety unit by preventing access of voltage spikes or currents to the processor, which are harmful to the processor. This can be attended to also by another arrangement, such as fuses or relays. The signal processing arrangement is connected at least between the signal terminal 501 and the processor. The fieldbus communicator according to the example comprises three fieldbus protocol units: the first fieldbus protocol unit 504, the second fieldbus protocol unit 505 and the third fieldbus protocol unit 506. Each fieldbus protocol unit is assigned to its respective fieldbus protocol. In this example, the first fieldbus proto- col unit supports the HART protocol, the second fieldbus protocol unit supports the FOUNDATION Fieldbus protocol, and the third fieldbus protocol unit supports the Profibus protocol. Control logic 503 selects which one of the fieldbus protocol units is active, i.e. which fieldbus protocol is used by the process calibrator. For communicating with the fieldbus and the fieldbus instruments therein a communi- cation unit is needed, which is described in connection with Figure 7. The control logic is controlled via the user interface, i.e. the fieldbus protocol to be used is selected in the user interface.

The fieldbus communicator comprises a voltage unit 512. This comprises an impedance selector 508 and a voltage source 509. The voltage source is connected between the signal terminal 501 and the earth terminal 502. The fieldbus instruments are mostly two-wire transmitters, i.e. they receive the necessary operating voltage through the same connections, through which they also communicate. The fieldbus communicator may either feed the supply voltage necessary for the fieldbus instrument by itself at the same time as it communicates, or the supply voltage may come from outside and the device only communicates with the fieldbus instrument. The supply voltage is usually ca. 24 VDC, but it may typically vary between ca. 9-32 VDC. The supply voltage can be adjusted to correspond to the used fieldbus protocol by the voltage source.

Impedances differ depending on the communication protocol. The HART protocol typically requires an impedance of ca. 250 ohm, whereas the FOUNDATION Fieldbus and Profibus protocols require an impedance of ca. 50 ohm. Impedance is converted to correspond to the communication protocol by the impedance selector 508.

The control unit 503 controls the voltage unit 512 with the user interface accord- ing to the selected communication protocol to be used. Thereby the voltage unit adjusts the voltage and the impedance to correspond to the communication protocol.

Above, some preferred embodiments according to the invention have been described. The invention is not limited to the solutions described above, but the in- ventive idea can be applied in numerous ways within the scope of the claims.

Claims

Claims . A fieldbus communicator (302; 400) with a processor (416; 511 ) and one pair of fieldbus connecting terminals with a signal terminal (501 ) and a ground terminal (502), characterized in that the fieldbus communicator further comprises

- at least two parallel fieldbus protocol units (404, 405, 406; 504, 505, 506) between the processor and the signal terminal of the pair of fieldbus connecting terminals, each fieldbus protocol unit being assigned to its own fieldbus protocol

- a selecting unit (403; 503) for selecting the fieldbus protocol unit

- a voltage unit (512) between the terminals of said pair of fieldbus connecting terminals, which voltage unit is arranged to adjust the voltage between said terminals and the impedance according to the selected fieldbus protocol unit.

2. The fieldbus communicator (302; 400) according to claim 1 , characterized in that the fieldbus communicator comprises at least one communication unit for communication with the fieldbus instruments of the fieldbus.

3. The fieldbus communicator (302; 400) according to claim 2, characterized in that the communication unit is a part of the fieldbus protocol unit.

4. The fieldbus communicator (302; 400) according to any one of claims 1-3, characterized in that it comprises input means for controlling of the fieldbus communicator.

5. The fieldbus communicator (302; 400) according to claim 4, characterized in that the input means is a touch screen (412).

6. The fieldbus communicator (302; 400) according to claim 5, characterized in that the touch screen (412) is arranged to show the user interface.

7. The fieldbus communicator (302; 400) according to any one of claims 1-6, characterized in that the voltage unit (512) is arranged to adjust the impedance with a regulating resistor.

8. The fieldbus communicator (302; 400) according to any one of claims 1-7, characterized in that the fieldbus communicator is portable.

9. The fieldbus communicator (302; 400) according to any one of claims 1-7, characterized in that the fieldbus communicator is fixedly mountable.

10. The process calibrator (302; 400) according to any one of claims 1-9, characterized in that the components and connections of the fieldbus communicator are arranged such that they can be used in possibly explosive atmospheres.

11. The fieldbus communicator (302; 400) according to any one of claims 1-10, characterized in that the selecting unit (403) for selecting the fieldbus protocol unit is arranged to be used manually.

12. The fieldbus communicator (302; 400) according to any one of claims 1-11 , characterized in that there are two fieldbus protocol units (404, 405, 406; 504, 505, 506), and the fieldbus protocols supported by them are some of the following: HART, FOUNDATION Fieldbus and Profibus.

13. The fieldbus communicator (302; 400) according to any one of claims 1-11 , characterized in that there are three fieldbus protocol units (404, 405, 406; 504, 505, 506), and the fieldbus protocols supported by them are: HART, FOUNDATION Fieldbus and Profibus.

14. The fieldbus communicator (302; 400) according to any one of claims 1-13, characterized in that the fieldbus communicator comprises a memory and device description files of the fieldbus instruments can be stored in the memory.