WO2012139640A1 - Système de transmission, unité centrale ou appareil de terrain dans un système de transmission de ce type et procédé de fonctionnement de ce système - Google Patents

Système de transmission, unité centrale ou appareil de terrain dans un système de transmission de ce type et procédé de fonctionnement de ce système Download PDF

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Publication number
WO2012139640A1
WO2012139640A1 PCT/EP2011/055830 EP2011055830W WO2012139640A1 WO 2012139640 A1 WO2012139640 A1 WO 2012139640A1 EP 2011055830 W EP2011055830 W EP 2011055830W WO 2012139640 A1 WO2012139640 A1 WO 2012139640A1
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WO
WIPO (PCT)
Prior art keywords
transmission system
field device
uart
sink
power source
Prior art date
Application number
PCT/EP2011/055830
Other languages
German (de)
English (en)
Inventor
Gerhard Hammer
Thomas Hauschulz
Original Assignee
Siemens Aktiengesellschaft
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens Aktiengesellschaft filed Critical Siemens Aktiengesellschaft
Priority to PCT/EP2011/055830 priority Critical patent/WO2012139640A1/fr
Publication of WO2012139640A1 publication Critical patent/WO2012139640A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/54—Systems for transmission via power distribution lines
    • H04B3/548—Systems for transmission via power distribution lines the power on the line being DC
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0264—Arrangements for coupling to transmission lines
    • H04L25/0272—Arrangements for coupling to multiple lines, e.g. for differential transmission
    • H04L25/0276—Arrangements for coupling common mode signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2203/00—Indexing scheme relating to line transmission systems
    • H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
    • H04B2203/5404—Methods of transmitting or receiving signals via power distribution lines
    • H04B2203/5412—Methods of transmitting or receiving signals via power distribution lines by modofying wave form of the power source
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2203/00—Indexing scheme relating to line transmission systems
    • H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
    • H04B2203/5462—Systems for power line communications
    • H04B2203/547—Systems for power line communications via DC power distribution

Definitions

  • Transmission system central processing unit or field device in such a transmission system and method of operation of the system
  • the invention relates to a transmission system, a central processing unit and / or a field device in such a transmission ⁇ system or for such a transmission system and a method for operating the system and / or the included or usable in such a system units, ie in particular central unit and field device.
  • a transmission system a central processing unit and / or a field device in such a transmission ⁇ system or for such a transmission system
  • a method for operating the system and / or the included or usable in such a system units ie in particular central unit and field device.
  • an outbound connection from the central unit to supply energy to the or each field device and a communication link to and from the field device ⁇ is simultaneously via a two-wire line be.
  • Transmission systems based on a two-wire line with a central unit and at least one field device are known per se.
  • An ⁇ in a transmission system having at least one central unit and at least one field device, frequently a plurality of field devices, wherein a connection to the power supply of the or each field device and a communicative connection from and to the field device simultaneously consists of a two-wire line, the following is provided:
  • the central processing unit comprises at least one DC source ⁇ and a communication module.
  • a communication module is a so-called UART (Universal Asynchronous Receiver Transmitter) into consideration.
  • the field device comprises at least a first and a second DC sink and also a communication ⁇ block.
  • a so-called UART is considered as a communication module.
  • An output signal of the communication module in particular ⁇ sondere a transmission signal as an output signal is superimposed directly one of the two-wire line impressed by the DC bus voltage source.
  • the direct storage is there ⁇ for example, without any additional coding, as her otherwise intended to ⁇ for transmission over two-wire lines to avoid an information-dependent DC component.
  • the direct superposition furthermore takes place, for example, as a unipolar, so-called NRZ signal.
  • the two-wire line is connected for data and energy transmission in the transmission system to the DC power source of the central unit and to the first and second DC sink of the or each field device.
  • the communication module of the central unit as the first communications module and the communications module of a field device are referred to as a second communication module ⁇ below.
  • the central unit has the DC power source either in the form of two independent DC power sources - first and second DC power sources - or in the form of a controlled DC power source.
  • two independent DC sources ⁇ is one of the direct current sources controlled.
  • Only one controlled DC source is basically to a summary of an independent first and second DC power source, one of which is controllable.
  • the advantage of the invention is that via a two-wire line, so two cable wires, a transmission of
  • the transmission is transparent to the respective proto ⁇ koll für and thus basically suitable for all common bus protocols.
  • the data and energy transfer is scalable in terms of data rate, cable length and energy requirements.
  • the transmission is independent of a specific topology and therefore suitable for star, tree and bus structures as well as end-to-end links.
  • the costs for the device interface are no higher than for a standard RS485 interface today.
  • An advantage of the invention is thus also that a transmission system similar to that shown in FIG 2 is possible, consisting of a the automation system associated central unit, one or more field devices and the required connection cables.
  • the field devices are from powered by the central unit and can communicate with it.
  • this communication takes place via the communication component integrated in almost every microcontroller and known by the name UART.
  • transmitter and receiver ie central unit and field device, in the proposed transmission ⁇ system but only a two-wire line is needed.
  • a constant supply voltage UK is applied to the transfer ⁇ transmission cable via the central unit, the field equipment can be found for its power supply a constant current IK and generate a voltage UV to supply the electronics and of the AN closed sensor or actuator.
  • the field equipment can be found for its power supply a constant current IK and generate a voltage UV to supply the electronics and of the AN closed sensor or actuator.
  • the central unit has at least one port, often via a plurality of ports, to each of which one or more field devices can be connected.
  • the number of ports and the number of field devices that can be connected to each port depend on the respective boundary conditions. As energy needs, necessary data rate, cable length, etc. So z. For example, for higher data rates, one field device per port can be connected if certain line lengths are exceeded.
  • the proposed transmission system combines the cost ⁇ advantages of a system with two lines for power and data transmission (four-wire system) with known two-wire systems, because the output of the communication module directly, ie without further coding or the like, one of the two-wire line impressed by the DC power source bus voltage is superimposed , This saves costs (omission of the encoder / decoder) and the full transparency of the physical layer is guaranteed.
  • Advantageous embodiments of the invention are the subject of the dependent claims.
  • the references used in this case point to the further development of the subject of the Hauptanspru ⁇ ches by the features of the respective dependent claim; they should not be construed as a waiver of obtaining independent, objective protection for the feature combinations of the dependent claims.
  • the transmission system and the field devices provided and designed for use in such a transmission system allow the fulfillment of all relevant EMC standards for the respective field devices.
  • the transmission system is generally eligible for certification according to EN 62061 (Functional Safety, Safety Integrity Level, SIL).
  • the transmission system allows the simple connection (plug & play) of other field devices as communication participants by avoiding false line terminations and / or polarity errors, especially in special embodiments.
  • the lowest possible power requirement of the field devices is not higher than the standard 4 to 20mA standard communication technology used today.
  • the central unit in a DC power source with two independent DC sources one of the DC sources as activatable DC source or a controlled DC power source , the controlled DC source as ge ⁇ controlled activatable DC power source and means for controlled activation of the activatable DC power source summarizes can be with each activation of the activatable DC power source of the two-wire line information, so an information in the form of a 1-bit data signal memorize.
  • the central unit has the DC power source in the form of two independent DC power sources - first and second DC power source - and that one of the DC power sources, eg. B. the second DC power source, which is ⁇ controlled activatable DC power source .
  • Activation of the activatable DC power source can, for. B. consist in that the activatable DC power source briefly short ⁇ closed. The two-wire line impressed by the DC power source bus voltage results in this
  • the second DC power source can also be called and understood as a communication source against this background.
  • the communication source is z. Short-circuited, in particular sondere to be transmitted by activation of a dedicated switching element when a technique called SPACE UART characters (ent ⁇ speaks logic "0"), ie, if the communication block a corresponding output signal, in particular transmit signal (TX) emits.
  • a terminating resistor comprises a terminating resistor and means for the controlled activation of the terminating resistor.
  • a terminator is z. B. on end-to-end commu- nication links switched.
  • a processing unit comes to the type of a microcontroller or a micro controller into account.
  • the processing unit may comprise the communication module.
  • the second DC sink as activatable
  • a field device of the two ⁇ wire line in addition to the current drawn from the first DC power source for power supply of the field device targeted additional power draw.
  • This additional current drain affects the two-wire line embossed bus voltage and thus is one of the two-wire line embossed in ⁇ formation, that is, a information in the form of a 1-bit data signal.
  • the additional current draw by controllably activating the second DC current sink especially comes into consideration, if by the field device is to be transmitted the UART character designated SPACE (see above), ie if the communication module of the respective field device outputs a corresponding output signal, in particular a transmission signal (TX).
  • To activate the second DC sink is a control of a designated switching element into consideration, in a parallel circuit of first and second DC sink so z.
  • the central unit and / or the or each field device comprises or have a signal conditioning unit and a decision unit, wherein the decision unit is upstream of the respective communication module and from a supplied signal based on a decision logic implemented in the decision logic and a predetermined or predeterminable decision threshold converts the supplied signal into a binary ⁇ signal and wherein the signal conditioning unit of the decision unit is preceded and causes a processing of the decision unit supplied signal, a splitting of the current transmitted via the two-wire line into a part for supplying power to the or each field device and one transmitted data possible part.
  • a decision unit feed ⁇ cash size of the decision threshold you can specify when a respective signal value is evaluated as a logical "0" or logic "1".
  • the decision unit thus makes a 0/1 decision for the generation of the binary signal for the respectively received signal.
  • the term 0/1 decision will also be used below.
  • the combination of signal conditioning unit and decision-making ⁇ unit will be referred to as a receiver.
  • the receiver is connected upstream in a central unit or a field device to the local communication module.
  • the recipient effects an analysis of the two-wire line via the respective received signal and its treatment, so that an output signal of the receiver by the respective Ltdu ⁇ nikationsbaustein is immediately processable.
  • signal conditioning unit comes z.
  • the output of the communi ⁇ cation block one of the two-wire line impressed by the DC bus voltage source directly, without spe- is encoded, the signal comprises an information-dependent DC component.
  • the information-dependent DC component is determined by the respective data pattern, there is a normalized and idle-mode average signal of a UART character with a start character, eight data characters, one parity character and one stop character, in total eleven characters, depending on Data content and parity mode between 9% ("one of eleven") and 91% ("ten of eleven"). Therefore, as an alternative to high-pass filtering or any other type of filtering, the following approach may be considered: In the data transmission over the two-wire line, a group of e.g. B. summarized eight bits of data and the combined data bits, ie z. As a data byte, are transferred to ⁇ next in its original form and then inverted (or vice versa) to the communication block.
  • This approach results in a fixed or largely fixed signal average. This is an averaging not at bit level, but based on the combined data bits, so z. B. at the byte level. This averaging works without additional hardware components or the like.
  • the decision unit can be defined in ⁇ for the 0/1-decision with the decision ⁇ threshold.
  • a compensation voltage is determined, which is impressed on the two-wire line in addition to the bus voltage generated by the DC power source, and / or on the part of the field device based on the field device via the two-wire line due to impressed bus voltage, a compensation current for additional When the first DC sink is triggered, the terminating resistor fault that is unavoidable with unipolar signals can be compensated.
  • a DC power source either in the form of two independent DC power sources - first and second DC source - or in the form of a controlled DC power source, and a communications module - first communication module ( UART) -, wherein the central unit comprises the ge ⁇ controlled DC power source at a DC power source having two independent DC power supplies one of the DC sources as activatable direct current source or a controlled DC power source as a controlled activatable DC ⁇ current source and means for controllably activating the acti ⁇ -activatable DC power source.
  • UART UART
  • the field device, the second DC sink as an activatable current sink and means for the controlled activation of second DC sink includes.
  • a proces ⁇ processing unit of a microcontroller for the controlled activation of the activatable DC power source and the second direct-current sink is a proces ⁇ processing unit of a microcontroller in the manner contemplated.
  • the drawings show a transmission system according to the prior art with a four-wire line as the communication medium and for the power supply of connected field devices, a transmission system according to the prior art with a two-wire line as the communication medium and for the power supply of connected field devices.
  • an embodiment of a transmission system according to the invention with a two-wire line as a communication medium and power supply connected field devices a graph comparing a superposition of data transmitted in the transmission system in the context of data transmission and a provided for power supply field devices DC voltage, a high and low pass filter as an example Means for separating a signal with transmitted data provided by the power supply for connected field devices DC voltage, and
  • FIG. 12 and FIG. 12 a signal waveform for received data in a high-pass filtering of a signal with direct current component
  • FIG. 12 and FIG. 12 a schematically simplified block diagram of a provided in a central unit and / or a field device of the transmission system according to FIG 3 receiver, a comparison of several data patterns to illustrate an information-dependent DC component, a dependency detected pulse lengths of a decision threshold in a decision unit of the receiver, a representation for clarification of the aspect of the unlike in the prior art not on bit level, but executed at the byte level mean ⁇ compensation, FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG. 12 and FIG.
  • FIG 15 two circuits showing an embodiment of a current sink with a Häticianstabili ⁇ tion by means of compensation.
  • FIG. 1 shows a transmission system 10 with a central unit 12 and a field device 14.
  • the transmission system 10 comprises a four-wire connection line as the line 16 for energy and data transmission, which connects the central unit 12 and the field device 14.
  • the illustrated transmission system 10 is a system as known under designations such as PROFIBUS DP or DeviceNet. Such transmission systems 10 are characterized by a scalability in terms of data rate and line length, since no speed-dependent blocks are necessary. Between a communication component UART which can be parameterized in its baud rate and the line 16, there is only one speed limit within limits
  • FIG 2 shows in so far a transmission system 10 with a central processing unit 12 and a field device 14.
  • the transmission system 10 comprises as line 16 for energy and data transmission a two-wire ⁇ line.
  • the CODEC (coder / decoder) and MAU (Medium Attachment Unit) modules shown in FIG. 2 considerably increase the cost of an interface.
  • all two-wire solutions have in common the property that on the transmitting side the data present as an NRZ signal with an information-dependent DC component is coded in such a way that a DC-free signal is produced, which is superimposed on a DC voltage serving for the energy supply. On the reception ⁇ side of this AC signal is split off and decoded by a high pass. Only then is there again an NRZ signal, which z. B. can be processed by a UART. Scalability over long distances and / or high data rates is achieved by using a line termination resistor 18. In the case of a two-wire solution with
  • the transmission system 10 comprises a central processing unit 12 and at least one field device 14 assigned to an automation system or automation device, not shown. Four field devices 14 are shown here.
  • the central unit 12 and the field devices 14 are connected via a two-wire line as line 16 for power and data transmission.
  • the structure of the transmission system 10 is similar to the transmission system 10 shown in FIG. 2.
  • the terms "line” will be used 16 and two-wire line 16 used synonymously.
  • the field devices 14 are supplied from the CPU 12 with Ener ⁇ energy and can communicate therewith.
  • This communication takes place, as in the known four-wire systems (cf., FIG. 1), via a communications module.
  • a communications module In the illustrated embodiment, is of a nearly in each microcontroller ( ⁇ ) integrated UART so-called assumed as a communication module ⁇ (Universal Asynchronous Receiver Transmitter).
  • ⁇ microcontroller
  • ⁇ Universal Asynchronous Receiver Transmitter
  • a constant supply voltage UK is applied to the line 16 via the central unit 12.
  • Each field device 14 draws a constant current IK for its power supply and generates a voltage UV for supplying the electronics and the connected sensor S or actuator. When sending the field devices 14 take an additional power IT.
  • the central unit has at least one port PI, P2 ... PN.
  • Each port PI, P2, PN may be or may be connected to one or more field devices 14.
  • the number of ports PI, P2, PN and the number of connected or connectable field devices 14 depends on the respective boundary conditions, such. B. Energy requirements, required data rate, cable length, etc.
  • the central unit 12 comprises two voltage sources, namely a first voltage source UK and a second voltage source UT.
  • the first voltage source UK supplies the supply voltage for the power supply of connected field devices 14 and a value of the supply voltage UK can either be controlled or fixed via the microcontroller ( ⁇ ).
  • the second clamping ⁇ voltage source UT can also be regarded as a communication source and referred to, and is short-circuited by the microcontroller when a UART character "SPACE" (corresponding lo- gisch "0") is to be transmitted. Then the voltage applied to the field devices 14 voltage UB decreases accordingly.
  • the first and the second voltage source UK, UT can be combined as an alternative to a correspondingly controlled voltage source (not shown).
  • a measuring resistor RM and for each port PI, P2, PN each have a limiting resistor R are provided.
  • Each limiting resistor R assumes a plurality of functions, namely first a one-sided termination of the line 16, then a limit current in use in a hazardous area, and finally ensuring suitability of the over- tragungssystems 10 and / or the central unit 12 to the fulfillment ⁇ development of the conditions referred to the so-called Fieldbus Intrinsically Safe Concept (FISCO) and / or for the preservation of explosion protection Ex-i.
  • FISCO Fieldbus Intrinsically Safe Concept
  • the field devices 14 must communicate with each other, as shown in the illustration in FIG 3 for the connected to the port PN two field devices 14.
  • the limiting resistance R can ent ⁇ fall.
  • a measuring unit MI By means of a measuring unit MI can be measured via the measuring resistor RM, both the static supply current IK, which is taken from the connected field devices 14, as well as the transmission current IT, which is additionally taken from a currently transmitting field device 14.
  • the separation of the dynamic part of the transferred via the line 16 stream from the static part takes place in a recipient ger E. There, the digital Emp ⁇ catch signal (AC signal; RX) is obtained from the dynamic part is extracted, which is supplied to the communica ⁇ tion module UART becomes.
  • the central unit 12 may also contain a combination of DC / DC voltage source UK, limiting resistor R and a transmitting / receiving unit / current sink, as described below as part of a field device 14.
  • a separate measuring resistor RM is omitted.
  • the current sink IT replaces the second clamping voltage source ⁇ UT.
  • the field devices 14 contain constant current sinks, which each remove the current IK from the line 16.
  • a current-voltage converter I / U;., For example, a zener diode
  • Ver ⁇ supply voltage UV for the field device 14.
  • a second current source draws an additional current IT if a UART character "SPACE" (corresponds to logical "0") is to be transmitted.
  • the necessary connection lines are a receiving line RX and a transmission line TX.
  • the illustrated further lines are optional and can be used for automatic parameterization of the interface by the microcontroller ( ⁇ ).
  • BT Bus Terminator, for connecting a terminating resistor (eg optionally switchable for end-to-end routes)
  • IK Constant current, for setting the size of the constant current (eg changeable, if the field device 14 temporarily has an increased power requirement)
  • UB bus voltage, to determine the voltage applied to the field device 14 (eg for diagnostics or parameterization).
  • FIG. 4 shows, for clarification in the upper part designated by a), a superimposition of a DC voltage provided for the purpose of energy supply with a DC-free data signal, as results in a transmission system 10 according to FIG.
  • a direct superposition of a provided for the power supply DC voltage below is shown with a UART output signal for discriminating in a designated b) part and an overlay ⁇ tion as shown in FIG arises in a transmission system 10.
  • Resistor R, a capacitor C and a comparator K are shown in FIG. 5 (left the low-pass filter, right the high-pass filter).
  • the high or low pass filter acts as a kind of "conventional" signal or 0/1 decision maker.
  • the transmission system 10 with a more ⁇ ter superposition of the energy supply is provided for
  • DC voltage with the UART output signal contains the transmitted data - ie according to the above terminology the signal - an information-dependent DC component.
  • the signal is filtered with a high-pass filter (FIG. 5, right), an exponential transient process initially occurs at the input of the comparator K.
  • the signal fluctuates greatly because of the low-frequency components by a fixed value.
  • This is (9-bit pattern) shown in FIG 6 the example ei ⁇ nes quasi-random signal.
  • the effects of such high-pass filtering can be presented even more clearly with a fixed, repeating bit pattern. In the pattern "1000 0000" shown in FIG.
  • the signal 20 after the high-pass filtering is shifted significantly upwards relative to the mean value 22, but clearly downwards in the case of the inverse pattern 24.
  • the receiver E (FIG. 3) of a central unit 12 and / or of a field device 14 comprises a signal conditioning unit AB and a decision unit EE, as shown in FIG.
  • the communication module UART is connected upstream, wherein by means of the decision unit EE an input and supplied in operation AC signal S is ⁇ based on a decision implemented in the decision unit EE decision logic and based on a predetermined or specifiable decision threshold UV in a binary signal BS ⁇ wherein the signal conditioning unit AB of the decision unit EE is connected upstream and a Aufberei ⁇ tion of the decision unit EE signal supplied be ⁇ acts.
  • the UART output signal consists of a start character ST, eight data characters DO... D7, one parity character P and one stop character SP, thus a total of eleven characters.
  • the data content and parity mode is an in an idle state (Idle state) of the Sprinttra ⁇ supply system 10 related, normalized signal averaging, so an information-dependent DC component, between 9% (1/11) and 91% (10/11).
  • FIG. 10 shows a dependence of detected pulse lengths on a decision threshold in the decision unit EE for different signal mean values MW. Therefore EE for the decision unit is provided that there implemen ⁇ oriented decision logic a predetermined or predeterminable threshold decision UV is fed.
  • the decision threshold UV can be suitably adjusted depending on different data and boundary conditions.
  • a particular embodiment is characterized in that it can be assumed that a fixed decision threshold UV. For this, a mean value compensation is initially provided and 9 showed the dependency of a signal ⁇ average MW from the respective data contents. However, it was recognized that an averaging can be achieved in a simple manner, when in the transmission of data over the two-wire line 16, a group of z. B. Eight data bits combined into one byte of data and the data ⁇ byte first in its original form and then inver ⁇ tiert (or vice versa) to the communication module (UART) is passed. FIG 11 shows as an example the then resulting conditions.
  • the mean value still fluctuates between the above-mentioned values 5/11 and 6/11, depending on the distribution of the EVEN and ODD bytes.
  • the decision threshold UV When setting the decision threshold UV to 0.5 the remaining systematic error is limited to a maximum of ⁇ 4.5%, whereby the resulting pulse length distortion and the loss of signal-to-noise ratio can be negligible.
  • the high-pass frequency is selected too high, the signal distortions due to pulse flattening ("sloping roof”) will worsen the result again if there is no signal change.
  • a low cutoff frequency causes a long transient process (see FIG. 6), so that the use of an adaptive decision threshold UV is expedient.
  • Such a mean value compensation avoids, unlike, for example, FIG. As a so-called Man ⁇ chester encoding, otherwise necessary, additional hardware components.
  • Manchester coding a fixed average is generated by inversely repeating the data content of one bit within a bit period. This link is made in a so-called Manchester encoder.
  • process coding and decoding with a corresponding computer program in the microcontroller, this would then have to be able to perform this task in parallel to the actual application, which usually requires a higher-performance microcontroller and a higher power requirement per se draws.
  • FIG 3 shows the output current limit for each strand by a respective limiting resistor R.
  • the current limitation by means of the limiting resistor R is especially required for operation in potentially explosive areas.
  • Each limiting resistor R also serves as a line terminating resistor.
  • the operating parameters are limited to UDCBUS ⁇ 17.5V and IDCBUS ⁇ 200mA.
  • the maximum transmission bandwidth should be 2 MBit to 6 MBit and the own energy demand of the communication electronics in a field device 14 should be so small that previous field devices 14 with analogous 4 to 2 OmA interface can only Job adaptation can continue to be used with 4mA operating current in this new digital communications system 10. This results in the following requirement profile for the communication hardware in a field device 14:
  • An increase of the controlling input voltage UE leads to increasing collector current of the small signal transistor TRK and the power transistor TRL.
  • the voltage at the current measuring resistor Rmess gets more negative regarding GND.
  • the transistors TRL, TRK and the Zener diode may also be components of other types, e.g. B. FETs or reference diodes or Vierpolscigenen.
  • the base-emitter voltage U BE is to be understood as any desired operating-point voltage.
  • the operating point voltage of transistors and FETs depends on the one hand on an ambient temperature and on the other hand on the respective copy strongly. Therefore, as a supplement to the circuit in FIG. 12, a stabilizing amplifier may also be considered, as shown in FIG.
  • the embodiment of a current sink with stabilizing amplifier shown in FIG. 13 is also known.
  • the ideal transfer function the current sink shown in FIG 13 shows the strong dependence of the penetrating current i of the temperature-dependent working ⁇ point voltage UBE.
  • the transfer function is and shows how the influence of the working point voltage ÜBE can be eliminated: with the dimensioning the transfer function becomes independent of the operating point voltage UBE and thus independent of temperature and copy:
  • the bias voltage UBE is a DC voltage
  • the compensation voltage can Ukomp as shown in the overall ⁇ circuit in Fig 14 by means of a "micropower" operational amplifier smaller bandwidth, are generated.
  • This circuit is functional, but does not fully meet the requirements profile set up at the beginning.
  • the fairly high base current of the power transistor TRL flows via TRK and the sensor electronics are lost.
  • the TRK input impedance is low and would require a very low-current current-drooping sizing of RR, RE and RE2.
  • the circuit has a high input resistance and the own power demand not provided by the sensor electronics is approx. 120 ⁇ at 3MHz bandwidth.
  • the compensation method described above is effective for each operating point to be stabilized, irrespective of the nature of the components used or four poles instead of the active building parts ⁇ .
  • the circuit in the illustrations in Figures 14 and 15 is an example of a current sink with a working ⁇ stabilizer compensation.
  • the approach presented here combines the advantages of previous two and four-wire solutions, which are not combinable without further ado.
  • the approach enables the transparent communication between UARTs and the power supply of field devices 14 via a two-wire connection 16 with only a small amount of hardware.
  • the number of a central unit 12 as a master to ⁇ closable subscriber (field devices 14) for applications in the hazardous area increases per strand (see FIG 3) by a factor of three.
  • the number of strands is unlimited, technically still easy to control are three strands per master.
  • the much higher transmission bandwidth can, for. This can be used, for example, for software services that are not possible with any of the current two-wire solutions due to a lack of bandwidth.

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  • Dc Digital Transmission (AREA)

Abstract

L'invention concerne notamment un système de transmission (10) comportant au moins une unité centrale (12) et au moins un appareil de terrain (14), une liaison d'alimentation en énergie de l'appareil de terrain (14) et une liaison de communication vers et à partir de l'appareil de terrain (14) existant simultanément par l'intermédiaire d'une ligne bifilaire (16). Le système de transmission (10) est caractérisé en ce qu'il comprend une unité centrale (12) comportant au moins une source de courant continu (UK, UT), soit sous la forme de deux sources de courant continu indépendantes - une première et une deuxième source de courant continu (UK, UT) - soit sous la forme d'une source de courant continu commandée, et un module de communications - premier module de communication(UART) -, au moins un appareil de terrain (14) comportant au moins un premier et un deuxième puits de courant continu (IK, IT) et un module de communication - deuxième module de communication (UART) -, une superposition directe d'un signal de sortie (TX) du module de communication (UART) et d'une tension de bus appliquée à la ligne bifilaire (16) par la source de courant continu, la ligne bifilaire (16) étant raccordée à la source de courant continu (UK, UT) de l'unité centrale (12) et au premier et deuxième puits de courant continu (IK, IT) de l'appareil de terrain (14).
PCT/EP2011/055830 2011-04-13 2011-04-13 Système de transmission, unité centrale ou appareil de terrain dans un système de transmission de ce type et procédé de fonctionnement de ce système WO2012139640A1 (fr)

Priority Applications (1)

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PCT/EP2011/055830 WO2012139640A1 (fr) 2011-04-13 2011-04-13 Système de transmission, unité centrale ou appareil de terrain dans un système de transmission de ce type et procédé de fonctionnement de ce système

Applications Claiming Priority (1)

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PCT/EP2011/055830 WO2012139640A1 (fr) 2011-04-13 2011-04-13 Système de transmission, unité centrale ou appareil de terrain dans un système de transmission de ce type et procédé de fonctionnement de ce système

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4663499A (en) * 1983-08-19 1987-05-05 La Detection Electronique Francaise-Protecbat Method for transmitting messages between a central station and several distant stations
DE68916190T2 (de) * 1988-11-04 1994-10-27 Merlin Gerin Automat zur technischen Verwaltung eines Gebäudes unter Verwendung einer Zweidrahtleitung zur Übertragung von Daten und Energie.
WO1996004735A1 (fr) * 1994-08-04 1996-02-15 Siemens Aktiengesellschaft Bus d'interconnexion
DE69231199T2 (de) * 1991-05-30 2000-11-23 Fuji Electric Co Ltd Verfahren und Vorrichtung zum Senden von Signalen auf einer Übertragungsleitung
DE10034087A1 (de) * 2000-07-13 2002-01-24 Schrom Harald Feldbussystem mit minimierter Hardwarearchitektur

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4663499A (en) * 1983-08-19 1987-05-05 La Detection Electronique Francaise-Protecbat Method for transmitting messages between a central station and several distant stations
DE68916190T2 (de) * 1988-11-04 1994-10-27 Merlin Gerin Automat zur technischen Verwaltung eines Gebäudes unter Verwendung einer Zweidrahtleitung zur Übertragung von Daten und Energie.
DE69231199T2 (de) * 1991-05-30 2000-11-23 Fuji Electric Co Ltd Verfahren und Vorrichtung zum Senden von Signalen auf einer Übertragungsleitung
WO1996004735A1 (fr) * 1994-08-04 1996-02-15 Siemens Aktiengesellschaft Bus d'interconnexion
DE10034087A1 (de) * 2000-07-13 2002-01-24 Schrom Harald Feldbussystem mit minimierter Hardwarearchitektur

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