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WO1998014854A1 - Circuit de telecommunication destine a un emetteur de commande de processus - Google Patents

Circuit de telecommunication destine a un emetteur de commande de processus

Info

Publication number
WO1998014854A1
WO1998014854A1 PCT/US1997/017611 US9717611W WO9814854A1 WO 1998014854 A1 WO1998014854 A1 WO 1998014854A1 US 9717611 W US9717611 W US 9717611W WO 9814854 A1 WO9814854 A1 WO 9814854A1
Authority
WO
WIPO (PCT)
Prior art keywords
link
transmitter
power
signal
coupled
Prior art date
Legal status (The legal status 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 status listed.)
Ceased
Application number
PCT/US1997/017611
Other languages
English (en)
Inventor
Randy J. Longsdorf
Grant B. Edwards
Richard L. Nelson
David L. Pederson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rosemount Inc
Original Assignee
Rosemount Inc
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
Priority claimed from US08/890,169 external-priority patent/US6006338A/en
Application filed by Rosemount Inc filed Critical Rosemount Inc
Priority to AU48034/97A priority Critical patent/AU4803497A/en
Publication of WO1998014854A1 publication Critical patent/WO1998014854A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/418—Total factory control, i.e. centrally controlling a plurality of machines, e.g. direct or distributed numerical control [DNC], flexible manufacturing systems [FMS], integrated manufacturing systems [IMS] or computer integrated manufacturing [CIM]
    • G05B19/4185—Total factory control, i.e. centrally controlling a plurality of machines, e.g. direct or distributed numerical control [DNC], flexible manufacturing systems [FMS], integrated manufacturing systems [IMS] or computer integrated manufacturing [CIM] characterised by the network communication
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
    • Y02P90/02—Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Definitions

  • This invention relates to transmitters of the type used in the process control industry. More specifically, this invention relates to a process transmitter having a communications circuit for transmitting information over a process link.
  • Process transmitters are used to monitor industrial processes and responsively transmit information relating to the industrial process to a process device, such as a control room, a controller, another process transmitter, or a process control such as a valve.
  • a process device such as a control room, a controller, another process transmitter, or a process control such as a valve.
  • various fluid process variables such as level, flow, mass, pressure, and temperature are monitored and transmitted to the process device at facilities such as oil refineries, wood pulp processing plants, or chemical plants.
  • Process transmitters are typically contained in an explosion- proof housing and are freguently located to monitor an industrial process in areas that are difficult to physically access with nearby hazards.
  • a process transmitter may be located in an area such as on top of a many thousand gallon tank or in a confined space. Hazards in the vicinity of process transmitters include machinery, chemicals, radiation, temperature extremes, and high voltage.
  • the process transmitter communicates an information signal to a process device over process link wires.
  • the wires coupling the process transmitter to the process device are configured with dedicated wires such as a process loop, and, in other applications, the wires are configured as common wires such as a process bus.
  • the information signal includes signals representing one or more process parameters and signals representing process transmitter information such as configuration and status. These signals may be digital signals, analog signals, or a combination of digital and analog signals configured according to a process communications protocol.
  • the information signal is transmitted over the process link to the process device where the information signal is interpreted and decisions are made concerning the process or the process transmitter based upon the information signal. In most previous transmitters, the process link requires power before the process transmitter is capable of generating an information signal.
  • a communicator such as a Rosemount® Model 268 HART® Smart Family interface for diagnostic testing and setup. Diagnostic testing is performed to validate that the process transmitter is operating according to the manufacturer 's specifications.
  • Process transmitter setup also known as commissioning, is performed to program the transmitter with information that relates to the particular process to be monitored such as transmitter configuration, transmitter address, installation temperature, and transmitter height.
  • Previous process transmitters require connection to a powered process link, which comprises a power supply such as a 10-30V DC battery and a load resistor such as a 250 ⁇ or greater resistor, to measure current flowing through the process link. Connection to the power supply and load resistor can make commissioning of a process transmitter inconvenient and time consuming.
  • Field diagnostic testing and set-up changes to installed process transmitters are sometimes difficult and dangerous because process transmitters are often located in areas that are difficult to access and potentially hazardous.
  • some previous process transmitters require connection to a powered process link comprising a power supply and load resistor. Physically transporting a power supply and a load resistor into a difficult to access and potentially hazardous area can make field diagnostic testing and set-up changes to an installed process transmitter inconvenient, time consuming, and dangerous.
  • the process transmitter communications circuit of the present invention has link terminals which are coupled to a process link which supplies power to the circuit.
  • a power source which is coupled to one of the link terminals and is independent from the power supplied from the process link.
  • Communications circuitry is coupled to the power source and link terminals, which transmits a transmitter signal over the process link, through the link terminals.
  • a power sensing component is coupled to at least one of the link terminals and the communications circuitry and senses whether the power supplied by the process link is inadequate to transmit the transmitter signal.
  • a power control component is coupled to the power source, the link terminals and the communications circuitry and selectively applies power from the power source to the communications circuitry for transmitting the information signal when the power sensing component senses there is inadequate power supplied by the process link.
  • the power sensing component includes a diode coupled between the power source and the link terminals. In some versions of the process transmitter communications circuit, the diode also serves as the power control component . In a second embodiment, the power sensing component includes a voltage divider and the power control component includes a microprocessor.
  • the present invention also includes a method for communicating with the process transmitter over the process link by sensing the process link voltage, determining whether there is inadequate power on the process link to transmit the transmitter signal and, if there is inadequate power, supplying adequate power to transmit the transmitter signal from the power source.
  • BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram of a process transmitter according to the present invention.
  • Figure 2 is a schematic of a first embodiment of the process transmitter communications circuit.
  • Figures 3a and 3b are signal timing diagrams of process link current and power component control current during operation of the first embodiment.
  • Figure 4 is a schematic of a second embodiment of the process transmitter communications circuit.
  • Figure 5 is a flowchart of the operation of the second embodiment.
  • Figures 6a-6c are signal timing diagrams of process link current, power component control current and process link voltage during operation of the second embodiment .
  • Figure 7 is a diagram illustrating a method for communicating during inadequate process link power used by the process transmitter communications circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • FIG. 1 is a block diagram of a process transmitter 10 which is connected to a process link 12, according to the present invention.
  • the process transmitter 10 includes a sensor 14, a signal processor 16, a modem 18, and a communications circuit 20.
  • the sensor 14 includes a transducer coupled to a process that produces an analog electrical sensor signal 22 which is representative of a process parameter such as level, mass, flow, pressure, or temperature.
  • the signal processor 16 takes the analog sensor signal 22 and generates a modified sensor signal 24 by converting the sensor signal to a digital signal and modifying the digital signal to improve characteristics such as linearity.
  • the modem 18 includes a receive signal line 30, a transmitter signal line 32, and a process signal line 34.
  • the modem 18 receives the modified sensor signal 24 and converts the modified sensor signal 24 into a process signal, which is representative of the measured process variable, and applies the process signal to the process signal line 34.
  • the process signal is typically analog and is compatible with a selected communications protocol.
  • Modem 18 also generates a digital, modulated transmitter information signal on the transmitter signal line 32, which may represent the measured process variable or status information, for example.
  • the modem 18 includes the capability to convert between analog signals and digital signals.
  • the signal processor 16 has a control line 26 that is coupled to a switch 28. When switch 28 is closed, the transmitter information signal may be applied directly to the process link 12 as a voltage, rather than being applied through the communications circuitry 42 as a modulated current.
  • the communications circuit 20 includes a power source 38, link terminals 40, communications circuitry 42, at least one power sensing component 44, and at least one power control component 46.
  • the power source 38 supplies power to the process transmitter 10 independently from the power available on the process link 12. In some configurations, the power source 38 also supplies power to other components of process transmitter 10 such as the modem 18 and signal processor 16. In embodiments having four wires the power source 38 includes a pair of wires which are connected to an external power supply (not shown) such as a 5-25V DC power supply. In embodiments having two wires, the power source 38 is internal to the process transmitter 10 and includes a battery or capacitor, for example.
  • the process transmitter 10 receives its operating power from the process link 12 through process link terminals 40.
  • the process link 12 provides connectivity between the process transmitter 10 and another process device 50 such as a communicator, a second process transmitter, or a process control to transmit an information signal 48.
  • a controller 51 such as found in a process control room is connected to the process link terminals 12.
  • Some of the most common types of process links 12 include a process loop, a process bus, a point- to-point, a daisy-chain, and a tree.
  • the communications circuitry 42 is coupled to the power source 38, the modem 18 and link terminals 40 to transmit the process signal and the transmitter information signal onto the process link 12 according to selected communications protocols.
  • the process signal is transmitted on the process link 12 by controlling the level of current through the process link 12 between 4- 20 mA, for example.
  • the information signal is shown as a modulated signal 48 on the current through the process link 12.
  • Two of the communications protocols available for the process transmitter 10 to communicate the transmitter information signal 48 are the Highway Addressable Remote Transducer (HART®) communications protocol, which is described in HART® Field Communications Protocol, A Technical Overview (1994) available from the HART Communications Foundation in Austin, Texas USA, and the Fieldbus communications protocols such as FoundationTM Fieldbus, Controller Area Network (CAN), Lonworks, and Profibus .
  • HART® Highway Addressable Remote Transducer
  • the analog process signal generated by the communications circuitry 42 over the process link 12 is preferably a 4-20 mA DC analog signal
  • the information signal 48 is a digital signal having a frequency of 1200 Hz and 2200 Hz at 1.0 mA peak-to-peak modulated on the analog process signal.
  • both the process signal and the transmitter signal are digital signals modulated on a substantially fixed current in the range from about 1-10 mA, preferably about 4 mA DC.
  • both the process signal and the transmitter signal are digital signals modulated on a substantially fixed current in the range from about 4-20 mA DC and preferably about 16 mA DC.
  • the power sensing component 44 is coupled to at least one link terminals 40 to measure the voltage on the process link 12 and determine whether there is inadequate power on the process link 12 to transmit the information signal 48.
  • the power sensing component 44 has a sense line 52 that is coupled to the signal processor 16.
  • the power control component 46 is coupled to the power source 38 and the link terminals 40. When the power sensing component 44 determines there is inadequate power on process link 12, the power control component 46 directs a predetermined amount of power from the power source 38 to the communications circuitry 42 which is modulated by the communications circuitry to generate the information signal 48.
  • FIG. 2 is a schematic diagram of the process transmitter communications circuit 20 according to a first embodiment of the present invention.
  • This embodiment includes a 4-20 mA loop transmitter, where the process signal is the analog 4-20 mA portion of the information signal, and the transmitter signal is the digital portion of the information signal which is superimposed on the analog portion.
  • the process transmitter communications circuit 20 includes the power source 38, link terminals 40, communications circuitry 42, and a diode 64.
  • Diode 64 is coupled in series with resistor 60, between power source 38 and one of the link terminals 40.
  • Diode 64 performs the functions of both the power sensing component 44 and the control component 46.
  • Diode 64 also isolates the power source 38 from power supplied over the process link 12.
  • the first embodiment shown in Figure 2 is preferred when the power source 38 is a relatively large power supply that can supply adequate current to maintain modulator 70 in the linear region which allows transmission of the digital portion of the information signal 48 when power on the process link 12 is interrupted. If the power source 38 operates at a lower level, the embodiment shown in Figure 2 will still operate to generate the digital portion of the information signal 48 until the current required to generate the analog portion of the information signal 48 exceeds the power source's capability.
  • the loop current on process link 40 flows through a current path formed between the link terminals 40, which includes resistor 62, modulator 70, diode 84 and resistor 86.
  • the resistors 60 and 62 are selected along with the other components connected between the link terminals 40 to establish a maximum current of about 20 mA between the link terminals 40.
  • the communications circuitry 42 includes a receive filter 66, an amplifier 68 and the modulator 70.
  • the receive filter 66 is an analog highpass filter coupled between one of the link terminals 40 and the receive signal line 30 of the modem 18.
  • the receive filter 66 is designed for a particular communications protocol to improve the signal to noise ratio. In some applications, the receive filter 66 will include additional capacitors and resistors that are configured to improve receive signal filtering for a particular environment .
  • the amplifier 68 is preferably an operational amplifier having a non-inverting input 72, an inverting input 74, and a coupling resistor 76.
  • the non-inverting input 72 is coupled through resistor 78 to a reference voltage of about 2.5 VDC to maintain about 2.5 VDC on the non-invertiny input 72, which positions the operational amplifier 68 near the center of its range.
  • the reference voltage is supplied by power source 38.
  • the process signal, which is applied on the process signal line 34, and the transmitter signal, which is applied on the transmitter signal line 32, are summed at node 80 and applied to the inverting input 74 of the operational amplifier 68 through resistor 82.
  • the transmitter signal is an AC signal that is capacitively coupled from the transmitter signal line 32 to the summing node 80, and the process signal is a pulse width modulated signal coupled from the modem process signal line 34 to the summing node 80.
  • the output of the operational amplifier 68 is capacitively coupled to its inverting input 74 to stabilize the operational amplifier 68.
  • a coupling resistor 76 provides voltage isolation between the operational amplifier 68 and the modulator 70.
  • the modulator 70 is an active device that controls the level of current flowing through the process link 12 and modulates the current in response to the output of the operational amplifier 68 to transmit the process signal and the transmitter signal.
  • the modulator 70 preferably includes a pair of transistors configured as a Darlington pair, the diode 84, the resistor 86, and a feedback circuit 88.
  • the diode 84 in combination with resistor 86 function to hold the output of the modulator 70 at a level above ground to improve performance of the operational amplifier 68.
  • the feedback circuit 88 includes resistors 90 and 92 and capacitor 94.
  • the feedback circuit 88 couples a representation of the information signal 48 to the inverting input 74 of operational amplifier 68 to improve the quality of the information signal 48.
  • Resistor 91 maintains a proper bias on the base f modulator 70.
  • Resistors 93 and 95 provide isolation between the process signal line 34 and the transmitter signal line 32 respectively.
  • the diode 64 performs the functions of both the power sensing component 44 and the power control component 46.
  • the diode 64 will be reverse biased when the voltage on the process link 12 exceeds the voltage at the output of the power source 38, and will be forward biased when the voltage on process link 12 drops below a sense threshold of about 0.7 V less than the voltage at the output of the power source 38. In this manner, diode 64 senses when there is inadequate power on process link 12 to transmit the information signal 48.
  • the diode 64 performs the function of the power control component 46 by becoming forward biased and thereby providing power to the modulator 70 when it determines that there is inadequate power on the process link 12.
  • the diode 64 directs enough current flow from the power source 38 through the link terminals 40 to meet the nominal current value for communications .
  • the nominal current required for communications is about 1.0 mA.
  • the diode 64 is reverse biased when there is adequate power on the process link 12.
  • Figures 3a and 3b are signal timing diagrams which illustrate the current through the process link 12 and the power control component (diode 64), respectively, and are arranged on the same time base.
  • the diode 64 is sensing the voltage on the process link 12, and the communications circuitry 42 is transmitting the information signal 48.
  • the transmitter signal 58 is shown modulated on the analog process signal 56.
  • the power on process link 12 rapidly drops below the sense threshold, as shown by the drop in current in Figure 3a.
  • the process transmitter 10 determines there is inadequate power to transmit the transmitter signal 58.
  • Diode 64 becomes forward biased and couples the power source 38 to the process link 12 to supply adequate power to the modulator 70 to transmit the transmitter signal, as shown in Figure 3b.
  • the power source 38 continues to provide current to the modulator 70 at a level that will support transmission of the transmitter signal.
  • the power on the process link 12 is restored, as shown by the increase in the current level in Figure 3a.
  • the diode 64 becomes reversed biased due to an increase in the voltage on the link terminals . This decouples the power source 38 from the modulator 70 and thereby stops the supply of power from the power source 38, as shown by the drop in current in Figure 3b.
  • the process transmitter 10 is communicating normally as described above under t,.
  • FIG 4 is a schematic diagram of a process transmitter communications circuit 96 according to a second embodiment of the present invention.
  • This embodiment includes a 4-20mA portion of the information signal, and the transmitter signal is the digital portion of the information signal which is superimposed on the analog portion.
  • the same reference numerals are used in Figure 4 as were used in Figures 1 and 2 for the same or similar elements.
  • the process transmitter communications circuit 96 is coupled to a sensor 14, a microprocessor 16 and a modem 18.
  • the process transmitter communications circuit 96 includes a power source 38, link terminals 40, communications circuitry 42, power sensing component 44, and power control component 46.
  • the power sensing component 44 includes a power sensing circuit 97 which is formed of a voltage divider 98, a buffer 104 and a filter 106.
  • Voltage divider 98 includes resistors 100 and 102, and provides buffer 104 with a voltage signal that is indicative of the level of power on the process link 12.
  • the buffer 104 receives the voltage signal and generates a voltage VSENSE which is applied to the microprocessor 16.
  • the buffer 104 and the filter 106 are removed.
  • the microprocessor 16 monitors the level of VSENSE and determines whether the power on the process link 12 is adequate to generate the process signal 56 by controlling the loop current between 4-20 mA as a function of the measured process variable and to modulate the transmitter signal on the process signal 56.
  • the function of the control component 46 is performed in part by the diode 64 and in part by the microprocessor 16.
  • the diode 64 becomes forward biased and applies current from the power source 38 to the modulator 70.
  • the microprocessor 16 determines there is inadequate power on the process link 12
  • the microprocessor 16 sets the DC current level through modulator 70 to a nominal level that will permit transmission of at least some of the information signal 48 for a particular protocol.
  • the nominal current level is about 1.0 mA.
  • the microprocessor 16 no longer controls the loop current between 4-20 mA as a function of the measured process variable.
  • current flow through the modulator 70 is below about 4.0 mA, there is inadequate current to transmit an effective analog process signal, but there is enough current to transmit the transmitter signal.
  • the microprocessor 16 controls the DC current level through the modulator 70 by providing a programmed signal on process signal transmission line 34. This signal passes through operational amplifier 68 to the current control input of the modulator 70, and thereby sets the current through the modulator to the nominal, fixed level.
  • the modulated signal on the transmitter signal line 32 is summed with the programmed signal on the process signal line 34 at summing node 80, thereby allowing transmission of the transmitter signal through the modulator 70 even though there is inadequate on the process link 12 to transmit the process signal 56.
  • the microprocessor 16 closes the switch 28 such that the modem 18 transmits the transmitter signal directly to the process link 12 as an analog voltage upon the occurrence of a predetermined condition such as low power on the process link 12.
  • the switch 28 is preferably compatible with an analog voltage signal and can include a solid state switch, a gate, or an electromechanical switch, for example.
  • the diode 64 is replaced with a switch which is controlled by the microprocessor 16 for selectively coupling the power source 38 to one of the link terminals 40 as a function of the VSENSE output ol operational amplifier 68.
  • An advantage of the second embodiment is that a more reliable transmitter signal can be communicated under inadequate power conditions since the current through modulator 70 is set to a fixed value, and the transmitter does not attempt to transmit the process signal 56 by controlling the current drawn from the power supply 38.
  • the process transmitter communications circuit 96 can operate in the range of about 5-10 VDC to communicate the transmitter signal.
  • the second embodiment also has the advantage of performing more consistently when inadequate power creates hysteresis in the power sensing component 44.
  • the process transmitter communications circuit 96 is configured for the HART communications protocol but could be configured for another communications protocol such as Fieldbus.
  • FIG. 5 is a flowchart showing the operation of the microprocessor 16 in the 3econd embodiment.
  • microprocessor 16 determines whether the power on the process link 12 is adequate or inadequate for transmission of the process signal 56. If the microprocessor 16 determines that the power is inadequate, then the microprocessor 16 sets the current through the modulator 70 to a predetermined level such as 1.0 mA, at step 152, and sets an error flag, at step 154.
  • the predetermined level of 1.0 mA has the advantage of being well below the range of most process signals, so a technician that is monitoring the current over the process link 12 is alerted that a low power condition exists. The 1.0 mA level does not mask the low power condition.
  • Microprocessor 16 returns to normal processing, at step 156, and repeats the power level check, at step 150, about once every second.
  • the microprocessor 16 uses a low threshold V LT and a high threshold V HT .
  • the difference between the low threshold V LT and the high threshold V ⁇ is the power sensing hysteresis for a particular environment.
  • the microprocessor 16 is programmed to instruct the process transmitter 10 to communicate a predetermined transmitter signal, such as a notice of a low power condition, to the process device 50 upon reaching a predetermined voltage threshold.
  • FIGS. 6a-6c are signal timing diagrams of the current through the modulator 70, the current from the power supply 38, and the voltage sensed by the power sensing component 44, respectively, and are arranged on the same time base.
  • the process transmitter communications circuit 96 of the second embodiment operates similarly to the first embodiment until the microprocessor 16 makes a determination that the power on the process link 12 is inadequate and sets the power to a fixed level.
  • the power on the process link 12 is being provided by the process device 50.
  • the power sensing component 44 is sensing the voltage on the process link 12.
  • the communications circuitry 42 is transmitting the process signal 56 by controlling the level of DC current through the modulator 70 and is transmitting the transmitter signal 58 by modulating the transmitter signal on the process signal 56.
  • Figure 6b shows substantially no current flowing from the power source 38 to the modulator 70 because diode 64 is reverse biased.
  • Figure 6c shows that the voltage on the process link 12 is well above both the high threshold V m and low threshold V LT .
  • the power sensing component 44 is continuously sensing the voltage on the process link 12.
  • the power on the process link 12 is interrupted.
  • Figure 6a shows the current through the modulator 70 dropping until diode 64 becomes forward biased.
  • current begins to flow from the power source 38 into the modulator 70 at a level I, which is above 1.0 mA, as shown in Figure 6b.
  • Figure 6c shows that the sensed voltage drops below the low threshold V LT .
  • the power sensing component 44 senses the drop in voltage and supplies the sensed voltage VSENSE to the microprocessor 16.
  • the microprocessor 16 has made a decision that there is inadequate power to transmit the process signal 56 by controlling the loop current between 4-20 mA.
  • the microprocessor 16 adjusts the current through the modulator 70 to a selected level, such as 1.0mA, that will support communication of the transmitter signal 58, rather than controlling the current as a function of the measured process variable.
  • Figures 6a and 6b show the current being set to 1.0 mA.
  • the interval between t 2 and t 3 is the time programmed for the microprocessor 16 to make the decision. This time period is preferably about 1.0 second.
  • Figure 6c shows that the sensed voltage continues to be below the low threshold V LT , indicating that there continues to be a need for the power source 38 to supply some or all of the current through the modulator 70.
  • the microprocessor 16 determines that the power on the process link 12 has been restored and no longer holds the current to about 1.0 mA. Thereafter, the microprocessor 16 varies the current level as a function of the measured process variable, which forms the process signal 56.
  • Figure 6b shows current from the power source 38 remains substantially stopped because the diode 64 continues to be reserved biased.
  • Figure 6c shows the sensed voltage returning to a level that corresponds with the 4-20 MA current through the process link 12.
  • the process transmitter is communicating normally as described above .
  • Figure 7 is a diagram illustrating a method for communicating with the process transmitter communications circuit 96 during inadequate process link power. Commissioning of the process transmitter to perform diagnostic testing and set up is significantly simplified by the improvement in the process transmitter communications circuit 42. During commissioning, the process transmitter link terminals 40 are connected to a remote controller such as a Rosemount® Model 268 HART® Smart Family interface in an area such as a shop workbench. A separate power source and load resistor are not required to be connected to the link terminals 40 during commissioning. Commissioning therefore requires less equipment, is faster because there are fewer connections, and is safer because less equipment is involved.
  • a remote controller such as a Rosemount® Model 268 HART® Smart Family interface
  • a separate power source and load resistor are not required to be connected to the link terminals 40 during commissioning. Commissioning therefore requires less equipment, is faster because there are fewer connections, and is safer because less equipment is involved.
  • Field diagnostic testing and set-up changes to an installed process transmitter 10 are also simplified.
  • a field technician need only carry a remote controller to the potentially difficult to access and hazardous field location to perform diagnostic testing and make set-up changes.
  • the field technician need not carry a separate power source along with a load resistor and wire to the field location to perform field diagnostic testing and make set-up changes.
  • Field test and set-up changes require less equipment, are faster because there are fewer connections, and are safer because less equipment is involved in potentially difricult to access and hazardous locations.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Quality & Reliability (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Arrangements For Transmission Of Measured Signals (AREA)

Abstract

Ce circuit de télécommunication (20, 96) destiné à un émetteur de commande de processus, présente des bornes de liaison (40) couplées à une liaison de commande de processus (12), laquelle fournit l'énergie au circuit. Une source d'énergie (38) est couplée à l'une des bornes et elle est indépendante de l'énergie fournie à partir de la liaison (12). Des circuits de télécommunication (42) sont couplés à la source d'énergie (38) et aux bornes (40), qui émettent un signal de sortie de l'émetteur sur la liaison (12), à travers les bornes (40). Un élément de détection d'énergie (44) est couplé à l'une au moins des bornes (40) et aux circuits de télécommunication (42), et il détecte si l'énergie fournie par la liaison (12) est inappropriée à l'émission du signal de sortie de l'émetteur. Un élément de commande d'énergie (46) est couplé à la source d'énergie (38), aux bornes (40) et aux circuits de communications (42) et il applique de manière sélective l'énergie provenant de la source (38) aux circuits de communications (42), afin que ceux-ci émettent le signal de sortie de l'émetteur lorsque l'élément de détection d'énergie (44) détecte que l'énergie fournie par la liaison (12) est inappropriée.
PCT/US1997/017611 1996-10-04 1997-09-30 Circuit de telecommunication destine a un emetteur de commande de processus Ceased WO1998014854A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU48034/97A AU4803497A (en) 1996-10-04 1997-09-30 Process transmitter communications circuit

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US72546096A 1996-10-04 1996-10-04
US08/725,460 1996-10-04
US08/890,169 1997-07-09
US08/890,169 US6006338A (en) 1996-10-04 1997-07-09 Process transmitter communication circuit

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WO1998014854A1 true WO1998014854A1 (fr) 1998-04-09

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006039170A3 (fr) * 2004-09-30 2006-06-01 Rosemount Inc Dispositif de traitement avec affichage de diagnostic
US7680944B1 (en) * 2003-02-28 2010-03-16 Comtrol Corporation Rapid transport service in a network to peripheral device servers

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US7680944B1 (en) * 2003-02-28 2010-03-16 Comtrol Corporation Rapid transport service in a network to peripheral device servers
WO2006039170A3 (fr) * 2004-09-30 2006-06-01 Rosemount Inc Dispositif de traitement avec affichage de diagnostic
RU2380732C2 (ru) * 2004-09-30 2010-01-27 Роузмаунт Инк. Технологическое устройство с диагностическим извещением
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