CA2073447A1 - Multifunction isolation transformer - Google Patents
Multifunction isolation transformerInfo
- Publication number
- CA2073447A1 CA2073447A1 CA002073447A CA2073447A CA2073447A1 CA 2073447 A1 CA2073447 A1 CA 2073447A1 CA 002073447 A CA002073447 A CA 002073447A CA 2073447 A CA2073447 A CA 2073447A CA 2073447 A1 CA2073447 A1 CA 2073447A1
- Authority
- CA
- Canada
- Prior art keywords
- output
- circuit
- transmitter
- sensor
- loop
- 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.)
- Abandoned
Links
Classifications
-
- G—PHYSICS
- G08—SIGNALLING
- G08C—TRANSMISSION SYSTEMS FOR MEASURED VALUES, CONTROL OR SIMILAR SIGNALS
- G08C19/00—Electric signal transmission systems
- G08C19/02—Electric signal transmission systems in which the signal transmitted is magnitude of current or voltage
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F19/00—Fixed transformers or mutual inductances of the signal type
- H01F19/04—Transformers or mutual inductances suitable for handling frequencies considerably beyond the audio range
- H01F19/08—Transformers having magnetic bias, e.g. for handling pulses
- H01F2019/085—Transformer for galvanic isolation
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Arrangements For Transmission Of Measured Signals (AREA)
- Coils Or Transformers For Communication (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A process transmitter (50) transmits a 4-20 mA current representing a sensed parameter to a loop (52) which energizes the transmitter (50). An output circuit (60) receives energization from the loop (52) and controls the 4-20 mA output as a function of a sensor data input. The output circuit (60) further generates a transformer driver output which also serves as a clock for isolated circuitry (106). A sensor circuit (82) generates a transformer driver output representing the sensed parameter. An isolation transformer (76) driven by the driver output excites the sensor circuit (82) and provides a clock reference as a function of the driver output oscillation to the sensor circuit (82). The isolation transformer (76) is a single coupling device which couples energization, clock reference, sensor data and programming data across an electrically insulating barrier between the output circuit (50) and the sensor circuit (82).
A process transmitter (50) transmits a 4-20 mA current representing a sensed parameter to a loop (52) which energizes the transmitter (50). An output circuit (60) receives energization from the loop (52) and controls the 4-20 mA output as a function of a sensor data input. The output circuit (60) further generates a transformer driver output which also serves as a clock for isolated circuitry (106). A sensor circuit (82) generates a transformer driver output representing the sensed parameter. An isolation transformer (76) driven by the driver output excites the sensor circuit (82) and provides a clock reference as a function of the driver output oscillation to the sensor circuit (82). The isolation transformer (76) is a single coupling device which couples energization, clock reference, sensor data and programming data across an electrically insulating barrier between the output circuit (50) and the sensor circuit (82).
Description
- 2 ~ 7 3 !~ ~ 7 PCI/l,'S91/0121/~
MULTIFUNCIION ISOLATlON'rRANSFORMER
BACKGROUND OF THE INVENTION
This invention relates to a transmitter having loop circuitry receiving energization from a current loop and controlling the loop current to represent a parameter sensed by sensor circuitry in the transmitter.
In transmitter circuits, a galvanic barrier is often desired between loop circuitry and sensor circuitry in order to block flow of undesirable ground currents through sensitive transmitter circuits.
Magnetic transformers and optocouplers have been used to couple signals and power between isolated circuits on opposite sides of the barrier, while providing DC
isolation ~etween them. Typically, the loop circuitr~
couples energization across the barrier to energize the sensor circuitry while the sensor circuitry returns a sensor signal indicating the sensed parameter bac~:
across the barrier to the loop circuitry. In U. S.
Pats. 3,764,880 and 4,206,397, for examples, a single transformer provides galvanic isolation between a circuit connected to a loop and sensor circuitry. The single transformer couples energization in one direction and a sensor signal in an opposite direction across the barrier.
Transmitters can be of a programmable type, progra~ned by a digital signal from a programming device connected to the loop. For each installation, there is a desire to adjust or program the transmitter to have an output range and other characteristics matched the installation. In some transmitter arrangements, i' is desirable to have the trans}nitter's sensor circuitr~- be programmable so that that sensing is specif icall~
adapted to the range of the input variable of n'eres.
wo 91~1~41? ~ ~ 7 ~ ~ d 7 PCr/US91/01211~
in a particular installation. However, the digital programming signals generated on the loop side of the galvanic ~arrier must be kept isolated from the sensor circuitry which is to be programmed on the other side of the barrier. There is thus a need to couple digital programming signals across the barrier, leading to an apparent need for another galvanically isolating coupling device to be added to the transmitter. Digital s~nsor circuitry typically would also require a timing refer~nce or clock for support of its functions, and there is ~urther a desire to have a single cloc~:
supporting circuitry on both sides of the barrier, leading to an apparent need for yet another galvanically isolating coupling device such as a transformer or optical coupler. Each additional coupling device can increase complexity and power consumption, which can be limited when the transmitter is energized by a milliampere level loop current such as a 4-20 mA loop current.
There is thus a desire to provide a transmitter which provides galvanically isolated coupling of energization, a signal representative of the the sensed parameter, a timing reference, and a programming signal across a barrier, but avoiding the cost, complexity and increased power consumption of addir.g multiple isolating coupling devices.
SUMMARY OF THE INVENTION
A transmitter is provided with a single galvanically insulating coupling device which isolates loop circuitry from sensor circuitry. Transmit~er circuitry is arranged to utili7e the single coupling device to isolatingly couple not only power and a representation of a sensed parameter, but aiso ~.
wog~ a~ . d~7Pcr/lS9l/ol21(~
programming data simultaneously across a galvanic barrier.
A tr~nsmitter sends its output representing a sens~d parameter to a loop or circuit which energizes the transmitter. An output circuit in the transmitter receives the energization from the loop and controls the transmitter output as a function of a sensor data input.
The output circuit ~urther generates an ~scillating driver output. A ~ensor circuit generates a sensor data output representing the sensed parameter. Isc)lation means driven by the driver output excite the sensor circuit and provide a clock reference as a function of the driver output oscillation to the sensor circuit. The isolation means couple the sensor data output bac~ to sensor data input. Isolation means include a singie coupling device which couples energization, clock reference, sensor data and programming data across an electrically insulating barrier between the output circuit and the sensor circuit.
In a preferred embodiment, the single coupling device is a magnetic transformer.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a first embodiment of a transmitter according to the invention.
FIG. 2 shows a second embodiment of a transmitter according ~o the invention.
FIG. 3 shows a transformer circuit corresponding to FIG. 2.
DETAILED DESCRIPTION OP THE PREFERRED E~BO~Ir~F~TS
In FIG. 1, a first embodiment of a transritte~
according to the invention is shown in bloc~: diagra, form. In FIG. 1, transmitter 50 is connecteG t- loop 52. Loop 52 can be a two wire 4-20 mA indus~rial WO g~ 7 2 ~ 7 ~ 7 pC~/~lS9l/0l21~) control loop or a "multidrop" :loop which supplies current to several transmitters in parallel. A 4 wire type circuit with 2 wires providing energization and t~o wires providing a 1-5 ~olt output can be used in p~ace of loop 52, as well. Loop 52 supplies all of ~he energization to transmitter 5Q. Transmitter 50 is al50 ccupled to a programming device 54 which can be a Rosemount Brand Model 268 providing programming ~ia two way HART Brand digital communication protocol superimposed on the loop current.
Loop 52 supplies energization to power supply 56 which, in turn, energizes circuitry 60 on the left side of galvanic barrier 58 shown in dashed line Eorm in FIG. 1. Current control 57 is coupled to the loop to control loop current and is coupled to microcomputer 66 to recPive instructions. Current control 57 comprises a digita~-to-analog current converter circuit. Cloc~
oscillator 62 generates a timing reference or cloc~:
which is provided along line 64 to microcomputer 66 and driver circuit 68. Programming device 54 communicates with microcomputer 66 along line 70 to provide programming instructions which are stored in microcomputer 66. Driver circuit 68 generates an oscillatory driver output on line 72 which has a fr~quency controlled by clock oscillator 62. The output fre~uency is selected to be high enough SQ that it can be conveniently amplitude modulated with lower fre~uency modulations which carry programming data and sensed process para~eter data. A drive frequency over 2QG
kilohertz is desirable to ensure fast enough upda~ing of the transmitter output with process para-eter information. A frequency range of 200 - lOOQ ~;ilohertz is acceptable for the drive frequency, witk a range of WO91/1~17 ~ 7 ~ PCT/US91/0121 200 - 500 ~ilohertz being preferred. Driver output orl line 72 is coupled to excite primary winding 7~ cf transformer 76. Microcomputer 66 couples a communication output on line 78 to control switch 80.
Control switch 80 modulates the excitation current o transformer primary 74 with a communication signa representing programming instructions to be received b~
sensor circuit 82. The modulation is preferabl~
amplitude modulation at a frequency lower than the excitation ~requency.
Transformer 76 comprises primary winding ,;
wh.ich is electrically insulated from secondary winding 75. Transformer 76 couples the modulated excitation to secondary 75. Secondary 75 is connected to diode 8~
which rectifies the trans~ormed isolated excitation and provides the excitation to filter B6. Filter 86 filters the excitation to extract the modulation provided by switch 80. The modulation is coupled al~ng line 88 to waveshaping c~rcuit 90 which provides further signal conditioning as needed. The output of waveshaper 90 provides the modulation which represents programming instructions to the sensor circuit 82. The sensor circuit 82 stores the programming instructions ~for programming the operation of the sensor circuit to adapt its characteristics to a particular measurement application. Characteristics such as span, zero, sampling rate, damping, calibration constants, and compensation for extraneous variables can be programmed in the sensor circuit 82 as desired. In the case cf transmitters which are adapted in the field to a selected sensor, the programming can also a~a~ Ine sensor circuit to a selected sensor. For e~:a.ple, ^
temperature transmitter can be programmed to adap_ il tC
WO 91tl3417 2 ~ 7 7 ~ ~ 1 PCTt~'S91/0121~1 different types of thermocouples or resistance temperature detectors ~RTD's~.
Line 88 also couples excitation to a power supply filter 92 which provides a filtered power suppl~
potential alon~ line 94 to sensor circuit 82. Secondar~
winding 75 is coupled along line 96 to pulse shaper 98 which, in turn, provides shaped excitation to sensor circuit 82 as a clock or frequency reference. Senso~
circuit 82 senses a process parameter lO0 which can be temperature, pressure, flow, and the like.. Sensor circuit 82 generates a serial diqital output representing the process variable conditioned by the programming data stored in it along line lO~ to control a switch 104 which modulates the power provided by the sec~ndary to circuitry 106 on the right side of the barrier 58. Sense winding 108 of transformer 76 senses the modulation of the power and provides the modulatio~
to microcomputer 66 via waveshaper llO to provide microcomputer 66 with a signal representative of the sensed parameter adjusted for the prvgrammed data stored in circuit 82. It is not essential that transformer 76 have three windings. Transformer 76 could also~ be configured with only two winding 74, 75, in which case waveshaper llO would simply receive its input fror, winding 74.
The transformer 76 in FIG. l thus is a single isolation device which provides electrcally insulated coupling of power, a clock frequency reference, a signal representative of the sensed parameter, and program~in~
instructions, as well. The single transforme- 76 of FIG. l thus provides galvanic isolation between loop circuitry such as output circuit 60 and sensor circuitr~
106. The single transformer 76 not onl~ coupieC
~O~1~i~17 PC~/~'~91/0121() ~,~t73~
eneryization and a signal represertative of the sensed parametert but also couples a cloc~ reference and programming signals across the ~arrier to maintain electrical isolation without providing additional transformers or other isolation devices in the transmitter.
In FIG. 2, a transmitter 150 is coupled to a two wire ~-20 milliampere loop 152 comprising a loop power supply 154 having a limited voltage and a readout device 156. As exp}ained above in connection with FIG.
1, a programming device 15~ is connected to the loop to provida programming to the trall~mitter. The programming device blocks lower frequency 4-20 mA loop current so that it doeæ not i~terfere with loop operation.
The loop circuit is grounded to a ground system l6~ at location 162. There. are other electrical devices which are grounded to ground system 160 which inject noise currents iN into the ground system at points 164. A sensor or sensors 166 are al50 coupled to ground system 160 at point 168. Because of the noise currents flowing in ground system 160, there is a noise potential difference ~N between points 162 and 16~. If transmitter 150 included a completed electric circuit between the loop 152 and the sensors 166, noise ground currents would flow through transmitter 150 and loop 152, disturbing the measurement at readout 156. To avoid this problem, transmitter 150 is provided with a galvanic barrier 170 between circuitry connected to the loop 152 and the sensors 166. The galvanic barrier is an electrical open circuit which blocks electrical noise current flow, but still allows energy and infor~ion bearing signals to pass across the barrier usir.
nonelectric transfer means such as~the magnetic field c WO 91/1:}'117 PCr/l 'S91/0121~) 2 ~ 17 ~ 7 a transformer. Each electrical aomponent which has connectivns on opposite sides of barrier 170 must be an i501ating component~ Typically, isolation voltages on the order of 1~000 volts or more are desired. While this explanation of barriers, grounding and ground systems has been explained in connection with FIG. 2, it applies generally to FIG. 1, as well.
In transmitter 150, current control circuit 172 is connected to loop 152 at terminals 17~. Current control circuit 172 is energized by curr~nt from loop 152 and provides energization along line 176 to other circuits on the left side of barrier 170. Current control 172 controls loop current as a function of a DAC
output received on line 178 from DAC 180. Current control circuit 172 passes serial digital communication signals back and forth along line 182 between programming device 158 and MODEM 184. The digital communication signals include programming instructions and constants, for storage in circuitry on the right side of barrier 170. DAC 180 and MODEM 184 communica~e along bus 186 with microcomputer 188. Microcomputer 18~
provides a digital word representativa of a parameter or parameters sensed by sensors 166 to both DAC 180~and MODEM 184. Microcomputer 188 stores programming constants provided by MODEM 184. Clock oscillator 190, which can be a crystal controlled oscillator, provides frequency or clock references to modem 18~, microcomputer 188 and driver 192. Reyulator 19~ is energized hy current control circuit 172 and provides a regulated supply potential along line 196 to d-iver lC~.
Driver 192 drives an input of isolation ~evice 198 along line 200 with an energy delivering wave'or~.
having a frequency controlled by clock oscillator 190.
WO 91/1341, PCr/l 'S91/0121() ~ 0 ~
_9_ The driver 192 modulates the waveform with data received on line 202 from microcomputer 188. The modulation represents programming constants for circuitry on the right side of barrier 170. Isolation device 19 electrically isolates lines 200, 204 from lines 206, 208, 209 while providing coupling across the barrier of energy and multiple signals using-nonelectric coupling such as a magnetic field or light.
The isolation device 198 provides isolated energization on line 208 which is coupled to regulator rectifier 210. Regulator-rectifier 210 provides energization potentials to circuitry on the right side of barrier 170 and may also provide energization to one or more sensors 166. The isolation device 198 provides an output on line 206 which is a cloc~ reference for analog to digital converter ~ADC) 212. The output on line 206 is also coupled to filter 214 which extracts modulation data and provides it along line 216 to program characteristics of ADC 212. AbC 212 samples the output of one or more sensors 166 and couples a digital signal representative of the sensed parameters adjusted by the programming along line 218 to driver 220. DriYer 220 modulates power drawn by isolation device 198 fro~
driver 192 on the other side of the barrier. The modulation is preferably in the form of a serial digital signal. The isolation device 198 provides this modulation along line 204 to filter 222. Filter 222 coupled the data contained in the power modulation to microcomputer 188 where it is stored as an update~
representation of the sensed parameter or paramete-s.
In FIG. 3, a circuit is sho~n wh~ch ca- be used in a transmitter such as the transmitte- sh^~
FIG. 2 to couple power and multiple signalc acrosC a ~ ~1/13417 P~/~'S91/0121() 2 ~
galvanic barrier using a single isolating device, transformer 250. Transformer 250 includes a primary winding 252 electrically insulated ~rom secondary winding 254 to form a galvanic barrier represented by dashed line 256. Drive transistor 258 is coupled in series with primary winding 252 and resistor 260 across a 10 volt power supply. Oscillating, and preferabl~
sinusoidal current ~upplied by this arrangement excites the transformer so that it can deliver isolated power at its secondary winding 254. The level of drlve is amplitude modulated by a ~ield effect transistor 262 which has its output coupled in parallel with resistor 260 to vary current level in primary 252.
5econdary winding 2$4 energizes a regulator circuit comprising rectifier diode 264, filter capacitor 266, resistors 268, 274, zener diode 270, and capacitor 274. The regulator provides a supply potential or power to circuitry on the right side of barrier 256 which corresponds to barrier 170 of FIG. 2. Secondary 254 is coupled through resistor 276 and capacitor 278 to provide a clock reference at the drive frequency of driver 258. Filter 280 is coupled to secondary 2~
through rectifier diode 264 and comprises resistors 2~2 and capacitors 286, 288. Filter 280 provides data at its output which represents the modulation provicled by transist~r 262. This modulation represents programr.ling constants. A signal representative of sensed parameters is presented in serial digital form on line 290 to FEI
292 which is connected in parallel across capacitcr 29~.
Capacitor 294 is connected in series with secondar~
winding 254. The arrangement modulates the power dra~.r.
from driver 258 with the data representative of sensed parameters. This modulation appears on line 29G wr.ic;~
W091/1~41- PcT/~ls9l/ol2l~
2 ~
carries the data to a microcomputer such as microcomputer 188 of FIG. 2.
~ lthough the present invention has bee~
described with reference to preferred embodiments, wo~kers skilled in the art will recognize that changes may be made in form and detail without departing fro~.
the spirit and scope of the invention.
MULTIFUNCIION ISOLATlON'rRANSFORMER
BACKGROUND OF THE INVENTION
This invention relates to a transmitter having loop circuitry receiving energization from a current loop and controlling the loop current to represent a parameter sensed by sensor circuitry in the transmitter.
In transmitter circuits, a galvanic barrier is often desired between loop circuitry and sensor circuitry in order to block flow of undesirable ground currents through sensitive transmitter circuits.
Magnetic transformers and optocouplers have been used to couple signals and power between isolated circuits on opposite sides of the barrier, while providing DC
isolation ~etween them. Typically, the loop circuitr~
couples energization across the barrier to energize the sensor circuitry while the sensor circuitry returns a sensor signal indicating the sensed parameter bac~:
across the barrier to the loop circuitry. In U. S.
Pats. 3,764,880 and 4,206,397, for examples, a single transformer provides galvanic isolation between a circuit connected to a loop and sensor circuitry. The single transformer couples energization in one direction and a sensor signal in an opposite direction across the barrier.
Transmitters can be of a programmable type, progra~ned by a digital signal from a programming device connected to the loop. For each installation, there is a desire to adjust or program the transmitter to have an output range and other characteristics matched the installation. In some transmitter arrangements, i' is desirable to have the trans}nitter's sensor circuitr~- be programmable so that that sensing is specif icall~
adapted to the range of the input variable of n'eres.
wo 91~1~41? ~ ~ 7 ~ ~ d 7 PCr/US91/01211~
in a particular installation. However, the digital programming signals generated on the loop side of the galvanic ~arrier must be kept isolated from the sensor circuitry which is to be programmed on the other side of the barrier. There is thus a need to couple digital programming signals across the barrier, leading to an apparent need for another galvanically isolating coupling device to be added to the transmitter. Digital s~nsor circuitry typically would also require a timing refer~nce or clock for support of its functions, and there is ~urther a desire to have a single cloc~:
supporting circuitry on both sides of the barrier, leading to an apparent need for yet another galvanically isolating coupling device such as a transformer or optical coupler. Each additional coupling device can increase complexity and power consumption, which can be limited when the transmitter is energized by a milliampere level loop current such as a 4-20 mA loop current.
There is thus a desire to provide a transmitter which provides galvanically isolated coupling of energization, a signal representative of the the sensed parameter, a timing reference, and a programming signal across a barrier, but avoiding the cost, complexity and increased power consumption of addir.g multiple isolating coupling devices.
SUMMARY OF THE INVENTION
A transmitter is provided with a single galvanically insulating coupling device which isolates loop circuitry from sensor circuitry. Transmit~er circuitry is arranged to utili7e the single coupling device to isolatingly couple not only power and a representation of a sensed parameter, but aiso ~.
wog~ a~ . d~7Pcr/lS9l/ol21(~
programming data simultaneously across a galvanic barrier.
A tr~nsmitter sends its output representing a sens~d parameter to a loop or circuit which energizes the transmitter. An output circuit in the transmitter receives the energization from the loop and controls the transmitter output as a function of a sensor data input.
The output circuit ~urther generates an ~scillating driver output. A ~ensor circuit generates a sensor data output representing the sensed parameter. Isc)lation means driven by the driver output excite the sensor circuit and provide a clock reference as a function of the driver output oscillation to the sensor circuit. The isolation means couple the sensor data output bac~ to sensor data input. Isolation means include a singie coupling device which couples energization, clock reference, sensor data and programming data across an electrically insulating barrier between the output circuit and the sensor circuit.
In a preferred embodiment, the single coupling device is a magnetic transformer.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a first embodiment of a transmitter according to the invention.
FIG. 2 shows a second embodiment of a transmitter according ~o the invention.
FIG. 3 shows a transformer circuit corresponding to FIG. 2.
DETAILED DESCRIPTION OP THE PREFERRED E~BO~Ir~F~TS
In FIG. 1, a first embodiment of a transritte~
according to the invention is shown in bloc~: diagra, form. In FIG. 1, transmitter 50 is connecteG t- loop 52. Loop 52 can be a two wire 4-20 mA indus~rial WO g~ 7 2 ~ 7 ~ 7 pC~/~lS9l/0l21~) control loop or a "multidrop" :loop which supplies current to several transmitters in parallel. A 4 wire type circuit with 2 wires providing energization and t~o wires providing a 1-5 ~olt output can be used in p~ace of loop 52, as well. Loop 52 supplies all of ~he energization to transmitter 5Q. Transmitter 50 is al50 ccupled to a programming device 54 which can be a Rosemount Brand Model 268 providing programming ~ia two way HART Brand digital communication protocol superimposed on the loop current.
Loop 52 supplies energization to power supply 56 which, in turn, energizes circuitry 60 on the left side of galvanic barrier 58 shown in dashed line Eorm in FIG. 1. Current control 57 is coupled to the loop to control loop current and is coupled to microcomputer 66 to recPive instructions. Current control 57 comprises a digita~-to-analog current converter circuit. Cloc~
oscillator 62 generates a timing reference or cloc~:
which is provided along line 64 to microcomputer 66 and driver circuit 68. Programming device 54 communicates with microcomputer 66 along line 70 to provide programming instructions which are stored in microcomputer 66. Driver circuit 68 generates an oscillatory driver output on line 72 which has a fr~quency controlled by clock oscillator 62. The output fre~uency is selected to be high enough SQ that it can be conveniently amplitude modulated with lower fre~uency modulations which carry programming data and sensed process para~eter data. A drive frequency over 2QG
kilohertz is desirable to ensure fast enough upda~ing of the transmitter output with process para-eter information. A frequency range of 200 - lOOQ ~;ilohertz is acceptable for the drive frequency, witk a range of WO91/1~17 ~ 7 ~ PCT/US91/0121 200 - 500 ~ilohertz being preferred. Driver output orl line 72 is coupled to excite primary winding 7~ cf transformer 76. Microcomputer 66 couples a communication output on line 78 to control switch 80.
Control switch 80 modulates the excitation current o transformer primary 74 with a communication signa representing programming instructions to be received b~
sensor circuit 82. The modulation is preferabl~
amplitude modulation at a frequency lower than the excitation ~requency.
Transformer 76 comprises primary winding ,;
wh.ich is electrically insulated from secondary winding 75. Transformer 76 couples the modulated excitation to secondary 75. Secondary 75 is connected to diode 8~
which rectifies the trans~ormed isolated excitation and provides the excitation to filter B6. Filter 86 filters the excitation to extract the modulation provided by switch 80. The modulation is coupled al~ng line 88 to waveshaping c~rcuit 90 which provides further signal conditioning as needed. The output of waveshaper 90 provides the modulation which represents programming instructions to the sensor circuit 82. The sensor circuit 82 stores the programming instructions ~for programming the operation of the sensor circuit to adapt its characteristics to a particular measurement application. Characteristics such as span, zero, sampling rate, damping, calibration constants, and compensation for extraneous variables can be programmed in the sensor circuit 82 as desired. In the case cf transmitters which are adapted in the field to a selected sensor, the programming can also a~a~ Ine sensor circuit to a selected sensor. For e~:a.ple, ^
temperature transmitter can be programmed to adap_ il tC
WO 91tl3417 2 ~ 7 7 ~ ~ 1 PCTt~'S91/0121~1 different types of thermocouples or resistance temperature detectors ~RTD's~.
Line 88 also couples excitation to a power supply filter 92 which provides a filtered power suppl~
potential alon~ line 94 to sensor circuit 82. Secondar~
winding 75 is coupled along line 96 to pulse shaper 98 which, in turn, provides shaped excitation to sensor circuit 82 as a clock or frequency reference. Senso~
circuit 82 senses a process parameter lO0 which can be temperature, pressure, flow, and the like.. Sensor circuit 82 generates a serial diqital output representing the process variable conditioned by the programming data stored in it along line lO~ to control a switch 104 which modulates the power provided by the sec~ndary to circuitry 106 on the right side of the barrier 58. Sense winding 108 of transformer 76 senses the modulation of the power and provides the modulatio~
to microcomputer 66 via waveshaper llO to provide microcomputer 66 with a signal representative of the sensed parameter adjusted for the prvgrammed data stored in circuit 82. It is not essential that transformer 76 have three windings. Transformer 76 could also~ be configured with only two winding 74, 75, in which case waveshaper llO would simply receive its input fror, winding 74.
The transformer 76 in FIG. l thus is a single isolation device which provides electrcally insulated coupling of power, a clock frequency reference, a signal representative of the sensed parameter, and program~in~
instructions, as well. The single transforme- 76 of FIG. l thus provides galvanic isolation between loop circuitry such as output circuit 60 and sensor circuitr~
106. The single transformer 76 not onl~ coupieC
~O~1~i~17 PC~/~'~91/0121() ~,~t73~
eneryization and a signal represertative of the sensed parametert but also couples a cloc~ reference and programming signals across the ~arrier to maintain electrical isolation without providing additional transformers or other isolation devices in the transmitter.
In FIG. 2, a transmitter 150 is coupled to a two wire ~-20 milliampere loop 152 comprising a loop power supply 154 having a limited voltage and a readout device 156. As exp}ained above in connection with FIG.
1, a programming device 15~ is connected to the loop to provida programming to the trall~mitter. The programming device blocks lower frequency 4-20 mA loop current so that it doeæ not i~terfere with loop operation.
The loop circuit is grounded to a ground system l6~ at location 162. There. are other electrical devices which are grounded to ground system 160 which inject noise currents iN into the ground system at points 164. A sensor or sensors 166 are al50 coupled to ground system 160 at point 168. Because of the noise currents flowing in ground system 160, there is a noise potential difference ~N between points 162 and 16~. If transmitter 150 included a completed electric circuit between the loop 152 and the sensors 166, noise ground currents would flow through transmitter 150 and loop 152, disturbing the measurement at readout 156. To avoid this problem, transmitter 150 is provided with a galvanic barrier 170 between circuitry connected to the loop 152 and the sensors 166. The galvanic barrier is an electrical open circuit which blocks electrical noise current flow, but still allows energy and infor~ion bearing signals to pass across the barrier usir.
nonelectric transfer means such as~the magnetic field c WO 91/1:}'117 PCr/l 'S91/0121~) 2 ~ 17 ~ 7 a transformer. Each electrical aomponent which has connectivns on opposite sides of barrier 170 must be an i501ating component~ Typically, isolation voltages on the order of 1~000 volts or more are desired. While this explanation of barriers, grounding and ground systems has been explained in connection with FIG. 2, it applies generally to FIG. 1, as well.
In transmitter 150, current control circuit 172 is connected to loop 152 at terminals 17~. Current control circuit 172 is energized by curr~nt from loop 152 and provides energization along line 176 to other circuits on the left side of barrier 170. Current control 172 controls loop current as a function of a DAC
output received on line 178 from DAC 180. Current control circuit 172 passes serial digital communication signals back and forth along line 182 between programming device 158 and MODEM 184. The digital communication signals include programming instructions and constants, for storage in circuitry on the right side of barrier 170. DAC 180 and MODEM 184 communica~e along bus 186 with microcomputer 188. Microcomputer 18~
provides a digital word representativa of a parameter or parameters sensed by sensors 166 to both DAC 180~and MODEM 184. Microcomputer 188 stores programming constants provided by MODEM 184. Clock oscillator 190, which can be a crystal controlled oscillator, provides frequency or clock references to modem 18~, microcomputer 188 and driver 192. Reyulator 19~ is energized hy current control circuit 172 and provides a regulated supply potential along line 196 to d-iver lC~.
Driver 192 drives an input of isolation ~evice 198 along line 200 with an energy delivering wave'or~.
having a frequency controlled by clock oscillator 190.
WO 91/1341, PCr/l 'S91/0121() ~ 0 ~
_9_ The driver 192 modulates the waveform with data received on line 202 from microcomputer 188. The modulation represents programming constants for circuitry on the right side of barrier 170. Isolation device 19 electrically isolates lines 200, 204 from lines 206, 208, 209 while providing coupling across the barrier of energy and multiple signals using-nonelectric coupling such as a magnetic field or light.
The isolation device 198 provides isolated energization on line 208 which is coupled to regulator rectifier 210. Regulator-rectifier 210 provides energization potentials to circuitry on the right side of barrier 170 and may also provide energization to one or more sensors 166. The isolation device 198 provides an output on line 206 which is a cloc~ reference for analog to digital converter ~ADC) 212. The output on line 206 is also coupled to filter 214 which extracts modulation data and provides it along line 216 to program characteristics of ADC 212. AbC 212 samples the output of one or more sensors 166 and couples a digital signal representative of the sensed parameters adjusted by the programming along line 218 to driver 220. DriYer 220 modulates power drawn by isolation device 198 fro~
driver 192 on the other side of the barrier. The modulation is preferably in the form of a serial digital signal. The isolation device 198 provides this modulation along line 204 to filter 222. Filter 222 coupled the data contained in the power modulation to microcomputer 188 where it is stored as an update~
representation of the sensed parameter or paramete-s.
In FIG. 3, a circuit is sho~n wh~ch ca- be used in a transmitter such as the transmitte- sh^~
FIG. 2 to couple power and multiple signalc acrosC a ~ ~1/13417 P~/~'S91/0121() 2 ~
galvanic barrier using a single isolating device, transformer 250. Transformer 250 includes a primary winding 252 electrically insulated ~rom secondary winding 254 to form a galvanic barrier represented by dashed line 256. Drive transistor 258 is coupled in series with primary winding 252 and resistor 260 across a 10 volt power supply. Oscillating, and preferabl~
sinusoidal current ~upplied by this arrangement excites the transformer so that it can deliver isolated power at its secondary winding 254. The level of drlve is amplitude modulated by a ~ield effect transistor 262 which has its output coupled in parallel with resistor 260 to vary current level in primary 252.
5econdary winding 2$4 energizes a regulator circuit comprising rectifier diode 264, filter capacitor 266, resistors 268, 274, zener diode 270, and capacitor 274. The regulator provides a supply potential or power to circuitry on the right side of barrier 256 which corresponds to barrier 170 of FIG. 2. Secondary 254 is coupled through resistor 276 and capacitor 278 to provide a clock reference at the drive frequency of driver 258. Filter 280 is coupled to secondary 2~
through rectifier diode 264 and comprises resistors 2~2 and capacitors 286, 288. Filter 280 provides data at its output which represents the modulation provicled by transist~r 262. This modulation represents programr.ling constants. A signal representative of sensed parameters is presented in serial digital form on line 290 to FEI
292 which is connected in parallel across capacitcr 29~.
Capacitor 294 is connected in series with secondar~
winding 254. The arrangement modulates the power dra~.r.
from driver 258 with the data representative of sensed parameters. This modulation appears on line 29G wr.ic;~
W091/1~41- PcT/~ls9l/ol2l~
2 ~
carries the data to a microcomputer such as microcomputer 188 of FIG. 2.
~ lthough the present invention has bee~
described with reference to preferred embodiments, wo~kers skilled in the art will recognize that changes may be made in form and detail without departing fro~.
the spirit and scope of the invention.
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A transmitter providing a transmitter output representing a sensed parameter to a loop which energizes the transmitter, comprising:
an output circuit receiving the energization from the loop and controlling the transmitter output as a function of a sensor data input, the output circuit further generating an oscillating driver output;
a sensor circuit generating a clocked sensor data output representing the sensed parameter; and isolation means driven by the driver output for exciting the sensor circuit and for providing a clock reference as a function of the driver output oscillation to the sensor circuit, the isolation means providing the sensor data output back to sensor data input, the isolation means including a single coupling device which couples energization, sensor data and programming data across an electrically insulating barrier between the output circuit and the sensor circuit.
an output circuit receiving the energization from the loop and controlling the transmitter output as a function of a sensor data input, the output circuit further generating an oscillating driver output;
a sensor circuit generating a clocked sensor data output representing the sensed parameter; and isolation means driven by the driver output for exciting the sensor circuit and for providing a clock reference as a function of the driver output oscillation to the sensor circuit, the isolation means providing the sensor data output back to sensor data input, the isolation means including a single coupling device which couples energization, sensor data and programming data across an electrically insulating barrier between the output circuit and the sensor circuit.
2. The transmitter of Claim 1 wherein the single coupling device further couples a clock. reference between the output circuit and the sensor circuit.
3. The transmitter of Claim 1 wherein the single coupling device is a magnetic transformer having a first winding coupled to the output circuit and a second winding electrically insulated from the first winding and coupled to the sensor circuit.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US48306290A | 1990-02-21 | 1990-02-21 | |
| US483,062 | 1990-02-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2073447A1 true CA2073447A1 (en) | 1991-08-22 |
Family
ID=23918489
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002073447A Abandoned CA2073447A1 (en) | 1990-02-21 | 1991-02-21 | Multifunction isolation transformer |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0518916B1 (en) |
| AU (1) | AU646847B2 (en) |
| CA (1) | CA2073447A1 (en) |
| DE (1) | DE69127075T2 (en) |
| WO (1) | WO1991013417A1 (en) |
Families Citing this family (31)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4343540C2 (en) * | 1993-12-14 | 1995-12-07 | Mannesmann Ag | Arrangement for the isolated transmission of direct and alternating current signals |
| US6008681A (en) * | 1998-06-02 | 1999-12-28 | Conexant Systems, Inc. | Method and apparatus for deriving power from a clock signal coupled through a transformer |
| DE10054740A1 (en) * | 2000-11-04 | 2002-05-16 | Rheintacho Messtechnik Gmbh | Circuit arrangement for operating a magnetic field and or eddy current transducer with which the transducer can be switched between programmable mode and measurement mode to reduce the requirement for sensor connections |
| US7773715B2 (en) * | 2002-09-06 | 2010-08-10 | Rosemount Inc. | Two wire transmitter with isolated can output |
| DE10255741A1 (en) * | 2002-11-28 | 2004-06-09 | Endress + Hauser Conducta Gesellschaft für Mess- und Regeltechnik mbH + Co. KG | Modular transmitter with galvanically isolated sensor |
| US8145180B2 (en) | 2004-05-21 | 2012-03-27 | Rosemount Inc. | Power generation for process devices |
| US8160535B2 (en) | 2004-06-28 | 2012-04-17 | Rosemount Inc. | RF adapter for field device |
| US7262693B2 (en) | 2004-06-28 | 2007-08-28 | Rosemount Inc. | Process field device with radio frequency communication |
| US7347099B2 (en) | 2004-07-16 | 2008-03-25 | Rosemount Inc. | Pressure transducer with external heater |
| US7391297B2 (en) | 2005-03-12 | 2008-06-24 | Lutron Electronics Co., Inc. | Handheld programmer for lighting control system |
| US8452255B2 (en) | 2005-06-27 | 2013-05-28 | Rosemount Inc. | Field device with dynamically adjustable power consumption radio frequency communication |
| US7679033B2 (en) * | 2005-09-29 | 2010-03-16 | Rosemount Inc. | Process field device temperature control |
| US8000841B2 (en) | 2005-12-30 | 2011-08-16 | Rosemount Inc. | Power management in a process transmitter |
| DE102006009506B4 (en) | 2006-02-27 | 2010-09-23 | Phoenix Contact Gmbh & Co. Kg | Bidirectional, galvanically isolated transmission channel |
| US7656687B2 (en) | 2007-12-11 | 2010-02-02 | Cirrus Logic, Inc. | Modulated transformer-coupled gate control signaling method and apparatus |
| US7796076B2 (en) | 2008-02-26 | 2010-09-14 | Cirrus Logic, Inc. | Transformer-isolated analog-to-digital converter (ADC) feedback apparatus and method |
| WO2009154748A2 (en) | 2008-06-17 | 2009-12-23 | Rosemount Inc. | Rf adapter for field device with low voltage intrinsic safety clamping |
| US8929948B2 (en) | 2008-06-17 | 2015-01-06 | Rosemount Inc. | Wireless communication adapter for field devices |
| US8694060B2 (en) | 2008-06-17 | 2014-04-08 | Rosemount Inc. | Form factor and electromagnetic interference protection for process device wireless adapters |
| US8847571B2 (en) | 2008-06-17 | 2014-09-30 | Rosemount Inc. | RF adapter for field device with variable voltage drop |
| CN102084626B (en) | 2008-06-17 | 2013-09-18 | 罗斯蒙德公司 | RF adapter for field device with loop current bypass |
| DE102009002009A1 (en) * | 2009-03-31 | 2010-10-07 | Endress + Hauser Gmbh + Co. Kg | Device for reducing or minimizing interference signals in a field device of process automation |
| US8626087B2 (en) | 2009-06-16 | 2014-01-07 | Rosemount Inc. | Wire harness for field devices used in a hazardous locations |
| US9674976B2 (en) | 2009-06-16 | 2017-06-06 | Rosemount Inc. | Wireless process communication adapter with improved encapsulation |
| US10761524B2 (en) | 2010-08-12 | 2020-09-01 | Rosemount Inc. | Wireless adapter with process diagnostics |
| US9310794B2 (en) | 2011-10-27 | 2016-04-12 | Rosemount Inc. | Power supply for industrial process field device |
| DE102012112234A1 (en) * | 2012-12-13 | 2014-06-18 | Endress + Hauser Gmbh + Co. Kg | Device for synchronizing clock frequencies |
| US9544027B2 (en) * | 2014-02-19 | 2017-01-10 | Texas Instruments Incorporated | Loop powered transmitter with a single tap data isolation transformer and unipolar voltage converters |
| WO2016101212A1 (en) | 2014-12-25 | 2016-06-30 | Texas Instruments Incorporated | Bi-directional electric energy meter |
| US10451468B2 (en) * | 2017-01-24 | 2019-10-22 | Magnetrol International, Incorporated | Through air radar level transmitter with flushing port |
| US10389407B2 (en) | 2017-11-17 | 2019-08-20 | Texas Instruments Incorporated | Electrical transformer to transmit data and power |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3764880A (en) * | 1972-05-08 | 1973-10-09 | Rosemount Inc | Two-wire current transmitter with isolated transducer circuit |
| US4206397A (en) * | 1978-03-13 | 1980-06-03 | Rosemount Inc. | Two wire current transmitter with improved voltage regulator |
| US4354190A (en) * | 1980-04-04 | 1982-10-12 | General Electric Company | Rotor measurement system using reflected load transmission |
| US4758836A (en) * | 1983-06-20 | 1988-07-19 | Rockwell International Corporation | Inductive coupling system for the bi-directional transmission of digital data |
-
1991
- 1991-02-21 DE DE69127075T patent/DE69127075T2/en not_active Expired - Fee Related
- 1991-02-21 CA CA002073447A patent/CA2073447A1/en not_active Abandoned
- 1991-02-21 EP EP91905145A patent/EP0518916B1/en not_active Expired - Lifetime
- 1991-02-21 AU AU73497/91A patent/AU646847B2/en not_active Ceased
- 1991-02-21 WO PCT/US1991/001210 patent/WO1991013417A1/en active IP Right Grant
Also Published As
| Publication number | Publication date |
|---|---|
| AU646847B2 (en) | 1994-03-10 |
| EP0518916A4 (en) | 1992-10-19 |
| DE69127075D1 (en) | 1997-09-04 |
| EP0518916A1 (en) | 1992-12-23 |
| EP0518916B1 (en) | 1997-07-30 |
| DE69127075T2 (en) | 1998-02-26 |
| AU7349791A (en) | 1991-09-18 |
| WO1991013417A1 (en) | 1991-09-05 |
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Legal Events
| Date | Code | Title | Description |
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| EEER | Examination request | ||
| FZDE | Dead |