JP3130314B2 - Optical transmitter for process variables - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a process variable transmitter that is optically energized and provides a light output representative of a process variable.

As used herein, the terms "light,""optical," and "radiation" refer to visible and invisible electromagnetic radiation (lines) having a wavelength less than about 100 microns (100,000 nm);
The terms "electrical" and "electrical" refer to lower frequency phenomena, such as those commonly encountered in electronic circuits operating at frequencies below 100MHz. The “process variable” is the pressure detected by transmitters such as process control and aerospace equipment,
Means temperature, flow rate, speed, specific gravity, etc.

SUMMARY OF THE INVENTION In the present invention, light coupled to a light input of a transmitter energizes an electrical circuit of the transmitter. Light coupled to the light input is modulated with instructions that control the operation of the transmitter. The instructions include instructions for programming one or more reprogrammable transmitter output parameters. The transmitter has sensor means for sensing the process variable and delivers a programmed light output representative of the process variable to a medium or light guide, which transmits the light output. The sensor means generates an electrical sensor output representative of the process variable. The electrical sensor output is connected to circuit means in the transmitter which generates an electrical transmitter output representative of a process variable adjusted or programmed by a changeable or programmable parameter stored in the circuit means. The circuit means has an energizing input for energizing the circuit means. The transmitter further has a conversion means for converting the programmed electrical output of the transmitter into a programmed optical output. The conversion means further includes light receiving means for receiving light, the light receiving means converting a first portion of the received light into electrical energy supplied to an energizing input and converting a second portion of the received light. Converting the changeable parameters stored in the circuit means into electrical outputs for controlling, thereby causing the programming of the transmitter outputs to be performed.

The transmitter is connected to an interface connected to the electrical data bus via a medium, that is, an optical transmission line. The interface includes a light generating means connected to the optical transmission line, the light generating means modulating a programmed light component to program the light output generation of the transmitter by adjusting a stored variable parameter. First means for generating. The light generating means further has a second means for generating an energizing light component for energizing the transmitter. The interface is further coupled to the light generating means for electrically controlling the modulation as a function of the first reference received from the bus and for electrically controlling the amplitude of the energizing light component as a function of the second reference in the control means. It has a control means for performing the control. The interface further includes receiving means for providing an electrical output on the bus representative of the programmed optical output received from the transmitter.

In a preferred multidrop arrangement, the optical transmission line is coupled to a plurality of optical process variable transmitters, and the light generating means further comprises a programming light component modulated to program the generation of light output by the plurality of addressable transmitters. Means for generating. The programming light component is preferably modulated according to a serial data protocol.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of one embodiment of an optical transmitter connected to an interface via an optical transmission line.

FIG. 2 is a block diagram of a second embodiment of an optical transmitter connected to an interface via an optical transmission line.

FIG. 3 is an example of a DC / DC converter circuit used for an optical transmitter.

FIG. 4 shows an example of the configuration of an optical transceiver connected to an optical transmission line.

FIG. 5 shows another example of the configuration of the optical transceiver connected to the optical transmission line.

FIGS. 6, 7, and 8 are block diagrams of a multi-branch arrangement optical transmitter connected to an optical transmission line.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, an optical pressure transmitter 10 is aware of process variables 12 and interfaces via optical transmission lines 14,16.
Communicate with 18. The interface 18 connects the optical signals on the optical transmission lines 14 and 16 to the electric bus 22 connected to the control system 24, so that bidirectional communication is established between the transmitter 10 and the control system 24, and the transmitter Galvanic isolation is provided by an electrically insulated optical transmission line between 10 and bus 22.

The sensed process variables 12 are pressure, temperature, flow, pH, etc. The optical transmission lines 14, 16 may be single or multiple fiber optic cables and may extend from short distances to thousands of meters depending on the particular application and desire. Transmitter 10
Electrical isolation from control system 24 by optical transmission lines 14, 16 that transmit light but do not allow current to flow prevents unwanted coupling of electrical energy between transmitter 10 and control system 24.

A light generator 26, which can be a laser generator, couples light to the transmitter 10 via the optical transmission path 14. The light generator 26 generates a first light component, and this light is transmitted through an optical transmission line.
Modulated to program the transmitter 10 so that the transmitter output on 16 is the programmed output. The modulation of the first light component is typically performed by FSK, such as Rosemount Inc.'s HART communication protocol or other standard protocol.
A serial data string in a standard serial communication protocol using technology. The program can include storing the span, zero, range, etc. settings in the memory of the transmitter 10 for scaling the transmitter output. The first light component can also be modulated to interrogate the transmitter. The transmitter has its installation position, constituent materials, diagnostic data,
Respond to questions based on previously stored data, such as compensation and linearization data.

Light generator 26 is a second light source for energizing transmitter 10.
Generates a light component that is not normally modulated. The controller 28 controls the operation of the light generator 26. The first reference supplied to the analog buffer 30 controls the modulation of the first light component. Since the second reference of the controller 28 controls the amplitude or magnitude of the second light component, the controlled light output (powe
r) is given to the optical transmission line 14. Controller 28 produces a modulated electrical output, which is supplied to the laser diode of light generator 26 to modulate its light output. Bus 22
Provides a first reference to the buffer 30, typically consisting of a serial digital word that indicates a change to the program of the transmitter 10 and also indicates the interrogation command to which the transmitter 10 should be sent.

The interface 18 is a light receiver 32, which can be an optical (photo) diode, and receives the optical output of the transmitter 10 from the optical transmission path 16. The light receiver 32 converts the received light output into an electric signal and transmits the electric signal to the bus 22.

The control system 24 includes a control means 34 consisting of a computer coupled to the bus 22 via a modem 36. Control computer 34 provides a reference to the bus, which reference is amplified in analog buffer 30. The control computer 34 receives information contained in the process variable from the bus 22 included in the optical output of the transmitter and uses this information to control the process (not shown) and the process parameters that generate the process variable 12. .

In the transmitter 10, a coupler 38 splits the light from the light generator 26, and in the preferred embodiment, converts about 1%
42 and the remainder after subtracting the loss at the coupler
Combine with 44. The converters 42 and 44 can be constituted by photodiodes, and are preferably constituted by gallium hidden photodiodes having high output voltage and high conversion efficiency. Converter 44
Is connected to a power conversion circuit 46 which, in a preferred embodiment, converts the relatively low voltage output of converter 44 (about 0.9 volts) to a higher voltage output (3,5 volts) suitable for driving MOS circuits. ~ 5 volts). Instead, the converter 44 comprises a plurality of photodiodes connected in series to generate a higher voltage, and the power converter
46 can be eliminated. The outputs 48A, 48B are supplied to and energize the sensor circuit 50. Preferably, the sensor circuit 50 comprises a MOS circuit and a process variable sensor for detecting the process variable 12. Sensor circuit 50 is a process variable
The electric outputs 52A and 52B representing the magnitude of 12 are output. Converter 42 senses the modulated component of the light on optical transmission line 14 and couples via line 54 to a circuit 50 of electrical signals representing the modulation. The driver circuit 56 is driven via lines 48A, 48B and is controlled by the output on lines 52A, 52B to modulate an emitter 58. Emitter 58 may be an emitting diode (LED). The emitter 58 couples the optical output of the transmitter 10 back to the interface 18 via the optical transmission line 16.

In the embodiment of FIG. 1, the control system 24 is activated to program the transmitter 10 with span, zero, temperature correction data, etc., to provide electrical connection to any other transmitter 10 other than via an optical transmission line. It receives the programmed transmitter output fed back from the transmitter 10 without the need for power. Transmitter 10
Is supplied by the optical transmission line 14.

FIG. 2 shows a more preferred embodiment of the optical communication system. The reference numerals corresponding to the aforementioned parts have the same function. In FIG. 2, only one optical transmission line 62 couples the transmitter 60 to the interface 66, the latter being further connected to a control system 68. Interface 66
Includes a coupler 70 that connects the light generator 26 and the light receiver 32 to the optical transmission line 62. The light output from light generator 26 is preferably the wavelength of the light output from transmitter 60 (eg, 66
0 nm) (for example, 800 nm). In this case, the coupler 70 is preferably a dichroic mirror that enhances the optical throughput (effective transmission rate) of the system, and a filter 72 is used to remove the remaining light coming from the light generator 26.

In the figure, device 64 is coupled to only one optical transmission line 62 to receive light from light generator 26 and transmits the optical output of the transmitter to interface 66 via optical transmission line 62.
The device 64 has a gallium secret photodiode and a power converter
It produces an electrical output on line 74 which is connected to 46. The output on line 74 is also connected to sensor circuit 50 via line 76.
And supplies the modulated component of the received light. Equipment 64
Further has an LED driven by the driver 56. The embodiment of FIG. 2 provides both communication and activation, similar to that of FIG. 1, but in FIG. 2 this is accomplished with a single optical transmission line between transmitter 60 and interface 66. To achieve the same energization and communication, the coupler shown in FIGS. 1 and 2 and the extracting modulatio
Various combinations of n) are available. In FIGS. 1 and 2, the light generator 26 supplies all the necessary energy for the transmitter, so that separate power supplies such as wiring, batteries, solar cells, etc. are not required. The electrical circuits and optical modulation in the transmitter are powered only by light received via the optical transmission path.

FIG. 3 shows a circuit of the power converter 46 connected to the gallium hidden photodiode 80 for receiving the light for activation from the optical transmission line 82. Photodiode 80 is a self-propelled multivibrator
Energize 84. The multivibrator 84 generates a pair of oscillation outputs 86A and 86B that are electrically in opposite phases. Photodiode 80 also energizes step-up transformer type power supply 88. output
86A and 86B are connected to transistors 90A and 90B, respectively.
Drives the primary winding of transformer 92. Secondary winding 92 of transformer 92
A is connected to a full-wave rectifier 94 and used to power the converter 46 (from a gallium shunt photodiode 80,
Voltage output (3,
5 to 5 volts). Transistor 90A, 90
B, 98 may be germanium transistors to allow operation at lower voltages.

FIG. 4 shows the device 64 of FIG. 2 or the converter 42 of FIG.
A solid state, that is, a semiconductor device 64A for realizing each function of the coupler 44 and the coupler 38 (LED 58) is shown. In the figure, the LED 106 generates light of the first wavelength. Layers 102, 104 are made of a material that effectively transmits light of the first wavelength. Light output from LED106 is layer
The light is coupled to the optical transmission line 100 through 102 and 104, and becomes an optical output from the transmitter. The layer 104 constitutes a photodiode sensor for detecting the modulation, and corresponds to the converter 42 in FIG. Layer 102 constitutes the sensor that provides the electrical energization and corresponds to converter 44 in FIG. The light for activation has a second wavelength different from the first wavelength, while the light for modulation has a third wavelength different from the first and second wavelengths. Tier 10
The two 104 sensors are each selected to be sensitive to the corresponding wavelength, and provide independent modulation and power outputs on leads 108. Alternatively, activation and modulation may be performed with the same waveform, in which case diode 104 may be omitted and both power and modulation may be sensed by a single photodiode in layer 102.

FIG. 5 shows another device 110 used for transmitting and receiving light in the transmitter, which transmits light to and receives light from an optical transmission line 112. The gallium secret photodiode 114 receives light for energizing the transmitter and converts it to electrical energy. The photodiode 116 receives the light and generates a modulation signal. When the modulation signal is obtained from the photodiode 114 as in FIG. 2 described above, the photodiode 116 can be omitted. Transmitter light output is 1
It can be generated by an LED 118 located at each location of 18A, 118B, or 118C. At position 118B, due to aperture 120 provided in photodiode 114, it was located at 118B
Light from the LED can reach the optical transmission line 112. At the position 118C, the light from the LED 118 is reflected by the photodiode 114 and reaches the optical transmission line 112. Photodiodes 114, 11
6, 118A may have any shape and arrangement as long as it is convenient for optical coupling with the optical transmission line 112. Preferably, the active elements effectively cover the light collection angle (numerical aperture) of the optical transmission line to reduce losses. The active area is concentric annular,
It can be part of a circle (sector) or any shape.

FIG. 6 shows a multi-branch arrangement of transmitters 60A, 60B, and 60C connected to one optical transmission line 62. Interface 66 (FIG. 2) couples sufficient light into optical transmission line 62 and provides energy to all of the plurality of transmitters. The optical output of each transmitter is generated as a digital word, which includes an address that identifies to the interface 66 the transmitter. Similarly, the modulation output from light generator 26 (FIG. 2) also comprises a digital word, which receives the digital word,
It also contains an address to identify the transmitter that is responding to it.

FIG. 7 shows an interface via one optical transmission line 62.
Multiple transmitters 60D, 60 coupled to 66 (FIG. 2)
E shows multiple embodiments of the E, 60F branch sequence. The light output from each transmitter can consist of serial digital data in a selected branch digital protocol, such as Rosemount Inc.'s HART digital protocol.

FIG. 8 shows a plurality of transmitters 60G, 60H, 60J coupled to an interface 66 (FIG. 2) via an optical transmission line 62.
A further embodiment of the multi-branch arrangement of the present invention is shown. Wavelength division couplers 130A, 130B, 130C provided for each transmitter are
It provides an optically separate coupling path for excitation and modulation at one wavelength and for transmitter light output at a second wavelength different from the first. A variety of known wavelength encoding and decoding means are available, and many known telecommunication protocols, including half-duplex and full-duplex schemes, can be adapted for use in optical communications over optical media.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Kucci, Gerald Earl. United States, 55403 Minnesota, Minneapolis, Apartment 223, LaSalle Avenue 1500 (72) Inventor Olson, Brian Jay. United States, 55426 Minnesota, St. Louis Park, Minnesota , Utah Avenue South 3065 (56) Reference JP-A-2-168397 (JP, A) JP-A-59-109998 (JP, A) JP-A-62-229499 (JP, A) JP-A-64-74833 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G08C 23/00

Claims (18)

(57) [Claims] 1. A transmitter having an optical input for energizing itself and providing an optical output representative of a process variable to an optical medium, the sensor means for generating an electrical sensor output indicative of the process variable; Circuit means for receiving the sensor output and generating an electrical output of the transmitter indicative of the process variable, further comprising circuit means having an energizing input for energizing the circuit means; and converting the transmitter output to an optical output. Converting means, further comprising converting means including receiving means for receiving light, wherein the circuit means outputs an electrical output of a transmitter indicating a process variable to a changeable parameter stored in the circuit means. Wherein the receiving means converts the first portion of the received light into electrical energy applied to the energizing input, and the second portion of the received light. , Transmitter and converting the electrical output to control the parameters. 2. The transmitter of claim 1 wherein said changeable parameters include a changeable measurement range of a process variable. 3. The transmitter according to claim 1, wherein said receiving means receives light received from an optical transmission line. 4. The transmitter according to claim 3, wherein said converting means includes an emitter surface for emitting light, and said receiving means includes a light receiving surface for converting received light. 5. The transmitter according to claim 4, wherein the optical transmission line receives and transmits light within a light collection angle. 6. The transmitter of claim 5, wherein said light emitting surface and said light receiving surface substantially cover the light collection angle of the light transmission path. 7. The light receiving surface is disposed along an optical path between a light transmission path and a light emitting surface, and the light receiving surface is arranged so that light can pass from the light emitting surface to the light transmission path along the light path. 7. The transmitter of claim 6 arranged. 8. The transmitter according to claim 7, wherein the light receiving surface has an opening for passing light from the light emitting surface. 9. The transmitter of claim 7, wherein the light receiving surface is at least partially transparent to allow light from the light emitting surface to pass. 10. The transmitter according to claim 7, wherein the light receiving surface reflects light from the light emitting surface to the optical transmission line. 11. The transmitter of claim 1, wherein the received light represents a function of the desired span setting, and wherein the parameters stored in the circuit means are a function of the desired span setting programmed by the received light. 12. The transmitter of claim 1, wherein the received light represents a linearity correction of the transmitter output, and wherein the parameters stored in the circuit means are a function of the linearity correction programmed by the received light. 13. The transmitter of claim 1, wherein the received light is representative of a temperature correction of the transmitter output, and wherein the parameters stored in the circuit means are a function of the temperature correction programmed by the received light. 14. An interface between an optical medium in communication with a remote optical process variable transmitter and an electrical bus, wherein the light generating means is coupled to an optical transmission line and measures the optical output of the transmitter. A light generating means including first means for generating a programmed light component that is modulated to program a changeable parameter for the first and second means for generating an energizing light component for energizing the transmitter; Control means coupled to the means for electrically controlling the modulation as a function of a first reference received from the bus and electrically controlling the amplitude of the energizing light component as a function of a second reference in the control means. Control means for controlling, and receiving means for providing to the bus an electrical output representative of the programmed optical output received from the transmitter. Range 1 to 13 either interface. 15. An optical transmission line coupled to a plurality of optical process variable transmitters, the first means further comprising means for generating a programmed light component modulated to program the generation of light output by the plurality of transmitters. Claim 14 interface. 16. The interface of claim 15, wherein the activation light component activates a plurality of optical process control transmitters. 17. The interface of claim 16, wherein the programmed optical output is coupled along an optical transmission path. 18. The interface of claim 17, wherein the receiving means converts programmed light outputs from the plurality of optical process transmitters to a common electrical bus.