CN110207775B - HART loop display instrument - Google Patents
HART loop display instrument Download PDFInfo
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- CN110207775B CN110207775B CN201910503303.8A CN201910503303A CN110207775B CN 110207775 B CN110207775 B CN 110207775B CN 201910503303 A CN201910503303 A CN 201910503303A CN 110207775 B CN110207775 B CN 110207775B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
- G01F15/06—Indicating or recording devices
- G01F15/061—Indicating or recording devices for remote indication
- G01F15/063—Indicating or recording devices for remote indication using electrical means
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- G—PHYSICS
- G08—SIGNALLING
- G08C—TRANSMISSION SYSTEMS FOR MEASURED VALUES, CONTROL OR SIMILAR SIGNALS
- G08C19/00—Electric signal transmission systems
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Abstract
The invention relates to the technical field of measuring instruments, in particular to a HART loop display instrument, which comprises a HART communication module, a display module and a power management module; the HART loop display instrument is in communication connection with an external active instrument through a HART communication module and displays the measurement data of the external active instrument through a display module; the power management module comprises a boosting module and a voltage regulating module, wherein the boosting module is used for being connected with a power output end of the external active instrument so as to amplify the voltage output by the external active instrument; the voltage regulating module is used for regulating the voltage amplified by the boosting module; and the voltage input ends of the HART communication module and the display module are connected with the output end of the voltage regulating module. Compared with the prior art, the HART loop display can work when being connected with a current loop of an external active instrument, an independent power supply is omitted, and the instrument can work normally.
Description
Technical Field
The invention relates to the technical field of measuring instruments, in particular to an HART loop display instrument.
Background
The HART display has a HART communication module and a display. The HART display may be communicatively coupled to an external active meter, such as a flow meter, via the HART communication module to obtain measurement data from the flow meter and display the obtained measurement data on the display. The HART display instrument can realize remote communication with the measuring instrument through the HART communication module, so that the HART display instrument can be installed at a low position or indoors, and meter reading of an operator is facilitated.
The HART communication module and the display have large power consumption, an independent power supply is generally required to be arranged to supply power to the HART communication module and the display, and the display cannot work if the independent power supply is not available.
Disclosure of Invention
In view of this, the present invention provides a HART loop display, which mainly solves the technical problems: how to enable the display instrument to work normally under the condition of omitting an independent power supply.
In order to achieve the purpose, the invention mainly provides the following technical scheme:
the embodiment of the invention provides a HART loop display instrument, which comprises a HART communication module, a display module and a power management module;
the HART loop display instrument is in communication connection with an external active instrument through a HART communication module and displays the measurement data of the external active instrument through a display module;
the power management module comprises a boosting module and a voltage regulating module, wherein the boosting module is used for being connected with the power output end of the external active instrument so as to amplify the voltage output by the external active instrument; the voltage regulating module is used for regulating the voltage amplified by the boosting module;
and the voltage input ends of the HART communication module and the display module are connected with the output end of the voltage regulating module.
The invention is further configured to: the boosting module comprises a boosting inductor L2 and a boosting control chip U3, and one end of the boosting inductor L2 is used for being connected with a power output end of an external active instrument;
the other end of the boosting inductor L2 is connected with an LX end of a boosting control chip U3;
the boost module outputs the amplified voltage through a boost control chip U3.
The invention is further configured to: the HART loop display instrument also comprises a resistor R5 and a voltage stabilizing diode D9 which are connected in series;
one end of the resistor R5, which is far away from the voltage stabilizing diode D9, is connected with the EXT end of the voltage boosting control chip U3 and is grounded, and one end of the voltage stabilizing diode D9, which is far away from the resistor R5, is connected with the VDD end of the voltage boosting control chip U3;
the CE end of the boost control chip U3 is connected between the resistor R5 and the voltage stabilizing diode D9.
The invention is further configured to: the HART loop display also comprises a resistor R13, a filter circuit and a capacitor C4;
one end of the capacitor C4 is connected with the one end of the boosting inductor L2 to form a first common end;
the first common end is respectively connected with a filter circuit and one end of a capacitor C4, the other end of the filter circuit is connected with one end of a resistor R13, and the other end of the capacitor C4 is grounded;
the boosting inductor L2 is connected with the power supply output end of an external active instrument through the other end of the resistor R13.
The invention is further configured to: the HART loop display also includes zener diode D1 and zener diode D2;
the negative terminals of the zener diode D1 and the zener diode D2 are connected to the one end of the boost inductor L2, and the negative terminals thereof are grounded.
The invention is further configured to: the HART loop display also comprises an energy storage capacitor C5 and an energy storage capacitor C6;
the positive terminals of the energy storage capacitor C5 and the energy storage capacitor C6 are connected with the one end of the boosting inductor L2, and the negative terminals of the energy storage capacitor C5 and the energy storage capacitor C6 are grounded.
The invention is further configured to: the voltage regulating module comprises a resistor R2, a resistor R4 and a resistor R7 which are sequentially connected in series;
the FB terminal of the boost control chip U3 is connected between a resistor R2 and a resistor R4 to form a second common terminal; one end of the resistor R7, which is far away from the resistor R4, is grounded; one end of the resistor R2 is connected with the VDD end of the boost control chip U3 to form a third common end;
and the voltage regulating module outputs the regulated voltage through the third common terminal.
The invention is further configured to: the HART loop display also comprises a voltage stabilizing diode D8 and a filter inductor L1;
the positive end of the voltage stabilizing diode D8 is connected between the boosting inductor L2 and the LX end of the boosting control chip U3, and the negative end of the voltage stabilizing diode D8 is connected with one end of the filter inductor L1;
the third common terminal is connected between the negative electrode of the zener diode D8 and the filter inductor L1 to output a regulated voltage through the other terminal of the filter inductor L1.
The invention is further configured to: the HART loop display further comprises a capacitor C7, a capacitor C8 and a capacitor C9;
one end of the capacitor C7, one end of the capacitor C8 and one end of the capacitor C9 are connected with a third common end, the other ends of the capacitor C7 and the capacitor C8 are grounded, and the other end of the capacitor C9 is connected with a second common end.
The invention is further configured to: the HART loop display instrument also comprises a resistor R3, an analog signal amplifying circuit and a controller;
one ends of the resistor R3 and the analog signal amplifying circuit are connected to form a fourth common end, and the fourth common end is used for being connected with a power supply output end of an external active instrument;
the other end of the resistor R3 is grounded;
the other end of the analog signal amplifying circuit is connected with a controller, and the controller is used for displaying on a display module according to data transmitted by the analog signal amplifying circuit;
and the voltage input end of the controller is connected with the output end of the voltage regulating module.
The invention is further configured to: the analog signal amplifying circuit comprises an operational amplifier U4A, an operational amplifier U4B, a resistor R9, a resistor R10, a resistor R11, a resistor R8, an energy storage capacitor C11 and a capacitor C12;
the analog signal amplifying circuit is connected with one end of a resistor R3 through one end of a resistor R10 and is connected with the controller through the output end of an operational amplifier U4B;
the other end of the resistor R10 is connected with one end of the resistor R11 to form a fifth common end; the fifth common end is respectively connected with a negative input end of an operational amplifier U4A and one end of a capacitor C12, and the other end of the capacitor C12 is connected with an output end of an operational amplifier U4A to form a sixth common end;
the other end of the resistor R11 is connected with the sixth common end, the sixth common end is connected with one end of a resistor R9, the other end of the resistor R9 is respectively connected with the positive input end of the operational amplifier U4B and the positive electrode of the energy storage capacitor C11, and the negative electrode of the energy storage capacitor C11 is grounded;
the negative electrode input end of the operational amplifier U4B is connected with the output end thereof;
the positive electrode input end of the operational amplifier U4A is connected with one end of the resistor R8, and the other end of the resistor R8 is grounded.
The invention is further configured to: the HART loop display instrument also comprises a HART communication matching circuit;
the HART communication matching circuit comprises a capacitor C1, a capacitor C2, a capacitor C3 and a resistor R6;
one end of the HART communication module is connected with one end of a capacitor C2, the other end of a capacitor C2 is respectively connected with one ends of a capacitor C1 and a resistor R6, the other end of the capacitor C1 is grounded, and the other end of the resistor R6 is connected with one end of a capacitor C3 to form a seventh common end;
the other end of the HART communication module is connected with the seventh public end;
and the HART communication module is in communication connection with an external active instrument through the other end of the capacitor C3.
The invention is further configured to: the display module is a display;
the display screen of the display is a dot matrix liquid crystal screen; and/or the display screen of the display is provided with a backlight source.
By means of the technical scheme, the HART loop display instrument at least has the following beneficial effects:
in the technical scheme provided by the invention, the voltage boosting module and the voltage regulating module are additionally arranged, the voltage boosting module can amplify the voltage output by the external active instrument, and the voltage regulating module can regulate the amplified voltage of the voltage boosting module to a proper size for the HART communication module and the display module to use.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following detailed description is given with reference to the preferred embodiments of the present invention and the accompanying drawings.
Drawings
Fig. 1 is a block diagram of a HART loop display according to an embodiment of the present invention;
fig. 2 is a schematic circuit diagram of a HART loop monitor according to an embodiment of the present invention.
Reference numerals: 1. a HART communication module; 2. a controller; 3. a display module; 4. a boost module; 5. a voltage regulation module; 6. an analog signal amplifying circuit; 7. a HART communication matching circuit; 100. an active meter.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It should be noted that, if directional indications (such as up, down, left, right, front, and back … …) are involved in the embodiment of the present invention, the directional indications are only used to explain the relative positional relationship between the components, the movement situation, and the like in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indications are changed accordingly. In addition, if there is a description of "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature.
As shown in fig. 1, a HART loop display according to an embodiment of the present invention includes a HART communication module 1, a display module 3 and a power management module. The HART loop display is connected to the external active meter 100 through the HART communication module 1, and displays the measurement data of the external active meter 100 through the display module 3. The external active meter 100 may be a liquid level meter, a flow meter, a level meter, or the like. The display module 3 can be a liquid crystal display and the like, and the display screen of the liquid crystal display can be a dot matrix liquid crystal screen, so that the display is visual and the operation is simple. The display screen of the liquid crystal display can be provided with a backlight source, and preferably, the backlight source is a white backlight source so as to facilitate night observation and meter reading.
The HART loop display device described above can realize long-distance communication by having the HART communication module 1. For example, in a tank farm, for a storage tank of more than 5m, a radar level gauge is mounted on the storage tank, and an operator must climb the tank to check the level of the radar level gauge on site. The HART loop display instrument can prevent an operator from climbing a tank, and particularly, the HART loop display instrument can be arranged under the tank and is communicated with the radar liquid level meter on the tank so as to synchronously display the measurement value of the radar liquid level meter on the tank, no extra cable or power supply is needed, and frequent climbing of the tank is avoided.
For another example, many pipelines in the chemical plant area are installed far away from the ground, and no matter the flow meter on the pipeline is set or the flow is checked, the pipeline needs to be climbed, so that the pipeline is dangerous and laborious. The HART loop display instrument can solve the problem, particularly, the HART loop display instrument can be arranged on the lower portion of a pipeline, can read flow data in real time, can set or check instrument parameters through HART communication, and is safe and convenient.
For another example, the installation height of the liquid level meter on the tower is far away from the ground, so that the liquid level is inconvenient to check or calibrate, and the HART loop display instrument can solve the problem.
For another example, in a coking enterprise, a temporary rest room is generally arranged on a tank for storing coke, people in the rest room need to go out regularly to check the material level in the cabin, and the outside environment is severe, so that the people always go out to check the material level inconveniently. Therefore, the HART loop display instrument can be installed in a rest room, workers can check the material level indoors, extra cables do not need to be added, and independent power supply is not needed.
As shown in fig. 1, the power management module described above may include a boost module 4 and a voltage regulation module 5. The boost module 4 is used for connecting with the power output end of the external active instrument 100 to amplify the voltage output by the external active instrument 100. The voltage regulating module 5 is used for regulating the voltage amplified by the boosting module 4. The voltage input ends of the HART communication module 1 and the display module 3 are both connected to the output end of the voltage regulating module 5.
Through the arrangement, the boosting module 4 and the voltage regulating module 5 are matched, so that the voltage output by the external active instrument 100 can be amplified and regulated to be output to high-power-consumption modules such as the HART communication module 1 and the display module 3 for use. Because the loop voltage drop of the external active instrument 100 is directly relied on for working, an additional independent power supply is not needed, and the cost is saved.
In a specific application example, the HART loop display instrument of the present invention is an instrument that works based on a 4-20mA current loop, and does not need an external power supply, and the instrument works by a loop voltage drop, and the loop voltage drop of the instrument is less than 2.5V. Wherein, the rated operating voltage of HART communication module 1 and display module 3 are both greater than 2.5V, and through the cooperation of boost module 4 and voltage regulation module 5, can make when input voltage is less than 2.5V, HART communication module 1 and voltage regulation module 5 still can normally work.
In order to realize the functions of the aforementioned boost module 4, in a specific application example, as shown in fig. 2, the aforementioned boost module 4 may include a boost inductor L2 and a boost control chip U3. One end of the boost inductor L2 is used to connect with the power output terminal of the external active meter 100. The other end of the boosting inductor L2 is connected with the LX end of the boosting control chip U3. The boost module 4 outputs the amplified voltage through the boost control chip U3.
In the above example, the boost inductor L2 boosts the input voltage first, and the boost control chip U3 controls the boost inductor L2 to boost the voltage continuously.
As shown in fig. 2, the HART loop display of the present invention may further comprise a resistor R5 and a zener diode D9 connected in series. One end of the resistor R5, which is far away from the voltage stabilizing diode D9, is connected with the EXT end of the boost control chip U3 and grounded. One end of the voltage stabilizing diode D9, which is far away from the resistor R5, is connected with the VDD end of the boost control chip U3. The CE terminal of the boost control chip U3 is connected between the resistor R5 and the zener diode D9.
Through the arrangement, the resistor R5 and the voltage stabilizing diode D9 are matched to realize the soft start of the boost control chip U3.
As shown in fig. 2, the HART loop display of the present invention may further include a resistor R13, a filter circuit and a capacitor C4. The filter circuit in the prior art can be selected as the filter circuit, and details are not described herein. One end of the capacitor C4 is connected to one end of the boost inductor L2 to form a first common terminal. The first common terminal is connected to one end of a filter circuit and one end of a capacitor C4, the other end of the filter circuit is connected to one end of a resistor R13, and the other end of the capacitor C4 is grounded. The boost inductor L2 is connected to the power supply output of the external active meter 100 through the other end of the resistor R13.
With the above arrangement, the filter circuit and the capacitor C4 can filter the input signal.
As shown in fig. 2, the HART loop display of the present invention may also include zener diode D1 and zener diode D2. Positive terminals of the zener diode D1 and the zener diode D2 are connected to one end of the boost inductor L2, and negative terminals thereof are grounded.
Through the arrangement, the two voltage stabilizing diodes are matched in a current loop to generate voltage drop, and the voltage drop is supplied to a circuit behind.
Further, as shown in fig. 2, the HART loop display of the present invention may further comprise a storage capacitor C5 and a storage capacitor C6. The positive terminals of the energy storage capacitor C5 and the energy storage capacitor C6 are connected with one end of the boosting inductor L2, and the negative terminals of the energy storage capacitor C5 and the energy storage capacitor C6 are grounded.
The energy storage capacitor C5 and the energy storage capacitor C6 can resist the impact of rear current after being charged.
In order to realize the functions of the voltage regulating module 5, in a specific application example, as shown in fig. 2, the voltage regulating module 5 may include a resistor R2, a resistor R4, and a resistor R7 connected in series. The FB terminal of the boost control chip U3 is connected between the resistor R2 and the resistor R4 to form a second common terminal. The end of the resistor R7 facing away from the resistor R4 is grounded. One end of the resistor R2 is connected with the VDD end of the boost control chip U3 to form a third common end. The voltage regulation module 5 outputs the regulated voltage through the third common terminal.
Through the arrangement, the resistor R2, the resistor R4 and the resistor R7 are matched, the voltage output by the VDD end of the boost control chip U3 can be adjusted, and the output voltage is fed back to the boost control chip U3 through different matching to adjust the output voltage, so that the voltage can be used by the HART communication module 1 and the display module 3 behind the voltage.
Further, as shown in fig. 2, the HART loop display of the present invention may further include a zener diode D8 and a filter inductor L1. The positive end of the voltage stabilizing diode D8 is connected between the boosting inductor L2 and the LX end of the boosting control chip U3, and the negative end of the voltage stabilizing diode D8 is connected with one end of the filter inductor L1. One end of the resistor R2 is connected to the VDD terminal of the boost control chip U3 to form a third common terminal, and the third common terminal is connected between the negative electrode of the zener diode D8 and the filter inductor L1, so as to output the regulated voltage through the other end of the filter inductor L1.
Through the arrangement, the voltage output by the boosting inductor L2 can output a DC voltage with extremely low ripple after passing through the voltage stabilizing diode D8 and then passing through the filter inductor L1.
As shown in fig. 2, the HART loop display of the present invention may further include capacitor C7, capacitor C8 and capacitor C9. One end of the capacitor C7, one end of the capacitor C8, and one end of the capacitor C9 are connected to the third common terminal, the other ends of the capacitor C7 and the capacitor C8 are grounded, and the other end of the capacitor C9 is connected to the second common terminal.
Through the arrangement, the capacitor C7, the capacitor C8 and the capacitor C9 are matched, and signal filtering processing in the circuit can be achieved.
As shown in fig. 2, the HART loop display of the present invention may further include a resistor R3, an analog signal amplification circuit 6 and a controller 2. One ends of the resistor R3 and the analog signal amplifying circuit 6 are connected to form a fourth common terminal. The fourth common terminal is used for connecting with the power output terminal of the external active meter 100. The other end of the resistor R3 is connected to ground. The other end of the analog signal amplifying circuit 6 is connected to the controller 2. The controller 2 is used for displaying on the display module 3 according to the data transmitted by the analog signal amplifying circuit 6. The voltage input end of the controller 2 is connected with the output end of the voltage regulating module 5.
The controller 2 may be a single chip or a microprocessor.
In the above example, the boost module 4 and the voltage regulation module 5 cooperate to output the regulated voltage to the controller 2 for use, so as to avoid providing an independent power supply to power the controller 2. The resistor R3 is matched with the analog signal amplifying circuit 6, and can measure the current signal on the external instrument to obtain the measurement data of the external instrument.
Specifically, the HART loop display of the present invention can acquire the measurement data of the external instrument through both the HART communication module 1 and the analog signal amplification circuit 6, and display the measurement data on the display module 3. What is different is, HART loop display appearance can also be through HART communication module 1 to outside instrument send the order to set up the parameter of external instrument, and the practicality is stronger.
In a specific application example, as shown in fig. 2, the aforementioned analog signal amplifying circuit 6 may include an operational amplifier U4A, an operational amplifier U4B, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a filter capacitor C11, and a capacitor C12. The analog signal amplifying circuit 6 is connected to one end of the resistor R3 through one end of the resistor R10, and is connected to the controller 2 through an output end of the operational amplifier U4B. The other end of the resistor R10 is connected with one end of the resistor R11 to form a fifth common end, the fifth common end is respectively connected with the negative input end of the operational amplifier U4A and one end of the capacitor C12, and the other end of the capacitor C12 is connected with the output end of the operational amplifier U4A to form a sixth common end. The other end of the resistor R11 is connected with a sixth common end, the sixth common end is connected with one end of a resistor R9, the other end of the resistor R9 is connected with the positive input end of the operational amplifier U4B and the positive electrode of the energy storage capacitor C11, and the negative electrode of the energy storage capacitor C11 is grounded. The negative input terminal of the operational amplifier U4B is connected to the output terminal thereof. The positive input terminal of the operational amplifier U4A is connected to one end of the resistor R8, and the other end of the resistor R8 is grounded.
Further, the HART loop display of the present invention may further comprise a resistor R1 and a capacitor C10. The power supply terminal of the operational amplifier U4A is connected between the resistor R1 and the capacitor C10, the other terminal of the resistor R1 is connected to the high level of 3V, and the other terminal of the capacitor C10 is grounded.
Through the arrangement, when a current loop passes through the resistor R3, a voltage difference is generated at two ends of the R3, the generated voltage is sent into the U4A to be amplified, the amplification factor is 1.87 times, the amplified voltage is filtered by the C11, noise is reduced to be low, the noise is sent into the U4B after filtering, the U4B is a voltage follower, the impedance matching effect of the front stage and the rear stage is achieved, and the voltage is sent into the controller 2 such as a single chip microcomputer after being output by the U4B.
As shown in fig. 2, the HART loop display of the present invention may further comprise a HART communication matching circuit 7. The HART communication matching circuit 7 includes a capacitor C1, a capacitor C2, a capacitor C3 and a resistor R6. One end of the HART communication module 1 is connected to one end of the capacitor C2, the other end of the capacitor C2 is connected to one end of the capacitor C1 and one end of the resistor R6, the other end of the capacitor C1 is grounded, and the other end of the resistor R6 is connected to one end of the capacitor C3 to form a seventh common end. The other end of the HART communication module 1 is connected to the seventh common terminal. HART communication module 1 is communicatively coupled to external active meter 100 via the other end of capacitor C3.
In the above example, the capacitor C3 may serve as an isolation from external circuitry, preventing external interference or affecting external current loops. The capacitor C1, the capacitor C2 and the resistor R6 cooperate to load the HART communication waveform onto the current loop of the external instrument to control the external instrument.
The working principle and preferred embodiments of the present invention are described below.
The HART loop display instrument can be set in a two-wire system, is an instrument working based on a 4-20mA current loop, does not need an external power supply, and works by depending on the loop voltage drop of an external instrument, wherein the voltage drop is less than 2.5V. The HART loop display instrument adopts dot matrix liquid crystal display, has visual display and simple operation, and only needs a client to set two parameters. The HART loop display instrument can display multivariable and simultaneously support Chinese and English bilingual menus. The HART loop display of the invention can be set in a normal mode and a HART mode. And large font display can be set in a common mode, and the display is visual. In HART mode, all parameters of the communicated instrument can be synchronously displayed, and the parameters of the communicated instrument can be set and viewed. Under HART communication mode, the loop voltage drop still can be less than 2.5V and stable work, and the instrument has fine interference killing feature when communicating. Under the condition that the loop voltage drop is 2.5V, the HART loop display instrument provided by the invention is provided with white backlight, so that the display is convenient to observe and read at night. The HART loop display instrument adopts double chambers, is convenient to wire, safe and durable, and simultaneously, the mask wiring mode on the terminal board is intuitive and easy to understand. The HART loop display instrument is provided with the explosion-proof key, and internal parameters of the instrument can be set on the premise of not opening the instrument cover. Meanwhile, an imported integrated circuit is adopted in the instrument, so that the instrument has the advantages of wide use temperature range, high sampling precision, small temperature influence on a sampling circuit, good interference resistance and good stability.
As shown in fig. 2, the circuit principle of the HART loop display of the present invention is as follows:
the current flow direction of the circuit in fig. 2 is: the 4-20mA current flows out of the active acquisition card or the active output instrument, flows into the passive instrument or the acquisition card through the voltage stabilizing diodes D1 and D2 and the resistor R3, and then flows back to the active acquisition card or the active output instrument.
The core circuit of the HART loop display instrument comprises an energy storage module (energy storage capacitors C5 and C6), a voltage stabilizing module (voltage stabilizing diodes D1 and D2), a boosting module 4 (a boosting inductor L2 and a boosting control chip U3), a HART communication matching circuit 7 and an analog signal amplifying circuit 6.
The working principle of the booster circuit is as follows: the boost circuit comprises a boost module 4 and a voltage regulation module 5. The boost module 4 comprises a boost control chip U3 and a boost inductor L2. The voltage regulating module 5 includes a resistor R2, a resistor R4, and a resistor R7. The booster circuit further comprises energy storage capacitors C5 and C6, a filter inductor L1, filter capacitors C8, C9, C4 and C7, a voltage stabilizing diode D8 and enabling adjusting devices D9 and R5.
The current loop generates a voltage not higher than 2.5V after passing through the voltage stabilizing diodes D1 and D2, and the voltage not higher than 2.5V charges the energy storage capacitors C5 and C6 so as to resist the impact of the rear current; the voltage is transmitted backwards, the voltage is boosted for the first time through the boosting inductor L2, the voltage output by the boosting inductor L2 continues current through the voltage stabilizing diode D8, and the voltage outputs a direct-current voltage with extremely low ripple waves after passing through the filter inductor L1 and the filter capacitor C8; the boost control chip U3 controls the boost inductor L2 to boost continuously, the output voltage is fed back to the boost control chip U3 by the voltage regulation resistors R2, R4 and R7 through different matching to regulate the output voltage, and meanwhile, the D9, R5 and an enabling pin CE of the boost control chip U3 are connected to realize the soft start of the boost control chip U3. The voltage output by the boost control chip U3 is supplied to a controller (such as a single chip microcomputer), a memory, a display module (such as a liquid crystal display), an explosion-proof button, a liquid crystal backlight, the HART communication module 1 and an amplifying circuit.
Working principle of HART communication module 1: the HART communication module 1 works in cooperation with the HART communication matching circuit 7. The HART communication matching circuit 7 includes a capacitor C1, a capacitor C2, a capacitor C3 and a resistor R6. The capacitor C3 acts as an isolation from external circuitry, preventing external interference or affecting external current loops. Wherein capacitor C1, capacitor C2, and resistor R6 are matched to load the HART communication waveform onto the current loop.
The HART loop display instrument also has the function of analog current measurement. Specifically, when the current loop passes through the sampling resistor R3, a voltage difference is generated at two ends of the resistor R3, the generated voltage is sent to the operational amplifier U4A to be amplified, the amplification factor is 1.87 times, the amplified voltage is filtered by the capacitor C11, the noise is reduced to be low, the filtered voltage is sent to the operational amplifier U4B, and the U4B is a voltage follower, so that the impedance matching function of the front stage and the rear stage is achieved. The voltage is output by an operational amplifier U4B and then is sent to the singlechip.
The HART loop display instrument has the following characteristics:
1. the loop can work after being connected in series without external independent power supply.
2. The loop voltage is reduced to less than 2.5V, mainly because in a 4-20mA system, if the voltage drop of equipment on the loop is too large, the voltage at two ends of the measuring instrument is too low, so that the instrument cannot work. The technical scheme of the invention realizes lower loop voltage drop by improving both software and hardware. In hardware, the two zener diodes D1 and D2 in the front end of the circuit can generate a voltage drop on the loop, and the generated voltage drop is 2.5V. Two storage capacitors C5 and C6 are arranged behind the two zener diodes D1 and D2, and the two storage capacitors C5 and C6 are charged when being powered on, so that electric energy is stored to resist rear impact. Two energy storage capacitor C5 and C6 are the boost circuit in the back, and boost inductance L2 can provide bigger energy, and boost control chip U3 adopts the mode of soft start, guarantees the reliable operation of circuit. The operational amplifiers U4A and U4B use low power consumption operational amplifiers. In terms of software, a starting time sequence can be optimized, after the power-on of the instrument is started, the single chip microcomputer starts to be started, after the energy storage capacitor is fully charged after a set time such as one second is waited, the single chip microcomputer controls the power-on of the liquid crystal and the backlight, and on the premise that the normal work of the instrument is guaranteed, the running frequency of the single chip microcomputer is reduced, so that the power consumption is reduced, the AD sampling mode is changed, and the power consumption is reduced. The singlechip adopts an intermittent operation mode. Through the mode, the HART loop display instrument provided by the invention realizes that the loop voltage drop generated by functions of HART communication, analog current acquisition, dot matrix liquid crystal display and liquid crystal backlight is lower than 2.5V and far lower than 5V voltage drops of other instruments.
3. HART communication can be carried out with the instrument, and all parameters of the instrument can be read and set in real time.
4. Dot matrix liquid crystal display and Chinese and English switching.
5. The display resolution is high 1/99999.
6. With backlight, the liquid crystal is convenient to observe.
7. The liquid crystal can be set to display in large font, which is convenient for observation.
8. And various variable parameter displays are supported.
9. The explosion-proof key is provided, and the internal parameters can be set without opening the cover.
10. An internal high-precision high-reliability integrated circuit.
11. The installation is convenient, and the maintenance is simple.
12. A separate wiring chamber.
13. Is affected by temperature to be less than or equal to 0.55 muA/DEG C.
14. The instrument has strong anti-interference capability and strong communication anti-interference capability.
Here, it should be noted that: in the case of no conflict, a person skilled in the art may combine the related technical features in the above examples according to actual situations to achieve corresponding technical effects, and details of various combining situations are not described herein.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.
Claims (6)
1. The HART loop display instrument is characterized by comprising a HART communication module (1), a display module (3) and a power management module; the HART loop display instrument is in communication connection with an external active instrument (100) through a HART communication module (1), and displays the measurement data of the external active instrument (100) through a display module (3);
the power management module comprises a boosting module (4) and a voltage regulating module (5), wherein the boosting module (4) is used for being connected with a power output end of the external active instrument (100) so as to amplify the voltage output by the external active instrument (100); the voltage regulating module (5) is used for regulating the voltage amplified by the boosting module (4);
the voltage input ends of the HART communication module (1) and the display module (3) are connected with the output end of the voltage regulation module (5);
the boosting module (4) comprises a boosting inductor L2 and a boosting control chip U3, wherein one end of the boosting inductor L2 is used for being connected with a power output end of an external active instrument (100); the other end of the boosting inductor L2 is connected with an LX end of a boosting control chip U3; the boosting module (4) outputs the amplified voltage through a boosting control chip U3; the HART loop display instrument also comprises a voltage stabilizing diode D1, a voltage stabilizing diode D2, an energy storage capacitor C5 and an energy storage capacitor C6; the positive terminals of the voltage-stabilizing diode D1 and the voltage-stabilizing diode D2 are connected with the one end of the boosting inductor L2, and the negative terminals of the voltage-stabilizing diode D1 and the voltage-stabilizing diode D2 are grounded; the positive terminals of the energy storage capacitor C5 and the energy storage capacitor C6 are connected with one end of the boosting inductor L2, and the negative terminals of the energy storage capacitor C5 and the energy storage capacitor C6 are grounded;
the voltage regulating module (5) comprises a resistor R2, a resistor R4 and a resistor R7 which are sequentially connected in series; the FB terminal of the boost control chip U3 is connected between a resistor R2 and a resistor R4 to form a second common terminal; one end of the resistor R7, which is far away from the resistor R4, is grounded; one end of the resistor R2 is connected with the VDD end of the boost control chip U3 to form a third common end; and the voltage regulating module (5) outputs the regulated voltage through the third common terminal.
2. The HART loop monitor of claim 1, further comprising a zener diode D8 and a filter inductor L1;
the positive end of the voltage stabilizing diode D8 is connected between the boosting inductor L2 and the LX end of the boosting control chip U3, and the negative end of the voltage stabilizing diode D8 is connected with one end of the filter inductor L1;
the third common terminal is connected between the negative electrode of the zener diode D8 and the filter inductor L1 to output a regulated voltage through the other terminal of the filter inductor L1.
3. The HART loop monitor of claim 1, further comprising a capacitor C7, a capacitor C8, and a capacitor C9;
one end of the capacitor C7, one end of the capacitor C8 and one end of the capacitor C9 are connected with a third common end, the other ends of the capacitor C7 and the capacitor C8 are grounded, and the other end of the capacitor C9 is connected with a second common end.
4. The HART loop display according to any of claims 1 through 3, further comprising a resistor R3, an analog signal amplifying circuit (6) and a controller (2);
one ends of the resistor R3 and the analog signal amplifying circuit (6) are connected to form a fourth common end, and the fourth common end is used for being connected with a power supply output end of an external active instrument (100);
the other end of the resistor R3 is grounded;
the other end of the analog signal amplifying circuit (6) is connected with the controller (2), and the controller (2) is used for displaying on the display module (3) according to data transmitted by the analog signal amplifying circuit (6);
and the voltage input end of the controller (2) is connected with the output end of the voltage regulating module (5).
5. The HART loop display of claim 4,
the analog signal amplifying circuit (6) comprises an operational amplifier U4A, an operational amplifier U4B, a resistor R8, a resistor R9, a resistor R10, a resistor R11, an energy storage capacitor C11 and a capacitor C12;
the analog signal amplification circuit (6) is connected with one end of a resistor R3 through one end of a resistor R10, and is connected with the controller (2) through the output end of an operational amplifier U4B;
the other end of the resistor R10 is connected with one end of the resistor R11 to form a fifth common end; the fifth common end is respectively connected with a negative input end of an operational amplifier U4A and one end of a capacitor C12, and the other end of the capacitor C12 is connected with an output end of an operational amplifier U4A to form a sixth common end;
the other end of the resistor R11 is connected with the sixth common end, the sixth common end is connected with one end of a resistor R9, the other end of the resistor R9 is respectively connected with the positive input end of the operational amplifier U4B and the positive electrode of the energy storage capacitor C11, and the negative electrode of the energy storage capacitor C11 is grounded;
the negative electrode input end of the operational amplifier U4B is connected with the output end thereof;
the positive electrode input end of the operational amplifier U4A is connected with one end of the resistor R8, and the other end of the resistor R8 is grounded.
6. HART loop display according to one of claims 1 to 3, 5, characterized by further comprising a HART communication matching circuit (7);
the HART communication matching circuit (7) comprises a capacitor C1, a capacitor C2, a capacitor C3 and a resistor R6;
one end of the HART communication module (1) is connected with one end of a capacitor C2, the other end of a capacitor C2 is respectively connected with one ends of a capacitor C1 and a resistor R6, the other end of the capacitor C1 is grounded, and the other end of the resistor R6 is connected with one end of a capacitor C3 to form a seventh common end;
the other end of the HART communication module (1) is connected with the seventh public end;
the HART communication module (1) is in communication connection with an external active instrument (100) through the other end of the capacitor C3.
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