CN100501349C - Intelligent liquid level sensor and measuring method thereof - Google Patents
Intelligent liquid level sensor and measuring method thereof Download PDFInfo
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- CN100501349C CN100501349C CNB2006100974038A CN200610097403A CN100501349C CN 100501349 C CN100501349 C CN 100501349C CN B2006100974038 A CNB2006100974038 A CN B2006100974038A CN 200610097403 A CN200610097403 A CN 200610097403A CN 100501349 C CN100501349 C CN 100501349C
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Abstract
The invention relates to a liquid level signal parameter measuring intelligent sensor and method, which comprises the sensor and the sensor control unit. Its features are: the pulse signal issued by the microcontroller passes through the differential electronic circuit and changes into a standard pulse signal, and then through a driving circuit to form the pulse signal, and then the signal drives two ultrasonic transmitting sensors; the loop wave signal of the said ultrasonic receiving sensor passes through the amplification circuit unit, and then through the comparison circuit unit to form a pulse signal to trigger mono-stable trigger circuit unit, and finally, the loop wave signal enters the microcontroller to analysis and process. The invention uses the ultrasonic measuring technique to spot and continuous measure the liquid level, and do not need special protection, to overcome existing liquid level sensor's inadequate that can not automatically adapt to the changes of environmental temperature, humidity, and media content, and its installation and maintenance are more convenient, structure and method relatively simple, low prices to meet the various needs of the measurement environment.
Description
Technical field
The present invention relates to a kind of sensor, relate in particular to a kind of intelligence sensor and measuring method thereof of liquid level signal parameter measurement.
Background technology
Level gauging has a wide range of applications in fields such as hydraulic department and meteorological department and chemical industry.Wherein ultrasonic measurement is an important method.Ultrasonic liquid level measuring has many advantages: it not only can be fixed a point and survey continuously liquid level, compares with other location technology, and it does not need special protection, and installation and maintenance is more convenient, and structure, method are all simpler, cheap.
In the ultrasonic liquid level measuring technology, most widely used is the ultrasonic pulse echo method.When sound wave from a kind of medium when another kind of medium is propagated, on the interphase of two kinds of density differences, medium that the velocity of sound is different, the direction of propagation just changes.Be that a part is reflected, a part is refracted in the adjacent media.Because the density of two media differs greatly, sound wave almost all is reflected.
Therefore, send ultrasonic pulse, pass to liquid level and return receiving sensor after reflection by emission sensor, measuring ultrasonic pulse receives the required time from being transmitted into, according to the velocity of sound in the medium, the distance between just obtaining from the sensor to the liquid level, thus determine liquid level.Data sees reference: instrumental technique and sensor o. 11th in 2005, based on the wireless liquid level measuring system of ultrasonic sensor; 2004 the 1st phases of instrumental technique and sensor, SCM Based liquid level measuring system.
Mainly there is following defective in actual use in the ultrasonic liquid level measuring of prior art:
1, because ultrasonic propagation velocity is subjected to Temperature Influence, must carry out temperature compensation, must increase temperature collecting cell the ultrasonic sensor measurement result.
If when 2 media of measuring changed, the ultrasonic sensor measurement result also must be changed accordingly, need artificially to demarcate.
3, ultrasonic sensor still can not carry out adaptive adjusting to the variation of environment temperature, humidity, medium.
Along with the development of field bus technique, the intelligence sensor with fieldbus output is proposed, it can reduce cost, improve dirigibility, is the direction of current sensor development.
Summary of the invention
The invention provides a kind of intelligent liquid level sensor, its purpose is can not carry out self-reacting deficiency to the variation to environment temperature, humidity, medium composition in order to overcome existing liquid level sensor, to satisfy the needs of various different measuring environment.
The technical solution adopted for the present invention to solve the technical problems is:
A kind of intelligent liquid level sensor is made of sensor and sensor control unit.It is characterized in that:
Described sensor comprises two ultrasonic emitting sensors and the distance measurement sensor that the ultrasound wave receiving sensor constitutes; Described sensor control unit comprises: the signal condition unit that is electrically connected with range sensor, micro controller unit and CAN bus communication unit behind the signal condition unit are linked in sequence.
Described signal condition unit comprises that the differentiating circuit that is connected with microcontroller, the driving circuit that is connected with emission sensor, order are connected electrically in amplifier circuit unit, comparator circuit unit, single-shot trigger trigger unit between ultrasound wave receiving sensor and the microcontroller.
The crystal oscillating circuit composition that described microcontroller comprises a single-chip microcomputer integrated chip and is arranged on the reset circuit of microcontroller reset terminal and is arranged on the microcontroller input end of clock.
Described CAN bus communication unit is connected into by the photoelectric isolating circuit chip and the CAN bus driving circuits integrated chip that are separately positioned on CANRX and CANTX end.
The measuring method of above-mentioned intelligent liquid level sensor, it is characterized in that: the pulse signal that described microcontroller sends is through becoming the pulse signal of a standard after the differentiating circuit, form pulse signal by driving circuit then, remove to drive two ultrasonic emitting sensors by this signal again; The echoed signal of described ultrasound wave receiving sensor forms a pulse signal through the comparator circuit unit again and triggers the single-shot trigger circuit unit through after the amplifier circuit unit, and last echoed signal enters the microcontroller analyzing and processing.
And the gap of 5-25cm is set between described two ultrasonic emitting sensors.Can guarantee that like this distance that measures has certain difference, and this difference is fixed.
In above-mentioned intelligence sensor, adopt the Serial Control bus of CAN (Controller Area Network) bus as this sensor.Because advantages such as the CAN bus has the communication speed height, real-time is good, carrying load ability is strong, reliability and good, the total line use ratio height of antijamming capability and hardware cost are low are very suitable for detecting, controlling the communication of distributed network.
Should guarantee the integrality of sampled data in the present invention, will make the transfer rate of CAN bus reach maximum simultaneously.Therefore, the data processing of CAN bus is designed to drives interrupts completely, when CPU handles foreground task, the CAN bus can be in background transfer, the interrupt priority level of regulation sampling simultaneously is higher than the bus interrupt priority level, is not promptly interrupted interrupting by bus when sampling, to guarantee the integrality of sampling process.Realize exchange data using event flag and data buffer between backstage (interrupt service routine) and the circulation of foreground master routine.Bus data and sensor data acquisition are finished by interrupt service routine, judge interrupt source according to interrupt identification, enter corresponding interruption branch process, put event flag simultaneously.System's master routine is absorbed in data processing by the query event sign and need not be concerned about the transmission and the data acquisition of bus data.
In above-mentioned intelligence sensor,,, adopt two ultrasonic emitting sensors A, B in order to eliminate this influence because ultrasonic propagation velocity is subjected to the influence of temperature, humidity, air pressure and gas componant; If it is T that ultrasonic emitting sensors A transponder pulse, ultrasound wave receiving sensor receive the echoed signal time
1, it is T that ultrasonic emitting sensor B transponder pulse, ultrasound wave receiving sensor receive the echoed signal time
2,
:
Because the value of d is known, then:
From formula (3) as can be seen, fully relevant apart from S with d and time, and irrelevant with the speed of ultrasonic propagation.
Can eliminate the error that causes owing to environmental factor like this, the compensation of saving temperature, pressure, humidity, composition, the precision of measurement is guaranteed by the precision of d and time measurement.
The present invention makes it to have following advantage and good effect compared with prior art owing to adopted above technical scheme:
The invention has the beneficial effects as follows:
1, adopt supersonic technique to fix a point and survey liquid level continuously, do not need special protection, installation and maintenance is more convenient, and structure, method are all simpler, cheap.
2, the present invention is owing to adopt two ultrasonic emitting sensors, a ultrasound wave receiving sensor, can be under the situation of the variation of environment temperature, humidity, medium composition, still can obtain correct result, the precision of measuring is unaffected, do not need artificial the adjusting and staking-out work, only relevant with the precision of sensor own.The adaptive ability and the dirigibility of sensor have been improved.
3, the present invention adopts the CAN bussing technique, makes networking convenient flexibly.
4, the microcontroller that adopts of the present invention has CAN control module, clock and the unit such as catches and reduced cost of development and improved level of integrated system.
5, the present invention can be put in to measure also can be put in the water or in other liquid in the air and measure, and does not need to regulate and demarcate, and only needs to do waterproof, preservative treatment in encapsulation, has enlarged range of application.
Description of drawings
Fig. 1 is a system principle diagram of the present invention.
Fig. 2 is the program flow diagram of Single-chip Controlling communication of the present invention, signal acquisition process
Fig. 3 is the interruption process flow diagram that signal capture of the present invention is handled
Fig. 4 is the interruption process flow diagram of CAN communication process of the present invention
Fig. 5 for the conditioning unit of sensor control unit signal of the present invention, the micro controller unit behind the signal condition unit and the circuit theory diagrams of CAN bus communication unit are linked in sequence.
Embodiment
See Fig. 1, this embodiment intelligent liquid level sensor comprises two ultrasonic emitting sensors and the distance measurement sensor 4 that the ultrasound wave receiving sensor constitutes; Described sensor control unit comprises: the signal condition unit 2 that is electrically connected with range sensor, micro controller unit 1 and CAN bus communication unit 3 after signal element are linked in sequence.
See Fig. 5, label is that the model of the microcontroller 1-1 of U1 is the PIC18F258 single-chip microcomputer, this single-chip microcomputer is integrated with the Flash memory under program of 32KB, the SRAM of 1536B and the EEPROM of 256B, have a lot of other single-chip microcomputers incomparable advantage: at first, its adopts Harvard's dual-bus structure, and the transfer bus of data and instruction separates fully, can conduct interviews to program and data simultaneously, improve the handling capacity of data.Secondly, it adopts the two-level pipeline structure, can get finger to next bar instruction in an instruction on carrying out, and has realized that the monocycle of instruction carries out.Then, adopt the instruction set of simplifying, make programming simple and flexible.In addition, embedded abundant special feature, as WDT, CCP and CAN controller etc. have been simplified the design of peripheral circuit greatly.The port RB3/CANRX of microcontroller 1-1 and RB2/CANTX are CAN bus communication control port; The port OSC1/CLK1 of microcontroller 1-1 is a crystal oscillator input end of clock mouth; The port of microcontroller 1-1, VFF/MCLR are the RESET input mouth; The port RC5 of microcontroller 1-1, RC4 are that ultrasonic pulse drives port; The port RC2 of microcontroller 1-1 is the input port of ultrasonic echo pulse.
See Fig. 5, crystal oscillating circuit 1-1 forms oscillatory circuit jointly by crystal oscillator and not gate and capacitance resistance, and the clock signal of output 20MHZ is input to the OSC1/CLK1 port of microcontroller, drives microcontroller work.
See Fig. 5, reset circuit 1-2 is made up of reset key and capacitance resistance, is input to microcontroller VFF/MCLR port, can realize that electrification reset and button reset.
See Fig. 1, ultrasonic signal conditioning unit 2 comprises ultrasonic pulse driver element 2-1 and ultrasonic echo detecting unit 2-2, and wherein ultrasound wave driver element 2-1 comprises differentiating circuit 2-1-1 and 2-1-3, driving circuit 2-1-2 and 2-1-4.
See Fig. 5, ultrasonic pulse driver element 2-1, this part is mainly formed 2-1-2,2-1-4 by differentiating circuit 2-1-1,2-1-3 and driving circuit.The pulse signal that CPU sends forms pulse signal by driving circuit 2-1-2 and 2-1-4 then through becoming the pulse signal of a standard after the differentiating circuit.Remove to drive ultrasonic probe by this signal again, electric energy is changed into mechanical energy, form ultrasound wave.
See Fig. 5, ultrasonic echo detecting unit 2-2 comprises amplifying circuit 2-2-3, comparator circuit 2-2-2 and trigger circuit 2-2-1; Circuit mainly is made up of amplifying circuit 2-2-3 and comparator circuit 2-2-2 and single-shot trigger circuit 2-2-1.After the pulse signal of the ultrasonic probe that collects amplifies through amplifying circuit 2-2-3 two-stage, again through forming a pulse signal after the comparator circuit 2-2-2.Remove to trigger single-shot trigger circuit 2-2-1 by this pulse signal, thereby form a narrow pulse signal.This signal removes to trigger the RP2/CPP1 pin of U1, forms capture events, produces to catch to interrupt.By record capture time computed range.Here the electric weight with sensor has converted frequency quantity to, is actually the measurement of frequency.The PIC18F258 single-chip microcomputer has a very important peripheral components CCP (Capture/Compare/PWM), realizes the period measurement of frequency signal with it.By control register it is operated under the Capture mode CCP, in case when having trigger event to take place on the RC2/CCP1 pin, 16 register CCP/R1 catches the value in the timer TMR1 register of noting at this moment immediately.The trigger event here, the D3-D0 by control register CCP1CON are selected a kind of in the middle of following four kinds: the monopulse negative edge triggers, the monopulse rising edge triggers, per four rising edge of a pulses trigger, the negative edge of per 16 pulses triggers.What this embodiment adopted is the rising edge triggering mode of monopulse.When the rising edge of frequency of occurrences signal on the RC2/CCP1 of the U1 pin, U1 can catch the content in the timer automatically, and produces one and catch and interrupt.The difference of two count values is the frequency signal cycle.(CCP) finishes timing measuring with capture function, and be convenient, simple, do not need to guarantee the synchronous of timing and input signal with external circuit, and the precision of timing is also higher.The timing cycle of PIC18F258 (equaling the machine cycle) is four frequency divisions of crystal oscillator frequency, and the timing cycle of other single-chip microcomputer such as AT89C52 single-chip microcomputer is 12 frequency divisions of crystal oscillator, just can reach higher accuracy of timekeeping for same crystal oscillator clock with the former.Crystal oscillator is elected 20MHz as in this embodiment.
See Fig. 5, differentiating circuit 2-1-1, by the filtering circuit that R9 and C8 form, the differentiating circuit that the operational amplifier LM741 of U8 and R10, R11 form is formed jointly;
See Fig. 5, differentiating circuit 2-1-3, by the filtering circuit that R15 and C12 form, label is that the LM741 of U9 and the differentiating circuit of R16, R17 composition are formed jointly.
See Fig. 5, driving circuit 2-1-2 is mainly by triode Q1, Q2, transformer T1, resistance R 12, R13, R14, capacitor C 9, C10, C11 form, the end of C11 links to each other with the base stage of Q2, and the other end is the input end of transformer T1, and the other end of transformer T1 is the output terminal of driving circuit 2-1-2.
See Fig. 5, driving circuit 2-1-4, mainly by triode Q3, Q4, transformer T2, resistance R 18, R19, R20, capacitor C 13, C14, C15 form, and the end of C15 links to each other with the base stage of Q4, the other end is the input end of transformer T2, and the other end of transformer T2 is the output terminal of driving circuit 2-1-4.
See Fig. 5, amplifying circuit 2-2-3, by capacitor C 16, C17, C18, C19, resistance R 21, R22, R23, R24, operational amplifier U5-1 and U5-2 form the two-stage amplifying circuit.First order amplifying circuit enlargement factor is one, plays the effect of Signal Spacing, makes signal more stable.
See Fig. 5, comparator circuit 2-2-2, by resistance R 25, R26, R27, R28, operational amplifier LM339 forms, and is output as high level when signal height ratio reference voltage is high, and output low level when lower than reference voltage becomes pulse signal to simulating signal.
See Fig. 5, single-shot trigger trigger 2-2-1, by resistance R 29, R30, capacitor C 20, single-shot trigger trigger 74LS121 form.Signal is input to the A1 end of U7, from the output of Q end, produces the capturing unit that a burst pulse is input to microcontroller U1.
See Fig. 1, this embodiment adopts the embedded CAN control module of microcontroller, by CAN bus driving circuits 3-2 interface unit sensor is inserted the CAN bus network, adds photoelectric isolating circuit 3-1 simultaneously betwixt, to strengthen antijamming capability.
See Fig. 5, this embodiment adopts the embedded CAN control module of single-chip microcomputer, by CAN bus driving circuits 3-2 interface unit sensor is inserted the CAN bus network.CAN bus driving circuits 3-2 is made up of CAN bus driver chip U2 and capacitor C 6, and the model of CAN bus driver chip U2 is MCP2551.Add simultaneously photoelectric isolating circuit 3-1 betwixt, to strengthen antijamming capability.Photoelectric isolating circuit 3-1 is by optocoupler U3, U4, capacitor C 4, C7, and resistance R 4, R5, R7, R8 form.Because the communication protocol of CAN realizes by the hardware module in the single-chip microcomputer, so microcontroller do not participate in the processing of CAN agreement directly, and system has more resources to carry out the processing of sensing data like this.The main task of microcontroller U1 is to gather sensing data, and sensing data is carried out conversion process, and the work of CAN protocol module is dispatched to finish the data transmission between CPU and fieldbus.
In this embodiment, should guarantee the integrality of sampled data; To make the transfer rate of CAN bus reach maximum simultaneously.Therefore, the data processing of CAN bus is designed to drives interrupts completely, when CPU handles foreground task, the CAN bus can be in background transfer, the interrupt priority level of regulation sampling simultaneously is higher than the bus interrupt priority level, is not promptly interrupted interrupting by bus when sampling, to guarantee the integrality of sampling process.Realize exchange data using event flag and data buffer between backstage (interrupt service routine) and the circulation of foreground master routine.Bus data and sensor data acquisition are finished by interrupt service routine, judge interrupt source according to interrupt identification, enter corresponding interruption branch process, put event flag simultaneously.System's master routine is by the query event sign, is absorbed in data processing and need not be concerned about the transmission and the data acquisition of bus data.
See Fig. 1, this embodiment adopts two ultrasonic emitting sensors A and ultrasonic emitting sensor B, and the distance of installing between two ultrasonic emitting sensors differs d, and d gets 10CM in this embodiment; A ultrasound wave receiving sensor, and the ultrasound wave receiving sensor is concordant with the installation site of ultrasonic emitting sensors A.
Because ultrasonic propagation velocity is subjected to the influence of temperature, humidity, air pressure and gas componant, in order to eliminate this influence, adopts two ultrasonic emitting sensors A, B; If it is T that ultrasonic emitting sensors A transponder pulse, ultrasound wave receiving sensor receive the echoed signal time
1, it is T that ultrasonic emitting sensor B transponder pulse, ultrasound wave receiving sensor receive the echoed signal time
2,
:
Because the value of d is known, then:
From formula (3) as can be seen, only relevant apart from S with d and time, and irrelevant with the speed of ultrasonic propagation.
Claims (6)
1, a kind of intelligent liquid level sensor, comprise sensor and control module, it is characterized in that: the sensor in the described intelligent liquid level sensor comprises the distance measurement sensor (4) that two ultrasonic emitting sensors (4-1) and a ultrasound wave receiving sensor (4-2) constitute, and described control module comprises the signal transmission unit (2) that is electrically connected with distance measurement sensor, microcontroller (1) and CAN bus communication unit (3) behind signal transmission unit are linked in sequence.
2, intelligent liquid level sensor according to claim 1 is characterized in that: described signal transmission unit (2) comprises that the differentiating circuit (2-1-1,2-1-3) that is connected with microcontroller (1), the driving circuit (2-1-2,2-1-4) that is connected with emission sensor (4-1), order are connected electrically in amplifier circuit unit (2-2-3), comparator circuit unit (2-2-2), single-shot trigger trigger unit (2-2-1) between ultrasound wave receiving sensor (4-2) and the microcontroller (1).
3, intelligent liquid level sensor according to claim 2 is characterized in that: the crystal oscillating circuit composition that described microcontroller (1) comprises a single-chip microcomputer integrated chip and is arranged on the reset circuit of microcontroller reset terminal and is arranged on microcontroller (1) input end of clock.
4, intelligent liquid level sensor according to claim 2 is characterized in that: described CAN bus communication unit (3) is connected into by the photoelectric isolating circuit chip and the CAN bus driving circuits integrated chip that are separately positioned on CANRX and CANTX end.
5, a kind of measuring method of intelligent liquid level sensor as claimed in claim 1, it is characterized in that: the pulse signal that described microcontroller (1) sends becomes the pulse signal of a standard through (2-1-1,2-1-3) after the differentiating circuit, form pulse signal by driving circuit (2-1-2,2-1-4) then, remove to drive two ultrasonic emitting sensors (4-1) by this signal again; The echoed signal of described ultrasound wave receiving sensor (4-2) through amplifier circuit unit (2-2-3) afterwards, pass through comparator circuit unit (2-2-2) again and form a pulse signal triggering single-shot trigger circuit unit (2-2-1), last echoed signal enters microcontroller (1) analyzing and processing.
6, the measuring method of intelligent liquid level sensor according to claim 5 is characterized in that: the gap that 5-25cm is set between described two ultrasonic emitting sensors (4-1).
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102323831A (en) * | 2011-08-04 | 2012-01-18 | 江南机器（集团）有限公司 | Liquid level controller of liquefied natural gas (LNG) storage tank |
| WO2018055128A1 (en) * | 2016-09-22 | 2018-03-29 | Plastic Omnium Advanced Innovation And Research | Method and system for determining a quantity of liquid in a tank |
| CN106600937B (en) * | 2017-01-10 | 2022-06-03 | 中山市中晶智能科技有限公司 | Electrical appliance for wireless transmission of measurement signals between base and machine body |
| CN108225389B (en) * | 2017-12-22 | 2020-10-23 | 联创汽车电子有限公司 | Ultrasonic sensor driving device and driving method thereof |
| CN110161507A (en) * | 2019-05-07 | 2019-08-23 | 生态环境部华南环境科学研究所 | A kind of siltation on-line monitoring system and method |
| CN113175523B (en) * | 2021-04-20 | 2022-06-17 | 中国北方车辆研究所 | Oil level signal processing system and method for AT automatic transmission |
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