CN102564530A - Intelligent two-wire photoelectric level transmitter with current ranging from 4mA to 20mA - Google Patents
Intelligent two-wire photoelectric level transmitter with current ranging from 4mA to 20mA Download PDFInfo
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- CN102564530A CN102564530A CN201110411608XA CN201110411608A CN102564530A CN 102564530 A CN102564530 A CN 102564530A CN 201110411608X A CN201110411608X A CN 201110411608XA CN 201110411608 A CN201110411608 A CN 201110411608A CN 102564530 A CN102564530 A CN 102564530A
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Abstract
The invention relates to an intelligent two-wire photoelectric level transmitter with current ranging from 4mA to 20mA, which is characterized by comprising a processor, a power conversion circuit, a photoelectric sensor control detecting unit, a DA (digital to analog) converter and a HART (highway addressable remote transducer) communication unit. The power conversion circuit, the photoelectric sensor control detecting unit, the DA converter and the HART communication unit are connected with the processor, the processor controls the photoelectric sensor control detecting unit and acquires liquid level signals from the photoelectric sensor control detecting unit, the liquid level signals are converted into standard signals with current ranging from 4mA to 20mA via the DA converter, simultaneously, carrier waves with current ranging from 4mA to 20mA meet Bell202 international standard protocol by the aid of the HART communication unit, and bidirectional digital communication between the transmitter and a control room is realized. The intelligent two-wire photoelectric level transmitter has the advantages that the intelligent two-wire photoelectric level transmitter is low in power consumption, wide in power supply range and high in stability and reliability, super-high error correcting capacity for data of a sensor is realized, maintenance intensity of field personnel is reduced, and the like.
Description
Technical field
The present invention relates to a kind of intelligent 4～20mA two-wire system photoelectricity level transmitter.
Background technology
The steel band level meter is used very extensively in oil product storage tank is measured, and the mode that in the steel band level meter, adopts infrared photoelectric sensor to detect liquid level is maximum.At the scene in the automated information managing and control system, the application of 4～20mA signal is generally admitted, and has also more and more being used widely of steel band level meter of 4～20mA output at present.But the photoelectricity fluid level transmitter in using at present is because the restriction of treatment circuit; Transmitter generally adopts three-wire system; Wherein two is power supply, and one is the output of 4～20mA signal, and this circuit working conditional request is higher and have many shortcoming and defect: in the field of employment that the intrinsic safe explosion-proof requirement is arranged; Because transmitter requirement supply voltage is higher, working current is big, the apolegamy safety barrier is difficulty very; The working method of transmitter three-wire system also can cause the increase of field engineering cable cost; Transmitter does not have carrier wave under 4～20mA three-wire system output form HART digital interface can't realize bidirectional data transfers with the pulpit, and instrument is difficult in maintenance; The infrared photoelectric sensor key component of transmitter Level Detection adopts common door circuit inherent logic to handle, and the data error rate is high; The transmitter infrared photoelectric sensor aging transport property that makes of work for a long time changes, and the increase of coupling deviation causes job stability to reduce; Gray code band manufacturing process requirement to the sensing liquid level is tight, production cost is high and on-the-spot operation maintenance working strength is big etc.
Summary of the invention
The technical matters that the present invention will solve provides a kind of intelligent 4～20mA two-wire system photoelectricity level transmitter, to overcome the defective that exists in the prior art.It has low-power consumption, service area is wide, and sensing data is had the super error ability, and reliability is high, and what reduce the field staff safeguards advantage such as intensity.
Technical scheme of the present invention is: a kind of intelligent 4～20mA two-wire system photoelectricity level transmitter is characterized in that: comprise processor, and the power-switching circuit that links to each other with processor, photoelectric sensor control detection unit, DA converter and HART communication unit; Wherein, Thereby processor control is gathered photoelectric sensor control detection unit and is obtained liquid level signal; This liquid level signal converts 4～20mA standard signal into through the DA converter; Meet the Bell202 international standard protocol through the HART communication unit at 4～20mA carrier wave simultaneously, realize the bi-directional digital communication between transmitter and the pulpit.
Comprise the polarity switching or the single diode that link to each other with power-switching circuit, to realize access to the not polarity of transmitter power supply.
Said polarity switching is the diode rectification bridge circuit.
Said power-switching circuit is the DC-DC change-over circuit, is used to convert into the system works power supply.
The processor of said processor adopting low-power consumption is to reduce system power dissipation.
Said DA converter adopts the D/I type DA converter that directly converts 4～20mA into, perhaps changes the compound change-over circuit that makes up for the D/V conversion with V/I.
Said HART communication unit adopts the HART chip that meets the Bell202 standard; The demodulation of HART communication unit is a communication instruction by the Bell202 carrier voltage signal that the pulpit sends; Then the transmitter data with on current forms modulated carrier to 4 ~ 20mA electric current loop, finally reach the bidirectional data exchange transmission between pulpit system and the transmitter equipment.
Technique effect of the present invention is:
1. transmitter has been realized the transmission of 4 ~ 20mA two-wire system signal, in like product, belongs to initiative;
2. the correcting data error processing power of transmitter is strong, and reliability improves a lot;
3. the transmitter service area is wide, has adapted in intrinsic safe explosion-proof occasion instrument more safety barrier is selected;
4. transmitter is supported the HART communication interface on the two-wire system basis, and convenient bidirectional data transmission and instrument are safeguarded;
5. transmitter has diagnostic function to the health status of self, can accomplish that fault foresees in advance and handle;
6. the enhancing of the raising of the performance of transmitter and adaptive faculty has reduced field staff's maintenance workload.
7. transmitter has adopted the treatment circuit of the strong photoelectric sensor of low-power consumption error correcting capability; Overall Power Consumption is low, power supply supplies wide ranges; Error correction capability is strong; Realized on the basis of the performance that improves the photoconduction level meter greatly that 4～20mA two-wire system becomes and sent output, made things convenient for the integrated of DCS data acquisition system (DAS).
Description of drawings
Fig. 1 is a synoptic diagram of the present invention.
Reference numeral is following:
1. polarity switching, 2. power-switching circuit, 3. processor, 4. photoelectric sensor control detection unit, 5.DA converter, 6.HART communication unit.
Embodiment
The present invention relates to the level measurement instrument technical field, relate to a kind of intelligent 4 ~ 20mA two-wire system photoelectricity level transmitter circuit specifically.
Referring to Fig. 1, being specially of a kind of intelligent 4～20mA two-wire system photoelectricity level transmitter that the present invention relates to:
Comprise processor 3, and the power-switching circuit 2 that links to each other with processor 3, photoelectric sensor control detection unit 4, DA converter 5 and HART communication unit 6; Wherein, Thereby processor 3 controls are gathered photoelectric sensor control detection unit 4 and are obtained liquid level signal; This liquid level signal converts 4～20mA standard signal into through DA converter 5; Meet the Bell202 international standard protocol through HART communication unit 6 at 4～20mA carrier wave simultaneously, realize the bi-directional digital communication between transmitter and the pulpit.
Also can comprise the polarity switching 1 or the single diode that link to each other with power-switching circuit 2 among the present invention, to realize access to the not polarity of transmitter power supply.It realizes the positive and negative not polarity of wiring of in-situ transducer, the device damage that this mode can make things convenient for the unnecessary polarity identification of user or cause thus.Said polarity switching 1 specifically can be the diode rectification bridge circuit.
Power-switching circuit 2 among the present invention can be the DC-DC change-over circuit, and being used for the power source conversion after the diode rectifier bridge rectification is the system works power supply.This change-over circuit wide input voltage range, conversion efficiency is high, to adapt to the on-the-spot wide power power supply and the requirement of transducer system power consumption.
Processor 3 among the present invention can adopt the processor of low-power consumption, to reduce system power dissipation.This processor 3 is connected and requires to accomplish according to its logic the acquisition process of liquid level data with photoelectric sensor control detection unit (4); Processor (3) and HART communication unit (6), DA converter circuit such as (5) are accomplished the realization of corresponding function.
Photoelectric sensor control detection unit 4 among the present invention, low in energy consumption, error correcting capability is strong, circuit logic level recognition capability is strong, adaptability is good, unfailing performance is high, is fit to very much the signal Processing of multichannel light power conversion circuit, and self diagnostic capability is arranged.The partial circuit of photoelectric sensor control detection unit 4 can like AD converter, comparer etc., to reduce peripheral components, reduce trouble spot quantity by being integrated in inner function module realization in the processor, improves product reliability.
DA converter 5 among the present invention can adopt the D/I type DA converter that directly converts 4～20mA into, also can be the compound change-over circuit of D/V conversion and V/I conversion combination.DA converter 5 adopts high precision DA digital-to-analogue 4～20mA change-over circuit; Digital quantity through processor 3 outputs directly converts the adjustment of the loop current of transmitter into 4～20mA simulating signal; Can also convert digital quantity into voltage analog through the DA converter; Converting the compound circuit that 4～20mA simulating signal is formed into through the V-I aanalogvoltage again, also can be by the digital quantity of pulse width modulation realization and the compound circuit of 4～20mA conversion.It is the simulating signal of 4～20mA that DA converter 5 is used for gathering digital data conversion.
HART communication unit 6 among the present invention adopts the HART chip that meets the Bell202 standard; This unit demodulation is a communication instruction by the Bell202 carrier voltage signal that the pulpit sends; Then the transmitter data with on current forms modulated carrier to 4～20mA electric current loop, finally reach the bidirectional data exchange transmission between pulpit system and the transmitter equipment.This unit is made up of HART modem chip and peripheral circuit thereof.This unit meets the Bell202 international standard protocol; Inner integrated modulator-demodular unit; Its digital interface links to each other with processor; Adopt the frequency shift keying fsk technology to modulate and be superimposed upon the carrier signal of encoding on 4～20mA simulating signal, and can demodulate the carrier signal that the HART unit receives and give processor, to realize the bidirectional data interaction transmission of the uplink and downlink between computing machine and the transmitter.
As shown in Figure 1, through polarity switching 1, carry out giving after the polar switching input end of power-switching circuit DC-DC to the external power source rectification of polarity not by external power source, power source conversion output system power supply supplies processor and other circuit uses.
Processor adopting super low-power consumption MSP430 Series MCU; Under the 1MHz work clock, the power consumption during the 2.2V power supply has only 280uA, minimum WV 1.8V; 8 road 12bitAD converters are arranged in the processor piece, and convenient function with photoelectric sensor control detection unit realizes; Processor is also accomplished the realization and the data operation processing of corresponding function simultaneously with circuit interfaces such as DA converter, HART communication units.
Processor is through control photoelectric sensor control detection circuit unit; Make the voltage output signal of the corresponding infrared sensor receiving cable of output; This signal is accomplished sampling by the inner AD converter of processor, and the threshold value through inner setting, carries out the logic error correction and judges and export corresponding level value.
A kind of monolithic high performance mode converter (numeral/electric current) that the conversion of 4～20mA current signal adopts U.S. ADI company to release; For 16bit serial SPI mode is imported; 4～20mA output, it provides high integrated, low-power consumption, high-precision conversion of signals scheme.
HART modem special chip is adopted in the HART communication, and the integrated modulator-demodular unit that meets the BELL202 standard in this chip slapper is realized the coding and decoding of HART agreement regulation digital communication with its peripheral circuit.The The data frequency shift keying fsk technology of HART communication is carried out modulation-demodulation signal, and the signal of modulation i.e. frequency of stack on 4～20mA simulating signal, and this frequency meets the BELL202 standard; 1200HZ representes " 0 "; 2200HZ representes " 1 ", and signal amplitude 0.5mA is in a signal period; The mean value of fsk signal is 0, can be to any influence of 4～20mA analogue signal generating; Also the frequency signal demodulation that receives is exported to processor to accomplish two-way data transmission simultaneously.
Claims (7)
1. intelligence 4～20mA two-wire system photoelectricity level transmitter; It is characterized in that: comprise processor (3), and the power-switching circuit (2) that links to each other with processor (3), photoelectric sensor control detection unit (4), DA converter (5) and HART communication unit (6); Wherein, Processor (3) control is gathered photoelectric sensor control detection unit (4) thereby is obtained liquid level signal; This liquid level signal converts 4～20mA standard signal into through DA converter (5); Meet the Bell202 international standard protocol through HART communication unit (6) at 4～20mA carrier wave simultaneously, realize the bi-directional digital communication between transmitter and the pulpit.
2. according to the said intelligent 4～20mA two-wire system photoelectricity level transmitter of claim 1, it is characterized in that: comprise the polarity switching (1) or the single diode that link to each other with power-switching circuit (2), to realize access to the not polarity of transmitter power supply.
3. according to the said intelligent 4～20mA two-wire system photoelectricity level transmitter of claim 2, it is characterized in that: said polarity switching (1) is the diode rectification bridge circuit.
4. according to the said intelligent 4～20mA two-wire system photoelectricity level transmitter of claim 3, it is characterized in that: said power-switching circuit (2) is the DC-DC change-over circuit, is used to convert into the system works power supply.
5. according to the said intelligent 4～20mA two-wire system photoelectricity level transmitter of claim 1, it is characterized in that: said processor (3) adopts the processor of low-power consumption, to reduce system power dissipation.
6. according to the said intelligent 4～20mA two-wire system photoelectricity level transmitter of claim 1; It is characterized in that: said DA converter (5) adopts the D/I type DA converter directly convert 4～20mA into, perhaps changes the compound change-over circuit that makes up for the D/V conversion with V/I.
7. according to the said intelligent 4～20mA two-wire system photoelectricity level transmitter of claim 1; It is characterized in that: said HART communication unit (6) adopts the HART chip that meets the Bell202 standard; HART communication unit (6) demodulation is a communication instruction by the Bell202 carrier voltage signal that the pulpit sends; Then the transmitter data with on current forms modulated carrier to 4 ~ 20mA electric current loop, finally reach the bidirectional data exchange transmission between pulpit system and the transmitter equipment.
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| CN201110411608.XA CN102564530B (en) | 2011-12-12 | 2011-12-12 | A kind of intelligence 4~20mA two-wire system photoelectricity level transmitters |
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| CN201110411608.XA CN102564530B (en) | 2011-12-12 | 2011-12-12 | A kind of intelligence 4~20mA two-wire system photoelectricity level transmitters |
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Cited By (4)
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| CN107219389A (en) * | 2017-05-27 | 2017-09-29 | 重庆编福科技有限公司 | One kind compensates stealing formula transmitter based on Darlington optocoupler from ring |
| CN107941294A (en) * | 2017-11-21 | 2018-04-20 | 江苏斯尔邦石化有限公司 | A kind of measuring instrument accumulates data synchronous |
| CN108765916A (en) * | 2018-04-08 | 2018-11-06 | 南京达凯电力自动化设备有限公司 | A kind of sensor that signal carrier encrypted state is controllable |
| CN109856534A (en) * | 2018-12-18 | 2019-06-07 | 南京南自电力仪表有限公司 | A kind of generator electric parameters transducer based on the Hart communication technology |
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| CN107941294A (en) * | 2017-11-21 | 2018-04-20 | 江苏斯尔邦石化有限公司 | A kind of measuring instrument accumulates data synchronous |
| CN108765916A (en) * | 2018-04-08 | 2018-11-06 | 南京达凯电力自动化设备有限公司 | A kind of sensor that signal carrier encrypted state is controllable |
| CN109856534A (en) * | 2018-12-18 | 2019-06-07 | 南京南自电力仪表有限公司 | A kind of generator electric parameters transducer based on the Hart communication technology |
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| CN102564530B (en) | 2017-09-29 |
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Effective date of registration: 20120913 Address after: The eastern city of Handan province Hebei Xuechi road 056005 Applicant after: Hebei Zhufeng Instrument & Meter Co., Ltd. Address before: 710077, building 1, Residence Du Commerce, 69 Kam Yip Road, hi tech Zone, Shaanxi, Xi'an Applicant before: Xi'an Fuan Innovation Consultation Co., Ltd. |
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