CN105091962A - Low-power-consumption electromagnetic flow converter - Google Patents
Low-power-consumption electromagnetic flow converter Download PDFInfo
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- CN105091962A CN105091962A CN201410214313.7A CN201410214313A CN105091962A CN 105091962 A CN105091962 A CN 105091962A CN 201410214313 A CN201410214313 A CN 201410214313A CN 105091962 A CN105091962 A CN 105091962A
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Abstract
The invention provides a low-power-consumption electromagnetic flow converter mainly comprising an exciter circuit, a power source, a sensor, a signal conditioning circuit and a single-chip microcomputer interface circuit. The low-power-consumption electromagnetic flow converter is characterized in that the exciting mode of the exciter circuit is pulse rectangular wave exciting; the power source has two combination modes of lithium thionyl chloride batteries; the signal conditioning circuit comprises an instrument amplifier, a low pass filtering circuit, a resistance-capacitance coupling circuit and a high gain amplifying circuit; the single-chip microcomputer interface circuit comprises a single-chip microcomputer, a reset circuit, a crystal oscillator, an A/D input unit, a display output unit, a 485 communication output unit, a storer circuit, and a JTAG debugging interface. The low-power-consumption electromagnetic flow converter is characterized by low power consumption, small size and field display and guarantees measuring accuracy.
Description
Technical field
The invention belongs to optical, mechanical and electronic integration application, relate to a kind of electromagnetic flowmeter, be specifically related to a kind of electromagnetic flux converter.
Background technology
Flowmeter is one of most important instrument in commercial measurement, is widely used in the every field of the national economy such as metallurgy, electric power, coal, chemical industry, oil, traffic, building, light textile, food, medicine, agricultural, environmental protection and people's daily life.In order to adapt to various uses, all kinds flowmeter is come out one after another.The flowmeter come into operation at present is more than kind more than 60.
Electromagnetic flowmeter is a kind of instrument measuring conducting liquid volumetric flow rate utilizing Faraday's electromagnetic induction law to make.In numerous flow instrument, electromagnetic flowmeter with himself feature, comprise structure simple, without choked flow part, the plurality of advantages such as linearly is strong, measurement range is wide, be widely used in the measurement to conductive fluid.World wide electromagnetic flowmeter output accounts for 5% ~ 10% of industrial flow instrument number of units in recent years.And apply increasingly extensive.Portable, the development of powered battery, small size integrated electromagnetic flow instrument is also taken seriously more.
Electromagnetic flowmeter is due to self inherent characteristics, and need exciting current to produce magnetic field, if exciting current is too little, the magnetic field of generation is too weak, and the Signal-to-Noise of now sensor electrode generation is too low, then the stability of flow metering and precision all can have impact.So electromagnetic flowmeter is compared to other flowmeters, the design of low-power consumption is more complex.In most application places, electromagnetic flowmeter is all adopt power frequency 220V Alternating Current Power Supply, fully can ensure that the excitation of electromagnetic flowmeter is powered needs.
But adopt power frequency 220V Alternating Current Power Supply, also there is certain weak point:
1, Hz noise is serious.The flow signal that electromagnetic sensor electrode produces is very faint, and power frequency interference signals is superimposed upon on flow signal, if Hz noise suppresses abundant not, can have a strong impact on the signal to noise ratio (S/N ratio) of signal, affect metric results.
2, applied environment restriction.Along with electromagnetic flowmeter application is increasingly extensive, installation site spreads all over city, each corner, rural.Some places physical features is remote, is inconvenient to connect up; Under some places are buried, physical features is moist, and this situation adopts 220V Alternating Current Power Supply to there is very large potential safety hazard.
3, along with science and technology is maked rapid progress, instrument is more intelligent, small size, so also more and more pay attention to the portability of electromagnetic flowmeter
4, the energy is our country of important substance basis of the national economic development is an energy resource consumption big country, and be in the high speed development stage, due to industrial or agricultural technical merit, to compare developed country relatively backward, so energy utilization rate is also very low, the energy-saving potential of China is huge.If energy utilization rate improves 1%, very objectively Social benefit and economic benefit will be brought.During power frequency full voltage starting, starting current is comparatively large, can produce certain impact, cause larger energy loss to electrical network.Even if enter mode of operation, power consumption is also between 10W-30W.So large electric energy loss, does not meet the policy sensing of national energy-saving reduction of discharging and the low-power consumption development trend of intelligent instrument.
In sum, along with electromagnetic flowmeter application is increasingly extensive, and the making rapid progress of electronic technology new material, the Electromagnetic Flow instrument of portable, small size, integration, low-power consumption, namely the development of powered battery type electromagnetic flowmeter is also taken seriously more.
Current existing powered battery type electromagnetic flowmeter, mainly has the following disadvantages:
One is outward appearance, and have plenty of and place separately a container with placing battery on instrument side, this does not meet, and flowmeter is portable, the development trend of small size; Be exactly that function reduces in addition, the even on-the-spot display had does not have yet, and only transmits flow information by remote transfer signal, makes troubles to situ industrial management maintenance.
Object of the present invention is exactly the low-power consumption being to realize electromagnetic flux converter, again small size, can carry out scene display, also must ensure measuring accuracy.
Summary of the invention
In order to solve the problems of the prior art, achieve the above object, the technical solution used in the present invention is: the low power consumption electromagnetic flow converter for electromagnetic flowmeter mainly comprises field circuit, power supply, signal conditioning circuit, interface microcontroller circuit, it is characterized in that in described field circuit, excitation mode is Pulse High Voltage excitation, the described power acquisition mode of the sub-battery combination of two kinds of lithiums, described signal conditioning circuit comprises instrumentation amplifier, low-pass filter circuit, resaistance-capacity coupling circuit and plus and blowup circuit, described interface microcontroller circuit comprises single-chip microcomputer, reset circuit, crystal oscillator, A/D inputs, display translation, 485 communications export, memory circuitry, JTAG debugging interface.
The difficult point of powered battery type electromagnetic flowmeter, mainly should ensure high-precision metering performance, ensures low-power consumption requirement again, also will require small size, easy to carry.Dual-frequency excitation is most advanced, excitation mode that technology content is the highest at present, but universal not enough, only has external several company to adopt in this way at present.And low-frequency rectangular ripple excitation mode is most widely used at present, it is also the excitation mode of comparative maturity.So the present invention is when considering excitation mode, Primary Reference low-frequency rectangular ripple excitation mode, and consider that the low-power consumption feature of electromagnetism power supply type flowmeter has carried out corresponding improvement.
Compare and power with industrial frequency AC 220V, in the present invention, excitation mode has changed Pulse High Voltage excitation into by low-frequency rectangular ripple excitation, and difference is mainly reflected in:
1, exciting current reduces greatly, and when industrial frequency AC 220V powers, exciting current is 125mA at least, at most 500mA.And powered battery type electromagnetic flowmeter, according to power consumption requirements, exciting current 80mA at most, at least 20mA, be reflected in above in coordinate diagram, the amplitude of signal greatly reduces.
2, excitation can adjust interval time.When industrial frequency AC 220V powers, the forward and reverse output of excitation is continuous print, and after namely a direction excitation exports, export excitation in the other direction, the excitation cycle is maximum with 160ms at once.When adopting powered battery, in order to save power consumption, inconvenience frequently exports excitation, therefore after a direction output excitation, certain interval of time exports excitation in the other direction, and interval time, according to the stability state of flow, can be set to 2s, 4s, 6s, 8s, 10s, 12s.Excitation interval arranges longer, and battery-powered time is longer.
3, excitation width can adjust.When industrial frequency AC 220V powers, the most common with the excitation width of 80ms.When adopting powered battery, in order to save power consumption, being set to 60ms at most, if stream condition is stablized, also can being set to 50ms, 40ms, 30ms, 20ms.Excitation width arranges shorter, and battery-powered time is longer.
Utilize Faraday's electromagnetic induction law, fluid is by the measuring guide of electromagnetic flow transducer, electromagnetic transducer can be delivered to by electrode generation weak voltage signals in measuring tube both sides, electromagnetic transducer is then main control unit with single-chip microcomputer, is carried out by the signal collected nursing one's health, showing and the teletransmission that communicates.
Battery provides electric energy for electromagnetic flowmeter whole system, and converter power is mainly divided into two parts, and one is field power supply, and consider that dissimilar sensor process parameter is different, the resistance of field coil and inductance parameters have very big-difference.Exciting current also according to circumstances may arrange and differ, nearly 80mA, at least 20mA.So the voltage that converter is supplied to field coil can not be too low.Current electromagnetic sensor coil resistance is usually at 100 below Ω, and export with the highest 80mA exciting current and consider, the field voltage being supplied to cell winding can not lower than 8V.Consider in circuit and also have some switching loss and constant-current circuits etc. also to need certain crushing, design battery is 10.8V to the voltage that field circuit provides.Other a part of power supply of converter is mainly supplied to signal processing circuit and digital circuit, comprises microprocessor, clock, display, communication etc., and the power supply that these functional modules need is all 3.6V.
Be correlated with amplifier device, single-chip microcomputer, display and communication module etc. of signal transacting all adopts low energy-consumption electronic device, by the switching of single-chip microcomputer activity pattern and low-power consumption mode, can ensure that the average current of 3.6V battery exports within 1mA completely.Adopt the sub-battery ER26500 of 3 joint lithium and connect: ER26500 is that a stored energy is at 9Ah, the battery that 3.6V exports, single overall dimensions are at 79x26x26mm, and 3 joint ER26500 also connect overall dimensions at 79x26x52mm, and usual converter shell is enough to receive this space of points.In addition from power consumption analysis, average current is defeated to be considered at 1mA, and 1 year is 0.001x24x365=8.76Ah, and within 2 years, power consumption is at 17.52Ah, and 3 joint ER26500 also connect power consumption at 27Ah, meet the power consumption that 3.6V exports 2 years completely.
Exciting current is maximum to be considered with 80mA, if press the excitation interval of 4s, the excitation width of 50ms is arranged, average current is calculated as follows: 0.05/4=0.0125, 0.0125x80=1mA, by this result, the exciting current power consumption of a year is also 8.76Ah, be limited with 2 years, require that power consumption is at 17.52Ah, if 3 joint ER26500 tandem compounds, output voltage is at 10.8V, storage power consumption is at 9Ah, after 2 every 3 joint ER26500 tandem compounds, Parallel opertation again, output voltage is at 10.8V, storage power consumption is at 18Ah, meet the demand of exciting current 17.52Ah.Certainly concrete excitation power consumption demand and battery tenure of use, depend primarily on excitation interval and arrange and the setting of excitation width.If sensor process is good, flow field is stablized, then excitation interval can be arranged length a bit, excitation width arranges shorter, then the powered battery time limit is longer, otherwise, likely do not arrive 2 years yet.The design mainly considers according to the intermediate value of parameters.From space angle consider, 6 joint ER26500 every 3 series winding after again two two-phases also, size, at 80x60x55mm, is enough to hold this space at the bonnet of converter shell.
3.6V exports by battery type selecting and 10.8V exports separately consideration, can reduce battery loss further.If only with 10.8V or only use 3.6V battery, meet the power demands of other a part of circuit, certainly exist DC/DC conversion, this is inevitable increase again extra transition loss, to the power consumption of battery and space requirement higher.
The signal produced due to electromagnetic sensor is feeble signal, and when adopting powered battery, because exciting current is less, excitation width is narrower, and the voltage signal in this case produced is just fainter.In order to ensure the loss of signal voltage in transmitting procedure as much as possible, must ensure that signal input channel has sufficiently high internal resistance, internal resistance is higher, and the loss of signal is less.In addition, the input amplifier of electromagnetic transducer, must meet high cmrr, Differential Input, Single-end output.For powered battery, also low-power consumption requirement must be met.Instrumentation amplifier in the present invention in signal conditioning circuit selects the instrumentation amplifier MAX641 of MAXIM company of the U.S., and enlargement factor is designed to 10, and external gain resistor gets 5.5K.In the connecting circuit application design of sensor and input instrumentation amplifier, MAX641 is single power supply pattern, and its minimum supply voltage can reach 2.7V, adopts 3.6V to power in design.The anti-phase input resistance of differential amplifier MAX641 and homophase input resistance R1, R2, gain setting resistor RG.In order to the homophase input and anti-phase input that ensure signal have sufficiently high impedance over the ground, R1 and R2 gets 47K Ω usually; The differential-mode input impedance of MAX641 self and common mode input impedance are also up to more than 100G Ω, are entering the decay in differential amplifier process to reduce signal as much as possible.The parameter characteristic of R1, R2 is symmetrical, and R1, R2, RG select high-accuracy resistance, and temperature coefficient is low, to ensure consistance and the stability of signal, reduces the impact that environment and the temperature difference are brought as far as possible.
The present invention adopts second-order low-pass filter circuit, and operational amplifier selects the OP81 of AD company of the U.S., and adopt single electric former power supply, service area is+1.6V ~+3.6V.In addition, its minimum 700V/mV of open-loop gain, higher common-mode rejection ratio, is very applicable to battery power supply system.Circuit has homophase input structure, and OP81 presses the anatomical connectivity of voltage follower, and direct current input resistance is very high, and output resistance is very low, has very strong carrying load ability.In circuit, operational amplifier connected mode is the form of voltage follower, so passband voltage gain is 1.Wherein build-out resistor electric capacity: R1=R2=47K, C1=C2=2.2nF.
Signal, after second-order low-pass filter circuit exports, connects resaistance-capacity coupling circuit, because the input of instrumentation amplifier exists zero signal, after instrumentation amplifier amplifies, probably will mask the electrode voltage signal that collects as output.Zero signal contains a large amount of differential mode direct current signals, and intensity is uncertain.After resaistance-capacity coupling circuit, the most of differential mode interference in signal is isolated out by electric capacity C3, although and flow signal is faint, but pulse signal, next stage circuit can be entered by electric capacity.When pulse signal is by electric capacity C3, there is charge and discharge effect in electric capacity C3, residual charge must discharge in time, and R4 is mainly in order to discharge the residual charge on electric capacity.But in order to ensure whole signalling channel high impedance over the ground, C3, R4 resistance must Rational choice: C3 gets about 1uF usually, and R4 is 1M Ω.
Signal is after R-C coupling, enter plus and blowup circuit, after the differential amplify of front end instrumentation amplifier, second-order low-pass filter circuit and resaistance-capacity coupling circuit, largely reducing the noise of the common mode interference in measured flux signal, interference at zero point and other frequencies.But its signal amplitude is still very little, does not also reach collection requirement, need the undistorted amplification of high multiple carrying out amplitude.In circuit, signal amplifier A3 still selects OP81, and enlargement factor selects 20-50 doubly herein, and at 200-500 doubly, signal enters follow-up AD and gathers whole like this signalling channel enlargement factor.R5, R6 are amplifier homophase input resistance and anti-phase input resistance, and R7 is gain resistor.The design R6 gets 5K Ω, and R7 gets 100K Ω, then enlargement factor is at about 20 times.The parameter of R5 determines the end of oppisite phase input impedance of balance A3 as far as possible, and the design gets 1K about Ω; C4 is integrating capacitor, and parameter gets 2.2nF, can suppress high frequency noise further.
In interface microcontroller circuit, described single-chip microcomputer selects the single-chip microcomputer of the MSP430 series of TIX as microprocessor, can carry out low power dissipation design and facilitate powered battery; Can use up to the low frequency collocation of the high frequency clock of 8M and 32K, signal transacting can be carried out timely fast, again can the saving power consumption of maximal efficiency.
Power circuit utilizes the low-power consumption feature of MSP single-chip microcomputer, and operating voltage is between 1.8 ~ 3.6V, so employing lithium battery is as power supply unit.Add a 0.1uf electric capacity at the power input of single-chip microcomputer and carry out filtering, reduce power supply disturbance.
Crystal oscillator adopts 8M high frequency crystal oscillator and 32.768K low frequency crystal oscillator dual-purpose, uses low frequency crystal oscillator to save power consumption under low-power consumption mode, enables high frequency crystal oscillator to carry out rapidly signal transacting and display refreshing under mode of operation.
Supply voltage monitor chip CAT823 is adopted to control the output that resets.When 3.6V power supply instability or the threshold voltage lower than voltage monitor being detected, voltage monitor output low level reset single-chip microcomputer.CAT823, except having function of voltage monitoring, also has watchdog reset to export.Export house dog clock by single-chip processor i/o mouth P6.3 in design, if single-chip microcomputer operation troubles enters endless loop, house dog tick interrupt, then CAT823 exports reset signal, restarts single-chip microcomputer work.
MSP430F169 is built-in 8 passages, the AD converter of 12bit, 20kbps, carries sampling holder.For the external voltage, the current signal that need to gather, as long as by signal conditioning circuit, be converted into the voltage signal of 0 ~ 3.3V, intelligent measure and control module just can be used to sample.The existing I/O function of P6 port of MSP430F169 single-chip microcomputer, also has AD input function.In program, the P6.7 of P6 port is inputted as simulating signal sampling.
Display translation selects LCD as the display panel of product, and its feature is that miniaturization, variation, display are more clear, and it is electrical to have more province.The P4 port defining single-chip microcomputer in design exports as display data, and the P5.0-P5.4 of P5 port controls to export as display, and the P2.4-P2.7 of P2 port is as key-press input.
For adapting to the developing direction of meter communication networking, powered battery type electromagnetic transducer carries out data exchange by RS485 bus and host computer.Select SP3485E as communication chip in design.SP3485E be a can the 3.3V low-power consumption Half-duplex transceiver of powering, meet the requirement of RS485 and RS422 serial protocol completely.In single-chip microcomputer, P3.4, P3.5 are I/O mouth, are again communication ports.In design, single-chip microcomputer carries out communication data transmitting-receiving control by port P30.Time idle, P30 is set low level by single-chip microcomputer, and now SP3485E chip is in data receiving state: if bus exists 485 signals, convert 232 signals to, enter single-chip microcomputer by P35 by SP3485E.After single-chip microcomputer receives data-signal, process by analysis, if judge to need return data, then set high by P30 level, data enter SP3485E by P34, are entering 485 buses.
FM24CL04 selected by storer, is mainly used in storing total amount information, prevents total amount information dropout after converter power-off.FM24CL04 is also low energy-consumption electronic device, and minimum power supply can beat 2.7V, and quiescent dissipation only has 1uA, power consumption also just 76uA under mode of operation.
During circuit connects, WP is chip enable end, effectively low, therefore ground connection, keep often imitating.During work, the P56 port output clock of single-chip microcomputer is held to the SCL of FM24CL04, and P57 port exports data and holds to the SDA of FM24CL04, R501 and R502 is the pull-up resistor of clock line and data line respectively, and data storage can be allowed more reliable.
JTAG is a kind of international standard test protocol (IEEE1149.1 is compatible), is mainly used in chip internal test.In the present invention, the TMS of jtag interface connects the Pin56 of single-chip microcomputer, the Pin57 that TCK connects, the Pin55 that TDI connects, the Pin58 that test lead connects, the Pin54 that TDO connects, the Pin11 that TX connects, the Pin22 that RX connects.
In Design of System Software, in order to save power consumption, ensureing that battery has enough tenure of use, is low-power consumption mode in the most of the time at excitation interval.Excitation interval is realized by interrupt timing, and excitation arrives interval time, enters interruption immediately, starts mode of operation, now opens high frequency clock, carries out signal sampling fast and in addition data processing, flow indication and communication export.
Accompanying drawing explanation
Fig. 1 is Pulse High Voltage excitation schematic diagram in the present invention;
Fig. 2 is electromagnetic flux converter theory diagram of the present invention;
Fig. 3 is the connecting circuit figure of sensor and input instrumentation amplifier in the present invention;
Fig. 4 is low-pass filter circuit figure in the present invention;
Fig. 5 is resaistance-capacity coupling circuit figure in the present invention;
Fig. 6 is plus and blowup circuit diagram in the present invention;
Fig. 7 is power supply and single-chip microcomputer connecting circuit figure in the present invention;
Fig. 8 is crystal oscillator and single-chip microcomputer connecting circuit figure in the present invention;
Fig. 9 is reset circuit territory single-chip microcomputer connecting circuit figure in the present invention;
Figure 10 is A/D input and single-chip microcomputer connecting circuit figure in the present invention;
Figure 11 is display translation and single-chip microcomputer connecting circuit figure in the present invention;
Figure 12 is 485 communicating circuit figure in the present invention;
Figure 13 is reservoir circuit diagram in the present invention;
Figure 14 is JTAG connection line figure in the present invention;
Figure 15 is main program flow chart of the present invention;
Figure 16 is mode of operation process flow diagram of the present invention.
Embodiment
Being described further the present invention below by drawings and Examples and describing, specific embodiment described herein only for explaining technology contents of the present invention, is not intended to limit the present invention.
Fig. 1 is excitation design part in the present invention, compares and powers with industrial frequency AC 220V, and in the present invention, excitation mode has changed Pulse High Voltage excitation into by low-frequency rectangular ripple excitation, and difference is mainly reflected in:
1, exciting current reduces greatly, and when industrial frequency AC 220V powers, exciting current is 125mA at least, at most 500mA.And powered battery type electromagnetic flowmeter, according to power consumption requirements, exciting current 80mA at most, at least 20mA, in FIG, the amplitude of signal greatly reduces in reflection.
2, excitation can adjust interval time.When industrial frequency AC 220V powers, the forward and reverse output of excitation is continuous print, and after namely a direction excitation exports, export excitation in the other direction, the excitation cycle is maximum with 160ms at once.When adopting powered battery, in order to save power consumption, inconvenience frequently exports excitation, therefore after a direction output excitation, certain interval of time exports excitation in the other direction, and interval time, according to the stability state of flow, can be set to 2s, 4s, 6s, 8s, 10s, 12s.Excitation interval arranges longer, and battery-powered time is longer.
3, excitation width can adjust.When industrial frequency AC 220V powers, the most common with the excitation width of 80ms.When adopting powered battery, in order to save power consumption, being set to 60ms at most, if stream condition is stablized, also can being set to 50ms, 40ms, 30ms, 20ms.Excitation width arranges shorter, and battery-powered time is longer.
Fig. 2 is present system schematic diagram, and electromagnetic flowmeter is primarily of electromagnetic transducer and electromagnetic sensor two parts composition.Because the present invention is mainly for powered battery type converter, so be mainly described with regard to the convenor section of electromagnetic flowmeter.Utilize Faraday's electromagnetic induction law, fluid is by the measuring guide of electromagnetic flow transducer, electromagnetic transducer can be delivered to by electrode generation weak voltage signals in measuring tube both sides, electromagnetic transducer is then main control unit with single-chip microcomputer, is carried out by the signal collected nursing one's health, showing and the teletransmission that communicates.
On power supply is in fig. 2 selected, because power supply is powered to field circuit incessantly, also to other energize portions in system, therefore the present invention adopts two kinds to combine the mode combining power supply, one adopts the sub-battery ER26500 of 3 joint lithium and connects: ER26500 is the battery that a stored energy exports at 9Ah, 3.6V, and single overall dimensions are at 79x26x26mm, 3 joint ER26500 also connect overall dimensions at 79x26x52mm, and usual converter shell is enough to receive this space of points.In addition from power consumption analysis, average current is defeated to be considered at 1mA, and 1 year is 0.001x24x365=8.76Ah, and within 2 years, power consumption is at 17.52Ah, and 3 joint ER26500 also connect power consumption at 27Ah, meet the power consumption that 3.6V exports 2 years completely.It is two by after 2 every 3 joint ER26500 tandem compounds, then Parallel opertation, and output voltage is at 10.8V, and storage power consumption, at 18Ah, meets the demand of exciting current 17.52Ah.6 joint ER26500 every 3 series winding after again two two-phases also, size, at 80x60x55mm, is enough to hold this space at the bonnet of converter shell.
With reference to Fig. 3, the feeble signal that electromagnetic sensor produces will carry out signal amplification by instrumentation amplifier MAX641, and enlargement factor is 10, MAX641 is single power supply pattern, and 3.6V powers.R1, R2 are anti-phase input resistance and the homophase input resistance of differential amplifier MAX641, and RG is gain setting resistor.R1, R2, RG select high-accuracy resistance, and temperature coefficient is low, R1 and R2 gets 47K Ω; RG is 5.5k Ω.
Signal after instrumentation amplifier amplifies continues through Fig. 4 low-pass filter circuit and carries out filtering process, and adopt second-order low-pass filter circuit, operational amplifier selects the OP81 of AD company of the U.S., and adopt single electric former power supply, service area is+1.6V ~+3.6V.In addition, its minimum 700V/mV of open-loop gain, higher common-mode rejection ratio, is very applicable to battery power supply system.Circuit has homophase input structure, and OP81 presses the anatomical connectivity of voltage follower, and direct current input resistance is very high, and output resistance is very low, has very strong carrying load ability.In circuit, operational amplifier connected mode is the form of voltage follower, so passband voltage gain is 1.Wherein build-out resistor electric capacity: R1=R2=47K, C1=C2=2.2nF.
Signal is after Fig. 4 low-pass filter circuit exports, and connection layout 5 resaistance-capacity coupling circuit, after resaistance-capacity coupling circuit, most of differential mode interference in signal is isolated out by electric capacity C3, although and flow signal is faint, but pulse signal, next stage circuit can be entered by electric capacity.When pulse signal is by electric capacity C3, there is charge and discharge effect in electric capacity C3, residual charge must discharge in time, and R4 is mainly in order to discharge the residual charge on electric capacity.In order to ensure whole signalling channel high impedance over the ground, C3 gets 1uF, and R4 is 1M Ω.
Signal, after Fig. 5 resaistance-capacity coupling circuit, enters Fig. 6 plus and blowup circuit, and signal amplifies A3 and selects OP81, and enlargement factor selects 20-50 doubly herein, and at 200-500 doubly, signal enters follow-up AD and gathers whole like this signalling channel enlargement factor.R5, R6 are amplifier homophase input resistance and anti-phase input resistance, and R7 is gain resistor.R6 gets 5K Ω, and R7 gets 100K Ω, and enlargement factor is at about 20 times.The parameter of R5 determines the end of oppisite phase input impedance of balance A3 as far as possible, gets 1K Ω; C4 is integrating capacitor, and parameter gets 2.2nF, can suppress high frequency noise further.
Signal enters Fig. 2 interface microcontroller circuit after the conditioning of Fig. 2 signal conditioning circuit, electromagnetic flux converter take single-chip microcomputer as core microprocessors, select the single-chip microcomputer of the MSP430 series of TIX as microprocessor in the present invention, low power dissipation design can be carried out and facilitate powered battery; Can use up to the low frequency collocation of the high frequency clock of 8M and 32K, signal transacting can be carried out timely fast, again can the saving power consumption of maximal efficiency.
As shown in Figure 7, utilize the low-power consumption feature of MSP single-chip microcomputer, operating voltage is between 1.8 ~ 3.6V for the connecting circuit of single-chip microcomputer and power supply.So adopt lithium battery as power supply unit.Add a 0.1uf electric capacity at the power input of single-chip microcomputer and carry out filtering, reduce power supply disturbance.
As shown in Figure 8, in the present invention, crystal oscillator adopts 8M high frequency crystal oscillator and 32.768K low frequency crystal oscillator dual-purpose, use low frequency crystal oscillator to save power consumption under low-power consumption mode, enable high frequency crystal oscillator under mode of operation to carry out rapidly signal transacting and display refreshing.
Reset circuit as shown in Figure 9, adopts supply voltage monitor chip CAT823 to control the output that resets.When 3.6V power supply instability or the threshold voltage lower than voltage monitor being detected, voltage monitor output low level reset single-chip microcomputer.CAT823, except having function of voltage monitoring, also has watchdog reset to export.Export house dog clock by single-chip processor i/o mouth P6.3 in design, if single-chip microcomputer operation troubles enters endless loop, house dog tick interrupt, then CAT823 exports reset signal, restarts single-chip microcomputer work.
The existing I/O function of P6 port of MSP430F169 single-chip microcomputer, also has AD input function.As shown in Figure 10, in program, the P6.7 of P6 port is inputted as simulating signal sampling.
Output display selects LCD LCD display output, and as shown in figure 11, the P4 port of single-chip microcomputer exports as display data, and the P5.0-P5.4 of P5 port controls to export as display, and the P2.4-P2.7 of P2 port is as key-press input.
For adapting to the developing direction of meter communication networking, powered battery type electromagnetic transducer carries out data exchange by RS485 bus and host computer.Select SP3485E as communication chip.SP3485E be a can the 3.3V low-power consumption Half-duplex transceiver of powering, meet the requirement of RS485 and RS422 serial protocol completely.In single-chip microcomputer, P3.4, P3.5 are I/O mouth as shown in figure 12, are again communication ports.In design, single-chip microcomputer carries out communication data transmitting-receiving control by port P30.Time idle, P30 is set low level by single-chip microcomputer, and now SP3485E chip is in data receiving state: if bus exists 485 signals, convert 232 signals to, enter single-chip microcomputer by P35 by SP3485E.After single-chip microcomputer receives data-signal, process by analysis, if judge to need return data, then set high by P30 level, data enter SP3485E by P34, are entering 485 buses.
FM24CL04 selected by storer, is mainly used in storing total amount information, prevents total amount information dropout after converter power-off.During circuit connects as shown in fig. 13 that, WP is chip enable end, effectively low, therefore ground connection, keep often imitating.During work, the P56 port output clock of single-chip microcomputer is held to the SCL of FM24CL04, and P57 port exports data and holds to the SDA of FM24CL04, R501 and R502 is the pull-up resistor of clock line and data line respectively, and data storage can be allowed more reliable.
Be JTAG connection line as shown in figure 14, the TMS of jtag interface connects the Pin56 of single-chip microcomputer, the Pin57 that TCK connects, the Pin55 that TDI connects, the Pin58 that test lead connects, the Pin54 that TDO connects, the Pin11 that TX connects, the Pin22 that RX connects.
In Design of System Software, in order to save power consumption, ensureing that battery has enough tenure of use, is low-power consumption mode in the most of the time at excitation interval.Excitation interval is realized by interrupt timing, and excitation arrives interval time, enters interruption immediately, starts mode of operation, now opens high frequency clock, carries out signal sampling fast and in addition data processing, flow indication and communication export.
Figure 15 is system main program flow chart, after system brings into operation, first carries out MCU initialization, then LCD initialization, after completing, interrupts unlatching and enters low-power consumption mode, after excitation arrives interval time, enter mode of operation, will return to low-power consumption mode after data processing.Figure 16 is system operating mode process flow diagram, after entering mode of operation, first opens high frequency clock, then excitation exports, and after having exported, AD starts, carry out Data Analysis Services by processor again, by LCD display translation, then will export through 485 communication bus communications after data processing completes.
Claims (9)
1. low power consumption electromagnetic flow converter, mainly comprise field circuit, power supply, signal conditioning circuit, interface microcontroller circuit, it is characterized in that in described field circuit, excitation mode is Pulse High Voltage excitation, the described power acquisition mode of the sub-battery combination of two kinds of lithiums, described signal conditioning circuit comprises instrumentation amplifier, low-pass filter circuit, resaistance-capacity coupling circuit and plus and blowup circuit, described interface microcontroller circuit comprises single-chip microcomputer, power circuit, reset circuit, crystal oscillator, A/D inputs, display translation, 485 communications export, memory circuitry, JTAG debugging interface.
2. low power consumption electromagnetic flow converter according to claim 1, is characterized in that: the exciting current scope of described Pulse High Voltage excitation is 20 ~ 80mA; Excitation interval can be set to 2s, 4s, 6s, 8s, 10s, 12s, and excitation interval arranges longer, and battery-powered time is longer; Excitation width can be set to 60ms, 50ms, 40ms, 30ms, 20ms, and excitation width arranges shorter, and battery-powered time is longer.
3. low power consumption electromagnetic flow converter according to claim 1, is characterized in that: the described power acquisition sub-battery combination mode of two kinds of lithiums, and the first saves the sub-battery ER26500 of lithium and connects by 3, meet the power consumption that 3.6V exports 2 years; It two is by after 2 every 3 joint ER26500 tandem compounds, Parallel opertation again, output voltage is at 10.8V, storage power consumption is at 18Ah, meet the power consumption demand of when exciting current is maximum 80mA 2 years, and converter shell is enough to receive this battery combination, power supply 3.6V is exported and 10.8V output separately consideration, reduce battery loss further.
4. low power consumption electromagnetic flow converter according to claim 1, is characterized in that: described instrumentation amplifier selects the instrumentation amplifier MAX641 of MAXIM company of the U.S., and external gain resistor gets 5.5K, and enlargement factor is 10.
5. low power consumption electromagnetic flow converter according to claim 1, it is characterized in that: described low filtering circuit adopts second-order low-pass filter circuit, operational amplifier selects the OP81 of AD company of the U.S., connected mode is the form of voltage follower, the resistance capacitance that coupling group is identical, resistance is 47K, and electric capacity is 2.2nF.
6. low power consumption electromagnetic flow converter according to claim 1, is characterized in that: in described resaistance-capacity coupling circuit, and be positioned in the middle of low filtering circuit and plus and blowup circuit, capacitance selection 11uF, resistance is 1M Ω.
7. low power consumption electromagnetic flow converter according to claim 1, it is characterized in that: in described plus and blowup circuit, the OP81 of AD company of the U.S. selected by amplifier, enlargement factor is 20-50 times, and at 200-500 doubly, signal enters follow-up AD and gathers whole signalling channel enlargement factor; Amplifier homophase input resistance is 1K Ω, amplifier anti-phase input resistance is 5K Ω, gain resistor is 100K Ω, and integrating capacitor is 2.2nF.
8. low power consumption electromagnetic flow converter according to claim 1, it is characterized in that: in described interface microcontroller circuit, described single-chip microcomputer selects the single-chip microcomputer of the MSP430 series of TIX as microprocessor, add a 0.1uf electric capacity at the power input of single-chip microcomputer in described power circuit design and carry out filtering, described reset circuit adopts supply voltage monitor to control the output that resets, described crystal oscillator adopts 8M high frequency crystal oscillator and 32.768K low frequency crystal oscillator dual-purpose, described display translation adopts liquid crystal display LCD as the display panel of product, described communication exports carries out data exchange by RS485 bus and host computer, FM24CL04 selected by described storer.
9. low power consumption electromagnetic flow converter according to claim 1, is characterized in that: in Design of System Software, and in order to save power consumption, ensureing that battery has enough tenure of use, is low-power consumption mode in the most of the time at excitation interval.Excitation interval is realized by interrupt timing, and excitation arrives interval time, enters interruption immediately, starts mode of operation, now opens high frequency clock, carries out signal sampling fast and in addition data processing, flow indication and communication export.
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Application publication date: 20151125 |