CN101398405B - Water electric conductivity intelligent sensor - Google Patents
Water electric conductivity intelligent sensor Download PDFInfo
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- CN101398405B CN101398405B CN2008102260582A CN200810226058A CN101398405B CN 101398405 B CN101398405 B CN 101398405B CN 2008102260582 A CN2008102260582 A CN 2008102260582A CN 200810226058 A CN200810226058 A CN 200810226058A CN 101398405 B CN101398405 B CN 101398405B
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Abstract
The invention discloses an intelligent sensor for the electrical conductivity of water quality. The sensor comprises a temperature-conductivity probe used for sensing the temperature and the electrical conductivity of the water; a signal conditioning module which is connected with the temperature-conductivity probe, forms a sensing circuit with the temperature-conductivity probe and carries out filtering and amplification to an output signal; a microprocessor which is connected with the signal conditioning module, is used for digitizing the signal input by the signal conditioning module and adopts IEEE1451 standards to carry out the calibration and alignment of channels; a bus interface module which is connected with the microprocessor and is used for the functions of networking and plugging and playing; and a power module which supplies power to the circuits of all parts of the sensor under the control of the microprocessor and realizes the characteristic of low power consumption. The invention can eliminate the polarization effect of the probe, has pollution resistance, large measuring range and low price, and is characterized by the functions of self alignment and compensation, self diagnosis and plugging and playing and high integrity.
Description
Technical field
The present invention relates to the water quality detection field, particularly relate to a kind of water electric conductivity intelligent sensor that detects the water body conductivity.
Background technology
Electrical conductivity of water has reflected the amount of its contained mineral acid, alkali, salt, and receives Influence of Temperature, and this index is usually used in inferring the total concentration or the salt content of water intermediate ion.Therefore dissimilar water have different electrical conductivity, and monitoring and control influence the water quality parameter that water body environment normally carries out and has important in theory and realistic meaning.
China's water quality online auto monitoring technology is started late, and at present domestic electric pole type conductivity probe all is two electric pole types generally, in case that its shortcoming is a detecting head surface is contaminated, will directly influence measurement result.And in monitoring water environment, conductivity meter probe need place water environment (river, river, lake, sea) for a long time, and some planktonic organisms in the water or dirt may be attached to detecting head surfaces, and this problem of intensive aquaculture is even more serious, causes that the result's is inaccurate.And electrode is a galvanic electrode in this two electrode technology measuring processes, is again voltage electrode.In fact, as long as have electric current to flow through solution on the electrode, and will produce polarizing voltage on the surface of contact of electrode, measurement will produce certain error.
At present, some companies develop four electrode electricity conductances probes both at home and abroad, and the flow through electric current of voltage electrode of four electrode electricity conductances probe is minimum, and to adopt frequency be the sine-wave excitation electric current of 10KHz, can effectively prevent electrode polarization; And can reduce the pollution caused measuring error of water body to probe.The model that HANNA company produces is HI7635 and two kinds of industrial Fourth Rings of HI7636 conductance electrode, this electrode antipollution, and range is big, has higher precision, the supporting industry on-line measurement, but do not have intelligently, need the special transmission device table of outfit.Domestic and international conductivity sensor ubiquity cost height, function singleness, integrated level and the low problem of intelligent degree.
The sensor that the measuring water quality conductivity is adopted is an electrochemical analytical instrument; Because the electrochemical analytical instrument complicacy does not have as yet to relate in the patent documentation of having announced at present and can realize that the water quality parameter monitoring has the content of the intelligent sensor device of field bus communication function.
Continuous development along with control, computing machine, communication and network; Measure and control instrument just develops towards intelligent, networking, integrated direction; Develop a kind of water electric conductivity intelligent sensor; Make it not only integrated advanced person's Fourth Ring electrode probe, modulate circuit is sent in the change of integrated field bus communication function simultaneously, and this sensor is with a wide range of applications and market outlook.
Summary of the invention
It is big to the purpose of this invention is to provide a kind of elimination probe polarization effect, antipollution, measurement range; Low price, and the water electric conductivity intelligent sensor that is used to detect the water body conductivity with self calibration compensation, self diagnosis, plug and play, managing power consumption function integration characteristics.
For achieving the above object, technical scheme of the present invention provides a kind of water electric conductivity intelligent sensor, and said sensor comprises: the temperature conductivity probe is used for the temperature and the conductivity of sensing water body; The signal condition module is connected with said temperature conductivity probe, constitutes sensing circuit with said temperature conductivity probe, and the output signal is carried out filtering and amplification; Microprocessor is connected with said signal condition module, is used for signal digitalized to the input of said signal condition module, and adopts the IEEE1451 standard to carry out passage and demarcate and calibration; Bus interface module is connected with said microprocessor, is used for networking and plug-and-play feature; Power module is given said sensor each several part circuit supply under the control of microprocessor, realize the low-power consumption characteristics.
Wherein, said temperature conductivity probe comprises incorporate temp probe and conductivity probe.
Wherein, said conductivity probe comprises: insulator, said insulator are provided with two galvanic electrodes, between said galvanic electrode, are provided with two voltage electrodes, and said insulator exterior is provided with insulation protective jacket.
Wherein, said ac electrode also is connected with sinusoidal current and constant-current circuit in turn, and said sinusoidal current is used to produce sine-wave current, and said constant-current circuit is used for the steady current waveform.
Wherein, said signal condition module comprises: peak-detector circuit is used to obtain the peak signal of said conductivity signal.
Wherein, give microprocessor power supply after the said power module voltage stabilizing, controlled to said sensor each several part circuit supply by microprocessor.
Wherein, the STIM module of the embedded IEEE1451 standard of said microprocessor module has the TEDS form, realizes conductivity measurement demarcation and self compensation function, directly exports quantities.
Wherein, said bus interface module adopts the RS485 bus on hardware is realized, on software protocol, supports the IEEE1451 standard to realize plug-and-play feature.
Technique scheme has following advantage:
1, the present invention uses custom-designed Fourth Ring conductance electrode, and this electrode performance has a series of advantage than the widely used two electrode electricity conductances probe in market.It can effectively prevent electrode polarization, prolongs electrode life, guarantees the accuracy of measurement data, reduces the pollution caused measuring error of water body to probe.
2, the present invention is owing to be integrated into a total temperature conductivity probe with temp probe and conductivity probe; Can carry out temperature and conductivity measurement to a measuring point simultaneously thus; Guarantee locational homogeneity in measured point and parameter real-time in time, adapted to the detection requirement of automatically-monitored technology.
3, the present invention adopts singlechip technology and Electrochemical Measurement Technology to combine, and has simplified hardware circuit, has expanded measurement function, and adopts the method for self compensation of IEEE1451.The simultaneity of two parameter acquiring is guaranteed, and through embedded compensation method, improves measuring accuracy.
4, the present invention's sensor output 4-20mA analog current standard signal pattern that discards tradition limit the problem of measurement range because of resolution is low, and adopts digital bus transmission, has expanded measurement range.
5, the present invention adopts the networked smart sensor based on the IEEE1451 standard, utilizes STIM module and electronic data sheet to carry out " plug and play " function that realizes sensor with the setting of actuator parameter of reading in of sensing data.And support the RS485 bus to connect.
6, the present invention supports low power operation, and has energy monitoring and automatic diagnostic function; Realize microminiaturization and integrated design, equipment good waterproof performance, reliability height.
Description of drawings
Fig. 1 is the structural representation of a kind of water electric conductivity intelligent sensor of the embodiment of the invention;
Fig. 2 is that the structure of a kind of conductivity probe of the embodiment of the invention is an one;
Fig. 3 is a kind of voltage-to-current four-end method circuit theory diagrams of the embodiment of the invention;
Fig. 4 is the circuit theory diagrams of a kind of sinusoidal current of the embodiment of the invention;
Fig. 5 is the circuit theory diagrams of a kind of constant-current circuit of the embodiment of the invention;
Fig. 6 is the circuit theory diagrams of a kind of peak-detector circuit of the embodiment of the invention;
The program flow diagram that a kind of water electric conductivity of Fig. 7 embodiment of the invention detects.
Wherein, 1: insulator; 2: voltage electrode; 3: galvanic electrode; 4: insulation protective jacket; 5: temp probe; 6: the water level viewport; 7: O-ring seal; 8: integrated circuit; 9: quad.
Embodiment
Below in conjunction with accompanying drawing and embodiment, specific embodiments of the invention describes in further detail.Following examples are used to explain the present invention, but are not used for limiting scope of the present invention.
See also shown in Figure 1ly, Fig. 1 is the hardware designs general principles figure of water electric conductivity intelligent sensor of the present invention.For the integrated level of enhanced system, microprocessor has adopted the MSP430 of American TI Company as main control chip.Certainly, also can select for use other can realize the chip of data processing, control.
Wherein, sensor sensing partly is one and is linked to be the temperature conductivity probe of forming for one by temp probe and conductivity probe; The conductivity probe structure is as shown in Figure 2, and it adopts current-voltage Fourth Ring electrode method, comprises two galvanic electrodes and two voltage electrodes; Measuring principle is to apply an AC signal and pass through electric current at two galvanic electrodes; In fluid media (medium), set up electric field, and induce voltage on two voltage electrodes, through measuring the potential drop between induction electrode; Draw the conductivity of corresponding water body, because the potential drop between induction electrode is directly proportional with the conductivity of solution.Potential drop between this electrode induction electrode and electrode surface pollute or circuitous resistance has nothing to do; Thereby avoided influence because of electrode surface pollution or passivation; Eliminate polarisation error, be applicable to various length cables or the like, and these just two electrode electricity conductances probe the shortcoming that can't eliminate.So-called current-voltage Fourth Ring electrode method is meant that test macro comprises 2 current terminals and 2 voltage ends.The annular electrode is fixed on the outside surface of cylindrical insulator 1, and two electrodes in outside are galvanic electrode 3, and two middle electrodes are voltage electrode 2.Whole column type insulator is immersed in the WS to be measured together with four electrodes fully.There is the insulation protective jacket 4 of a tubular outside of electrode, and electrode is had the effect of protection, can prolong electrode life.Temp probe 5 is arranged on the lowermost end of insulator 1.In addition, insulator 1 is used to observe water level also being provided with water level viewport 6 above a galvanic electrode 3 topmost.The upper end of insulator 1 is connected with integrated circuit 8 through O-ring seal 7, integrated circuit such as microprocessor, bus interface module, signal condition module in the integrated circuit 8.Integrated circuit 8 is drawn through a quad 9, and quad 9 connects power supply, ground connection, RS485 both positive and negative polarity.Apply an AC signal and pass through electric current at two galvanic electrodes, in fluid media (medium), setting up electric field has two voltage electrodes to respond to the voltage of generation.Use the purpose of AC signal to be to eliminate galvanic polarization, improve the accuracy of measuring.Through detecting the electric potential difference of 2 voltage ends, just can converse the conductivity of dielectric material (water body).Connect temperature and conductivity probe simultaneously, become synchronously and send the collection two paths of signals, utilize the automatic calibrated channel difference of microprocessor; Improve the consistance of electric conductivity intelligent sensor; Utilize the temperature signal that obtains synchronously simultaneously, compensate conductivity measurements automatically, improve the conductivity measurement precision.
The input signal of galvanic electrode is a sinusoidal signal.The generation circuit of pumping signal comprises the sinusoidal current and the constant-current circuit of the sinusoidal signal generation that connects successively.Sinusoidal current and constant-current circuit are respectively like Fig. 4, shown in Figure 5.The used chip of sinusoidal current is that integrated function generator 8038,8038 can be exported sawtooth wave, square wave, and sinusoidal wave, four kinds of different waveforms of triangular wave, what use is sinusoidal wave here.Oscillation frequency the f=0.3/ [(R of circuit
10+ 1/2R
P1) C].Regulate R
P1, R
P2Can make sinusoidal wave distortion reach comparatively ideal degree.The purpose of constant-current circuit is to export stable current waveform.Make the constant current source working stability, sampling resistor R52 need adopt high performance resistance, and amplifier adopts high-gain, low drift, low noise and the good operational amplifier of frequency characteristic.T1, T2 adopt high span and little penetrating current and the good triode of frequency characteristic.
Because the input of the electric current utmost point is sine wave signal, the signal that voltage pole detects also is a sinusoidal signal, therefore, before carrying out the AD conversion, must handle earlier this voltage signal.It is to transform to standard signal to of different nature, different input resistance signal through electronic technology such as amplification, filtering that the signal condition module mainly acts on.Signal condition module of the present invention comprises peak-detector circuit.For example exciting current is the sinusoidal current of 10KHz, and the signal of probe output must be again through amplifying behind the process peak detection.Peak-detector circuit adopts the diode envelope to survey the peak method, through this circuit, detects sinusoidal wave peak value, and last signal is input to amplifying circuit signal is amplified.Peak-detector circuit is as shown in Figure 6, utilizes the method for diode wave-shape amplitude detection, obtains the positive peak of signal.Analog to digital converter (ADC, Analog to Digital Converter) in the direct current peak voltage signal input MSP430 sheet is realized digitizing.The networked smart sensor of IEEE1451 standard (IEEE Standard for a Smart Transducer Interface for Sensors andActuators); It comprises intelligence sensor interface module (STIM; Smart Transducer Interface Module) promptly through sensor electronic data sheet (TEDS, Transducer Electronic Data Sheet) thus carry out " plug and play " function that realizes sensor with the setting of parameter of reading in of sensing data.Electric conductivity intelligent sensor of the present invention is realized the STIM module of IEEE1451.The STIM core is to include a sensor electronic data sheet (TEDS) and an intelligent bus interface of supporting the IEEE1451 standard.Wherein TEDS is can be the demarcation to sensor, and the work such as correction of data are converted into the routine mission that microprocessor is born, and it is the basis of intelligent functions such as intelligence sensor self calibration, self compensation.Bus form: the present invention does not adopt the TII interface among the IEEE1451.2, uses RS485 bus more widely but adopt.EBI has connected hot-swappable circuit, can realize the hot-swappable of intelligence sensor interface module.The upgrading of sensor electronic data sheet content and renewal for ease, system adopts asynchronous serial port to download Flash in the sheet of read-only electronic data sheet TEDS to MSP430.Use the storage space of the interior Flash of MSP430 sheet as variable TEDS.
In this instance, the temp probe 5 inductive head models that adopted are thermal resistance, range: 0-100 ℃, and precision: 0.2 ℃.
Among the present invention, the model that microcontroller adopts is the MSP430 series monolithic IC chip of American TI Company.The MSP430 series monolithic is 16 super low power consuming single chip processors of TI company research and development, is fit to very much the low occasion of various power requirements, is particularly suitable for the occasion or the handheld device of battery applications.This single-chip microcomputer is under the clock condition of 1.8V-3.6V voltage, 1MHz, and the power consumption electric current is between 0.1-400 μ A; Contain P
0-P
6Totally 7 I/O mouths, 2 timer TimerA, Timer B, 1 house dog, the ROM of inner integrated 2K and the RAM of 60K can 100,000 overprograms; The RAM of MSP430 series ROM and 60K can 100,000 overprograms; The MSP430 series monolithic is the product of technical grade, and operating ambient temperature is-40 ℃-+85 ℃; And the general unit price of MSP430 series monolithic has only dozens of yuan.This shows that the cost performance of MSP430 series monolithic is high, can satisfy the needs of system development fully.
The MSP430 single-chip microcomputer has 12 8 road A/D converter functions and DMA control module, can be respectively systematic sampling circuit and tcp data segment and adopt, and makes that the hardware circuit of system is more integrated, miniaturization.And the result after the conversion carries out in microcontroller inside, carries out match according to influencing each other between temperature, the conductivity, eliminate sensor self because working environment changes the variation that causes through the method for software, so data is objective and accurate.
Aspect STIM, mainly realize the TEDS Data Structure Design.Wherein TEDS is one of core content of IEEE1451 standard, and it is the form in a kind of STIM of being embedded in module.Its complete definition STIM module various piece logical message storage and interoperability form, also be the basic data structure that each channel sensor data of STIM are proofreaied and correct.A standard compliant sensor self has internal information, comprising: the limit of manufacturer, data code, sequence number, use and calibration factor etc.When system powered on, these data can offer NCAP (Network Capable Application Process, network adapter) and other part of system.
TEDS is divided into 8 addressable parts, and wherein the electronic data sheet of two indispensabilities is: Meta-TEDS and Channel-TEDS, all the other can be selected as required.Meta-TEDS describes the port number of TEDS information, data structure and support and the overall information of relevant STIM such as passage limit time parameter; Each STIM passage comprises 1 Channel-TEDS, mainly is used for to each passage specifying information, as describing the passage physical attribute, correcting the timing information of type, return data type and form passage etc.Owing to use the sensor self-correcting function, the Calibration-TEDS electronic data sheet is also used in invention.The storage space that general TEDS takies is less, is to deposit the optimal place of TEDS with FLASH in the single-chip microcomputer.
Aspect EBI, carry out communication through bus interface module and host computer or miscellaneous equipment, the present invention has designed the RS485 bus and has connected.Introduce being connected and communication of single-chip microcomputer MSP430 and RS485 interface chip SN75LBC184 below.
Because microprocessor MSP430 single-chip microcomputer can not directly connect the RS485 interface, therefore also must add the change-over circuit of RS485.A kind of RS485 interface chip SN75LBC184 chip that RS485 change-over circuit design Selection American TI Company is produced.
It adopts single power supply Vcc SN75LBC184, and voltage can both operate as normal in+3-+5.5V scope.It is compared with common RS485 chip, the impact that it not only can anti lightning but also can bear the static voltage up to 8kV.Therefore, it can significantly improve and prevent that thunder and lightning from damaging the reliability of device.The scene more abominable to some environment, can be directly and transmission line join and without any need for adding protecting component.This chip also has a unique design, and when input end was opened a way, it was output as high level, in the time of can guaranteeing that like this receiver input end cable has open fault, does not influence the operate as normal of system.In addition, its input impedance is 2 times (>=24K Ω) of the input impedance of RS485 standard, so can on bus, connect 64 transceivers.Chip internal has designed the limit slope drive, makes the output signal edge can be not steep excessively, makes on the transmission line and can not produce too much high fdrequency component, produces thereby effectively control electromagnetic interference (EMI).
Single-chip microcomputer of the present invention is communicated by letter with RS485 interface chip SN75LBC184's; Select the COM2 interface of PC for use; But 9 ports of COM2 only use wherein RTS, RXD, TXD and four ports of GND; To constitute easy four line communication lines, the photoelectrical coupler TLP521 of quaternity lets has not had getting in touch of electricity fully between single-chip microcomputer and the SN75LBC184 chip, has improved the reliable character of work.Basic functional principle: when single-chip microcomputer P3.4=0, the lumination of light emitting diode of photoelectrical coupler, the phototriode conducting, output HIGH voltage (+5V), choose the DE end of RS485 interface chip, allow to send.When single-chip microcomputer P3.4=1, the light emitting diode of photoelectrical coupler is not luminous, not conducting of phototriode, and output LOW voltage (0V) chooses the RE of RS485 interface chip to hold, and allows to receive.The R end (receiving end) of SN75LBC184 and the principle of D end (transmitting terminal) and above-mentioned similar.Consider the special circumstances (like the breakdown short circuit of RS485 chip of a certain node) of circuit; For preventing that the communication of other extension sets is affected in the bus; At the signal output part of SN75LBC184 connected resistance R 1 and the R5 of 2 20 Ω, hardware fault of the present invention so just can not make the communication of whole bus be affected.In the site operation of application project; Because communications carrier is twisted-pair feeder, its characteristic impedance is about 120 Ω, so during line design; Should meet a build-out resistor R3 with 120 Ω at the top of RS485 Network transmission line with terminal, with the reflection of transmission signals on the minimizing circuit.
In addition, the water electric conductivity intelligent sensor of present embodiment also comprises power module, and power module is connected with microprocessor, and this module is directly imported supply voltage, through the electric resistance partial pressure method, satisfies the requirement of A/D input voltage, for the power supply situation self diagnosis provides foundation.In addition; Also be provided with power management module between power module and the microprocessor: improve input voltage accommodation through mu balanced circuit on the one hand; Strengthen the stability of chip voltage; Cooperate with microprocessor on the other hand, realize pulsed power supply, electric conductivity intelligent sensor is moved under super low-power consumption each module of hardware circuit.
Software section: whole software part process flow diagram is as shown in Figure 7.The power-up initializing hardware state accesses the TEDS parameter that is stored among the FLASH, and self-diagnostic program is measured signals such as supply voltage, probe interface, judges whether to exist fault.In order to reduce power consumption, microprocessor control peripheral hardware gets into dormant state afterwards, and wait task triggers.Under the request of timing triggering collection, carry out the A/D data acquisition with and call that STIM demarcates and calibration procedure, temp probe realizes that conductivity demarcates and temperature compensation.The aspect receives the outer setting parameter, triggers the request of measuring, reading parameter and measurement result through serial line interface in addition.
The above only is a preferred implementation of the present invention; Should be pointed out that for those skilled in the art, under the prerequisite that does not break away from know-why of the present invention; Can also make some improvement and retouching, these improvement and retouching also should be regarded as protection scope of the present invention.
Claims (7)
1. a water electric conductivity intelligent sensor is characterized in that, said sensor comprises:
The temperature conductivity probe is used for the temperature and the conductivity of sensing water body;
The signal condition module is connected with said temperature conductivity probe, constitutes sensing circuit with said temperature conductivity probe, and the output signal is carried out filtering and amplification;
Microprocessor is connected with said signal condition module, is used for signal digitalized to the input of said signal condition module, and adopts the IEEE1451 standard to carry out passage and demarcate and calibration;
Bus interface module is connected with said microprocessor, is used for networking and plug-and-play feature;
Power module is given said sensor each several part circuit supply under the control of microprocessor, realize the low-power consumption characteristics;
Said temperature conductivity probe comprises incorporate temp probe and conductivity probe, and said conductivity probe comprises:
Insulator, said insulator are provided with two galvanic electrodes, between said galvanic electrode, are provided with two voltage electrodes.
2. water electric conductivity intelligent sensor as claimed in claim 1 is characterized in that said insulator exterior is provided with insulation protective jacket.
3. water electric conductivity intelligent sensor as claimed in claim 1 is characterized in that said galvanic electrode also is connected with sinusoidal current and constant-current circuit in turn, and said sinusoidal current is used to produce sine-wave current, and said constant-current circuit is used for the steady current waveform.
4. water electric conductivity intelligent sensor as claimed in claim 1 is characterized in that, said signal condition module comprises:
Peak-detector circuit is used to obtain the peak signal of said conductivity signal.
5. water electric conductivity intelligent sensor as claimed in claim 1 is characterized in that, gives microprocessor power supply after the said power module voltage stabilizing, controlled to said sensor each several part circuit supply by microprocessor.
6. water electric conductivity intelligent sensor as claimed in claim 1 is characterized in that, the STIM module of the embedded IEEE1451 standard of said microprocessor module has the TEDS form, realizes conductivity measurement demarcation and self compensation function, directly exports quantities.
7. water electric conductivity intelligent sensor as claimed in claim 1 is characterized in that, said bus interface module adopts the RS485 bus on hardware is realized, on software protocol, supports the IEEE1451 standard to realize plug-and-play feature.
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