CN106291119B - A kind of conductivity measuring method, circuit and conductance instrument - Google Patents
A kind of conductivity measuring method, circuit and conductance instrument Download PDFInfo
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- CN106291119B CN106291119B CN201610583932.2A CN201610583932A CN106291119B CN 106291119 B CN106291119 B CN 106291119B CN 201610583932 A CN201610583932 A CN 201610583932A CN 106291119 B CN106291119 B CN 106291119B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/22—Measuring resistance of fluids
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Abstract
The present invention is suitable for solution fields of measurement, provides a kind of conductivity measuring method, this method comprises: generating ac square wave signal；Amplify ac square wave signal；One end that amplified square-wave signal is passed through to conducting wire connection electrode generates an alternating electric field in electrolyte solution；The faint ac current signal that electrolyte solution results from conductivity meter electrode both ends in alternating electric field is detected by the other end of electrode；Faint ac current signal is transformed into ac voltage signal；It rectified, filtered to obtain steady dc voltage signal；D. c. voltage signal is converted to corresponding conductivity to show.The present invention judges the signal detected, to control the frequency of relay switching input square-wave signal, amplitude and detection range, reaches the control to the software cost, hardware cost of instrument, extends electrode life.
Description
Technical field
The invention belongs to solution fields of measurement more particularly to a kind of conductivity measuring methods, circuit and conductance instrument.
Background technique
Conductivity is the electricity physical quantity of a measurement aqueous conductive ability, is the inverse of resistivity, generally uses Greece
Alphabetical κ indicates (or γ), the ρ of κ=1/.In general sense, the measurement temperature of conductivity is normal temperature (25 DEG C).In liquid
In, the conductivity of water is to measure an important indicator of water quality.The measurement of conductivity has in daily production and life compares
It is widely applied, the conductivity for such as measuring drinking water is used to detect the concentration of contained electrolyte in water, for measuring under littoral
The conductivity of water checks that its underground water receives the Invasive degree of seawater, can also distinguish gutter oil with the mode of measurement conductivity
Deng.
In recent years, with microelectronics industry cleaning treatment, drinking pure water, medicinal distilled water, biological products water, power
Boiler and Generator Set cooling water demand sharply increase, and more and more products, technology start to lead medium
Electrical property, composition require to provide accurately analysis and evaluation, and higher want is proposed in terms of real-time, accuracy
It asks.
Two electrode methods of domestic most conductivity meters detect at present, however, detecting conductivity with two electrode methods, no
It can automatically switch square-wave signal frequency and square-wave signal amplitude, and long-time output drive signal, influence electrode working life.
Summary of the invention
The embodiment of the present invention is designed to provide a kind of conductivity measuring method, it is intended to solve it is existing with two electrode methods come
Conductivity is detected, square-wave signal frequency and square-wave signal amplitude, and long-time output drive signal can not be automatically switched, is influenced
The problem of electrode working life.
The embodiments of the present invention are implemented as follows, and a kind of conductivity measuring method, the method includes the following steps:
Generate ac square wave signal；
Amplify the ac square wave signal, to improve load capacity；
One end that amplified square-wave signal is passed through to conducting wire connection electrode generates an alternation electricity in electrolyte solution
?；
The faint exchange that electrolyte solution results from electrode both ends in alternating electric field is detected by the other end of electrode
Current signal；
Faint ac current signal is transformed into ac voltage signal；
The ac voltage signal is rectified, is filtered, steady dc voltage signal is obtained；
The d. c. voltage signal is converted to corresponding conductivity to show.
It is a further object of the present invention to provide a kind of electrical conductivity measurement circuit, the circuit includes:
Excitation generates unit, for generating ac square wave signal as excitation；
Amplifying unit, for amplifying the ac square wave signal, the input terminal of the amplifying unit and the excitation are generated
The excitation output end of unit connects；
Buffer cell, for improving load capacity, the output end of the input terminal of the buffer cell and the amplifying unit
Connection, the output end of the buffer cell pass through one end of conducting wire connection electrode, and an alternation electricity is generated in electrolyte solution
?；
I/V converting unit detects electrolyte solution for the other end by electrode and results from electrode in alternating electric field
The ac current signal at both ends, and faint ac current signal is transformed into ac voltage signal, the I/V converting unit
Input terminal is connected by the other end of conducting wire and electrode；
Rectification filtering unit generates steady dc voltage letter for being rectified, being filtered to the ac voltage signal
Number, the input terminal of the rectification filtering unit is connect with the output end of the I/V converting unit；
Conductivity converting unit, for the d. c. voltage signal to be converted to corresponding conductivity, the conductivity turns
The input terminal for changing unit is connect with the output end of the rectification filtering unit；
Display unit, for showing conductivity, the input terminal of the display unit is defeated with the conductivity converting unit
Outlet connection.
It is a further object of the present invention to provide a kind of conductance instruments using above-mentioned electrical conductivity measurement circuit.
The embodiment of the present invention judges the signal detected by PLC, to control relay switching input square wave
Frequency, amplitude and the detection range of signal, reach the control to the software cost, hardware cost of instrument, no matter is obtained data
It is the linearity or precision, or in the case where automatically switching and not switching, has all reached the other requirement of technical grade, and
Extend electrode life.
Detailed description of the invention
Fig. 1 is the scatter plot of existing non-automatic switching range；
Fig. 2 is the scatter plot after automatic switching range of the embodiment of the present invention；
Fig. 3 is the flowage structure figure of conductivity measuring method provided in an embodiment of the present invention；
Fig. 4 is the structure chart of electrical conductivity measurement circuit provided in an embodiment of the present invention；
Fig. 5 is the exemplary circuit structure chart of electrical conductivity measurement circuit provided in an embodiment of the present invention.
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to the accompanying drawings and embodiments, right
The present invention is further elaborated.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, and
It is not used in the restriction present invention.As long as in addition, technical characteristic involved in the various embodiments of the present invention described below
Not constituting a conflict with each other can be combined with each other.
The embodiment of the present invention judges the signal detected by PLC, to control relay switching input square wave
Frequency, amplitude and the detection range of signal, reach the control to the software cost, hardware cost of instrument, extend electrode use
Service life.
Fig. 3 shows the flowage structure of conductivity measuring method provided in an embodiment of the present invention, for ease of description, only shows
Part related to the present invention is gone out.
As an embodiment of the present invention, this method includes the following steps:
In step s101, ac square wave signal is generated；
In embodiments of the present invention, which passes through PLC (Programmable Logic as excitation
Controller, programmable logic controller (PLC)) it generates, duty ratio 50%, frequency is 800Hz -4000Hz.
In step s 102, amplify ac square wave signal, to improve load capacity；
In step s 103, one end that amplified square-wave signal is passed through to conducting wire connection electrode, in electrolyte solution
Generate an alternating electric field；
In step S104, electrolyte solution is detected by the other end of electrode and results from conductivity meter in alternating electric field
The faint ac current signal at electrode both ends；
In step s105, by I/V conversion circuit, faint ac current signal is transformed into ac voltage signal；
In step s 106, it rectified, filtered by rectification circuit, filter circuit, obtain steady dc voltage letter
Number；
In step s 107, d. c. voltage signal corresponding conductivity is converted to show.
As an embodiment of the present invention, can also include: after step S105
Judgement is compared by PLC in d. c. voltage signal by step S108, if exceeding instrument range, is automatically selected
Higher range.
In non-automatic switching range, data are as follows, and scatter plot is referring to Fig. 1:
Data when by automatic switching range of the embodiment of the present invention are as follows, scatter plot referring to fig. 2:
The embodiment of the present invention judges the signal detected by PLC, to control relay switching input square wave
Frequency, amplitude and the detection range of signal, reach the control to the software cost, hardware cost of instrument, no matter is obtained data
It is the linearity or precision, or in the case where automatically switching and not switching, has all reached the other requirement of technical grade, and
Extend electrode life.
Fig. 4 shows the structure of electrical conductivity measurement circuit provided in an embodiment of the present invention, for ease of description, illustrates only
Part related to the present invention.
As an embodiment of the present invention, which includes:
Excitation generates unit 11, for generating ac square wave signal as excitation；
Amplifying unit 12, for amplifying ac square wave signal, the input terminal of amplifying unit 12 and excitation generate unit 11
Motivate output end connection；
Buffer cell 13, for improving load capacity, the input terminal of buffer cell 13 and the output end of amplifying unit 12 connect
It connects, the output end of buffer cell 13 passes through one end T101A-IN of conducting wire connection electrode, and a friendship is generated in electrolyte solution
Changed electric field；
I/V (current/voltage) converting unit 14 detects electrolyte solution for the other end T102A+IN by electrode and exists
The ac current signal at electrode both ends is resulted from alternating electric field, and faint ac current signal is transformed into alternating voltage letter
Number, the input terminal of I/V converting unit 14 passes through the other end T102A+IN connection of conducting wire and electrode；
Rectification filtering unit 15 is converted to ac voltage signal stable straight for by rectification circuit, filter circuit
Voltage signal is flowed, the input terminal of rectification filtering unit 15 is connect with the output end of I/V converting unit 14；
Conductivity converting unit 16, for d. c. voltage signal to be converted to corresponding conductivity, conductivity converting unit
16 input terminal is connect with the output end of rectification filtering unit 15；
Display unit 17, for showing conductivity, the input terminal of display unit 17 and the output of conductivity converting unit 16
End connection.
As an embodiment of the present invention, unit and electricity can be generated as excitation using programmable logic controller (PLC) (PLC)
Conductance converting unit, referring to Fig. 5, at this point, the excitation output end of PLC is the excitation output end and amplification list that excitation generates unit 11
The input terminal connection of member 12, the input terminal of PLC are the output of the input terminal and rectification filtering unit 15 of conductivity converting unit 16
End connection, the display output end of PLC are that the output end of conductivity converting unit 16 is connect with display unit 17.
The embodiment of the present invention judges the signal detected by PLC, to control relay switching input square wave
Frequency, amplitude and the detection range of signal, reach the control to the software cost, hardware cost of instrument, no matter is obtained data
It is the linearity or precision, or in the case where automatically switching and not switching, has all reached the other requirement of technical grade, and
Extend electrode life.
Fig. 5 shows the exemplary circuit structure of electrical conductivity measurement circuit provided in an embodiment of the present invention, for ease of description,
Only the parts related to the present invention are shown.
As an embodiment of the present invention, amplifying unit 12 includes:
Resistance R109, resistance R110, resistance R111 and the first operational amplifier U103-B；
One end of resistance R111 is the input terminal of amplifying unit 12, the other end of resistance R111 and the first operational amplifier
The reverse input end of U103-B connects, the reverse input end of the first operational amplifier U103-B also simultaneously with resistance R109 and resistance
One end of R110 connects, and the other end of resistance R109 and resistance R110 are respectively the first, second feedback end of amplifying unit 12, the
The positive input of one operational amplifier U103-B is grounded, and the output end of the first operational amplifier U103-B is amplifying unit 12
Output end.
Buffer cell 13 can realize using second operational amplifier U103-A, wherein second operational amplifier U103-A
Positive input is the input terminal of buffer cell 13, the reverse input end of second operational amplifier U103-A and the second operation amplifier
The output end of device U103-A connects, and the output end of second operational amplifier U103-A is the output end of buffer cell 13.
I/V converting unit 14 includes:
Resistance R101, resistance R102, resistance R104 and third operational amplifier U101；
The reverse input end of third operational amplifier U101 be I/V converting unit 14 input terminal simultaneously with resistance R101 and
One end of resistance R102 connects, and the other end of resistance R101 and resistance R102 are respectively the first, second anti-of I/V converting unit 14
End is presented, the positive input of third operational amplifier U101 is grounded by resistance R104, the output of third operational amplifier U101
End is the output end of I/V converting unit 14.
As a preferred embodiment of the present invention, the electrical conductivity measurement circuit can also include:
Range switch unit 18, it is automatic to select if exceeding instrument range for judgement to be compared to d. c. voltage signal
Higher range is selected, the input terminal of range switch unit 18 is connect with the output end of rectification filtering unit 15, range switch unit
18 first group of switch terminal is connect with the output end of amplifying unit 12 and feedback end, second group of switch terminal of range switch unit 18
It is connect with the output end of I/V converting unit 14 and feedback end.
Preferably, range switch unit 18 may further include:
Switching control module 181 and PLC；
It is worth noting that PLC herein can be multiplexed the PLC in above-described embodiment；
The input terminal of PLC is the input terminal of range switch unit, switching output end and the switching control module 181 of PLC
Input terminal connection, multiple output ends of switching control module 181 are respectively two groups of switch terminals of range switch unit.
Preferably, switching control module 181 includes:
Resistance R126, resistance R127, diode D106, switching tube Q101, relay K101 and single-chip microcontroller U1；
The input terminal of single-chip microcontroller U1 is that the input terminal of switching control module 181 and the switching output end of PLC connect, single-chip microcontroller
The output end of U1 is connect with one end of resistance R126, and the other end of resistance R126 is connect with the control terminal of switching tube Q101, switch
The control terminal of pipe Q101 also passes through resistance R127 and is grounded, the output end of switching tube Q101 ground connection, the input terminal of switching tube Q101 with
The anode of diode D106 connects, the cathode connection+5V supply voltage of diode D106,1 foot of relay K101 and 8 feet difference
The cathode and anode of diode D106 are connected, 2 feet of relay K101,3 feet, first group that 4 feet are range switch unit 18 are cut
Change end, 5 feet of relay K101,6 feet, second group of switch terminal that 7 feet are range switch unit 18, the and (2-7 of relay K101
Foot) be switching control module 181 multiple output ends, wherein 2 feet and 4 feet of relay K101 respectively with amplifying unit 12
The first feedback end and the connection of the second feedback end, 3 feet of relay K101 connect with the output end of amplifying unit 12, relay
5 feet and 7 feet of K101 are connect with the first feedback end of I/V converting unit 14 and the second feedback end respectively, 6 feet of relay K101
It is connect with the output end of I/V converting unit 14.
In embodiments of the present invention, 1 foot of relay K101 and 8 feet are control terminal, 2 feet and 3 when control terminal is low level
Foot closure, 7 feet and 6 feet are closed, and 4 feet and 3 feet closure, 5 feet and 6 feet are closed when control terminal is high level.
In embodiments of the present invention, (its duty ratio is 50% to the ac square wave signal that PLC is generated, and frequency is 800Hz-
4000Hz) through the amplification electricity of resistance R111, the first operational amplifier U103-B and feedback resistance R110 or R109 composition
Square-wave signal is amplified on road, using second operational amplifier U103-A to improve load capacity, at this point, square-wave signal is by leading
One end of line connection electrode, generates an alternating electric field in electrolyte solution, and the other end detection electrolyte solution of electrode exists
The faint ac current signal that conductivity meter electrode both ends are resulted from alternating electric field, by by third operational amplifier
The I/V conversion circuit of U101, resistance R104 and feedback resistance R101 or R102 composition, faint ac current signal is turned
Become voltage signal and be input to PLC after filter rectification, PLC is exported after d. c. voltage signal is converted to corresponding conductivity
It is shown to display unit.
It is noted that the d. c. voltage signal that PLC can also export filter rectification unit judges, in direct current
Voltage signal is connected when being greater than threshold value by single-chip microcontroller U1 control switch pipe Q101, and then is controlled relay K101 conducting and be attracted,
Change the selection of feedback resistance in amplifying unit 12 and I/V converting unit 14, to realize the switching of detection range.
Here the resistance value of resistance R109 can be set to 10 times of resistance R110, and the resistance value of resistance R101 can be set to electricity
10 times for hindering R1102, to realize the adjusting of range, switching, certainly, the resistance value ratio of feedback resistance is not limited to 10 times,
It can be arranged according to practical application.
The embodiment of the present invention judges the signal detected by PLC, to control relay switching input square wave
Frequency, amplitude and the detection range of signal, reach the control to the software cost, hardware cost of instrument, no matter is obtained data
It is the linearity or precision, or in the case where automatically switching and not switching, has all reached the other requirement of technical grade, and
Extend electrode life.
The above is merely preferred embodiments of the present invention, be not intended to limit the invention, it is all in spirit of the invention and
Made any modifications, equivalent replacements, and improvements etc., should all be included in the protection scope of the present invention within principle.
Claims (5)
1. a kind of electrical conductivity measurement circuit, which is characterized in that the circuit includes:
Excitation generates unit, for generating ac square wave signal as excitation；
Amplifying unit, for amplifying the ac square wave signal, the input terminal of the amplifying unit and the excitation generate unit
Excitation output end connection；
Buffer cell, for improving load capacity, the input terminal of the buffer cell is connect with the output end of the amplifying unit,
The output end of the buffer cell passes through one end of conducting wire connection electrode, and an alternating electric field is generated in electrolyte solution；
I/V converting unit detects electrolyte solution for the other end by electrode and results from electrode both ends in alternating electric field
Ac current signal, and faint ac current signal is transformed into ac voltage signal, the input of the I/V converting unit
End is connected by the other end of conducting wire and electrode；
Rectification filtering unit, it is raw for being rectified, being filtered to the ac voltage signal by rectification circuit, filter circuit
At steady dc voltage signal, the input terminal of the rectification filtering unit is connect with the output end of the I/V converting unit；
Conductivity converting unit, for the d. c. voltage signal to be converted to corresponding conductivity, the conductivity conversion is single
The input terminal of member is connect with the output end of the rectification filtering unit；
Display unit, for showing conductivity, the output end of the input terminal of the display unit and the conductivity converting unit
Connection；
Range switch unit, if exceeding instrument range, automatically selects higher for judgement to be compared to d. c. voltage signal
Range, the input terminal of the range switch unit connect with the output end of the rectification filtering unit, and the range switching is single
First group of switch terminal of member is connect with the output end of the amplifying unit and feedback end, and second group of the range switch unit is cut
End is changed to connect with the output end of the I/V converting unit and feedback end；
The range switch unit includes switching control module and PLC；
The input terminal of the PLC is the input terminal of the range switch unit, and the switching output end of the PLC and the switching are controlled
The input terminal of molding block connects, and multiple output ends of the switching control module are respectively that two groups of the range switch unit are cut
Change end；
The switching control module includes:
Resistance R126, resistance R127, diode D106, switching tube Q101, relay K101 and single-chip microcontroller U1；
The input terminal of the single-chip microcontroller U1 is that the input terminal of the switching control module is connect with the switching output end of the PLC,
The output end of the single-chip microcontroller U1 is connect with one end of the resistance R126, the other end and the switching tube of the resistance R126
The control terminal of Q101 connects, and the control terminal of the switching tube Q101 also passes through the resistance R127 ground connection, the switching tube Q101
Output end ground connection, the input terminal of the switching tube Q101 connect with the anode of the diode D106, the diode D106
Cathode connection+5V supply voltage, 1 foot and 8 feet of the relay K101 be separately connected the diode D106 cathode and
Anode, 2 feet of the relay K101,3 feet, first group of switch terminal that 4 feet are the range switch unit, the relay
5 feet of K101,6 feet, second group of switch terminal that 7 feet are the range switch unit, and the 2-7 foot of the relay K101 is
Multiple output ends of the switching control module, wherein 2 feet and 4 feet of the relay K101 respectively with the amplifying unit
The first feedback end and the connection of the second feedback end, 3 feet of the relay K101 connect with the output end of the amplifying unit, institute
5 feet and 7 feet for stating relay K101 are connect with the first feedback end of the I/V converting unit and the second feedback end respectively, described
6 feet of relay K101 are connect with the output end of the I/V converting unit.
2. circuit as described in claim 1, which is characterized in that the amplifying unit includes:
Resistance R109, resistance R110, resistance R111 and the first operational amplifier；
One end of the resistance R111 is the input terminal of the amplifying unit, the other end of the resistance R111 and first fortune
Calculate amplifier reverse input end connection, the reverse input end of first operational amplifier also simultaneously with the resistance R109 and
One end of the resistance R110 connects, and the other end of the resistance R109 and the resistance R110 are respectively the amplifying unit
First, second feedback end, the positive input ground connection of first operational amplifier, the output end of first operational amplifier
For the output end of the amplifying unit.
3. circuit as described in claim 1, which is characterized in that the I/V converting unit includes:
Resistance R101, resistance R102, resistance R104 and third operational amplifier；
The reverse input end of the third operational amplifier be the I/V converting unit input terminal simultaneously with the resistance R101
It is connected with one end of the resistance R102, the other end of the resistance R101 and the resistance R102 are respectively the I/V conversion
The positive input of first, second feedback end of unit, the third operational amplifier is grounded by the resistance R104, described
The output end of third operational amplifier is the output end of the I/V converting unit.
4. circuit as described in claim 1, which is characterized in that it is multiple that the excitation generates unit, the conductivity converting unit
With the PLC in the range switch unit, the excitation output end of the PLC is the excitation output end that the excitation generates unit,
The input terminal of the PLC is the input terminal of the conductivity converting unit simultaneously, and the display output end of the PLC is the conductance
The output end of rate converting unit.
5. a kind of conductance instrument, which is characterized in that the conductance instrument includes conductivity as described in claim 1
Measuring circuit.
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| CN201610583932.2A CN106291119B (en) | 2016-07-22 | 2016-07-22 | A kind of conductivity measuring method, circuit and conductance instrument |
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| CN201610583932.2A CN106291119B (en) | 2016-07-22 | 2016-07-22 | A kind of conductivity measuring method, circuit and conductance instrument |
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| CN106291119B true CN106291119B (en) | 2019-06-28 |
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| CN107228886B (en) * | 2017-04-24 | 2019-09-10 | 费尔德（北京）科学仪器有限公司 | The measuring device and method of the conductivity Resistivity testing of water |
| CN109212319B (en) * | 2018-08-27 | 2020-12-18 | 古之恒信息科技（苏州）有限公司 | Fuel conductivity measuring circuit and measuring instrument |
| CN109142463A (en) * | 2018-10-09 | 2019-01-04 | 李晨天 | Transient DC method for measuring conductance and device |
| CN112014434A (en) * | 2020-07-29 | 2020-12-01 | 桂林优利特医疗电子有限公司 | Water quality real-time detection method and detection device for biochemical immunoassay analyzer |
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| CN2195761Y (en) * | 1994-04-15 | 1995-04-26 | 核工业第四研究设计院 | Intelligent diagometer |
| JPH11281687A (en) * | 1998-03-31 | 1999-10-15 | Matsushita Electric Ind Co Ltd | Electric conductivity sensor |
| CN201322773Y (en) * | 2008-12-16 | 2009-10-07 | 河南省日立信电子有限公司 | Electrical conductivity measuring instrument |
| CN102426296B (en) * | 2011-09-30 | 2014-01-29 | 浙江大学 | Surface water conductivity non-contact measurement device and method |
| CN105652092A (en) * | 2014-11-14 | 2016-06-08 | 佛山市顺德区美的电热电器制造有限公司 | Testing apparatus of conductivity and electrical equipment |
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