CN207440174U - A kind of conductance instrument - Google Patents
A kind of conductance instrument Download PDFInfo
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- CN207440174U CN207440174U CN201721555968.6U CN201721555968U CN207440174U CN 207440174 U CN207440174 U CN 207440174U CN 201721555968 U CN201721555968 U CN 201721555968U CN 207440174 U CN207440174 U CN 207440174U
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Abstract
The utility model is related to a kind of conductance instruments, including conductivity sensor, further include the exiting signal generating circuit that driving source is provided for conductivity sensor, the amplification and rectification circuit of shaping is amplified to the output signal of conductivity sensor, DC converting circuit, analog-to-digital conversion circuit and controller, exiting signal generating circuit includes square wave excitation source and filter circuit, square wave excitation source, filter circuit, conductivity sensor, amplification and rectification circuit, DC converting circuit, analog to digital conversion circuit and controller are sequentially connected, controller is connected with square wave excitation source and provides clock signal for square wave excitation source, conductance instrument further includes temperature-compensation circuit, temperature-compensation circuit is connected by analog to digital conversion circuit with controller.Conductivity measuring instrument result provided by the utility model is accurate, conductivity sensor will not be polarized, calculating process is simplified, more power saving.
Description
Technical field
The utility model is related to conductivity measurement technique field more particularly to a kind of conductance instruments.
Background technology
Electrical conductivity is one of key character of substance, and the testing principle of electrical conductivity is simple, detection device is at low cost, electricity
The detection of conductance is widely used in material classification technology, material analysis techniques, environmental protection technology and industrial production control
In technology.
Existing conductance instrument applies voltage signal conduct by being obtained using C-V characteristic, to measured matter
Pumping signal reads the current signal for flowing through measured matter, electrical conductivity is obtained according to voltage signal and current signal.But such as
Fruit, as pumping signal, can cause the polarization of conductivity sensor using DC voltage；If using alternating voltage as excitation
Signal, the amplitude and frequency of alternating voltage must the sufficiently stable precision that just can guarantee conductivity measurement, and alternating voltage is made
The calculating process for making electrical conductivity for pumping signal is complicated, and test result is unable to compatible with digital circuit for analog signal, therefore cannot
Intuitively test result is provided, for the substance of high conductivity, can not accurately be tested.
The content of the invention
Technical problem to be solved in the utility model is in view of the above shortcomings of the prior art, to provide a kind of electrical conductivity and survey
Instrument is measured, on the premise of ensureing that conductivity sensor is not polarized, more accurately carries out measuring, simplifying electrical conductivity for electrical conductivity
Calculating process and also more power saving.
The technical solution that the utility model solves above-mentioned technical problem is as follows：A kind of conductance instrument, including electrical conductivity
Sensor further includes and provides the exiting signal generating circuit of driving source, to the conductivity sensors for the conductivity sensor
The output signal of device is amplified the amplification and rectification circuit of shaping, DC converting circuit, analog-to-digital conversion circuit and controller, institute
Stating exiting signal generating circuit includes square wave excitation source and filter circuit, the square wave excitation source, filter circuit, conductivity sensors
Device, amplification and rectification circuit, DC converting circuit, analog to digital conversion circuit and controller are sequentially connected, the controller with it is described
Square wave excitation source connects and provides clock signal for the square wave excitation source, and the conductance instrument further includes temperature-compensating electricity
Road, the temperature-compensation circuit are connected by analog-digital conversion circuit as described with the controller.
The beneficial effects of the utility model are：Using square wave excitation source and filter circuit generate without direct current and amplitude and
The all stable sinusoidal signal of frequency, the sinusoidal signal amplitude and frequency stabilization, the pumping signal as conductivity sensor can be with
Ensure that conductivity sensor is not polarized and can ensure measurement accuracy.Amplification and rectification circuit believes the measurement of conductivity sensor
It number is amplified and denoising.Ac voltage signal is converted to d. c. voltage signal by DC converting circuit, and d. c. voltage signal is just
In calculating of the controller to electrical conductivity.The d. c. voltage signal is converted to digital DC voltage signal by analog to digital conversion circuit, number
Word d. c. voltage signal is compatible with controller so that controller can carry out it electrical conductivity is calculated.Controller is simultaneously
Square wave excitation source provides clock signal so that square wave excitation source need not be chronically at working condition, but following controller when
Clock signal break sex work so that conductance instrument more power saving.Temperature-compensation circuit is to results of conductivity measurement into trip temperature
Compensation so that measurement result is more accurate.
Based on the above technical solutions, the utility model can also do following improvement：
Further：The filter circuit include wave filter IC1, resistance R1, resistance R2, resistance R3, resistance R4, capacitance C1,
Capacitance C2, capacitance C3 and capacitance C4；
The output terminal in the square wave excitation source is connected with one end of the resistance R1, and the other end of the resistance R1 passes through institute
State the reverse input end of the capacitance C2 connections wave filter IC1, the in-phase input end ground connection of the wave filter IC1, the filtering
By the resistance R4 connections conductivity sensor, the common port of the resistance R1 and capacitance C2 lead to the output terminal of device IC1
The output terminal of the capacitance C1 connections wave filter IC1 is crossed, the reverse input end of the wave filter IC1 passes through described in resistance R3 connections
The common port of the output terminal of wave filter IC1, the resistance R1 and capacitance C2 are grounded by resistance R2, and the wave filter IC1's is defeated
Outlet is grounded by capacitance C3, and the common port of the resistance R4 and conductivity sensor is grounded by capacitance C4.
The advantageous effect of above-mentioned further scheme is：The square-wave signal that filter circuit generates square wave excitation source is filtered
Ripple filters out d. c. voltage signal, obtains without d. c. voltage signal and amplitude frequency stabilization sinusoidal signal, is believed with the sine
Number as pumping signal, avoid the test electrode polarization of conductivity sensor and test result is precise and stable.
Further：The amplification and rectification circuit includes the first operational amplifier U1, second operational amplifier U2, the one or two pole
Pipe D1, the second diode D2, resistance R10, resistance R20, feedback resistance R30, feedback resistance R40, resistance R50 and capacitance C10；
The conductivity sensor connects the reverse input end of the first operational amplifier U1, first operation amplifier
The in-phase input end connection power supply of device U1, the cathode of the output terminal of the first operational amplifier U1 and the first diode D1
Connection, the anode of the first diode D1 are connected by resistance R10 with the in-phase input end of the second operational amplifier U2,
The second operational amplifier U2 in-phase input ends connect power supply by resistance R50, and the second operational amplifier U2's is reversed defeated
Enter output terminal of the end by the feedback resistance R40 connections second operational amplifier U2, the second operational amplifier U2
Output terminal be connected with the DC converting circuit；
The cathode of the second diode D2 is connected with the reverse input end of the first operational amplifier U1, and described second
The anode of diode D2 is connected with the output terminal of the first operational amplifier U1, and the both ends of the capacitance C10 connect institute respectively
The anode of the first diode D1 and the cathode of the second diode D2 are stated, the feedback resistance R30 is connected in parallel on the two of the capacitance C10
End, the both ends of the resistance R20 connect the reverse input end and second operational amplifier of the first operational amplifier U1 respectively
The reverse input end of U2.
The advantageous effect of above-mentioned further scheme is：Amplification and rectification circuit includes the first operational amplifier, the second computing is put
Big device and the shaping unit formed by the first diode and the second diode, the measurement result of conductivity sensor is through the first fortune
After calculating amplifier tentatively amplification, shaped unit shaping, removal noise, after input second operational amplifier again and secondary put
Greatly, to obtain the pure muting signal of amplitude bigger, noise is avoided to be amplified.
Further：The DC converting circuit uses the direct current conversion chip of model AD8436.
The advantageous effect of above-mentioned further scheme is：Direct current conversion chip by through amplification and rectification circuit amplify shaping after friendship
Stream voltage signal is converted to direct current signal so that during follow-up calculating electrical conductivity, sinusoidal plan need not be carried out to ac voltage signal
It is total to calculate, simplify the calculating process of electrical conductivity.
Further：Analog-digital conversion circuit as described uses the modulus conversion chip of model TLC1543.
The advantageous effect of above-mentioned further scheme is：Modulus conversion chip is electric by the analog DC Jing Guo DC conversion modules
Pressure signal is converted to digital DC voltage signal, compatible with controller, convenient for the calculating processing of controller.
Further：The temperature-compensation circuit includes divider resistance R5 and thermistor R6, the divider resistance R5 and heat
Quick resistance R6 is series between power supply and ground, and the common port of the divider resistance R5 and thermistor R6 pass through the analog-to-digital conversion
Circuit connects the controller.
The advantageous effect of above-mentioned further scheme is：Temperature-compensation circuit carries out temperature to the test result of conductivity sensor
Degree compensation so that measurement result is more accurate.
Further：The controller is microcontroller.
The advantageous effect of above-mentioned further scheme is：Microcontroller is common controller, is easily obtained, and cost is relatively low, is led to
It is stronger with property.
Description of the drawings
Fig. 1 is a kind of structure diagram of conductivity measurement provided by the utility model；
Fig. 2 is a kind of circuit diagram of the filter circuit of conductivity measurement provided by the utility model；
Fig. 3 is a kind of circuit diagram of the amplification and rectification circuit of conductivity measurement provided by the utility model；
Fig. 4 is a kind of circuit diagram of the temperature-compensation circuit of conductivity measurement provided by the utility model.
In attached drawing, parts list represented by the reference numerals is as follows：
1st, conductivity sensor, 2, exiting signal generating circuit, 21, square wave excitation source, 22, filter circuit, 3, amplification it is whole
Shape circuit, 4, direct current conversion circuit, 5, analog to digital conversion circuit, 6, controller, 7, temperature-compensation circuit.
Specific embodiment
The principle and feature of the utility model are described below in conjunction with attached drawing, example is served only for explaining this practicality
It is new, it is not intended to limit the scope of the utility model.
Below in conjunction with the accompanying drawings, the utility model is illustrated.
As shown in Figure 1, the utility model embodiment provides a kind of conductivity measurement, including conductivity sensor 1, also wrap
Include the exiting signal generating circuit 2 for providing driving source for the conductivity sensor 1, the output to the conductivity sensor 1
Signal is amplified the amplification and rectification circuit 3 of shaping, DC converting circuit 4, analog-to-digital conversion circuit 5 and controller 6, described to swash
Encouraging signal generating circuit 2 includes square wave excitation source 21 and filter circuit 22, the square wave excitation source 21, filter circuit 22, conductance
Rate sensor 1, amplification and rectification circuit 3, DC converting circuit 4, analog to digital conversion circuit 5 and controller 6 are sequentially connected, the control
Device 6 processed is connected with the square wave excitation source 21 and provides clock signal, the conductance instrument for the square wave excitation source 21
Temperature-compensation circuit 7 is further included, the temperature-compensation circuit 7 is connected by analog-digital conversion circuit as described 5 with the controller 6.
The all stable sinusoidal letter of without direct current and amplitude and frequency is generated using square wave excitation source 21 and filter circuit 22
Number, pumping signal of the sinusoidal signal as conductivity sensor 1, it is ensured that the test electrode of conductivity sensor 1 not by
It polarizes and measurement result is accurate.The measuring signal of conductivity sensor 1 through amplification and rectification circuit 3 amplify shaping after amplified and
Muting voltage signal, the voltage signal are ac voltage signal, and d. c. voltage signal is converted to through DC converting circuit 4,
The Sine-Fitting that d. c. voltage signal avoids ac voltage signal calculates, and the calculating for simplifying electrical conductivity is long.Analog-to-digital conversion
D. c. voltage signal is converted to digital DC voltage signal by circuit 5, and digital DC voltage signal is compatible with controller 6, control
Device 6 calculates electrical conductivity according to the digital DC voltage signal.Temperature signal is transferred to analog to digital conversion circuit by temperature-compensation circuit 7
5, temperature signal is converted to digital temperature signal and is transmitted to controller 6 by analog to digital conversion circuit 5, and controller 6 is to conductivity meter
It calculates result and carries out temperature-compensating so that measurement result is more accurate.Controller 6 also provides clock signal for square wave excitation source so that
Electricity is saved according to the intermittent generation square-wave signal of clock signal of controller in square wave excitation source.
The conductance instrument that the utility model embodiment provides uses excitation of the sinusoidal signal as conductivity sensor
Signal, the sinusoidal signal frequency reproduction are stablized so that the measurement result of electrical conductivity is accurate, and conductivity sensor will not be by pole
Change.By follow-up amplification and rectification circuit, DC converting circuit, analog to digital conversion circuit and temperature-compensation circuit to measurement result into
Row processing is calculated and corrected so that Conductivity Calculation result is more accurate, calculating process is more simplified.Pass through control simultaneously
Device control square wave excitation source periodically generates square-wave signal, saves electricity.
The upper embodiment of optimization, as shown in Fig. 2, the filter circuit 22 includes wave filter IC1, resistance R1, resistance R2, electricity
Hinder R3, resistance R4, capacitance C1, capacitance C2, capacitance C3 and capacitance C4；
The output terminal in the square wave excitation source 21 is connected with one end of the resistance R1, and the other end of the resistance R1 passes through
The reverse input end of the capacitance C2 connections wave filter IC1, the in-phase input end ground connection of the wave filter IC1, the filter
The output terminal of ripple device IC1 is by the resistance R4 connections conductivity sensor 1, the common port of the resistance R1 and capacitance C2
By the output terminal of the capacitance C1 connections wave filter IC1, the reverse input end of the wave filter IC1 passes through resistance R3 connections institute
State the output terminal of wave filter IC1, the common port of the resistance R1 and capacitance C2 are grounded by resistance R2, the wave filter IC1's
Output terminal is grounded by capacitance C3, and the common port of the resistance R4 and conductivity sensor is grounded by capacitance C4.
Wave filter IC1 can be π bandpass filters, and the square-wave signal that filter circuit generates square wave excitation source is filtered,
Direct current component is filtered out, obtains the sinusoidal signal without direct current.
The upper embodiment of optimization, as shown in figure 3, the amplification and rectification circuit 3 includes the first operational amplifier U1, the second fortune
Calculate amplifier U2, the first diode D1, the second diode D2, resistance R10, resistance R20, feedback resistance R30, feedback resistance R40,
Resistance R50 and capacitance C10；
The conductivity sensor 1 connects the reverse input end of the first operational amplifier U1, and first computing is put
The in-phase input end connection power supply VCC of big device U1, the output terminal of the first operational amplifier U1 and the first diode D1
Cathode connection, the anode of the first diode D1 passes through the homophase input of the resistance R10 and second operational amplifier U2
End connection, the second operational amplifier U2 in-phase input ends connect power supply VCC, the second operational amplifier by resistance R50
The reverse input end of U2 passes through the output terminal of the feedback resistance R40 connections second operational amplifier U2, second fortune
The output terminal for calculating amplifier U2 is connected with the DC converting circuit 4；
The cathode of the second diode D2 is connected with the reverse input end of the first operational amplifier U1, and described second
The anode of diode D2 is connected with the output terminal of the first operational amplifier U1, and the both ends of the capacitance C10 connect institute respectively
The anode of the first diode D1 and the cathode of the second diode D2 are stated, the feedback resistance R30 is connected in parallel on the two of the capacitance C10
End, the both ends of the resistance R20 connect the reverse input end and second operational amplifier of the first operational amplifier U1 respectively
The reverse input end of U2.
Amplification and rectification circuit is amplified shaping to the measurement result of conductivity sensor, is amplified and muting letter
Number.Amplification and rectification circuit provided in this embodiment is by three once amplification, shaping, secondary amplification steps realizations, the first computing
Amplifier U1 realizations are once amplified, and the first diode D1 and the second diode D2 realize shaping, and second operational amplifier U2 is realized
Secondary amplification, due in raw measured signal there are noise, the amplification factor once amplified should not be too large, and avoid noise
It is amplified, shaping denoising is carried out to signal after once amplifying, then carry out secondary amplification, the amplification factor of secondary amplification is more than one
The amplification factor of secondary amplification obtains pure muting amplified signal.
The upper embodiment of optimization, the DC converting circuit 4 use the direct current conversion chip of model AD8436 (in figure not
Show), the direct current conversion chip includes alternating voltage input interface and direct voltage output interface, AD8436 conversion chips
Alternating voltage input interface is No. 6 pins, and the direct voltage output interfaces of AD8436 conversion chips is No. 10 pins, the exchange
Control source interface is connected with the output terminal of second operational amplifier U2 in the amplification and rectification circuit, the direct voltage output
Interface is connected with analog-digital conversion circuit as described 5.The measurement result that conductivity sensor 1 exports is ac voltage signal, and direct current turns
It changes circuit 4 and ac voltage signal is converted into d. c. voltage signal, d. c. voltage signal is convenient for calculating, convenient and simplified electricity
The calculating process of conductance.
The upper embodiment of optimization, analog-digital conversion circuit as described 5 is using the modulus conversion chip of model TLC1543 (in figure
It is not shown), the modulus conversion chip includes analog input interface and digital signal output interface.TLC1543 moduluses turn
The 1-9 pins for changing chip are analog input interface, and No. 16 pins are digital signal output interface.By No. 1 pin with
The direct voltage output interface connection of the DC converting circuit 4, No. 16 pins are connected with the controller 6.Analog-to-digital conversion core
Analog voltage signal is converted to digital voltage signal by piece, and digital voltage signal is compatible with controller so that controller can be right
It is calculated, and obtains electrical conductivity.
The upper embodiment of optimization, as shown in figure 4, the temperature-compensation circuit 7 includes divider resistance R5 and thermistor R6,
The divider resistance R5 and thermistor R6 are series between power supply VCC and ground, the divider resistance R5 and thermistor R6's
Common port connects the controller 6 by the analog conversion circuit 5.The common port of the divider resistance R5 and thermistor R6
Connect No. 2 pins of TLC1543 modulus conversion chips.The divider resistance R5 and thermistor R6 composition bleeder circuits, by temperature
Degree voltage signal is transmitted to analog to digital conversion circuit 5, and controller 6 is transmitted to after analog to digital conversion circuit 5 is converted into digital signal, controls
Device 6 processed carries out temperature-compensating to the electrical conductivity that conductivity sensor 1 measures.
The upper embodiment of optimization, the controller 6 are microcontroller.The present embodiment selects the monolithic of model MSP430F413
Machine, control logic use existing control logic.
The above is only the preferred embodiment of the present invention, is not intended to limit the utility model, all in this practicality
Within new spirit and principle, any modifications, equivalent replacements and improvements are made should be included in the guarantor of the utility model
Within the scope of shield.
Claims (7)
1. a kind of conductance instrument, including conductivity sensor (1), which is characterized in that further include as the conductivity sensors
Device (1) provides the exiting signal generating circuit (2) of driving source, the output signal of the conductivity sensor (1) is amplified
Amplification and rectification circuit (3), the DC converting circuit (4) of shaping, analog-to-digital conversion circuit (5) and controller (6), the excitation letter
Number occur circuit (2) include square wave excitation source (21) and filter circuit (22), the square wave excitation source (21), filter circuit
(22), conductivity sensor (1), amplification and rectification circuit (3), DC converting circuit (4), analog to digital conversion circuit (5) and control
Device (6) is sequentially connected, and the controller (6) is connected with the square wave excitation source (21) and is provided for the square wave excitation source (21)
Clock signal, the conductance instrument further include temperature-compensation circuit (7), and the temperature-compensation circuit (7) passes through the mould
Number conversion circuit (5) is connected with the controller (6).
2. conductance instrument according to claim 1, which is characterized in that the filter circuit (22) includes wave filter
IC1, resistance R1, resistance R2, resistance R3, resistance R4, capacitance C1, capacitance C2, capacitance C3 and capacitance C4；
The output terminal of the square wave excitation source (21) is connected with one end of the resistance R1, and the other end of the resistance R1 passes through institute
State the reverse input end of the capacitance C2 connections wave filter IC1, the in-phase input end ground connection of the wave filter IC1, the filtering
The output terminal of device IC1 is by the resistance R4 connections conductivity sensor (1), the common port of the resistance R1 and capacitance C2
By the output terminal of the capacitance C1 connections wave filter IC1, the reverse input end of the wave filter IC1 passes through resistance R3 connections institute
State the output terminal of wave filter IC1, the common port of the resistance R1 and capacitance C2 are grounded by resistance R2, the wave filter IC1's
Output terminal is grounded by capacitance C3, and the common port of the resistance R4 and conductivity sensor is grounded by capacitance C4.
3. conductance instrument according to claim 1, which is characterized in that the amplification and rectification circuit (3) includes first
Operational amplifier U1, second operational amplifier U2, the first diode D1, the second diode D2, resistance R10, resistance R20, feedback
Resistance R30, feedback resistance R40, resistance R50 and capacitance C10；
The conductivity sensor (1) connects the reverse input end of the first operational amplifier U1, first operation amplifier
The in-phase input end connection power supply of device U1, the cathode of the output terminal of the first operational amplifier U1 and the first diode D1
Connection, the anode of the first diode D1 are connected by resistance R10 with the in-phase input end of the second operational amplifier U2,
The second operational amplifier U2 in-phase input ends connect power supply by resistance R50, and the second operational amplifier U2's is reversed defeated
Enter output terminal of the end by the feedback resistance R40 connections second operational amplifier U2, the second operational amplifier U2
Output terminal be connected with the DC converting circuit (4)；
The cathode of the second diode D2 is connected with the reverse input end of the first operational amplifier U1, the two or two pole
The anode of pipe D2 is connected with the output terminal of the first operational amplifier U1, and the both ends of the capacitance C10 connect described respectively
The cathode of the anode of one diode D1 and the second diode D2, the feedback resistance R30 are connected in parallel on the both ends of the capacitance C10,
The both ends of the resistance R20 connect the reverse input end of the first operational amplifier U1 and second operational amplifier U2 respectively
Reverse input end.
4. conductance instrument according to claim 1, which is characterized in that the DC converting circuit (4) uses model
For the direct current conversion chip of AD8436.
5. conductance instrument according to claim 1, which is characterized in that analog-digital conversion circuit as described (5) uses model
For the modulus conversion chip of TLC1543.
6. conductance instrument according to claim 1, which is characterized in that the temperature-compensation circuit (7) includes partial pressure
Resistance R5 and thermistor R6, the divider resistance R5 and thermistor R6 are series between power supply and ground, the divider resistance
The common port of R5 and thermistor R6 connect the controller (6) by analog-digital conversion circuit as described (5).
7. conductance instrument according to claim 1, which is characterized in that the controller (6) is microcontroller.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201721555968.6U CN207440174U (en) | 2017-11-20 | 2017-11-20 | A kind of conductance instrument |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201721555968.6U CN207440174U (en) | 2017-11-20 | 2017-11-20 | A kind of conductance instrument |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN207440174U true CN207440174U (en) | 2018-06-01 |
Family
ID=62286357
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201721555968.6U Active CN207440174U (en) | 2017-11-20 | 2017-11-20 | A kind of conductance instrument |
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| Country | Link |
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| CN (1) | CN207440174U (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109002989A (en) * | 2018-07-20 | 2018-12-14 | 广东工业大学 | A kind of concrete structure repairs detection method, system equipment and storage medium |
| CN109211331A (en) * | 2018-11-05 | 2019-01-15 | 北京林业大学 | The soil and environment measuring circuit of one plant growth |
| CN109212319A (en) * | 2018-08-27 | 2019-01-15 | 古之恒信息科技（苏州）有限公司 | A kind of fuel oil electrical conductivity measurement circuit and measuring instrument |
| CN110646678A (en) * | 2019-10-10 | 2020-01-03 | 杭州绿洁环境科技股份有限公司 | Conductivity measuring device |
| CN110677150A (en) * | 2019-09-02 | 2020-01-10 | 安徽华东光电技术研究所有限公司 | Device for converting AC small signal into DC signal |
| CN112798866A (en) * | 2020-12-31 | 2021-05-14 | 中天海洋系统有限公司 | Conductivity signal acquisition circuit and testing device |
-
2017
- 2017-11-20 CN CN201721555968.6U patent/CN207440174U/en active Active
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109002989A (en) * | 2018-07-20 | 2018-12-14 | 广东工业大学 | A kind of concrete structure repairs detection method, system equipment and storage medium |
| CN109212319A (en) * | 2018-08-27 | 2019-01-15 | 古之恒信息科技（苏州）有限公司 | A kind of fuel oil electrical conductivity measurement circuit and measuring instrument |
| 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 |
| CN109211331A (en) * | 2018-11-05 | 2019-01-15 | 北京林业大学 | The soil and environment measuring circuit of one plant growth |
| CN110677150A (en) * | 2019-09-02 | 2020-01-10 | 安徽华东光电技术研究所有限公司 | Device for converting AC small signal into DC signal |
| CN110677150B (en) * | 2019-09-02 | 2023-06-06 | 安徽华东光电技术研究所有限公司 | Device for converting alternating current small signal into direct current signal |
| CN110646678A (en) * | 2019-10-10 | 2020-01-03 | 杭州绿洁环境科技股份有限公司 | Conductivity measuring device |
| CN112798866A (en) * | 2020-12-31 | 2021-05-14 | 中天海洋系统有限公司 | Conductivity signal acquisition circuit and testing device |
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