CN107314799A - A kind of weak capacitive detection circuit for nanoliter level liquid level sensor - Google Patents
A kind of weak capacitive detection circuit for nanoliter level liquid level sensor Download PDFInfo
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- CN107314799A CN107314799A CN201710710314.4A CN201710710314A CN107314799A CN 107314799 A CN107314799 A CN 107314799A CN 201710710314 A CN201710710314 A CN 201710710314A CN 107314799 A CN107314799 A CN 107314799A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/26—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields
- G01F23/263—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields by measuring variations in capacitance of capacitors
- G01F23/266—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields by measuring variations in capacitance of capacitors measuring circuits therefor
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- Measurement Of Resistance Or Impedance (AREA)
- Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
Abstract
A kind of weak capacitive detection circuit for nanoliter level liquid level sensor, using closed loop mode localized measurement principle, first oscillation circuit, the second oscillation circuit, coupled capacitor and see-saw circuit input connection, see-saw circuit output is connected by backfeed loop with bandpass filter input, bandpass filter is exported and the first oscillation circuit, the second oscillation circuit are connected, when liquid level changes, output capacitance is caused to change, the electric capacity Δ C of change is connected in parallel on the electric capacity two ends of oscillation circuit；First oscillation circuit is connected with the 3rd buffer, second oscillation circuit is connected with the 3rd buffer, first oscillation circuit, the second oscillation circuit, coupled capacitor common port are connected with the first buffer, oscillation circuit does not need the AC drive voltage signal of external frequency conversion, only need to provide direct-current working volts to each amplifier；The present invention realizes on-line real time monitoring capacitance variations, can easily and fast, accurately read the situation of change of capacitance level transducer weak capacitive.
Description
Technical field
The present invention relates to liquid level sensor technical field, more particularly to a kind of faint electricity for nanoliter level liquid level sensor
Hold detection circuit.
Background technology
MEMS capacitive sensor has good environmental adaptability, and the characteristics of sensitivity is high is widely used in industrial circle.
The appearance of continuous level gauging and fluid level announciator based on MEMS technology, it is possible to achieve μm (10-6m)/nL(10-9L) rank liquid
Position measurement, while the features such as capacitance level transducer has preferable environmental suitability and temperature stability, can fill up normal
The blank of the liquid level sensor application field under technique is advised, petrochemical industry, bio-pharmaceuticals micro flow control is widely used in
The fields such as system, and to high accuracy, small size, machine with wide range develops.
Capacitive MEMS liquid level sensor uses MEMS (MEMS) processing technology, and liquid level signal is converted into electricity by it
Signal, can be with equivalent into a testing capacitance changed with liquid level, and capacitance variations interval is in 1-200pF (10-12F between).For
Below 10pF electric capacity, because the parasitic capacitance produced by PCB has reached this magnitude, is difficult to use traditional method
Measurement, is badly in need of proposing new method of testing solving.Existing wood is read for the PCB ranks electric capacity that refined the sixth of the twelve Earthly Branches, Jin Xiangliang et al. use
Circuit, the former is needed by the way of PCB circuits weld illusory electric capacity, it is difficult to overcome capacitance selection error, and the latter passes through phase
Close double-sampling and eliminate offset voltage, while being integrated with digital analog converter, stray capacitance compensated array is static inclined to offset
The influence of shifting, but there is a situation where that quantization error and circuit design are excessively complicated, may cause step by step noise add up.
A kind of low g value capacitor MEMS acceleration meter and its mode localized measurement circuit propose first mode localization with
High sensitivity difference adds the method that meter is combined, and is that capacitance measurement technique opens new approaches.This method is shaken using two equivalent LRC
Loop is swung, is coupled by coupled capacitor, the capacitance variations of mems accelerometer are converted into mode localization circuit
Curent change, the response current linear variation relation approximate with capacitance variations of two loops of circuit.But this mode needs
One extra signal generator carries out frequency sweep operation, and need to record lower frequency-current signal in real time, could be counted offline
Calculate, it is impossible to obtain signal results in real time, and stability is not good, it may occur however that the excessive situation of frequency drift, this open loop approach
Also there are many problems in actual applications.
The content of the invention
In order to overcome the shortcoming of above-mentioned prior art, the purpose of the present invention is to propose to a kind of closed loop mode localized measurement electricity
Path method, for the weak capacitance detection of nanoliter level liquid level sensor, reading capacitance level transducer easily and fast is faint
The situation of change of electric capacity.
To reach above-mentioned purpose, the present invention is adopted the technical scheme that：
A kind of weak capacitive detection circuit for nanoliter level liquid level sensor, it is former using closed loop mode localized measurement
Reason, including electric capacity C3、C4, electric capacity C3、C4After being connected in series, with the resistance R being sequentially connected in series1, inductance L1, electric capacity C1Parallel connection, simultaneously
With the resistance R being sequentially connected in series2, inductance L2, electric capacity C2Parallel connection, wherein electric capacity C4Right-hand member and electric capacity C1, electric capacity C2Right-hand member is connected, electric capacity
C3Left end and resistance R1, resistance R2Left end is connected, electric capacity C3、C4Coupled capacitor 6 in series；Resistance R1, inductance L1, electric capacity C1With
The electric capacity C of series connection3、C4Constitute the first oscillation circuit 1, resistance R2, electric capacity C2With inductance L2With the electric capacity C connected3、C4Constitute second
Oscillation circuit 2；Electric capacity C3、C4Common port altogether, electric capacity C in the first oscillation circuit 1, the second oscillation circuit 21、C2、C4Right-hand member lead to
Cross resistance R3It is input to the first amplifier (Op-amp) inverting input, the first amplifier inverting input and resistance R4One end phase
Even, resistance R4The other end and the first amplifier out are connected, the first amplifier in-phase input end ground connection, resistance R3、R4With first
Amplifier constitutes see-saw circuit 3；The output end of see-saw circuit 3 passes through backfeed loop 4 and the input phase of bandpass filter 5
Even, the output end of bandpass filter 5 and divider resistance R5One end is connected, divider resistance R5The other end and resistance R1, resistance R2Left end connects
Connect；
When liquid level changes, output capacitance is caused to change, the electric capacity Δ C of change is connected in parallel on electric capacity C2Two ends；
Electric capacity C3, resistance R1, resistance R2Left end is connected with the first buffer 7, resistance R1With inductance L1Between be connected with the 3rd
Buffer 9, resistance R2With inductance L2Between be connected with the second buffer 8.
3rd buffer 9, the output end of the second buffer 8 are respectively connected to single-pole double-throw switch (SPDT) S12A, b node, S12's consolidates
Fixed end and resistance R9One end is connected, resistance R9The other end accesses the second amplifier inverting input, the second amplifier inverting input
With resistance R10One end is connected, resistance R10The other end and the second amplifier out are connected, the second amplifier in-phase input end and electricity
Hinder R12One end is connected, resistance R12The other end is grounded；The output end of first buffer 7 and resistance R11One end is connected, resistance R11The other end
It is connected with the second amplifier inverting input；Second amplifier out and resistance R13One end is connected, resistance R13The other end and
Four amplifier inverting inputs are connected, the 4th amplifier inverting input and resistance R14One end is connected, resistance R14The other end and
Four amplifier outs are connected, the 4th amplifier in-phase input end and resistance R15One end is connected, resistance R15The other end is grounded.
Described the first buffer 7, the second buffer 8, the 3rd buffer 9 are using identical structure, i.e. signaling point and the
Five amplifier inverting inputs are connected, the 5th amplifier inverting input and output end short circuit.
The described signal input part in of bandpass filter 5 and resistance R6One end is connected, resistance R6The other end and electric capacity C5Phase
Even, electric capacity C5The other end is connected with the 6th amplifier inverting input, the 6th amplifier in-phase input end ground connection, the 6th amplifier
Inverting input and resistance R8One end is connected, resistance R8The other end and the 6th amplifier out are connected, the 6th amplifier out
With electric capacity C6One end is connected, electric capacity C6The other end and resistance R6, electric capacity C5Common port is connected, resistance R6, electric capacity C5Common port and electricity
Hinder R7One end is connected, resistance R7The other end and the 6th amplifier in-phase input end are altogether.
Compared with prior art, the present invention at least has the advantages that：In the present invention, system oscillation loop is not required to
The alternating voltage drive signal of external frequency conversion is wanted, only direct-current working volts need to be provided to each amplifier；Returned by forming closed loop
Road, can be achieved on-line real time monitoring input change electric capacity situation, greatly improves the feasibility and real-time of capacitance detecting.
Brief description of the drawings
Fig. 1 is closed loop mode localization circuit theory diagrams of the present invention.
Fig. 2 is signal processing circuit schematic diagram of the present invention.
Fig. 3 is the structural representation of buffer.
Fig. 4 is the structural representation of bandpass filtering unit.
Fig. 5 is mode localization open loop detection principle diagram.
Fig. 6 is the flow chart of signal transacting of the present invention.
Fig. 7 is that embodiment measures one group of data.
Embodiment
The present invention is described in detail with reference to the accompanying drawings and examples.
As shown in figure 1, a kind of weak capacitive detection circuit for nanoliter level liquid level sensor, using closed loop mode local
Change measuring principle, including electric capacity C3、C4, electric capacity C3、C4After being connected in series, with the resistance R being sequentially connected in series1, inductance L1, electric capacity C1And
Connection, at the same with the resistance R that is sequentially connected in series2, inductance L2, electric capacity C2Parallel connection, wherein electric capacity C4Right-hand member and electric capacity C1, electric capacity C2Right-hand member phase
Even, electric capacity C3Left end and resistance R1, resistance R2Left end is connected, electric capacity C3、C4Coupled capacitor 6 in series；Resistance R1, inductance L1、
Electric capacity C1With the electric capacity C connected3、C4Constitute the first oscillation circuit 1, resistance R2, electric capacity C2With inductance L2With the electric capacity C connected3、C4
Constitute the second oscillation circuit 2；Electric capacity C3、C4Common port altogether, electric capacity C in the first oscillation circuit 1, the second oscillation circuit 21、C2、C4
Right-hand member pass through resistance R3It is input to the first amplifier (Op-amp) inverting input, the first amplifier inverting input and resistance
R4One end is connected, resistance R4The other end and the first amplifier out are connected, the first amplifier in-phase input end ground connection, resistance R3、
R4See-saw circuit 3 is constituted with the first amplifier；The output end of see-saw circuit 3 passes through backfeed loop 4 and bandpass filter 5
Input is connected, the output end of bandpass filter 5 and divider resistance R5One end is connected, divider resistance R5The other end and resistance R1, resistance
R2Left end is connected；
When liquid level changes, output capacitance is caused to change, the electric capacity Δ C of change is connected in parallel on electric capacity C2Two ends；
Electric capacity C3, resistance R1, resistance R2Left end is connected with the first buffer 7, resistance R1With inductance L1Between be connected with the 3rd
Buffer 9, resistance R2With inductance L2Between be connected with the second buffer 8.
The electric capacity Δ C of change is input to electric capacity C2Two ends, the first oscillation circuit 1, the poised state quilt of the second oscillation circuit 2
The change electric capacity Δ C of introducing breaks, and causes mode localization phenomenon, causes corresponding oscillating current i1、i2, change；The
First, the coupled capacitor C that the second oscillation circuit passes through series connection3、C4Weak coupling is formed, signal is from C4Right-hand member is input to inverting amplifier
3, amplified entrance bandpass filter 5 removes Ripple Noise, through resistance R5Feed back input is to resistance R after partial pressure1Left end；Coupling
Electric capacity C3、C4The effect of regulation feedback intensity, its ratio are also acted as simultaneouslyAs regulation parameter, circuit stability can be made efficient
Vibration is got up.
Reference picture 2, the 3rd buffer 9, the output end of the second buffer 8 are respectively connected to single-pole double-throw switch (SPDT) S12A, b node,
S12 fixing end and resistance R9One end is connected, resistance R9The other end accesses the second amplifier inverting input, and the second amplifier is anti-
Phase input and resistance R10One end is connected, resistance R10The other end and the second amplifier out are connected, and the second amplifier is with mutually defeated
Enter end and resistance R12One end is connected, resistance R12The other end is grounded；The output end of first buffer 7 and resistance R11One end is connected, resistance
R11The other end is connected with the second amplifier inverting input；Second amplifier out and resistance R13One end is connected, resistance R13Separately
One end and the connection of the 4th amplifier inverting input, the 4th amplifier inverting input and resistance R14One end is connected, resistance R14Separately
One end is connected with the 4th amplifier out, the 4th amplifier in-phase input end and resistance R15One end is connected, resistance R15The other end
Ground connection.
The corresponding signaling point parameter of detection is passed through difference by the first buffer 7, the second buffer 8, the 3rd buffer 9 respectively
Amplification is divided to calculate, wherein single-pole double-throw switch (SPDT) S12According to measurement sequential, divide and be switched on a points and b points, inputted with the first buffer 7
Signal do calculus of differences；Wherein when the 3rd buffer 9 is connected, the signal and the first oscillation circuit i monitored1It is related；Its
In when the second buffer 8 is connected, the signal and the second oscillation circuit i monitored2It is related；Signal enters the 4th amplifier, warp
It is output to after anti-phase amplification in DSP and makees further computing.
3 voltage signal V are obtained by the first buffer 7, the second buffer 8, the sampling of the 3rd buffer 97、V8、V9Make the difference
Divide enhanced processing, that is, obtain resistance R1、R2On current value：
Wherein K is the multiplication factor of the 4th amplifier.
Reference picture 3, described the first buffer 7, the second buffer 8, the 3rd buffer 9 use identical structure, that is, believe
Number point is connected with the 5th amplifier inverting input, the 5th amplifier inverting input and output end short circuit.
Buffer is made up of an operational amplifier, and signal is entered by in-phase input end, and input is to be decayed
Less voltage signal；5th amplifier out and inverting input short circuit, theoretical output impedance are infinitely great, can be as far as possible
Influence of the small reduction to oscillation circuit.
Reference picture 4, the described signal input part of bandpass filter 5 and resistance R6One end is connected, resistance R6The other end and electric capacity
C5It is connected, electric capacity C5The other end is connected with the 6th amplifier inverting input, the 6th amplifier in-phase input end ground connection, and the 6th puts
Big device inverting input and resistance R8One end is connected, resistance R8The other end and the 6th amplifier out are connected, and the 6th amplifier is defeated
Go out end and electric capacity C6One end is connected, electric capacity C6The other end and resistance R6, electric capacity C5Common port is connected, resistance R6, electric capacity C5Common port
With resistance R7One end is connected, resistance R7The other end and the 6th amplifier in-phase input end are altogether.
According to default centre frequency fpCalculation formula sets bandpass filtering parameter, obtains below equation：
Wherein C5=C6=C=1nF, BwFor design bandwidth, simultaneous equations can solve resistance R6、R7、R8Parameter.
The present invention operation principle be：
Using closed loop mode localization Cleaning Principle, change changing for loop oscillation electric current above and below causing by input capacitance
Become, closed loop is constituted after amplified, bandpass filtering link；Made comparisons by two branch current signals, lower branch road electricity can be obtained
Hold variable quantity.
First, second oscillation circuit can obtain the differential equation by Kirchhoff's second law：
In above formula, L1=L2The inductance value of the loop of=L indication circuits first, second, R1=R1=R is represented on ASIC circuit
The resistance value of lower loop, CCRepresent coupling capacitance (i.e. electric capacity C between two loops3、C4Series electrical capacitance), C represents first,
The reference capacitance value of second oscillation circuit, q1, q2For two loop i of circuit1,i2Integration, vsIt is backfeed loop R5It is input to
The energy of one oscillation circuit, the second oscillation circuit, f is the frequency of oscillation after two return circuit couplings.Solved by above formula：
Wherein wd1And wd2For the resonance angular frequency of mode localization circuit, u (t) for mode localization circuit feature to
Amount.S represents the corresponding complex frequencies of time domain time t, Q after Laplace transform1And Q2Q is corresponded to respectively1、q2By Laplce
Value after change.
In resonance angular frequency wd1And wd2On, q1,q2Peak value is taken, its value changes and changed with Δ C, wd1And wd2Likewise as
Δ C changes and changed, thus, it is possible to obtain w by calculatingd1And wd2Under q1,q2Corresponding peak value, and q1, q2For ASIC circuit
Two loop i1,i2Integration, you can to obtain i under resonant frequency1,i2With the relation that Δ C changes, and then obtain i1,i2With
The relation of liquid level change.
As shown in figure 5, Fig. 5 is existing open loop mode localized measurement principle：Two groups of RLC oscillation circuits for being coupled together
10th, RLC oscillation circuits 11, pass through coupled capacitor CCConstitute weak coupling, oscillation circuit by external communication source input energy, it is necessary to
Oscillating current i caused by being recorded in real time using relevant device under alternating current source signal intensity1,i2Situation of change, and need offline mark
Remember resonance angular frequency wd1And wd2Upward peak and frequency, calculating process are very long, it is impossible to record information in real time.And the present invention is built
Close loop control circuit is to realize more convenient, intuitively reading manner.Closed-loop system will not need alternating current source, pass through closed loop feedback
Circuit, can maintain the first oscillation circuit, the second oscillation circuit in corresponding wd1And wd2Peak point current on, realize Quick Acquisition,
It is quick to calculate.
As shown in fig. 6, the flow of signal transacting of the present invention is as follows：
1) system reset data later before understanding；
2) the capacitance variations scope of anticipation liquid level sensor；
3) the first oscillation circuit 1 of selection, the C of the second oscillation circuit 21、C2Parameter value, according to weak coupling design principle, is selected
Coupled capacitor C3、C4Value；Select bandpass filter parameter, inverting amplifier access D/C voltage starting of oscillation；
4) signal that the first buffer 7, the second buffer 8, the 3rd buffer 9 are measured is read using differential amplifier circuit,
Calculate the oscillating current peak value i of the first oscillation circuit 1, the second oscillation circuit 21,i2；
5) it will obtain calculating in the incoming DSP of data, output capacitance value.
Embodiment：Design parameter C1The dark C of=100nF2The dark L of=95nF1=L2=10mH, sets bandpass filter C3=100 μ
F, C4=20 μ F, centre frequency 5.4KHz, bandwidth 1KHz, gain is 1.Set Δ C/C1For input disturbance.Set and work as Δ C=5nF
When the first oscillation circuit 1, the gained electric current of the second oscillation circuit 2 be reference current i10、i20, gained frequency is reference frequency f0.Through
Experiment measurement is crossed, the frequency signal after 100 times of the current signal measured and expansion is drawn as shown in Figure 7.Obtain the closed loop mould
The detection sensitivity (current curve slope) of state localization method is far above traditional frequency detecting method.
Fundamental frequency f is measured under undisturbed0=5.4KHz, it is 1Hz that frequency, which reads minimum resolution, frequency slope k in Fig. 7=
0.013382Hz/nF, so the minimum capacity resolution ratio of frequency detecting mode is
And the use of the resolution ratio of mode localization capacitance detecting mode is more than 100 times of Frequency Patterns, so it is of the invention
The minimum resolution of disclosed mode localization capacitive detection circuit is at least fF (10-15F) rank.
Claims (4)
1. a kind of weak capacitive detection circuit for nanoliter level liquid level sensor, it is characterised in that：Using closed loop mode local
Change measuring principle, including electric capacity C3、C4, electric capacity C3、C4After being connected in series, with the resistance R being sequentially connected in series1, inductance L1, electric capacity C1And
Connection, at the same with the resistance R that is sequentially connected in series2, inductance L2, electric capacity C2Parallel connection, wherein electric capacity C4Right-hand member and electric capacity C1, electric capacity C2Right-hand member phase
Even, electric capacity C3Left end and resistance R1, resistance R2Left end is connected, electric capacity C3、C4Coupled capacitor (6) in series；Resistance R1, inductance
L1, electric capacity C1With the electric capacity C connected3、C4Constitute the first oscillation circuit (1), resistance R2, electric capacity C2With inductance L2With the electric capacity connected
C3、C4Constitute the second oscillation circuit (2)；Electric capacity C3、C4Common port altogether, electric capacity in the first oscillation circuit 1, the second oscillation circuit 2
C1、C2、C4Right-hand member pass through resistance R3It is input to the first amplifier (Op-amp) inverting input, the first amplifier anti-phase input
End and resistance R4One end is connected, resistance R4The other end and the first amplifier out are connected, the first amplifier homophase input termination
Ground, resistance R3、R4See-saw circuit (3) is constituted with the first amplifier；See-saw circuit (3) output end passes through backfeed loop
(4) it is connected with bandpass filter (5) input, bandpass filter (5) output end and divider resistance R5One end is connected, divider resistance
R5The other end and resistance R1, resistance R2Left end is connected；
When liquid level changes, output capacitance is caused to change, the electric capacity Δ C of change is connected in parallel on electric capacity C2Two ends；
Electric capacity C3, resistance R1, resistance R2Left end is connected with the first buffer (7), resistance R1With inductance L1Between be connected with the 3rd delay
Rush device (9), resistance R2With inductance L2Between be connected with the second buffer (8).
2. a kind of weak capacitive detection circuit for nanoliter level liquid level sensor according to claim 1, its feature exists
In：3rd buffer (9), the second buffer (8) output end are respectively connected to single-pole double-throw switch (SPDT) S12A, b node, S12 fixation
End and resistance R9One end is connected, resistance R9The other end access the second amplifier inverting input, the second amplifier inverting input and
Resistance R10One end is connected, resistance R10The other end and the second amplifier out are connected, the second amplifier in-phase input end and resistance
R12One end is connected, resistance R12The other end is grounded；First buffer (7) output end and resistance R11One end is connected, resistance R11The other end
It is connected with the second amplifier inverting input；Second amplifier out and resistance R13One end is connected, resistance R13The other end and
Four amplifier inverting inputs are connected, the 4th amplifier inverting input and resistance R14One end is connected, resistance R14The other end and
Four amplifier outs are connected, the 4th amplifier in-phase input end and resistance R15One end is connected, resistance R15The other end is grounded.
3. a kind of weak capacitive detection circuit for nanoliter level liquid level sensor according to claim 1, its feature exists
In：Described the first buffer (7), the second buffer (8), the 3rd buffer (9) are using identical structure, i.e. signaling point and the
Five amplifier inverting inputs are connected, the 5th amplifier inverting input and output end short circuit.
4. a kind of weak capacitive detection circuit for nanoliter level liquid level sensor according to claim 1, its feature exists
In：The signal input part in and resistance R of described bandpass filter (5)6One end is connected, resistance R6The other end and electric capacity C5It is connected,
Electric capacity C5The other end is connected with the 6th amplifier inverting input, and the 6th amplifier in-phase input end ground connection, the 6th amplifier is anti-
Phase input and resistance R8One end is connected, resistance R8The other end and the 6th amplifier out are connected, the 6th amplifier out and
Electric capacity C6One end is connected, electric capacity C6The other end and resistance R6, electric capacity C5Common port is connected, resistance R6, electric capacity C5Common port and resistance
R7One end is connected, resistance R7The other end and the 6th amplifier in-phase input end are altogether.
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| CN109752046A (en) * | 2018-10-19 | 2019-05-14 | 江苏未来智慧信息科技有限公司 | Wireless vibration temperature sensor circuit |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109752046A (en) * | 2018-10-19 | 2019-05-14 | 江苏未来智慧信息科技有限公司 | Wireless vibration temperature sensor circuit |
| CN109752046B (en) * | 2018-10-19 | 2024-04-02 | 江苏未来智慧信息科技有限公司 | Wireless vibration temperature sensor circuit |
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