CN106289451B - Merogenesis condenser type low temperature liquid-level converter - Google Patents
Merogenesis condenser type low temperature liquid-level converter Download PDFInfo
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- CN106289451B CN106289451B CN201610601428.0A CN201610601428A CN106289451B CN 106289451 B CN106289451 B CN 106289451B CN 201610601428 A CN201610601428 A CN 201610601428A CN 106289451 B CN106289451 B CN 106289451B
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- 239000007788 liquid Substances 0.000 title claims abstract description 63
- 230000010363 phase shift Effects 0.000 claims abstract description 38
- 238000003199 nucleic acid amplification method Methods 0.000 claims abstract description 24
- 230000003321 amplification Effects 0.000 claims abstract description 23
- 239000003990 capacitor Substances 0.000 claims description 49
- 230000005669 field effect Effects 0.000 claims description 10
- 230000005284 excitation Effects 0.000 claims description 9
- 238000001514 detection method Methods 0.000 claims description 8
- 230000005611 electricity Effects 0.000 claims description 6
- 238000005086 pumping Methods 0.000 claims description 4
- 238000001914 filtration Methods 0.000 claims description 3
- 238000005070 sampling Methods 0.000 claims description 3
- 238000011896 sensitive detection Methods 0.000 claims description 2
- 238000005259 measurement Methods 0.000 abstract description 13
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 abstract description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 abstract description 6
- 239000001257 hydrogen Substances 0.000 abstract description 6
- 229910052739 hydrogen Inorganic materials 0.000 abstract description 6
- 229910052757 nitrogen Inorganic materials 0.000 abstract description 3
- 238000009413 insulation Methods 0.000 abstract description 2
- 230000004044 response Effects 0.000 abstract description 2
- 125000004435 hydrogen atom Chemical class [H]* 0.000 abstract 1
- 238000010586 diagram Methods 0.000 description 16
- 239000003795 chemical substances by application Substances 0.000 description 6
- 238000002474 experimental method Methods 0.000 description 6
- 239000000446 fuel Substances 0.000 description 6
- 239000007800 oxidant agent Substances 0.000 description 6
- 230000001590 oxidative effect Effects 0.000 description 5
- 230000008859 change Effects 0.000 description 4
- 150000002431 hydrogen Chemical class 0.000 description 4
- 239000003350 kerosene Substances 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 238000000034 method Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 2
- 241000208340 Araliaceae Species 0.000 description 1
- 241000301144 Dendrolimus kikuchii Species 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 235000005035 Panax pseudoginseng ssp. pseudoginseng Nutrition 0.000 description 1
- 235000003140 Panax quinquefolius Nutrition 0.000 description 1
- 239000008186 active pharmaceutical agent Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000000872 buffer Substances 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 235000008434 ginseng Nutrition 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 102220112179 rs3743602 Human genes 0.000 description 1
- 102220123496 rs557896607 Human genes 0.000 description 1
- 238000000844 transformation Methods 0.000 description 1
Classifications
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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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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Electromagnetism (AREA)
- Thermal Sciences (AREA)
- Fluid Mechanics (AREA)
- General Physics & Mathematics (AREA)
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
Abstract
The present invention provides a kind of merogenesis condenser type low temperature liquid-level converters, it include: hardware detecting circuit, wherein, the hardware detecting circuit involves DC amplification circuit including at least wien oscillator circuit, cascade transformer sample circuit, exchange two-stage amplifying circuit, AC signal phase-shift circuit, demodulator circuit, low pass filtered.The present invention is mainly used to matching with capacitive low temperature liquid level sensor and is continuously measured low-temperature insulation medium liquid level, this merogenesis capacitance type liquid level converter has the characteristics that rapid dynamic response speed, test scope are wide, measurement accuracy is high, and the continuous precise measurement to cryogenic medias such as liquid hydrogen, liquid nitrogen, liquid oxygen is especially suitable for Capacitance-type low-temperature liquid level sensor cooperation.
Description
Technical field
The present invention relates to field of industrial measurement, and in particular, to a kind of merogenesis condenser type low temperature liquid-level converter.
Background technique
The liquid level of fuel agent and oxidant in tank technical indicator important during being rocket launching, with depleted shutdown
For liquid level sensor, the level condition of fuel agent and oxidant determines the unused time of rocket engine.If level gauging
Inaccuracy, the rocket unused time can postpone or in advance, the rocket unused time postpones the fuel agent that will lead into rocket engine
Variation is not enough or matched with the amount of oxidant, to easily cause rocket launching failure.The rocket unused time can lead in advance
Fuel agent and oxidant is caused to utilize insufficient, rocket is possible to that planned orbit cannot be reached.
In short, fuel agent and the accurate measurement of oxidant liquid level are very important for entire rocket system, often
Rocket oxidizer is liquid oxygen medium, and common fuel agent is kerosene and liquid hydrogen, they belong to insulating properties medium, opposite to be situated between
Electric constant is very small (0.1Mpa pressure, kerosene 2.2, liquid oxygen 1.485, liquid hydrogen 1.22), and liquid oxygen, liquid hydrogen operating temperature arrival-
150 DEG C hereinafter, existing capacitance type liquid level converter is primarily present following two deficiency: measurement accuracy is not high.
The measuring principle of capacitance type liquid level converter is that electric capacitance change linear transformation caused by changing medium liquid level is
The variation of voltage, liquid level variation is small, the small then electric capacitance change of dielectric permittivity is small, however is for the detection of small capacitances amount
Relatively difficult, therefore the measurement accuracy of existing capacitance type liquid level converter is difficult to accomplish 1%, especially dielectric constant very
Small liquid hydrogen, liquid oxygen and kerosene is just more difficult to accomplish；Detected capacitor is easy be interfered external electromagnetic environmental disturbances and transmission
The influence of cable distribution capacity in the process.
Summary of the invention
For the defects in the prior art, the object of the present invention is to provide a kind of merogenesis condenser type low temperature liquid-level converters.
The merogenesis condenser type low temperature liquid-level converter provided according to the present invention, including hardware detecting circuit, the hardware inspection
Slowdown monitoring circuit include: wien oscillator circuit, cascade transformer sample circuit, exchange two-stage amplifying circuit, AC signal phase-shift circuit,
Demodulator circuit, low pass filtered involve DC amplification circuit；Wherein:
The wien oscillator circuit, for being used to generate low frequency sinusoidal pumping signal, driver transformer；
The cascade transformer sample circuit, for generate with liquid level it is linear exchange sampled signal；
The exchange two-stage amplifying circuit for amplifying to exchange sampled signal, and is exported to AC signal phase shift
Circuit；
The AC signal phase-shift circuit, for carrying out 90 ° of phase shifts respectively to sinusoidal excitation signal；
The demodulator circuit, for carrying out the sinusoidal excitation signal after phase shift with the amplified sampled signal that exchanges with frequency
Demodulation；
The low pass filtered involves DC amplification circuit, for extracting the DC component demodulated.
Preferably, the wien oscillator circuit includes: operational amplifier, field-effect tube, power operational amplifier, accurate electricity
Appearance, resistance, diode；The wien oscillator circuit constitutes RC oscillator, for generating low frequency sinusoidal pumping signal；Wherein, field
Effect pipe is equivalent to a thyrite, realizes that wien oscillator circuit output signal is automatic using field-effect tube and operational amplifier
Fixed ampllitude, and the range stability of signal can reach 1%, while use precision capacitance, resistance, so that the frequency of output signal
Stability reaches 5 ‰.
Preferably, the cascade transformer sample circuit includes: cascade transformer, odd number capacitor Cj, even number capacitor Co, ginseng
Capacitor C0, sample resistance are examined, cascade transformer electric bridge is carried out seeking poor, summation operation, be taken to odd number capacitor Cj and even number capacitor Co
Ac small signal after sample is transmitted to exchange two-stage amplifying circuit.
Preferably, the exchange two-stage amplifying circuit includes: binary channels operational amplifier, precision capacitance, precision resistance,
In, operational amplifier is two homophase input amplifiers, and two homophase input amplifiers are cascade connection, and amplification factor is two
The product of the amplification factor of in-phase amplifier.
Preferably, the AC signal phase-shift circuit includes: operational amplifier, precision capacitance, resistance, the AC signal
Sinusoidal excitation signal is carried out 90 ° of phase shift, carrier signal of the signal as demodulator circuit after phase shift by phase-shift circuit.
Preferably, the demodulator circuit includes: demodulation chip, filter capacitor, variable resistance, and demodulator circuit is used for two
The AC signal of a input does multiplying and carries out phase sensitive detection, two input exchange signals frequency having the same and phase,
Two input exchange signals are respectively the sinusoidal signal after the sampled signal of two-stage exchange amplification and 90 ° of phase shifts.
Preferably, the low pass filtered involves DC amplification circuit using three rank Butterworth active filter circuits, comprising: fortune
Amplifier chip, resistance, capacitor are calculated, for carrying out low-pass filtering to the AC signal after demodulation, is taken out straight in AC signal
Ingredient is flowed, while direct current signal is amplified, so that the amplitude of direct current signal is adjusted to the range of setting.
Compared with prior art, the present invention have it is following the utility model has the advantages that
The present invention overcomes conventional condenser low temperature liquid-level converter detection accuracy is low, measurement result is easy to be interfered
Merogenesis capacitance signal is converted into d. c. voltage signal by hardware detection by problem, and the series of transformations device dynamic response is fast, measures
Range is wide, detection accuracy is high (by taking liquid oxygen as an example, level sensing error is not more than ± 2mm), is particularly suitable for passing with merogenesis condenser type
Sensor cooperation carries out the continuous liquid level measuring of the super low temperature insulations media such as liquid nitrogen, liquid hydrogen, liquid oxygen.
Detailed description of the invention
Upon reading the detailed description of non-limiting embodiments with reference to the following drawings, other feature of the invention,
Objects and advantages will become more apparent upon:
Fig. 1 is merogenesis capacitance type liquid level converter hardware circuit principle block diagram；
Fig. 2 is wien oscillator circuit diagram；
Fig. 3 is transformer sample circuit schematic diagram；
Fig. 4 is exchange two-stage amplifying circuit schematic diagram；
Fig. 5 is AC signal phase-shift circuit schematic diagram；
Fig. 6 is demodulator circuit schematic diagram；
Fig. 7 is that low pass filtered involves DC amplification circuit schematic diagram；
Fig. 8 is capacitor and signal, capacitor difference signal and level gauging relational graph；
Fig. 9 is that measured curve and theoretical curve amplify comparison diagram.
Specific embodiment
The present invention is described in detail combined with specific embodiments below.Following embodiment will be helpful to the technology of this field
Personnel further understand the present invention, but the invention is not limited in any way.It should be pointed out that the ordinary skill of this field
For personnel, without departing from the inventive concept of the premise, several changes and improvements can also be made.These belong to the present invention
Protection scope.
The merogenesis capacitance type liquid level converter provided according to the present invention, comprising: hardware detecting circuit, the hardware detection electricity
The odd number capacitor Cj for being used to characterize liquid level that continuous low-temperature liquid level sensor inputs and even number capacitor Co are converted linearly by road
The variation of DC voltage amount, wherein merogenesis number locating for the capacitance characterization liquid level of Cj+Co, the capacitance of Co-Cj characterize liquid level
Exact position in certain section；Using merogenesis condenser type detection method, in circuit using odd number capacitor Cj and even number capacitor Co
Addition and subtraction is carried out, other capacitance interferences generated on cable and on signal path are eliminated, to further provide for sensor
Measurement accuracy.
The merogenesis condenser type low temperature liquid-level converter, including hardware detecting circuit, hardware detecting circuit part are mainly made
It is transformed into voltage variation with by electric capacitance change, the hardware detecting circuit includes at least: wien oscillator circuit, cascade transformation
Device sample circuit, exchange two-stage amplifying circuit, AC signal phase-shift circuit, demodulator circuit, low pass filtered involve DC amplification circuit；
The wien oscillator circuit is used to generate Low Frequency Sine Signals with driving transformer,
The cascade transformer sample circuit be used to generate with liquid level it is linear exchange sampled signal, cascade transformation
Sensor odd number capacitor and even number capacitor ask poor, summation by device electric bridge sample circuit, and output amplitude and liquid level at
The exchange sampled signal of linear relationship；
The sampled signal is amplified by exchange two-stage amplifying circuit, while the sinusoidal excitation signal of two frequencies point
Not carry out 90 ° of phase shifts, the sinusoidal signal after phase shift is identical as the same frequency signal phase in sampled signal, for frequency demodulate,
The demodulator circuit carries out same frequency demodulation according to the frequency of input signal, phase, in demodulator circuit output signal
Flip-flop is linear with liquid level, and the demodulator circuit output signal passes through low-pass filter circuit and DC amplification circuit will
Direct current signal takes out.
Further,
The wien oscillator circuit includes: operational amplifier, field-effect tube, power operational amplifier, precision capacitance, precision
Resistance, diode, the essence in wien oscillator circuit is RC oscillator, can be used to generate Low Frequency Sine Signals, wien oscillator electricity
Lu Zhong, field-effect tube are equivalent to a thyrite, realize wien oscillator circuit using field-effect tube and operation amplifier circuit
Output signal auto_steady amplitude, and the range stability of signal can reach 1%, while use high-precision resistor and capacitor
Device, so that the frequency stability of output signal reaches 5 ‰, the sinusoidal excitation signal driving transformer that wien oscillator circuit generates.
The cascade transformer electric bridge sample circuit includes: cascade transformer, odd number capacitor Cj, even number capacitor Co, reference
Capacitor C0, sample resistance R；Cascade transformer electric bridge carries out seeking poor, summation operation to odd number capacitor Cj and even number capacitor Co, sampling
Signal afterwards is exported to ac amplifier circuit；
The AC signal phase-shift circuit includes: operational amplifier, precision capacitance, precision resistance, and phase-shift circuit will be sinusoidal
Signal carries out 90 ° of phase shift, carrier signal of the signal as demodulator circuit after phase shift；
The exchange two-stage amplifying circuit includes: operational amplifier, capacitor, resistance；Two-stage amplifying circuit is exchanged by two
Homophase input amplifier cascade composition, amplification factor is the product of the amplification factor of two in-phase amplifiers.
The demodulator circuit includes: demodulation chip, filter capacitor, variable resistance, and demodulator circuit major function is by two
The AC signal of a input does multiplying, and two input signals are respectively to pass through the sampled signal and 90 ° that two-stage exchange is amplified
Sinusoidal signal after phase shift.
The low pass filtered involves the filter module in amplifying circuit using three rank Butterworth active filter circuits, mainly by
Operational amplifier chip, resistance, capacitor are constituted；Amplifier active filter is small in size, light-weight, there is no inductance brings to be lost
With it is non-linear, while amplifier amplifies and buffers；Low pass filtered involves amplifying circuit main function: to the exchange after demodulation
Signal does low-pass filtering, takes out the flip-flop in AC signal, while can amplify to direct current signal, so that direct current is believed
Number amplitude be adjusted to be suitble to measurement range.
The present invention is further described with reference to the accompanying drawings and detailed description.
As shown in Figure 1, merogenesis capacitance type liquid level converter hardware detecting circuit functional block diagram, the detection processing of capacitance signal
Process；Shown in hardware circuit principle, the carrier signal of two different frequencies is separately input in two demodulator circuits, and demodulation obtains
The corresponding amplitude direct current signal of two frequency components, the two direct current signals are directly proportional to capacitor and capacitance difference respectively；Capacitance difference
Signal reflects that liquid level holds situation in ring in a certain economize on electricity, and which specific economize on electricity is held in the sensor for capacitor and signal reflection liquid level
Ring.
As shown in Fig. 2, wien oscillator circuit diagram, wherein R1=R2=R, C1=C2=C, wien oscillator circuit are one
Kind RC oscillating circuit, for generating Low Frequency Sine Signals excitation, when amplitude output signal is smaller, due toElectricity
Road generates self-oscillation, and amplitude output signal increases, field-effect tube RDSAlso with increase, then the gain of circuit reduces, and limits
Amplitude output signal continues growing, and final output signal amplitude reaches stable；The frequency of sinusoidal signal is 2 π R, sinusoidal signal
Frequency can be adjusted by R and C, two-way wien oscillator circuit generate two different frequencies sinusoidal signal for motivate sampling
Circuit.
As shown in figure 3, cascade transformer electric bridge sample circuit schematic diagram, odd number capacitor C36 and even number capacitor C37 are by sensing
Device structure division is connected on sample circuit by shielding line；By sample circuit, one and capacitor and value (C36+C37) are exported
Directly proportional, directly proportional to capacitive differential (C36-C37) mixed signal.Capacitor C35 be reference capacitance, its adjustable capacitor and
The amplitude of value signal.
As shown in figure 4, exchange two-stage amplifying circuit schematic diagram, due to the corresponding capacitance signal very little of liquid level, their sum
Value signal and difference signal also very little, therefore sampled signal is carried out two-stage with mutually amplifying, amplification factor are two with mutually amplifying
The product of the amplification factor of circuitAmplification factor can be adjusted by R40 and R45.
As schemed, 5 show, AC signal phase-shift circuit schematic diagram, the input signal of phase-shift circuit be wien oscillator circuit just
String output signal, relationship is between phase shift output signal and input signalWherein
R18=R19=R, w are sinusoidal ac signal frequenciesTherefore when sinusoidal ac signal source frequency f is equal with 2 π R, output
Phase shift between signal and input signal is 90 °, that is, resistance R17 in phase-shift circuit, capacitor C17 and Dendrolimus kikuchii is required to vibrate
Resistance R1, the capacitor C1 of circuit are consistent.
As shown in fig. 6, demodulator circuit schematic diagram, input signal is the output signal FD_OUT of amplifying circuit, carrier signal
For the output signal YX_OUT of phase-shift circuit；Input signal and carrier signal are done multiplication by demodulator circuit, are letters on corresponding frequency domain
Number convolution, will move to origin and 2w Frequency point with the frequency domain of the component of carrier signal same frequency in such input signal, thus
It can demodulate to obtain direct current signal.
As shown in fig. 7, low pass filtered involves DC amplification circuit schematic diagram, third-order filter is filtered by second order filter and single order
Wave device composition, each lower order filter is mutually indepedent, is also convenient for debugging；The cutoff frequency of firstorder filter is determined by R26 and C27
Fixed, the cutoff frequency of second order filter is determined by R23, R24, C23 and C24；Due to including DC component in the signal after demodulation
Signal, harmonic signal and harmonic signal etc., low-pass filter can extract direct current signal, and direct current amplification can be with
Direct current signal amplitude is amplified to the range for being suitble to measurement.
As shown in figure 8, capacitor and signal, capacitor difference signal and level gauging relational graph, entire sensor are divided into 6 sections, often
250mm is saved, total effective range is 1500mm.In sensor confirmatory experiment, biography is accurately controlled using accurate experimental provision
The liquid level of sensor, sensor liquid level, sensor output capacitance and signal and capacitor difference signal are adopted by NI data collecting card
Collection；In liquid level variation, odd number capacitor, even number capacitor alternately change, the difference formation triangular signal of two groups of capacitance signals, and two
Group capacitance signal forms single adjusting wave signal with value；The i.e. merogenesis unit of the liquid level for representing merogenesis capacitor on one side of triangular wave
Physical length can calculate liquid level in the position of each section capacitor cell according to triangle wave voltage；Single adjusting wave signal and liquid level
It is highly linear, it can then be tied with the merogenesis number of discriminating sensor in the medium by the size of continuous voltage output valve
Accurate liquid level can be calculated by closing triangular signal.
As shown in figure 9, measured curve and theoretical curve amplify comparison diagram, before confirmatory experiment, sensor voltage is measured first
With the minimum value 0V and maximum value 5V of voltage differential signal, and corresponding liquid level 0mm and 250mm is recorded, liquid level is then calculated
With the theoretical curve of capacitor and signal, capacitor difference signal；It can recorde the voltage data of actual measurement in experiment by data collecting card
With liquid level data and generate measured curve, theoretical curve and measured curve are compared, the voltage value of each liquid level point in experiment
Error between the theoretical voltage value of same point is less than ± 40mV, i.e., each measurement liquid level point tolerance is less than ± 2mm.By multiple
The experiment of room temperature kerosene medium and the experiment of multiple low temperature liquid nitrogen medium be all satisfied measurement error less than ± 2mm.
Specific embodiments of the present invention are described above.It is to be appreciated that the invention is not limited to above-mentioned
Particular implementation, those skilled in the art can make a variety of changes or modify within the scope of the claims, this not shadow
Ring substantive content of the invention.In the absence of conflict, the feature in embodiments herein and embodiment can any phase
Mutually combination.
Claims (6)
1. a kind of merogenesis condenser type low temperature liquid-level converter, which is characterized in that including hardware detecting circuit, the hardware detection electricity
Road includes: two wien oscillator circuits, cascade transformer sample circuit, exchange two-stage amplifying circuit, two AC signal phase shifts
Circuit, two demodulator circuits, two low pass filtereds involve DC amplification circuit；Wherein:
Described two wien oscillator circuits, for generate low frequency sinusoidal pumping signal input the cascade transformer sample circuit with
And an AC signal phase-shift circuit, driver transformer are inputted respectively；
The cascade transformer sample circuit, for generate with liquid level it is linear exchange sampled signal；
The exchange two-stage amplifying circuit for amplifying to exchange sampled signal, and is exported to AC signal phase-shift circuit；
Described two AC signal phase-shift circuits, for carrying out 90 ° of phase shifts respectively to sinusoidal excitation signal；
Described two demodulator circuits are separately connected the output end of described two AC signal phase-shift circuits, for will be after phase shift
Sinusoidal excitation signal demodulate with frequency with the amplified sampled signal that exchanges；
Described two low pass filtereds involve DC amplification circuit, the output end of described two demodulator circuits are separately connected, for extracting
The DC component demodulated；
The cascade transformer sample circuit includes: cascade transformer, odd number capacitor Cj, even number capacitor Co, reference capacitance C0, takes
Sample resistance, cascade transformer electric bridge carry out seeking poor, summation operation to odd number capacitor Cj and even number capacitor Co, and the exchange after sampling is small
Signal is transmitted to exchange two-stage amplifying circuit.
2. merogenesis condenser type low temperature liquid-level converter according to claim 1, which is characterized in that the wien oscillator circuit
It include: operational amplifier, field-effect tube, power operational amplifier, precision capacitance, resistance, diode；The wien oscillator circuit
RC oscillator is constituted, for generating low frequency sinusoidal pumping signal；Wherein, field-effect tube is equivalent to a thyrite, utilizes field
Effect pipe and operational amplifier realize wien oscillator circuit output signal auto_steady amplitude, and the range stability of signal can reach
To 1%, while precision capacitance, resistance are used, so that the frequency stability of output signal reaches 5 ‰.
3. merogenesis condenser type low temperature liquid-level converter according to claim 1, which is characterized in that the exchange two-stage amplification
Circuit includes: binary channels operational amplifier, precision capacitance, precision resistance, wherein operational amplifier is two homophase input amplifications
Device, two homophase input amplifiers are cascade connection, and amplification factor is the product of the amplification factor of two in-phase amplifiers.
4. merogenesis condenser type low temperature liquid-level converter according to claim 1, which is characterized in that the AC signal phase shift
Circuit includes: operational amplifier, precision capacitance, resistance, and sinusoidal excitation signal is carried out 90 ° by the AC signal phase-shift circuit
Phase shift, carrier signal of the signal as demodulator circuit after phase shift.
5. merogenesis condenser type low temperature liquid-level converter according to claim 1, which is characterized in that the demodulator circuit packet
Include: demodulation chip, filter capacitor, variable resistance, demodulator circuit be used for by two input AC signal do multiplying into
Row phase sensitive detection, two input exchange signals frequency having the same and phase, two input exchange signals are respectively to pass through two
The sampled signal of grade exchange amplification and the sinusoidal signal after 90 ° of phase shifts.
6. merogenesis condenser type low temperature liquid-level converter according to claim 1, which is characterized in that the low pass filtered involves directly
Current amplifier uses three rank Butterworth active filter circuits, comprising: operational amplifier chip, resistance, capacitor, for solution
AC signal after tune carries out low-pass filtering, takes out the flip-flop in AC signal, while amplifying to direct current signal, makes
The amplitude for obtaining direct current signal is adjusted to the range of setting.
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| CN108362355B (en) * | 2017-12-18 | 2019-12-20 | 北京遥测技术研究所 | Liquid level measurement method and device based on segmented capacitor and electronic equipment |
| CN111142458B (en) * | 2019-12-05 | 2020-09-08 | 北京星际荣耀空间科技有限公司 | Solid carrier rocket engine exhaustion judging method, device and equipment |
| CN112798077B (en) * | 2020-12-29 | 2023-04-07 | 北京金迈捷科技股份有限公司 | Liquid level height analysis method, device, equipment, storage medium and system |
| CN119374697B (en) * | 2025-01-02 | 2025-05-02 | 上海航天设备制造总厂有限公司 | Method and system for measuring liquid level height of cascade liquid level sensor in flight process |
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