CN102798431B - Piezoelectric crystal oscillation and detection device - Google Patents
Piezoelectric crystal oscillation and detection device Download PDFInfo
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- CN102798431B CN102798431B CN201210317167.1A CN201210317167A CN102798431B CN 102798431 B CN102798431 B CN 102798431B CN 201210317167 A CN201210317167 A CN 201210317167A CN 102798431 B CN102798431 B CN 102798431B
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Abstract
The invention discloses a piezoelectric crystal oscillation and detection device, which comprises a power supply switching circuit, a DC-DC boosting converting circuit, a PWM-wave waveform generating circuit, a voltage-control electronic switch, piezoelectric crystal, a resonance body and an oscillation detection circuit. Due to the implementation of the technical scheme of the invention, not only is the power consumption of a system greatly reduced to facilitate oscillation starting and realize continuous and stable oscillation, but also the parameter values of energy storing elements of the system and the excitation voltage of the piezoelectric crystal are reduced remarkably to provide the system with the important characteristics of intrinsic safety and the like. Therefore, the piezoelectric crystal oscillation and detection device is extremely suitable for the flammable and explosive industrial sites and other industrial sites with high safety requirements.
Description
Technical field
The present invention relates to electronic information and automatic control technology field, in particular, relate in particular to a kind of piezoelectric crystal oscillating and pick-up unit.
Background technology
At present, piezoelectric crystal oscillating and detection technique thereof, be a kind of very important detection means, is widely used in industrial and agricultural production, especially in process control engineering field.The principle of work of piezoelectric crystal oscillating and detection technique thereof is, the voltage signal of alternation acts on the electric axis signal input part of piezoelectric crystal, at its mechanical axis axis direction, just can produce periodic vibration, when this oscillation frequency is consistent with the resonant body being attached thereto (such as tuning fork) natural mode shape, resonant body just can produce resonance.When the resonant body in resonance is arranged in different media, its oscillation frequency and amplitude can change, and by detecting the variation of its oscillation frequency and amplitude, just can measure the interface of solid or liquid material level, reach the object of level gauging.
In implementation procedure of the present invention, inventor finds:
At present, among pierce oscillator of the prior art, alternating voltage signal generally adopts analog voltage signal, square wave by CPU output some cycles, by the filtering device of the forms such as low-pass filtering RC, square wave is become to the pulsating waveform of near sinusoidal or cosine signal, this pulsating wave signal carries out differential amplification by differential amplifier again, become the two paths of differential signals that phase difference value is 180 degree, after boosting by transformer again, two paths of signals is added to respectively to the signal input part of piezoelectric crystal, thereby causes the mechanical oscillation of piezoelectric crystal.At present, exist energy storage component parameter value excessive in traditional piezoelectric crystal oscillating and pick-up unit, be difficult to reach essential safety requirement, power consumption is too high, analog device and analog signal transmission and processing, starting of oscillation difficulty, the shortcomings such as easy failure of oscillation.
Summary of the invention
The object of this invention is to provide a kind of piezoelectric crystal oscillating and pick-up unit, can make system power dissipation greatly reduce, be easy to starting of oscillation, and vibration is continual and steady.
The object of the invention is to be achieved through the following technical solutions:
The embodiment of the present invention provides a kind of piezoelectric crystal oscillating and pick-up unit, comprising:
Power-switching circuit, the signal input part of described power-switching circuit is connected with external power source input end, and the signal output part of power-switching circuit is connected with the signal input part of DC-DC boost conversion circuit, for generating higher operating voltage;
DC-DC boost conversion circuit, the signal output part of described DC-DC boost conversion circuit is connected with the power end of voltage-controlled electronic switch, for carrying out low-voltage to high-tension boost in voltage operation, produces the higher operating voltage that meets piezoelectric crystal oscillating needs;
PWM waveform circuit for generating, the signal output part of described PWM waveform circuit for generating is connected with the signal input part of voltage-controlled electronic switch, for generation of the PWM pulse-width modulation waveform of two-way at least, to form the needed voltage control signal of voltage-controlled electronic switch;
Voltage-controlled electronic switch, the signal output part of described voltage-controlled electronic switch is connected with the signal input part of described piezoelectric crystal, for producing the alternating voltage signal of the needed higher voltage value of piezoelectric crystal oscillating under controlling at PWM pulse-width signal;
Piezoelectric crystal, the signal input part of described piezoelectric crystal, is connected with voltage-controlled electronic switch signal output terminal, under the effect of alternation variable voltage signal, produces mechanical oscillation; Meanwhile, described piezoelectric crystal and described resonant body are closely fixed together, and the mechanical vibration of its generation can directly be conducted to resonant body; Described piezoelectric crystal is also closely fixed together with detecting piezoelectric crystal simultaneously, and the mechanical vibration of its generation can directly be passed to detection piezoelectric crystal, and be made to detect the Voltage-output signal that piezoelectric crystal produces certain amplitude simultaneously.
Resonant body, described resonant body is physical construction body, for more stable resonance frequency is provided, described resonant body and piezoelectric crystal and detection piezoelectric crystal are closely fixed together.When the oscillation frequency of piezoelectric crystal and the natural frequency of described resonant body are when consistent, described resonant body just can resonate, and produces lasting mechanical oscillation;
Oscillation detection circuit, changes and amplitude variations situation for detecting in real time the oscillation frequency of resonant body.
Further, described device also comprises:
Central processing unit, the signal output part of described oscillation detection circuit is connected with central processing unit place main circuit signal input part, the signal output part of the main circuit at described central processing unit place is connected with feedback output circuit, for described oscillation detection circuit output signal is carried out to sampling processing; Meanwhile, according to the data message after processing, output PWM pulse-width signal.
Feedback output circuit, for the signal after central processing unit is processed, exports in the mode of 4-20mA.
Further, described power-switching circuit comprises:
Rectification and second protection device, current-voltage conversion and voltage-stabilizing device, filtering device and linear voltage-stabilizing circuit;
Wherein, described rectification is connected with outside input power signal with the input end of second protection device, and described rectification is connected with the signal input part of voltage-stabilizing device with current-voltage conversion with the signal output part of second protection device; Described current-voltage conversion is connected with the signal output part of voltage-stabilizing device and the signal input part of filtering device; The signal output part of described filtering device is connected with the current input terminal of DC-DC boost conversion circuit with the input end of linear voltage-stabilizing circuit respectively.
Further, described DC-DC boost conversion circuit comprises:
Telefault, DC-DC special chip and accessory circuit, rectification circuit and feedback and voltage regulation filtering network;
Wherein, the input end of described telefault and the current output terminal of described power-switching circuit are connected; The output terminal of described telefault is connected with the input end of described DC-DC special chip and accessory circuit and described rectification circuit; The output terminal of described rectification circuit is connected with the signal input part of voltage regulation filtering network with described feedback; Described feedback is connected with the feedback signal output terminal of voltage regulation filtering network and the feedback signal input end of DC-DC special chip and accessory circuit thereof.
Further, described feedback output circuit comprises:
Interface circuit, the input end of described interface circuit is connected with the central processing unit of main circuit;
Wireless transmission circuit, is connected with the output terminal of described interface circuit, for described sampled signal is transmitted wirelessly;
Wire transmission circuit, is connected with the output terminal of described interface circuit, for described sampled signal is transmitted in wired mode.
Further, described wire transmission circuit comprises:
Switch optocoupler, triggering shaping circuit, D/A converter, analog voltage amplifier, current amplifier and negative-feedback circuit;
Wherein, the signal output part of described central processing unit is connected with the signal input part of described switch optocoupler by interface circuit; The signal output part of switch optocoupler is connected with the signal input part of described triggering shaping circuit; Triggering the signal output part of shaping circuit and the signal input part of described D/A converter is connected; The signal output part of D/A converter is connected with the signal input part of described analog voltage amplifier; The signal output part of analog voltage amplifier is connected with the signal input part of described current amplifier; The signal output part of current amplifier is connected with the signal input part of described negative-feedback circuit; The signal output part of negative-feedback circuit is connected with the signal input part of described analog voltage amplifier.
Further, described wireless transmission circuit adopts FM transmission technology, and described sampled signal is transmitted.
Further, the input power signal of described power-switching circuit is any one in 4-20mA, HART bus signals and 24V direct supply.
Further, described power-switching circuit, DC-DC boost conversion circuit, PWM waveform circuit for generating and voltage-controlled electronic switch, can also be for as universal circuit, to piezo electric valve or solenoid valve is voltage-controlled can drive control by execution unit.
As seen from the above technical solution provided by the invention, a kind of piezoelectric crystal oscillating and pick-up unit that the embodiment of the present invention provides, used DC-DC boost conversion circuit to replace traditional step-up transformer; With PWM waveform circuit for generating and voltage-controlled electronic switch, replace traditional analog differential amplifier and wave filter; With PWM ripple, replace traditional sine or cosine signal as the pumping signal of piezoelectric crystal; Power-switching circuit can compatible 4-20mA electric current, HART bus signals and 24V DC power signal; PWM waveform circuit for generating, can produce multi-channel PWM and drive signal, drives multichannel piezoelectric crystal and resonant body work, realizes multichannel and detects.At work, utilize dynamic digital sweep frequency technique, adjust in real time crystal oscillation frequency, make it dynamically to follow the tracks of the variation of resonant body natural mode shape.Technical scheme of the present invention can significantly reduce system power dissipation, and structure simplifies, piezoelectric crystal is easier to starting of oscillation, and resonant body vibration is continual and steady, there is the key characters such as Sefe antiexplosion simultaneously, be extremely applicable to the industry spot higher to safety requirements such as inflammable, explosive.
Accompanying drawing explanation
In order to be illustrated more clearly in the technical scheme of the embodiment of the present invention, below the accompanying drawing of required use during embodiment is described is briefly described, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, do not paying under the prerequisite of creative work, can also obtain other accompanying drawings according to these accompanying drawings.
The piezoelectric crystal oscillating that Fig. 1 provides for the embodiment of the present invention and the structural representation of pick-up unit;
Fig. 2 is the circuit theory diagrams of power conversion that the embodiment of the present invention provides and DC-DC boost conversion circuit;
Fig. 3 is the schematic diagram of high precision that the embodiment of the present invention provides feedback output circuit.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described, obviously, described embodiment is only the present invention's part embodiment, rather than whole embodiment.Based on embodiments of the invention, those of ordinary skills, not making the every other embodiment obtaining under creative work prerequisite, belong to protection scope of the present invention.
Below in conjunction with accompanying drawing, the embodiment of the present invention is described in further detail.
As shown in Figure 1, the embodiment of the present invention provides a kind of piezoelectric crystal oscillating and pick-up unit, comprising:
Power-switching circuit 1, for generating operating voltage;
DC-DC boost conversion circuit 2, for carrying out low-voltage to high-tension boost in voltage operation, produces the higher operating voltage that meets piezoelectric crystal oscillating needs;
PWM waveform circuit for generating 5, for generation of the PWM pulse-width modulation waveform of two-way at least, to form the needed voltage control signal of voltage-controlled electronic switch;
Voltage-controlled electronic switch 3 produces the needed higher alternating voltage signal of piezoelectric crystal oscillating under controlling at PWM pulse-width signal;
Wherein, the signal input part of described power-switching circuit is connected with external power source input end, and the signal output part of power-switching circuit is connected with the signal input part of DC-DC boost conversion circuit; The signal output part of described DC-DC boost conversion circuit is connected with the power end of voltage-controlled electronic switch; The signal output part of described PWM waveform circuit for generating is connected with the signal input part of voltage-controlled electronic switch; The signal output part of described voltage-controlled electronic switch is connected with the signal input part of described piezoelectric crystal; The signal output part of described piezoelectric crystal is connected with the signal input part of resonant body; The signal output part of described resonant body is connected with oscillation detection circuit.
Further, described device can also comprise:
Central processing unit (CPU) 8, the signal output part of described oscillation detection circuit is connected with central processing unit place main circuit signal input part, the output terminal of described central processing unit is connected with feedback output circuit, for the signal of described oscillation detection circuit output is carried out to sampling processing; Meanwhile, be also connected with PWM waveform circuit for generating, for exporting PWM pulse width modulated wave.
The circuit theory diagrams that are illustrated in figure 2 power conversion that the embodiment of the present invention provides and DC-DC boost conversion circuit etc., described power-switching circuit further can comprise:
Rectification and second protection device 21, current-voltage conversion and voltage-stabilizing device 22, filtering device 23 and linear voltage-stabilizing circuit 24;
Wherein, described rectification is connected with outside input power signal with the input end of second protection device, and described rectification is connected with the signal input part of voltage-stabilizing device with current-voltage conversion with the signal output part of second protection device; Described current-voltage conversion is connected with the signal output part of voltage-stabilizing device and the signal input part of filtering device; The signal output part of described filtering device is connected with the current input terminal of DC-DC boost conversion circuit 2 with the input end of linear voltage-stabilizing circuit respectively.
The input power signal of described power-switching circuit can adapt to any one input power signal in 4-20mA, HART bus signals and 24V direct supply.From outside power supply signal; such as 4-20mA current signal; by described rectification and second protection device 21, the conversion of described current-voltage and voltage-stabilizing device 22 and described filtering device 23 etc.; complete rectification and second protection, voltage pick-up, voltage stabilizing and preliminary filtering etc., produce the DC voltage with certain numerical value.This voltage, through described linear voltage-stabilizing circuit 24, produces the stable voltage signal of normally working for circuit units such as CPU.
Further, described DC-DC boost conversion circuit can comprise:
Telefault 25, DC-DC special chip and accessory circuit 26 thereof, rectification circuit 27 and feedback and voltage regulation filtering network 28;
Wherein, the input end of described telefault and the current output terminal of described power-switching circuit are connected; The output terminal of described telefault is connected with the input end of described DC-DC special chip and accessory circuit and described rectification circuit; The output terminal of described rectification circuit is connected with the signal input part of voltage regulation filtering network with described feedback; Described feedback is connected with the feedback signal output terminal of voltage regulation filtering network and the feedback signal input end of DC-DC special chip and accessory circuit thereof.By adjusting correlation parameter, lower input voltage value can be elevated to required numerical value.
Based on technique scheme specifically, by described power-switching circuit 1, can form multiple voltage, to meet the described DC-DC boost conversion circuit 2 needed voltage of the normal work of the element circuits such as required voltage and Fig. 2 neutral line mu balanced circuit that boosts, by described DC-DC boost conversion circuit 2, complete by low-voltage to high-tension boost in voltage function, generation meet 4 vibrations of described piezoelectric crystal required compared with high working voltage, by described PWM waveform generator 5, produce two-way Huo Shuo road PWM pulse-width modulation waveform, form the needed voltage control signal of described voltage-controlled electronic switch 3, described voltage-controlled electronic switch 3 produces the needed higher alternating voltage signal of described piezoelectric crystal 4 vibration under PWM pulse-width signal is controlled, when the oscillation frequency of piezoelectric crystal 4 and the natural frequency of described resonant body 7 are when consistent, described resonant body 7 just can resonate, produce lasting mechanical oscillation, by described oscillation detection circuit 6, just can detect in real time oscillation frequency and the amplitude variations situation of resonant body, and then carry out detection and the measurement of related physical quantity.
In addition, the output of pwm signal and detection, can adopt digital dynamic sweep frequency technique, dynamically adjusts PWM frequency wave period, to compensate the resonant body natural frequency offset problem causing due to factors such as temperature variation.Driving voltage frequency-tracking resonant body natural frequency is changed.
As shown in Figure 3, described feedback output circuit can comprise:
Wire transmission circuit, is connected with the output terminal of described interface circuit, for described sampled signal is transmitted in wired mode.
Further, described wire transmission circuit can comprise:
Wherein, the signal output part of described central processing unit is connected with the signal input part of described switch optocoupler by interface circuit; The signal output part of switch optocoupler is connected with the signal input part of described triggering shaping circuit; Triggering the signal output part of shaping circuit and the signal input part of described D/A converter is connected; The signal output part of D/A converter is connected with the signal input part of described analog voltage amplifier; The signal output part of analog voltage amplifier is connected with the signal input part of described current amplifier; The signal output part of current amplifier is connected with the signal input part of described negative-feedback circuit; The signal output part of negative-feedback circuit is connected with the signal input part of described analog voltage amplifier.
Further, described wireless transmission circuit adopts FM transmission technology, and described sampled signal is transmitted.Data message is arrived to far-end by wireless network transmissions, and in remote circuitry, data message can be exported with 4-20mA isotype.
In wire transmission module, data output to described switch optocoupler 310, after described triggering shaping circuit 311, input described D/A converter 312, D/A converter 312 is converted to digital signal after corresponding simulating signal, this simulating signal is amplified through described analog voltage amplifier 313 and is exported current amplifier 314 to, and between negative-feedback circuit 315, form close loop negative feedback loop, by this loop, complete after Voltage-current conversion and steady flow measure, the final 8mA of formation and 16mA loop current form or other signal transfer modes are exported, thereby improved the transmission precision of described feedback loop output signal.
In addition, power-switching circuit described in the embodiment of the present invention, DC-DC boost conversion circuit, PWM waveform circuit for generating and voltage-controlled electronic switch, also for as universal circuit, job control that can execution unit to piezo electric valve and solenoid valve.
The technical scheme providing based on the invention described above embodiment can be found out, by using DCDC boost conversion circuit, replace traditional step-up transformer, use PWM waveform circuit for generating and voltage-controlled electronic switch to replace traditional analog differential amplifier and wave filter, use the square wave through the modulation of PWM technology to replace traditional sinusoidal alternating signal as the pumping signal of piezoelectric crystal, in described feedback output channel, increase wired, wireless two kinds of patterns, increased the dirigibility of output signal.
By in valve position feedback output loop, increase Current Negative Three-Point Capacitance output unit circuit design, improved the stability of workload-adaptability and current signal output; At the valve position feedback output of valve position transmitter, adopt switch light-coupled isolation and digital transmission, reduced the bit error rate of signal transmission, improved signal transmission distance.
Not only system power dissipation reduces greatly, is easy to starting of oscillation, and vibration is continual and steady, and tool significantly reduced the parameter value of system stored energy element and the driving voltage of piezoelectric crystal, thereby makes system have the key characters such as Sefe antiexplosion.Therefore, be extremely applicable to the industry spot higher to safety requirements such as inflammable, explosive.
The above; be only the present invention's embodiment preferably, but protection scope of the present invention is not limited to this, is anyly familiar with in technical scope that those skilled in the art disclose in the present invention; the variation that can expect easily or replacement, within all should being encompassed in protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain of claims.
Claims (9)
1. piezoelectric crystal oscillating and a pick-up unit, is characterized in that, comprising:
Power-switching circuit, the signal input part of described power-switching circuit is connected with external power source input end, and the signal output part of power-switching circuit is connected with the signal input part of inductive type switching mode DC-DC boost conversion circuit, for generating operating voltage;
DC-DC boost conversion circuit, the signal output part of described DC-DC boost conversion circuit is connected with the power end of voltage-controlled electronic switch, for carrying out low-voltage to high-tension boost in voltage operation, produces the higher operating voltage that meets piezoelectric crystal oscillating needs;
Pulse width modulation (PWM) waveform circuit for generating, the signal output part of described PWM waveform circuit for generating is connected with the signal input part of voltage-controlled electronic switch, for generation of the PWM pulse-width modulation waveform of two-way at least, to form the needed voltage control signal of voltage-controlled electronic switch;
Voltage-controlled electronic switch, the signal output part of described voltage-controlled electronic switch is connected with the signal input part of described piezoelectric crystal, for producing the alternating voltage signal of the needed higher voltage value of piezoelectric crystal oscillating under controlling at PWM pulse-width signal;
Piezoelectric crystal, the signal input part of described piezoelectric crystal, is connected with voltage-controlled electronic switch signal output terminal, under the effect of alternation variable voltage signal, produces mechanical oscillation; Meanwhile, described piezoelectric crystal and resonant body are closely fixed together, the mechanical vibration of its generation, and directly conduction is to resonant body; Described piezoelectric crystal is also closely fixed together with detecting piezoelectric crystal simultaneously, and the mechanical vibration of its generation are directly passed to detection piezoelectric crystal, and made to detect the Voltage-output signal that piezoelectric crystal produces certain amplitude simultaneously;
Resonant body, described resonant body is physical construction body, for more stable resonance frequency is provided, described resonant body and piezoelectric crystal and detection piezoelectric crystal are closely fixed together; When the oscillation frequency of piezoelectric crystal and the natural frequency of described resonant body are when consistent, described resonant body just can resonate, and produces lasting mechanical oscillation;
Oscillation detection circuit, changes and amplitude variations situation for detecting in real time the oscillation frequency of resonant body.
2. device according to claim 1, is characterized in that, described device also comprises:
Central processing unit, the signal output part of described oscillation detection circuit is connected with central processing unit place main circuit signal input part, the signal output part of the main circuit at described central processing unit place is connected with feedback output circuit,, is also connected with PWM waveform circuit for generating meanwhile; Central processing unit, for the signal of described oscillation detection circuit output is carried out to sampling processing, meanwhile, is exported PWM ripple;
Feedback output circuit, for the signal after central processing unit is processed, exports in the mode of 4-20mA.
3. device according to claim 2, is characterized in that, described power-switching circuit comprises:
Rectification and second protection device, current-voltage conversion and voltage-stabilizing device, filtering device and linear voltage-stabilizing circuit;
Wherein, described rectification is connected with outside input power signal with the input end of second protection device, and described rectification is connected with the signal input part of voltage-stabilizing device with current-voltage conversion with the signal output part of second protection device; Described current-voltage conversion is connected with the signal output part of voltage-stabilizing device and the signal input part of filtering device; The signal output part of described filtering device is connected with the current input terminal of DC-DC boost conversion circuit with the input end of linear voltage-stabilizing circuit respectively.
4. device according to claim 2, is characterized in that, described DC-DC boost conversion circuit comprises:
Telefault, DC-DC special chip and accessory circuit, rectification circuit and feedback and voltage regulation filtering network;
Wherein, the input end of described telefault and the current output terminal of described power-switching circuit are connected; The output terminal of described telefault is connected with the input end of described DC-DC special chip and accessory circuit and described rectification circuit; The output terminal of described rectification circuit is connected with the signal input part of voltage regulation filtering network with described feedback; Described feedback is connected with the feedback signal output terminal of voltage regulation filtering network and the feedback signal input end of DC-DC special chip and accessory circuit thereof.
5. device according to claim 2, is characterized in that, described feedback output circuit comprises:
Interface circuit, the input end of described interface circuit is connected with the central processing unit of main circuit;
Wireless transmission circuit, is connected with the output terminal of described interface circuit, for the signal of described central processing unit output is transmitted wirelessly;
Wire transmission circuit, is connected with the output terminal of described interface circuit, for the signal of described central processing unit output is transmitted in wired mode.
6. device according to claim 5, is characterized in that, described wire transmission circuit comprises:
Switch optocoupler, triggering shaping circuit, D/A converter, analog voltage amplifier, current amplifier and negative-feedback circuit;
Wherein, the signal output part of described central processing unit is connected with the signal input part of described switch optocoupler by interface circuit; The signal output part of switch optocoupler is connected with the signal input part of described triggering shaping circuit; Triggering the signal output part of shaping circuit and the signal input part of described D/A converter is connected; The signal output part of D/A converter is connected with the signal input part of described analog voltage amplifier; The signal output part of analog voltage amplifier is connected with the signal input part of described current amplifier; The signal output part of current amplifier is connected with the signal input part of described negative-feedback circuit; The signal output part of negative-feedback circuit is connected with the signal input part of described analog voltage amplifier.
7. device according to claim 5, is characterized in that, described wireless transmission circuit adopts FM transmission technology, and the signal of described central processing unit output is transmitted.
8. according to arbitrary described device in claim 1-6, it is characterized in that, the input power signal of described power-switching circuit is any one in 4-20mA or HART bus signals and 24V direct supply.
9. according to arbitrary described device in claim 1-6, it is characterized in that, described power-switching circuit, DC-DC boost conversion circuit, PWM waveform circuit for generating and voltage-controlled electronic switch, also for as universal circuit, to piezo electric valve or solenoid valve is voltage-controlled can drive control by execution unit.
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| CN103017862B (en) * | 2012-12-06 | 2015-08-26 | 宁海县盛源激光科技有限公司 | Position in storehouse intelligent device for measuring |
| CN103063292B (en) * | 2012-12-10 | 2015-12-02 | 中国飞机强度研究所 | A kind of piezoelectric crystal plate resonant frequency measurement method |
| CN106225867B (en) * | 2016-07-27 | 2019-05-14 | 北京小米移动软件有限公司 | Cistern water level measurement method and device |
| CN108401476B (en) * | 2018-03-09 | 2021-09-17 | 深圳市汇顶科技股份有限公司 | Crystal oscillator |
| CN108692410B (en) * | 2018-04-25 | 2024-02-23 | 上海菱沃铂智能技术有限公司 | Efficient vibration device and method for vibration plate of ultrasonic humidifier |
| CN108828356A (en) * | 2018-06-11 | 2018-11-16 | 南京尤尼泰信息科技有限公司 | It is a kind of suitable for plurality of specifications crystal oscillator for electrical test circuit |
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| CN201007675Y (en) * | 2007-02-13 | 2008-01-16 | 北京京仪海福尔自动化仪表有限公司 | Tuning fork level message reporting device |
| CN201053893Y (en) * | 2007-05-14 | 2008-04-30 | 瑞达电子股份有限公司 | Strong vibration adjustable tuning fork material-position measuring meter |
| JP4625494B2 (en) * | 2007-12-25 | 2011-02-02 | 日本電波工業株式会社 | Oscillation frequency control circuit |
| CN101865718B (en) * | 2009-04-17 | 2013-09-11 | 深圳迈瑞生物医疗电子股份有限公司 | Liquid level detection circuit, device and calibration method thereof |
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Effective date of registration: 20180903 Address after: 100013 Hepingli North Street, Dongcheng District, Beijing 6 Patentee after: Beijing Far East Instrument Co., Ltd. Address before: 100011 16 ande Road, Dongcheng District, Beijing Patentee before: Beijing Jing Yi-HIFOR Automation Instrument Co.,Ltd. |
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