CN103499386B - A kind of method and apparatus of precision measurement frequency - Google Patents
A kind of method and apparatus of precision measurement frequency Download PDFInfo
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- CN103499386B CN103499386B CN201310445423.XA CN201310445423A CN103499386B CN 103499386 B CN103499386 B CN 103499386B CN 201310445423 A CN201310445423 A CN 201310445423A CN 103499386 B CN103499386 B CN 103499386B
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Abstract
A method and apparatus for precision measurement frequency, by vibration measurement sensor, capacitance-voltage conversion circuit, the composition such as signal processing circuit and display device.Vibration measurement sensor is primarily of staving, bung, conical gas section composition that liquid is housed, and wherein bung is capacitive transducer.Signal processing circuit forms primarily of amplifying circuit, filtering circuit, analog to digital converter, FPGA and CPU (central processing unit).Vibration measurement sensor is the Amplitude amplification of mechanical vibration, and change is converted into the change of electric capacity.Capacitance-voltage conversion circuit is converted to voltage signal capacitance signal, and amplifying circuit amplifies this voltage signal, the impurity signal in this voltage signal of filtering circuit filtering.The cycle of measuring the signal that capacitance-voltage conversion circuit exports just can realize the measurement of frequency, and display device is used for the frequency that display frequency meter is finally measured.Because the present invention can realize High Precision Frequency.
Description
Technical field
The invention belongs to sophisticated sensor and detection technique field, be specifically related to a kind of measuring instrument utilizing mechanical vibration amplitude multiplying arrangement precision measurement vibration frequency.
Background technology
During a lot of mechanical hook-up work, capital is with certain frequency vibration, but its Oscillation Amplitude is very low, when direct survey sensor is measured, because signal is too weak, be not easy to directly measure with sensor, so mechanical parameter is before entering sensor, amplification process should be carried out to mechanical parameter.
Traditional frequency measurement is nearly all utilize the cycle of the counter module of processor to measured signal to measure, although the method can reach Real-time and Dynamic Detection, and whole frequency measuring process can be made to keep high stability, high precision, but counter is when carrying out period measurement, all obtain by the cycle of signal with the clock period that the count value of counter is multiplied by counter, when the cycle of clock signal is greater than the cycle of measured signal, just can not measure the frequency of measured signal, and when utilizing counter counts, it can only be the integral multiple of counter clock cycle.Utilize A/D to change to sample to measured signal, the method for recycling linear interpolation carries out discrete digital signal processing the cycle that just can calculate signal more accurately.
Patent documentation CN101526393B discloses a kind of method and apparatus of measuring vibrations frequency, it is that the change of scattered light during object vibration is passed to the special photomultiplier of photon counting by light transmitting fiber, convert the signal into electric signal and flow to photoimpact counter, again through subsequent treatment, obtain vibration frequency.Although the method achieves the non-contact measurement of frequency, but also there is a lot of weak points: one, when the material of testee is the transparent materials such as glass, when incident ray is irradiated to testee surface, incident light can enter other medium with the form of refraction, can not to reflex in the medium identical with incident ray, such photo detecting unit just cannot detect the scattered light after testee scattering; Its two, scattered light is before being detected by photo detecting unit, and the propagation of scattered light is affected by environment very large, and the granule of such as air suspension can make light generation diffraction etc.
Summary of the invention
The present invention is directed to the problems referred to above, a kind of high-resolution vibration frequency measuring method and vibration frequency measuring instrument are proposed, by vibration measurement sensor, FPGA circuit and digital subdividing interpolation algorithm, can the measurement realizing nsec under the prerequisite measuring real-time ensured, thus realize the measurement of high precision vibration frequency.
The technical solution used in the present invention is:
The present invention is for the signal processing circuit realizing the device involving vibrations survey sensor of high-precision frequency measurement, the capacitance-voltage conversion circuit be connected with sensor, the amplifying circuit be connected with capacitance-voltage conversion circuit, the filtering circuit be connected with amplifying circuit and be connected with filtering circuit.
Described vibration measurement sensor is equipped with the staving of liquids and gases by one and forms as the bung of capacitive transducer; Liquid in staving is the water can propagating vibration, it is gas section on liquid, as vibration amplitude multiplying arrangement, the top of bung is the metal polar plate of fixing conduction, this metal polar plate is as the fixed plate of capacitive transducer, be the film being coated with conducting metal below fixed plate, this film can vibrate with the vibration in the external world.
Described gas section is pyramidal structure, lower end area is greater than upper end area, when vibration characteristics propagates into multiplying arrangement lower end by WATER AS FLOW MEDIUM, multiplying arrangement lower end also can with liquid with certain frequency and amplitude vibrations, vibration characteristics can propagate into multiplying arrangement top by gas multiplying arrangement, because the vibrational energy of harmonic motion becomes positively related relation with its amplitude, so, according to law of conservation of energy, the Oscillation Amplitude at multiplying arrangement top is greater than the Oscillation Amplitude bottom multiplying arrangement.
The signal processing circuit of this measuring instrument comprises analog to digital converter (A/D), FPGA (FPGA) and CPU (central processing unit) (CPU).
Described A/D converter is used for simulating signal to be converted to digital signal, and inputs FPGA.
Described FPGA circuit completes the sampling of capacitance-voltage conversion circuit output signal, and data existence is configured in the memory block of FPGA inside.
Described central processing unit CPU connects on-site programmable gate array FPGA, control on-site programmable gate array FPGA and send the order of A/D controlling of sampling, after sampling completes, central processing unit CPU is responsible for the A/D sampled data reading voltage signal in FPGA, the moment corresponding to data origination and terminal is calculated by built-in segmentation interpolation algorithm module, and then determine the time of each group data, the frequency of mechanical vibration is then accurately calculated according to the relation of time and frequency.
The circuit that capacitance-voltage conversion circuit of the present invention is is core with integrated package CAV424, it can be converted into the change of electric capacity the change of voltage.Amplifying circuit adopts series voltage negtive backword amplifying circuit, its feature be sue for peace in the form of voltage, can regulated output voltage, belong to voltage-controlled voltage source.
The High Precision Frequency method that the present invention proposes is as follows:
The staving of vibration transducer is just being placed on vibration source, central processing unit CPU controls on-site programmable gate array FPGA and sends A/D sampling control signal, vibration measurement sensor is converted to electric signal mechanical vibration, export vibration signal, after amplifying circuit amplifies the electric signal after convert of capacitor to voltage, carry out filtering by filtering circuit to voltage signal again, sampled by A/D change-over circuit to voltage signal, sampled data is first stored in the memory block that is configured in FPGA.
After having sampled, first central processing unit CPU reads the A/D sampled data of voltage signal in FPGA, adopts and accurately calculates moment corresponding to data origination and terminal by segmentation interpolation algorithm module, and then accurately determine the time of each group data.Then the frequency of mechanical vibration is accurately calculated according to the relation of time and frequency.
Because vibration characteristics is by the liquid in the bucket of vibration transducer, gas multiplying arrangement passes to bucket top, the capacitive transducer on bucket top will be converted to change in electric characteristic mechanical vibration performance, vibration transducer electric signal is out a Variable Amplitude cyclical signal, the starting point moment often organizing data can be the moment corresponding to arbitrary zero crossing, moment corresponding to this zero crossing can be determined by segmentation interpolation algorithm, often organizing the data endpoint moment is the moment after first zero passage corresponding to the 8th zero crossing, moment corresponding to this zero crossing also can be determined by segmentation interpolation algorithm.Therefore, segmentation interpolation algorithm module is provided with in central processing unit CPU.
Described segmentation interpolation algorithm module is the moment determining corresponding to former and later two sampled points of zero crossing (ratio zero large, a ratio zero is little) according to the A/D sampled signal stored in FPGA; Last with former and later two sampled points of zero crossing for benchmark, carry out segmentation interpolation by the method for matching to sampled point, determine the moment corresponding to voltage signal zero crossing, its precision depends primarily on the resolution that A/D samples.
Mechanical vibration amplitude, owing to have employed the vibration transducer of special construction, can be amplified and can not change the vibration frequency of mechanical vibration by the present invention dexterously.After mechanical vibration amplitude is exaggerated, capacitive transducer is easier sense mechanism Vibration Parameter just.
Meanwhile, the present invention adopts hardware circuit based on FPGA and segmentation interpolation algorithm module, can realize the time measurement of nanosecond precision, thus realize high-precision frequency measurement, and ensure good real-time.
The present invention can be widely used in the fields such as precise frequency measurement and control.
Accompanying drawing explanation
Fig. 1 is the structural representation of high precision vibration frequency measuring instrument;
Fig. 2 is that measured physical quantity is converted to voltage signal circuit theory diagram;
Fig. 3 is the principle of work schematic diagram of hardware circuit;
The schematic diagram in moment corresponding to Fig. 4 determination signal zero crossing time.
Embodiment
Below in conjunction with Figure of description, technical scheme of the present invention is described in further detail.
See Fig. 1, this vibration frequency measuring instrument is formed primarily of taper encapsulation staving 10, bung 16, convert of capacitor to voltage (C/V) circuit 11, amplifying circuit 12, filtering circuit 13, A/D change-over circuit 14, FPGA FPGA16, central processing unit CPU 17, LCD display 18 and keyboard 19.
Liquids and gases in staving 10, bung 16 and bucket form vibration measurement sensor.
Liquid in bucket is the water that can transmit vibration characteristics, gas section on liquid is as vibration amplitude multiplying arrangement, gas section is pyramidal structure, lower end area is greater than upper end area, when vibration characteristics propagates into multiplying arrangement lower end by WATER AS FLOW MEDIUM, multiplying arrangement lower end also can with liquid with certain frequency and amplitude vibrations, vibration characteristics can propagate into multiplying arrangement top by gas multiplying arrangement, because the vibrational energy of harmonic motion becomes positively related relation with its amplitude, so, according to law of conservation of energy, the Oscillation Amplitude at multiplying arrangement top is greater than the Oscillation Amplitude bottom multiplying arrangement.
Bung 16 is capacitive transducer, and the top of bung is the metal polar plate of fixing conduction, and this metal polar plate is as the fixed plate of capacitive transducer, and be the film being coated with conducting metal below fixed plate, this film can vibrate with the vibration in the external world.
Convert of capacitor to voltage (C/V) circuit 11 is for being converted into the change of electric capacity the voltage signal of the circuit identification that can be processed, filtering circuit 13 for the noise signal in filtering voltage signal, the frequency values that LCD display circuit 15 calculates for display treatment circuit.
See convert of capacitor to voltage (C/V) schematic block circuit diagram of Fig. 2, the measuring principle of CAV424 drives two construct symmetrical integrator and make them synchronous on time and phase place by the reference oscillator of an an external concussion electric capacity 21 and Inner Constitution frequency-adjustable.The amplitude of two controlled integrators is decided by electric capacity C122 and Cx23, and C1 electric capacity for referencial use and Cx are as measured capacitance here.C1 and Cx contains all electric capacity that input end is held with ground, and they are characteristically consistent.Like this, during environmental change, two input ends of chip change simultaneously, and its difference remains unchanged substantially.When measured capacitance sensor capacitance changes, because integrator has very high common-mode rejection ratio and resolution, so the signal that the difference comparing two amplitudes obtains reflects the relative variation of two electric capacity C1 and Cx; This difference signal arrives the differential output stage of adjustable gain by low-pass filter 27 rectifying and wave-filtering of rear class.
See Fig. 4, be the voltage signal that filtering circuit exports, the voltage of the V representation signal in figure, t represents the time.
See Fig. 3, after central processing unit CPU 17 sends beginning sample command to the data sampling circuit 32 in FPGA16, data sampling circuit provides clock to external A/D converter and the RAM memory block be implemented in FPGA simultaneously, the electric signal that convert of capacitor to voltage (C/V) circuit 11 exports, after operational amplification circuit 12 amplifies, is connected to A/D change-over circuit 14 after circuit 13 filtering after filtering.Simulating signal is converted to digital signal by the sample circuit 32 control A/D change-over circuit 14 of FPGA inside, and sampled value one by one stored in the RAM memory block 31 be implemented in FPGA.After having sampled, FPGA16 sends sampling done state information to CPU17, and CPU17 terminates once to sample after receiving sampling done state information.
After sampling terminates, CPU17 sends read data order, read the data be temporary in RAM memory block 31, after digital independent completes, can with the time corresponding to arbitrary data for true origin set up rectangular coordinate system, using the time corresponding to this moment as with reference to zero point (true origin).
After determining time ginseng initial point reference zero (true origin), the computing method carrying out calculating voltage signal frequency according to Fig. 4 are:
First point-by-point comparison A/D sampled point, the maximal value finding out sampled point just can determine the amplitude of waveform easily;
Secondly, see Fig. 4, the zero crossing P corresponding to voltage signal is determined
0a sampled point P and below a sampled point P ' above, obviously in one-period ripple, the sampled value of sampled point P is greater than zero, and the sampled value of sampled point P ' is less than zero;
Finally, using moment corresponding to sampled point P and P ' 2 as benchmark, can accurately calculate zero crossing P with segmentation interpolation algorithm (the segmentation interpolation algorithm module that CPU is built-in)
0in the corresponding moment, circular is as follows:
If the sample frequency of A/D is F
a/D, the time between adjacent two sampled points and sampling period are T
a/D; Hits from reference zero to sampled point P is N, and the sampled value that sampled point P is corresponding is V
1, the moment corresponding to sampled point P is T
1; The sampled value of sampled point P ' correspondence is V
2; Moment corresponding to sampled point P is T
1, sampled point P and zero crossing P
0between time be T
2, zero crossing P
0the corresponding moment is t
0, then:
In the region that near zero-crossing point is less, the waveform of voltage signal, close to straight line, can determine T according to the method for linear interpolation
2:
In moment then corresponding to zero crossing, first namely corresponding after reference zero zero crossing moment is:
From above formula, the resolution in moment corresponding to zero crossing is:
See Fig. 4, suppose that the frequency of vibration transducer converted signals is 1M, then the cycle is 1us; The resolution of A/D is 12, so the amplitude of signal can be divided into 4096 parts, if the sample frequency of A/D is 32MHz, then in the half period of the positive maximal value of sine wave to negative maximal value, 16 points can be adopted at most, if maximal value positive for sine wave is regarded as straight line to the waveform in the half period of negative maximal value, then obviously known:
Observe sinusoidal wave positive maximal value can find out to the waveform in the half period of the maximal value born, near zero-crossing point slope of a curve much larger than slope of a curve near peak value, then
V
1-V
2＞256
See Fig. 4, be that one group of data is to carry out the calculating of frequency values with eight zero crossings, wherein starting point (P0) and terminal (P8) need by above-mentioned interpolation algorithm of subdivision module accurate Calculation out, intermediate point (P1, P2, P3, P4, P5, P6, P7) only need judge that its former and later two sampled point contrary sign can judge that it is as zero crossing, meanwhile, terminal (P8) is also the starting point of next group data.
Calculate the time corresponding to starting point (P0) and terminal (P8) according to above-mentioned interpolation algorithm, count t respectively
0and t
8, as shown in Figure 4, t
0to t
8between time Δ t be 4 times of signal period, then the frequency of measured signal is:
Because the moment often organized corresponding to data origination and terminal is all calculate gained by Software interpolation segmentation, then often the resolution of the time Δ t of group corresponding to data depends on the resolution in moment corresponding to starting point and terminal, then corresponding to each group data, the resolution of time was less than for 0.244 nanosecond.
Claims (6)
1. a device for precision measurement frequency, involving vibrations survey sensor, the capacitance-voltage conversion circuit be connected with sensor, the amplifying circuit be connected with capacitance-voltage conversion circuit, the filtering circuit be connected with amplifying circuit and the signal processing circuit be connected with filtering circuit; It is characterized in that:
Described vibration measurement sensor is equipped with the staving of liquids and gases by one and forms as the bung of capacitive transducer; Liquid in staving is the water can propagating vibration, it is gas section on liquid, as vibration amplitude multiplying arrangement, the top of bung is the metal polar plate of fixing conduction, this metal polar plate is as the fixed plate of capacitive transducer, be the film being coated with conducting metal below fixed plate, this film can vibrate with the vibration in the external world; Described gas section is pyramidal structure, lower end area is greater than upper end area, when vibration characteristics propagates into vibration amplitude multiplying arrangement lower end by WATER AS FLOW MEDIUM, vibration amplitude multiplying arrangement lower end with liquid with certain frequency and amplitude vibrations, vibration characteristics propagates into vibration amplitude multiplying arrangement top by gas section, because the vibrational energy of harmonic motion becomes positively related relation with its amplitude, according to law of conservation of energy, the Oscillation Amplitude at vibration amplitude multiplying arrangement top is greater than the Oscillation Amplitude bottom vibration amplitude multiplying arrangement;
Described signal processing circuit comprises analog to digital converter, field programmable gate array and CPU (central processing unit);
Described analog to digital converter is used for simulating signal to be converted to digital signal, and inputs field programmable gate array;
Described field programmable gate array completes the sampling of capacitance-voltage conversion circuit output signal, and data existence is configured in the memory block of on-site programmable gate array internal;
Described CPU (central processing unit) connects field programmable gate array, control field programmable gate array and send the order of analog to digital converter controlling of sampling, after sampling completes, CPU (central processing unit) is responsible for the analog to digital converter sampled data reading voltage signal in field programmable gate array, CPU (central processing unit) built-in segmentation interpolation algorithm module, the moment corresponding to data origination and terminal is calculated by segmentation interpolation algorithm module, and then determine the time of each group data, the frequency of mechanical vibration is then accurately calculated according to the relation of time and frequency.
2. according to the device of the precision measurement frequency described in claim 1, it is characterized in that: the circuit that described capacitance-voltage conversion circuit is is core with integrated package CAV424, it is converted into the change of voltage the change of electric capacity.
3. according to the device of the precision measurement frequency described in claim 1, it is characterized in that: described amplifying circuit adopts series voltage negtive backword amplifying circuit, and it is sued for peace in the form of voltage, regulated output voltage.
4. according to the device of the precision measurement frequency described in claim 1, it is characterized in that: described segmentation interpolation algorithm module determines the moment corresponding to former and later two sampled points of zero crossing according to the analog to digital converter sampled signal stored in field programmable gate array; Then with former and later two sampled points of zero crossing for benchmark, by the method for matching, segmentation interpolation is carried out to sampled point, determines the moment corresponding to voltage signal zero crossing.
5. utilize the device of the precision measurement frequency described in any one of claim 1-3 to carry out the method for vibration frequency measurement, it is characterized in that: first sample, the staving of vibration transducer is just being placed on vibration source, analog to digital converter sampling control signal is sent by central processing unit controls field programmable gate array, after amplifying circuit amplifies the electric signal after convert of capacitor to voltage, by filtering circuit, filtering is carried out to voltage signal again, sampled by analog-digital converter for voltage signal, sampled data is first stored in the memory block that is configured in field programmable gate array, after having sampled, first in field programmable gate array, the analog to digital converter sampled data of voltage signal is read by CPU (central processing unit), employing accurately calculates the moment corresponding to data origination and terminal by segmentation interpolation algorithm module, and then accurately determine the time of each group data, the frequency of mechanical vibration is then accurately calculated according to the relation of time and frequency.
6. according to the vibration frequency measuring method described in claim 5, it is characterized in that: described segmentation interpolation algorithm module is the moment determining corresponding to former and later two sampled points of zero crossing according to the analog to digital converter sampled signal stored in field programmable gate array; Then with former and later two sampled points of zero crossing for benchmark, by the method for matching, segmentation interpolation is carried out to sampled point, determines the moment corresponding to voltage signal zero crossing.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105928604A (en) * | 2016-05-27 | 2016-09-07 | 深圳艾瑞斯通技术有限公司 | Signal acquisition and processing method of optical fiber sensor and device |
| CN110537082B (en) * | 2017-04-21 | 2022-06-03 | 三菱电机工程技术株式会社 | Vibration detection device and abnormality determination system |
| CN108037731B (en) * | 2017-11-09 | 2019-08-20 | 西安理工大学 | A kind of frequency difference interference signal high-resolution subdivision system of phase integral operation transform |
| CN108036853B (en) * | 2017-12-29 | 2023-07-25 | 河南科技大学 | Vibration detection method for detecting unidirectional vibration |
| CN114216636A (en) * | 2021-12-03 | 2022-03-22 | 深圳市云顶信息技术有限公司 | Vibration testing device and vibration testing method |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1314586A (en) * | 2001-04-26 | 2001-09-26 | 上海交通大学 | Optic fibre resonant method measuring micro vibration |
| CN101526393A (en) * | 2008-12-31 | 2009-09-09 | 济南大学 | Method for measuring oscillation frequency and oscillation frequency measuring device |
| CN101769786A (en) * | 2010-01-22 | 2010-07-07 | 田陆 | Pendulum pin type vibration detecting device |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1314586A (en) * | 2001-04-26 | 2001-09-26 | 上海交通大学 | Optic fibre resonant method measuring micro vibration |
| CN101526393A (en) * | 2008-12-31 | 2009-09-09 | 济南大学 | Method for measuring oscillation frequency and oscillation frequency measuring device |
| CN101769786A (en) * | 2010-01-22 | 2010-07-07 | 田陆 | Pendulum pin type vibration detecting device |
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