Measuring device and Doppler velocimeter

Abstract

The present invention relates to the technical field of flow measurement, and discloses a measuring device and a Doppler velocimeter. A measuring device is formed by setting a transmitting unit, a receiving unit and a signal processing system. The transmitting unit transmits laser to particles in the measured fluid to generate scattered light; the receiving unit receives the scattered light and performs frequency mixing to obtain the Doppler frequency difference, converts the Doppler frequency difference into an electrical signal and outputs the electrical signal; the signal processing system receives the electrical signal, determines the movement direction of the measured fluid based on the electrical signal and determines the movement speed of the particles; and determines the movement speed of the measured fluid according to the movement speed of the particles. In the technical solution of the present invention, laser Doppler technology and ultrasonic ranging technology are used to realize non-contact measurement of pipeline water velocity and flow, which solves the technical problem that the prior art is difficult to realize low flow velocity measurement of pipeline water, high-precision flow velocity and flow measurement, and identifiable water direction.

Description

Technical Field

[0001] The present invention relates to the technical field of flow measurement, and particularly to a measuring device and a Doppler velocimeter. Background Art

[0002] Currently, the testing technologies for water level, flow velocity, and flow rate in drainage pipes mainly rely on sensor contact. Due to water quality, garbage, silt, etc. in the water, the monitoring is inaccurate and requires regular offline manual maintenance. Real-time monitoring incurs high costs. The existing non-contact Doppler radar technology measures the flow velocity on the water surface of the pipe, which cannot truly reflect the cross-sectional flow velocity of the water body, resulting in large measurement errors. Moreover, its use of high-frequency (GHz level) radar waves leads to a high starting velocity, so it cannot measure low flow velocities and is also affected by the fluctuations of the water surface. There may be a situation where there is no water flow below, but the radar measures water flow. Therefore, the accuracy of using the non-contact Doppler radar technology to measure water flow velocity is not high.

[0003] The above content is only used to assist in understanding the technical solution of the present invention and does not represent an admission that the above content is prior art. Summary of the Invention

[0004] The main object of the present invention is to provide a measuring device and a Doppler velocimeter, aiming to solve the technical problems in the prior art that it is difficult to measure low flow velocities of the water body in the pipe, measure high-precision flow velocities and flow rates, and identify the water body direction.

[0005] To achieve the above object, the present invention provides a measuring device, which includes a transmitting unit, a receiving unit, and a signal processing system; wherein,

[0006] The transmitting unit is configured to emit laser to particles in the fluid to be measured to generate scattered light;

[0007] The receiving unit is configured to receive the scattered light for mixing to obtain a Doppler frequency difference, convert the Doppler frequency difference into an electrical signal, and output the electrical signal;

[0008] The signal processing system is configured to receive the electrical signal, determine the movement direction of the fluid to be measured based on the electrical signal, and determine the movement speed of the particles;

[0009] The signal processing system is further configured to determine the movement speed of the fluid to be measured according to the movement speed of the particles.

[0010] Preferably, the transmitting unit includes a semiconductor laser, a beam splitting prism, a first transmitting lens, a second transmitting lens, a first total reflection prism, a second total reflection prism, and an acousto-optic frequency shifter, wherein,

[0011] The semiconductor laser is configured to emit laser to the beam splitting prism;

[0012] The beam splitting prism is configured to receive the laser and split the laser into incident light and reference light with equal intensities;

[0013] The first emission lens is configured to receive the reference light and direct the reference light onto the particles in the fluid to be measured to generate first scattered light;

[0014] The first total reflection prism and the second total reflection prism are configured to receive the incident light, so that the incident light undergoes two total reflections and is output to the acousto-optic frequency shifter;

[0015] The acousto-optic frequency shifter is configured to perform frequency modulation on the incident light to cause a relative frequency shift in the incident light and output frequency-modulated incident light;

[0016] The second emission lens is configured to receive the frequency-modulated incident light and direct the frequency-modulated incident light onto the particles in the fluid to be measured to generate second scattered light.

[0017] Preferably, the receiving unit includes: a receiving converging lens and a photodetector, where

[0018] The receiving converging lens is configured to converge the first scattered light and the second scattered light;

[0019] The photodetector is configured to receive the first scattered light and the second scattered light, perform mixing to obtain a Doppler frequency difference, convert the Doppler frequency difference into an electrical signal, and output the electrical signal.

[0020] Preferably, the signal processing system includes a voltage follower and a high-pass filter. The voltage follower is connected to the photodetector; the voltage follower is connected to the high-pass filter; where

[0021] The voltage follower is configured to output the electrical signal to the high-pass filter without loss and without introducing noise;

[0022] The high-pass filter is configured to receive the electrical signal, filter out the low-frequency base signal in the electrical signal, and output a filtered electrical signal.

[0023] Preferably, the signal processing system further includes a variable gain amplifier and an AD converter. The variable gain amplifier is connected to the high-pass filter, and the variable gain amplifier is connected to the AD converter, where

[0024] The variable gain amplifier is configured to amplify the filtered electrical signal to the amplitude required by the AD converter and stabilize the power of the filtered electrical signal, and output an amplified electrical signal;

[0025] The AD converter is configured to receive the amplified electrical signal and convert the amplified electrical signal into a digital signal.

[0026] Preferably, the signal processing system further includes a main control chip, and the main control chip is connected to the AD converter. Among them,

[0027] The main control chip is configured to receive the digital signal, perform a fast Fourier transform operation, and obtain the spectrum of the digital signal;

[0028] Extract the Doppler frequency difference according to the spectrum;

[0029] Based on the Doppler frequency difference and the relative frequency shift, calculate the moving speed of the particles in the fluid to be measured, and the moving speed of the particles is the moving speed of the fluid to be measured.

[0030] Preferably, the main control chip is further configured to judge the moving direction of the fluid to be measured;

[0031] When the Doppler frequency difference is greater than the relative frequency shift, the moving direction of the fluid to be measured is the same as the moving direction of the particles;

[0032] When the Doppler frequency difference is equal to the relative frequency shift, the fluid to be measured is stationary;

[0033] When the Doppler frequency difference is less than the relative frequency shift, the moving direction of the fluid to be measured is opposite to the moving direction of the particles.

[0034] Preferably, the signal processing system further includes a first communication configuration interface, a second communication configuration interface, and an ultrasonic level gauge. The first communication configuration interface is connected to the main control chip, the second communication configuration interface is connected to the main control chip, and the second communication configuration interface is connected to the ultrasonic level gauge. Among them,

[0035] The first communication configuration interface is used for external communication;

[0036] The second communication configuration interface is configured to receive the water level information of the fluid to be measured measured by the ultrasonic level gauge and send the water level information to the main control chip;

[0037] The main control chip is further configured to receive the water level information and calculate the flow rate of the fluid to be measured according to the velocity-area method and the moving speed of the particles in the fluid to be measured.

[0038] Preferably, the measuring device further includes a power supply circuit; the power supply circuit includes a switching power supply and a linear power supply. Among them,

[0039] The switching power supply is connected to an external DC power supply, and the switching power supply outputs a first voltage to the signal processing system;

[0040] The linear power supply is connected to the switching power supply, and the linear power supply outputs a second voltage to the signal processing system.

[0041] To achieve the above object, the present invention further provides a Doppler velocimeter, which includes the measuring device as described above.

[0042] The technical solution of the present invention forms a measuring device by setting a transmitting unit, a receiving unit and a signal processing system. The transmitting unit emits laser to particles in the fluid to be measured to generate scattered light; the receiving unit receives the scattered light for mixing to obtain a Doppler frequency difference, converts the Doppler frequency difference into an electrical signal and outputs the electrical signal; the signal processing system receives the electrical signal, determines the movement direction of the fluid to be measured based on the electrical signal and determines the movement speed of the particles; determines the movement speed of the fluid to be measured according to the movement speed of the particles. In the technical solution of the present invention, non-contact measurement of the water flow velocity in the pipeline is realized by using laser Doppler technology, and non-contact measurement of the water flow rate in the pipeline is realized by using laser Doppler technology and ultrasonic ranging technology, solving the technical problems that it is difficult to measure the low water flow velocity in the pipeline, high-precision flow velocity measurement and water direction identification in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0044] Figure 1 It is a first functional module diagram of an embodiment of the measuring device of the present invention;

[0045] Figure 2 It is a schematic optical path diagram of an embodiment of the measuring device of the present invention;

[0046] Figure 3 It is a schematic structural diagram of an embodiment of the measuring device of the present invention;

[0047] Figure 4 It is a schematic Doppler effect optical path diagram of an embodiment of the measuring device of the present invention;

[0048] Figure 5 It is a second functional module diagram of an embodiment of the measuring device of the present invention.

[0049] Description of the attached reference numerals:

[0050]

[0051]

[0052] The realization, functional features and advantages of the object of the present invention will be further described in conjunction with the embodiments and with reference to the accompanying drawings. Detailed implementation manners

[0053] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0054] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0055] In addition, the descriptions involving "first", "second", etc. in the present invention are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions appears to be contradictory or unable to be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention. Detailed implementation manners

[0057] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0058] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0059] In addition, the descriptions involving "first", "second", etc. in the present invention are for descriptive purposes only, and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between various embodiments may be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0060] The present invention provides a measuring device.

[0061] Referring to Figure 1 , in an embodiment of the present invention, the measuring device includes a transmitting unit 100, a receiving unit 200, and a signal processing system 300; wherein,

[0062] The transmitting unit 100 is configured to emit laser light to particles in the fluid to be measured to generate scattered light. In this embodiment, according to the Doppler effect, when laser light irradiates particles moving in the fluid, the laser light is scattered by the moving particles. Based on the principle that the Doppler frequency shift obtained by comparing the frequency of the scattered light with the frequency of the incident light is proportional to the flow velocity, the fluid flow rate is measured. Therefore, the transmitting unit 100 emits laser light to particles in the fluid to be measured to generate scattered light. The transmitting unit 100 includes a semiconductor laser 101, a beam splitting prism 102, a first transmitting lens 103, a second transmitting lens 104, a first total reflection prism 105, a second total reflection prism 106, and an acousto-optic frequency shifter 107. The semiconductor laser 101 emits laser light to the beam splitting prism 102; the beam splitting prism 102 divides the laser light into incident light and reference light with equal intensity; the first transmitting lens 103 makes the reference light incident on the particles in the fluid to be measured to generate first scattered light; the first total reflection prism 105 and the second total reflection prism 106 cause the incident light to undergo two total reflections and output it to the acousto-optic frequency shifter for frequency modulation, so that the incident light generates a relative frequency shift amount and outputs frequency-modulated incident light; the second transmitting lens 104 makes the frequency-modulated incident light incident on the particles in the fluid to be measured to generate second scattered light.

[0063] The receiving unit 200 is configured to receive the scattered light for mixing to obtain a Doppler frequency difference amount, convert the Doppler frequency difference amount into an electrical signal, and output the electrical signal. In this embodiment, the receiving unit 200 includes a receiving converging lens 201 and a photodetector 202. The receiving converging lens 201 converges the first scattered light and the second scattered light to the photodetector 202, performs mixing to obtain a Doppler frequency difference amount, converts the Doppler frequency difference amount into an electrical signal, and outputs the electrical signal. The photodetector 202 transforms the optical information amount into an electrical information amount, and further amplifies and processes it through a circuit to achieve the purpose of electrical signal output.

[0064] The signal processing system 300 is configured to receive the electrical signal, determine the movement direction of the fluid to be measured based on the electrical signal, and determine the movement speed of the particle. In this embodiment, the signal processing system 300 receives the electrical signal, converts the electrical signal into a digital signal, performs a fast Fourier transform operation to obtain the spectrum of the digital signal; extracts the Doppler frequency difference amount according to the spectrum; calculates the movement speed of the particle in the fluid to be measured based on the Doppler frequency difference amount and the relative frequency shift amount. The signal processing system 300 determines the movement direction of the fluid to be measured according to the Doppler frequency difference amount and the relative frequency shift amount; when the Doppler frequency difference amount is greater than the relative frequency shift amount, the movement direction of the fluid to be measured is the same as the movement direction of the particle; when the Doppler frequency difference amount is equal to the relative frequency shift amount, the fluid to be measured is stationary; when the Doppler frequency difference amount is less than the relative frequency shift amount, the movement direction of the fluid to be measured is opposite to the movement direction of the particle.

[0065] The signal processing system 300 is further configured to determine the movement speed of the fluid to be measured according to the movement speed of the particle. In this embodiment, the signal processing system 300 receives the electrical signal, converts the electrical signal into a digital signal, performs a fast Fourier transform operation to obtain the spectrum of the digital signal; extracts the Doppler frequency difference amount according to the spectrum; calculates the movement speed of the particle in the fluid to be measured based on the Doppler frequency difference amount and the relative frequency shift amount, and the movement speed of the particle is the movement speed of the fluid to be measured.

[0066] The technical solution of the present invention forms a measuring device by setting a transmitting unit 100, a receiving unit 200 and a signal processing system 300. The transmitting unit 100 emits laser to particles in the fluid to be measured to generate scattered light; the receiving unit 200 receives the scattered light for mixing to obtain a Doppler frequency difference, converts the Doppler frequency difference into an electrical signal and outputs the electrical signal; the signal processing system 300 receives the electrical signal, judges the movement direction of the fluid to be measured based on the electrical signal and determines the movement speed of the particles; and determines the movement speed of the fluid to be measured according to the movement speed of the particles. In the technical solution of the present invention, non-contact measurement of the water flow velocity in a pipeline is realized by using laser Doppler technology, and non-contact measurement of the water flow rate in a pipeline is realized by using laser Doppler technology and ultrasonic ranging technology, solving the technical problems in the prior art that it is difficult to measure the low water flow velocity in a pipeline, measure the flow velocity and flow rate with high precision, and identify the water body direction.

[0067] Further, referring to Figures 1 to 2 , the transmitting unit 100 includes a semiconductor laser 101, a beam splitting prism 102, a first transmitting lens 103, a second transmitting lens 104, a first total reflection prism 105, a second total reflection prism 106 and an acousto-optic frequency shifter 107, wherein,

[0068] The semiconductor laser 101 is used to emit laser to the beam splitting prism 102;

[0069] The beam splitting prism 102 is used to receive the laser and divide the laser into incident light and reference light with equal intensity;

[0070] The first transmitting lens 103 is used to receive the reference light, and make the reference light incident on the particles in the fluid to be measured to generate first scattered light;

[0071] The first total reflection prism 105 and the second total reflection prism 106 are used to receive the incident light, so that the incident light is output to the acousto-optic frequency shifter after two total reflections;

[0072] The acousto-optic frequency shifter 107 is used to perform frequency modulation on the incident light, so that the incident light generates a relative frequency shift amount and outputs frequency-modulated incident light;

[0073] The second transmitting lens 104 is used to receive the frequency-modulated incident light, and make the frequency-modulated incident light incident on the particles in the fluid to be measured to generate second scattered light.

[0074] In this embodiment, the semiconductor laser 101 emits laser light to the beam splitting prism 102. The semiconductor laser 101, also known as a laser diode, is the most practical type of laser. It is small in size, long in lifespan, and can be pumped by a simple method of injecting current. Its operating voltage and current are compatible with integrated circuits, so it can be monolithically integrated with them. It can also directly modulate the current at a frequency up to GHz to obtain a laser output with high-speed modulation. This embodiment does not limit the type of laser used.

[0075] The beam splitting prism 102 receives the laser light and splits it into incident light and reference light with equal intensity. Among them, the reference light passes through the first emission lens 103 and is incident on the particles in the fluid to be measured, generating first scattered light; the incident light passes through the first total reflection prism 105 and the second total reflection prism 106, undergoing total reflection twice, which can keep the incident light and the reference light in the same phase.

[0076] After the incident light undergoes total reflection twice, it passes through the acousto-optic frequency shifter 107 for frequency modulation, causing the incident light to generate a relative frequency shift amount and outputting frequency-modulated incident light. The frequency-modulated incident light passes through the second emission lens 104 and is incident on the particles in the fluid to be measured, generating second scattered light. As Figure 2 described, the fluid cross-section 400 is the cross-section of the fluid to be measured, which contains moving particles. The reference light passes through the first emission lens 103 and is incident on the particles in the fluid to be measured, and the frequency-modulated incident light passes through the second emission lens 104 and is incident on the particles in the fluid to be measured. That is, the two laser beams intersect on the surface of the moving particles, forming an elliptical interference spot with bright and dark stripes inside, and the generated first scattered light and second scattered light carry Doppler signals.

[0077] Furthermore, referring to Figures 1 to 2 , the receiving unit 200 includes: a receiving converging lens 201 and a photodetector 202, where

[0078] The receiving converging lens 201 is used to converge the first scattered light and the second scattered light.

[0079] The photodetector 202 is used to receive the first scattered light and the second scattered light for mixing to obtain the Doppler frequency difference amount, convert the Doppler frequency difference amount into an electrical signal, and output the electrical signal.

[0080] In this embodiment, the first scattered light and the second scattered light with Doppler signals are converged by the receiving converging lens 201 onto the probe of the photodetector 202. The photodetector 202 receives the first scattered light and the second scattered light for mixing to obtain a Doppler frequency difference quantity, converts the Doppler frequency difference quantity into an electrical signal, and outputs the electrical signal. The photodetector 202 transforms the optical information quantity into an electrical information quantity, and further amplifies and processes it through a circuit to achieve the purpose of electrical signal output.

[0081] It should be noted that the receiving unit 200 may further include a small hole aperture (not shown). The receiving converging lens 201 converges the first scattered light and the second scattered light to reach the photodetector 202 via the small hole aperture. The use of the small hole aperture can effectively enable the image formed by the receiving converging lens 201 to accurately pass through, prevent stray light in the edge region from entering the photodetector 202, and improve the signal-to-noise ratio of the electrical signal.

[0082] Further, referring to Figures 1 to 3 , the signal processing system 300 includes a voltage follower 301 and a high-pass filter 302. The voltage follower 301 is connected to the photodetector 202; the voltage follower 301 is connected to the high-pass filter 302; wherein,

[0083] The voltage follower 301 is used to output the electrical signal to the high-pass filter 302 without loss and without introducing noise. In this embodiment, the voltage follower 301 can be composed of a common collector circuit formed by a triode. The common collector circuit has a high input impedance and a low output impedance, which enables the voltage follower 301 to play an impedance matching role in the signal processing system 300 and enables the subsequent circuit to work better. When the input impedance is very high, it is equivalent to an open circuit for the previous stage circuit. When the output impedance is very low, it is equivalent to a constant voltage source for the subsequent circuit, that is, the output voltage is not affected by the impedance of the subsequent circuit. Being equivalent to an open circuit for the previous stage circuit and the output voltage not being affected by the subsequent impedance means that the voltage follower 301 makes the front and rear stage circuits not affect each other. Therefore, the voltage follower 301 is used as an intermediate stage to "isolate" the influence between the front and rear stages, and is also called a buffer stage. Utilizing the characteristics of the high input impedance and low output impedance of the voltage follower 301, it plays an impedance matching role in the signal processing system 300. In this embodiment, the voltage follower 301 can adopt the LMV772 model. Therefore, the voltage follower 301 outputs the electrical signal to the high-pass filter 302 without loss and without introducing noise.

[0084] The high-pass filter 302 is configured to receive the electrical signal, filter out the low-frequency base signal in the electrical signal, and output a filtered electrical signal. In this embodiment, considering the influence of the Gaussian beam, the electrical signal output by the photodetector 202 contains not only the Doppler frequency difference but also the low-frequency base signal. In traditional laser velocimetry techniques, the common method to filter out the base signal is to use a high-pass filter 302 to filter out the low-frequency base signal. However, traditional laser velocimetry techniques are thus unable to measure low flow rates. In this embodiment, the acousto-optic frequency shifter 107 is utilized to perform frequency modulation on the incident light, causing the incident light to generate a relative frequency shift and outputting frequency-modulated incident light. Therefore, after adding the modulation of the acousto-optic frequency shifter 107, even at low or ultra-low speeds, the frequency of the electrical signal only changes slightly around the bias frequency, and the high-pass filter 302 can easily filter out the low-frequency base signal without affecting the measurement of low flow rates.

[0085] Further, referring to Figures 1 to 3 , the signal processing system 300 further includes a variable gain amplifier 303 and an AD converter 304. The variable gain amplifier 303 is connected to the high-pass filter 302, and the variable gain amplifier 303 is connected to the AD converter 304. Among them,

[0086] The variable gain amplifier 303 is configured to amplify the filtered electrical signal to the amplitude required by the AD converter 304 and stabilize the power of the filtered electrical signal, and output an amplified electrical signal.

[0087] The AD converter 304 is configured to receive the amplified electrical signal and convert the amplified electrical signal into a digital signal.

[0088] In this embodiment, the variable gain amplifier 303 amplifies or attenuates the filtered electrical signal, plays a role in stabilizing the power of the output signal, and at the same time amplifies the filtered electrical signal to the amplitude required by the AD converter 304, and finally outputs the amplified electrical signal to the AD converter 304. The AD converter 304 converts the amplified electrical signal into a digital signal.

[0089] Further, referring to Figures 1 to 4 , the signal processing system 300 further includes a main control chip 305. The main control chip 305 is connected to the AD converter 304. Among them,

[0090] The main control chip 305 is configured to receive the digital signal and determine the motion speed of the fluid to be measured according to the digital signal.

[0091] In this embodiment, the main control chip 305 is configured to receive the digital signal, perform a fast Fourier transform operation to obtain the spectrum of the digital signal; extract the Doppler frequency difference amount according to the spectrum; and calculate the movement speed of the particles in the fluid to be measured based on the Doppler frequency difference amount and the relative frequency shift amount, where the movement speed of the particles is the movement speed of the fluid to be measured.

[0092] It should be noted that referring to Figure 4 , two beams of light W1 and W2 are respectively incident on the surface of the particles moving with the fluid, and both beams of light will be scattered. When the two beams of light are symmetrically distributed along the normal of the particle surface, where W1 and W2 are the reference light and the incident light respectively. After the incident light undergoes two total reflections, it passes through the acousto-optic frequency shifter 107 for frequency modulation to generate a relative frequency shift amount for the incident light. The incident light passing through the acousto-optic frequency shifter 107 is modulated so that the frequencies of the reference light and the incident light differ by fc, where fc is the relative frequency shift amount. The two scattered lights generated by the reference light and the incident light, namely the first scattered light and the second scattered light, are mixed in the photodetector 202 to obtain the Doppler frequency difference amount f D ,

[0093]

[0094] where, given the incident light angle θ and the laser wavelength λ, the value of v can be calculated as

[0095]

[0096] That is, by measuring the Doppler frequency difference f D the movement speed v of the particles can be obtained, and the movement speed of the particles is the movement speed of the fluid to be measured.

[0097] Furthermore, referring to Figures 1 to 4 , the main control chip 305 is further configured to judge the movement direction of the fluid to be measured according to the Doppler frequency difference amount and the relative frequency shift amount.

[0098] In this embodiment, the main control chip 305 is further configured to judge the movement direction of the fluid to be measured; when the Doppler frequency difference amount is greater than the relative frequency shift amount, the movement direction of the fluid to be measured is the same as the movement direction of the particles; when the Doppler frequency difference amount is equal to the relative frequency shift amount, the fluid to be measured is stationary; when the Doppler frequency difference amount is less than the relative frequency shift amount, the movement direction of the fluid to be measured is opposite to the movement direction of the particles.

[0099] It should be noted that referring to Figure 4, two beams of light W1 and W2 are respectively incident on the surface of impurity particles moving with the fluid, and both beams of light will be scattered. Among them, λ is the laser wavelength, n s is the unit vector of the scattered light of the moving particle, n 1 is the unit vector of the incident light in the direction of W1, n 2 is the unit vector of the incident light in the direction of W2, and θ is the angle between the incident light ray and the normal of the particle surface. For the incident light in the direction of W1, examine the frequency f of the scattered light in the S direction s1 is

[0100]

[0101] For the incident light in the direction of W2, examine the frequency f of the scattered light in the S direction s2 is

[0102]

[0103] It is easy to understand that W1 and W2 are the reference light and the incident light respectively. After the incident light undergoes two total reflections, it passes through the acousto-optic frequency shifter 107 for frequency modulation to generate a relative frequency shift for the incident light, that is, the incident light passing through the acousto-optic frequency shifter 107 is modulated so that the frequencies of the reference light and the incident light differ by f C , f C is the relative frequency shift, that is, fw 2 = fw 1 + f c , the two beams of scattered light generated by the reference light and the incident light, namely the first scattered light and the second scattered light, are mixed in the photodetector 202 to obtain the Doppler frequency difference f D ,

[0104]

[0105] That is, when the detected Doppler frequency difference is greater than the relative frequency shift f C , the moving direction of the measured fluid is the same as the moving direction of the particle; when the detected Doppler frequency difference is equal to the relative frequency shift f C , the measured fluid is stationary; when the detected Doppler frequency difference is less than the relative frequency shift f C , the moving direction of the measured fluid is opposite to the moving direction of the particle. The premise of judging the moving direction of the measured fluid by this method of generating a relative frequency shift for the incident light through the acousto-optic frequency shifter 107 is that the frequency of the reverse movement of the particle cannot exceed the relative frequency shift f C , otherwise the direction cannot be judged.

[0106] Furthermore, referring to Figures 1 to 3, the signal processing system 300 further includes a first communication configuration interface 306, a second communication configuration interface 307, and an ultrasonic level gauge 308. The first communication configuration interface 306 is connected to the main control chip 305, the second communication configuration interface 307 is connected to the main control chip 305, and the second communication configuration interface 307 is connected to the ultrasonic level gauge 308. Among them,

[0107] The first communication configuration interface 306 is used for communicating with the outside;

[0108] The second communication configuration interface 307 is used to receive the water level information of the measured fluid measured by the ultrasonic level gauge 308 and send the water level information to the main control chip 305;

[0109] The main control chip 305 is further used to receive the water level information and determine the flow rate of the measured fluid according to the velocity-area method and the movement velocity of the particles in the measured fluid.

[0110] In this embodiment, the first communication configuration interface 306 and the second communication configuration interface 307 can adopt communication configuration interfaces of model RS485. RS485 is a standard that defines the electrical characteristics of drivers and receivers in a balanced digital multi-point system. This standard is defined by the Telecommunications Industry Association and the Electronic Industries Alliance. Digital communication networks using this standard can effectively transmit signals under long-distance conditions and in environments with high electronic noise. The first communication configuration interface 306 is used for communicating with the outside, that is, through the first communication configuration interface 306, operators can achieve remote control.

[0111] The second communication configuration interface 307 is used to receive the water level information of the measured fluid measured by the ultrasonic level gauge 308 and send the water level information to the main control chip 305. The ultrasonic level gauge 308 is a digital level instrument controlled by a microprocessor. In the measurement, ultrasonic pulses are emitted by a sensor (transducer). The sound waves are reflected by the liquid surface and then received by the same sensor or an ultrasonic receiver, and are converted into electrical signals through piezoelectric crystals or magnetostrictive devices. The distance from the sensor to the surface of the measured liquid is calculated by the time between the emission and reception of the sound waves. The ultrasonic level gauge 308 is used for non-contact measurement, and the measured medium is hardly restricted and can be used for the measurement of various liquids. The water level information of the measured fluid measured by the ultrasonic level gauge 308 is sent to the main control chip 305 through the second communication configuration interface 307.

[0112] It is easy to understand that by measuring the water level information with the ultrasonic level gauge 308, the cross-sectional area s of the fixed pipeline can be obtained. Then the instantaneous flow rate Q = v * s, where v is the Doppler frequency difference f measured DThe obtained moving speed of the particle, and the moving speed of the particle is the moving speed of the fluid to be measured. Since the laser Doppler technology measures the moving speed of the particles flowing with the water body, it can better reflect the flow velocity of the water body section of the pipeline, and has higher accuracy than the water surface speed measured by the Doppler radar speedometer.

[0113] Further, referring to Figure 5 , the measuring device further includes a power supply circuit 500; the power supply circuit 500 includes a switching power supply and a linear power supply, wherein,

[0114] The switching power supply is connected to an external DC power supply, and the switching power supply outputs a first voltage to the signal processing system 300;

[0115] The linear power supply is connected to the switching power supply, and the linear power supply outputs a second voltage to the signal processing system 300.

[0116] In this embodiment, the power supply circuit is used to supply power to the measuring device. The power supply circuit includes a switching power supply and a linear power supply. The input of the switching power supply is an external DC power supply. The switching power supply outputs a first voltage to the voltage follower 301, variable gain amplifier 303, and AD converter 304 in the signal processing system 300; the linear power supply outputs a second voltage to the main control chip 305 in the signal processing system. It should be noted that the power supply circuit can supply power according to the required voltages of different circuits in the signal processing system 300, and this embodiment does not limit this.

[0117] To achieve the above object, the present invention also proposes a Doppler speedometer, and the Doppler speedometer includes the measuring device as described above. The specific structure of the measuring device refers to the above embodiment. Since the Doppler speedometer of the present invention adopts all the technical solutions of the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, and will not be elaborated here one by one.

[0118] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made by using the description and drawings of the present invention under the inventive concept of the present invention, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A measuring device, characterized in that: The measuring device comprises a transmitting unit, a receiving unit and a signal processing system; wherein, The transmitting unit is used to transmit laser light to particles in the measured fluid to generate scattered light; The receiving unit is used to receive the scattered light, mix it to obtain a Doppler frequency difference, convert the Doppler frequency difference into an electrical signal and output the electrical signal; The signal processing system is used to receive the electrical signal, determine the moving direction of the measured fluid and determine the moving speed of the particle based on the electrical signal; The signal processing system is further used to determine the movement speed of the measured fluid according to the movement speed of the particles; The transmitting unit includes a semiconductor laser, a beam splitter, a first transmitting lens, a second transmitting lens, a first total reflection prism, a second total reflection prism and an acousto-optic frequency shifter, wherein: The semiconductor laser is used to emit laser light to the beam splitter prism; The beam splitter prism is used to receive the laser light and split the laser light into incident light and reference light of equal intensity; The first emitting lens is used to receive the reference light and incident the reference light onto particles in the measured fluid to generate first scattered light; The first total reflection prism and the second total reflection prism are used to receive the incident light, so that the incident light is output to the acousto-optic frequency shifter after two total reflections; The acousto-optic frequency shifter is used to frequency modulate the incident light, so that the incident light produces a relative frequency shift, and outputs frequency-modulated incident light; The second emitting lens is used to receive the frequency-modulated incident light and transmit the frequency-modulated incident light to particles in the measured fluid to generate second scattered light.

2. The measuring device according to claim 1, characterized in that The receiving unit comprises: a receiving converging lens and a photoelectric detector, wherein: The receiving converging lens is used to converge the first scattered light and the second scattered light; The photoelectric detector is used to receive the first scattered light and the second scattered light, mix them to obtain a Doppler frequency difference, convert the Doppler frequency difference into an electrical signal and output the electrical signal.

3. The measuring device according to claim 2, characterized in that The signal processing system includes a voltage follower and a high-pass filter, wherein the voltage follower is connected to the photodetector; the voltage follower is connected to the high-pass filter; wherein, The voltage follower is used to output the electrical signal to the high-pass filter without loss and without introducing noise; The high-pass filter is used to receive the electrical signal, filter out the low-frequency base signal in the electrical signal, and output a filtered electrical signal.

4. The measuring device according to claim 3, characterized in that The signal processing system further includes a variable gain amplifier and an AD converter, wherein the variable gain amplifier is connected to the high pass filter, and the variable gain amplifier is connected to the AD converter, wherein: The variable gain amplifier is used to amplify the filtered electrical signal to the amplitude required by the AD converter, stabilize the power of the filtered electrical signal, and output the amplified electrical signal; The AD converter is used to receive the amplified electrical signal and convert the amplified electrical signal into a digital signal.

5. The measuring device according to claim 4, characterized in that The signal processing system further includes a main control chip, which is connected to the AD converter, wherein: The main control chip is used to receive the digital signal, perform a fast Fourier transform operation, and obtain the frequency spectrum of the digital signal; Extracting the Doppler frequency difference according to the frequency spectrum; Based on the Doppler frequency difference and the relative frequency shift, the moving speed of the particles in the measured fluid is calculated, and the moving speed of the particles is the moving speed of the measured fluid.

6. The measuring device according to claim 5, characterized in that The main control chip is also used to determine the movement direction of the measured fluid; When the Doppler frequency difference is greater than the relative frequency shift, the moving direction of the measured fluid is the same as the moving direction of the particles; When the Doppler frequency difference is equal to the relative frequency shift, the measured fluid is stationary; When the Doppler frequency difference is smaller than the relative frequency shift, the moving direction of the measured fluid is opposite to the moving direction of the particles.

7. The measuring device according to claim 6, characterized in that The signal processing system also includes a first communication configuration interface, a second communication configuration interface and an ultrasonic level meter, wherein the first communication configuration interface is connected to the main control chip, the second communication configuration interface is connected to the main control chip, and the second communication configuration interface is connected to the ultrasonic level meter, wherein: The first communication configuration interface is used for communicating with the outside; The second communication configuration interface is used to receive the water level information of the measured fluid measured by the ultrasonic liquid level meter, and send the water level information to the main control chip; The main control chip is also used to receive the water level information and calculate the flow rate of the measured fluid according to the velocity area method and the movement speed of particles in the measured fluid.

8. The measuring device according to any one of claims 1 to 7, characterized in that The measuring device also includes a power supply circuit; the power supply circuit includes a switching power supply and a linear power supply, wherein: The switching power supply is connected to an external DC power supply, and the switching power supply outputs a first voltage to the signal processing system; The linear power supply is connected to the switching power supply, and the linear power supply outputs a second voltage to the signal processing system.

9. A Doppler velocimeter, characterized in that: The Doppler velocimeter comprises a measuring device as claimed in any one of claims 1 to 8.

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