A frequency-selective gain conversion circuit and its working method

Abstract

The present invention relates to the technical field of frequency signal measurement, and discloses a working method of a frequency-selective gain conversion circuit, including: using a sustaining amplifier and a sensor in a conversion circuit to generate an oscillator; changing the phase of a signal from a pickup element according to the sustaining amplifier, and amplifying the phase, providing the amplified signal to an excitation coil, presetting a loop gain threshold and a phase shift value, and the sensor self-starting under the preset loop gain threshold and phase shift value; the sustaining amplifier provides a signal, the signal is amplified by times around the loop, and the amplitude continues to grow until the signal is limited by the amplifier and reaches a stable state; when using the conversion circuit for density measurement, measuring the resonant time period of the sustaining amplifier output, using a calibration equation, using the time period to measure the output periods of multiple sensors, and taking an average value over the output period. The present invention also discloses a frequency-selective gain conversion circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of frequency signal measurement, in particular to a frequency-selective gain conversion circuit and a working method thereof, which are used to improve the parameters of a traditional resonant density measurement method and have good performance in measurement accuracy, repeatability and long-term working stability. Background Art

[0002] The measurement principle of the resonant signal conversion circuit is realized through the vibration characteristics of the resonator. The resonator can be equivalent to a single-degree-of-freedom system during operation, vibrating at the natural frequency of the system. The natural frequency of the system is only related to the equivalent mass and equivalent elastic coefficient in the system. The elastic sensitive element in the system contacts the liquid, thereby changing the equivalent mass of the system, causing the natural frequency of the system to change. By measuring the change in the natural frequency of the system, the density of the liquid to be measured is determined. The main technical indicators of this circuit directly applied in the industrial field basically meet the requirements, but there are still certain defects in properties such as measurement accuracy and long-term working stability.

[0003] Therefore, there is an urgent need for a circuit that can be used to improve the parameters of the traditional resonant density measurement method and has good performance in measurement accuracy, repeatability and long-term working stability. Summary of the invention

[0004] The purpose of the present invention is to provide a frequency-selective gain conversion circuit and a working method thereof, so as to realize the function of improving the parameters of the traditional resonant density measurement method, and to perform well in measurement accuracy, repeatability and long-term working stability.

[0005] The present invention is implemented by the following technical solution: a working method of a frequency-selective gain conversion circuit, comprising the following steps:

[0006] Step S1. Using a sustaining amplifier and a sensor to generate an oscillator in a conversion circuit;

[0007] Step S2. Changing the phase of the signal from the pickup element according to the maintaining amplifier, amplifying the phase, providing the amplified signal to the excitation coil, presetting the loop gain threshold and the phase shift value, and the sensor self-starting under the preset loop gain threshold and the phase shift value;

[0008] Step S3. The amplifier is maintained to provide a signal, and the signal is amplified by multiples around the loop, and the amplitude continues to grow until the signal is limited by the amplifier and reaches a stable state;

[0009] Step S4. When using the conversion circuit for density measurement, measure the resonance time period of the amplifier output, use the calibration equation, use the time period to measure the output period of multiple sensors, and take the average value over the output period.

[0010] In the present technical solution, the maintaining amplifier forms an oscillator together with the sensor, whose output frequency is determined by the resonant frequency of the sensor vibrating cylinder, and the maintaining amplifier must provide positive feedback so that when the power supply is connected, the self-oscillation occurs spontaneously in the required resonant mode. The maintaining amplifier changes the phase of the signal from the pickup element and amplifies it, and provides the modified signal to the excitation coil to increase the frequency required by the system. At the resonant frequency, the loop gain is greater than 1, and the sensor will start at the correct frequency when the phase shift is 0. Initially, the noise from the amplifier provides a small signal, which is amplified around the loop, and the amplitude continues to grow until it is limited by the amplifier and reaches a stable state. In order to achieve density measurement, the system must measure the resonant time period of the maintaining amplifier output and apply the calibration equation. The time period measurement is averaged over multiple sensor output periods to reduce noise and improve resolution. This period is the reference clock. The above positive feedback loop can provide a reference clock with high stability and accuracy, thereby improving the accuracy of density measurement.

[0011] In order to better implement the present invention, further, step S1 includes:

[0012] The sustaining amplifier provides positive feedback;

[0013] The output frequency of the oscillator is determined by the resonant frequency of the sensor's vibrating cylinder.

[0014] In order to better implement the present invention, further, step S2 includes:

[0015] The preset loop gain threshold is 1 and the phase shift value is 0;

[0016] At the resonant frequency, when the loop gain is greater than the loop gain threshold of 1 and the phase shift value is 0, the sensor self-starts at the correct frequency.

[0017] In order to better implement the present invention, further, step S4 includes:

[0018] Set up the time period to measure the output period of multiple sensors as the reference clock.

[0019] In order to better realize the present invention, further, the present invention also proposes a frequency-selective gain conversion circuit, comprising a power supply circuit, a band-pass filter circuit, a high-pass filter circuit, an amplifying gain circuit and a comparator circuit, wherein the power supply circuit, the band-pass filter circuit, the high-pass filter circuit, the amplifying gain circuit and the comparator circuit are connected in sequence;

[0020] The bandpass filter circuit constitutes stage 1, and the high-pass filter circuit constitutes stage 2;

[0021] The noise generated by the amplifier in the gain amplification circuit generates a pulse signal through the excitation coil and forms pulsation, causing the vibration tube in the density sensor to vibrate at a small amplitude resonance frequency and generate a sine wave frequency signal. The vibration pickup element captures the vibration and generates an induced potential. The amplifier amplifies the induced potential and then positively feeds it back to the excitation coil, causing the vibration tube to vibrate at a large amplitude resonance frequency.

[0022] The sine wave frequency signal enters the conversion circuit and is converted into a square wave signal. After the frequency selection gain is obtained, the microprocessor performs frequency measurement to obtain the fuel density.

[0023] In order to better implement the present invention, further, phase 1 generates a phase shift and outputs a sine wave;

[0024] Stage 2 introduces additional phase shift, outputting a sine wave at startup until the amplifier limits.

[0025] The square wave output by the sensor gives a count of sensor cycles and clock samples. The sensor clock period is (us), Nc is the cycle count of the reference clock, Fc is the reference clock frequency, and Ns is the cycle count of the sensor; the processor determines the liquid density after measuring the sensor cycle. The formula for determining the liquid density is D=K0+K2T 2 , where K0 and K2 are sensor coefficients, which are determined by the internal calibration resistors of the sensor, and T is the sensor clock period in microseconds.

[0026] In order to better implement the present invention, further, the vibration tube is made to maintain oscillation at a relatively large amplitude according to positive feedback.

[0027] In order to better realize the present invention, further, it includes:

[0028] The amplifier in the gain amplification circuit generates a pulse signal and forms pulsation by exciting the coil. After the pulsation is formed, the vibration tube in the density sensor vibrates at a small amplitude resonance frequency to generate a sinusoidal wave frequency signal.

[0029] In order to better realize the present invention, further, it includes:

[0030] The conversion circuit captures and amplifies the signal from the vibration cylinder and provides it to the excitation coil, causing the vibration cylinder to vibrate at a large-amplitude resonant frequency. The positive feedback mode allows the vibration cylinder to maintain oscillation.

[0031] In order to better realize the present invention, further, it includes:

[0032] The sine wave frequency signal enters the conversion circuit and is converted into a square wave signal. The microprocessor measures the frequency to obtain the fuel density.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0034] (1) The present invention provides a frequency-selective gain conversion circuit to improve the parameters of the traditional resonant density measurement method, and has good performance in measurement accuracy, repeatability and long-term working stability;

[0035] (2) The present invention can improve the accuracy of density measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention is further described in conjunction with the following drawings and embodiments, and all the concepts and innovations of the present invention should be regarded as the disclosed contents and the protection scope of the present invention.

[0037] Figure 1 The present invention discloses a flow chart of a working method of a frequency-selective gain conversion circuit.

[0038] Figure 2 The present invention is a schematic structural diagram of a frequency-selective gain conversion circuit disclosed in the present invention. DETAILED DESCRIPTION

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. It should be understood that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments, and therefore should not be regarded as limiting the scope of protection. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technical personnel in this field without making creative work are within the scope of protection of the present invention.

[0040] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "disposed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] Embodiment 1:

[0042] A working method of a frequency-selective gain conversion circuit of this embodiment is as follows: Figure 1As shown, in this embodiment, the noise generated by the amplifier in the gain amplification circuit generates a pulse signal through the excitation coil and forms a pulsation, causing the vibration tube in the density sensor to vibrate at a small amplitude resonant frequency, generating a sine wave frequency signal. The vibration pickup element captures the vibration and generates an induced potential. The amplifier amplifies the potential and then positively feeds it back to the excitation coil, causing the vibration tube to vibrate at a large amplitude resonant frequency. The above positive feedback mode can enable the vibration tube to maintain oscillation at a relatively large amplitude. The sine wave frequency signal enters the measurement circuit and is converted into a square wave signal, and the microprocessor performs frequency measurement to obtain the fuel density.

[0043] Embodiment 2:

[0044] This embodiment is further optimized on the basis of embodiment 1. In this embodiment, the amplifier is maintained together with the sensor to form an oscillator, whose output frequency is determined by the resonant frequency of the sensor vibration tube. The amplifier must provide positive feedback to enable spontaneous self-oscillation in the desired resonant mode when the power supply is connected.

[0045] The other parts of this embodiment are the same as those of Embodiment 1, and thus will not be described in detail.

[0046] Embodiment 3:

[0047] This embodiment is further optimized on the basis of the first embodiment. In this embodiment, the amplifier changes the phase of the signal from the pickup element and amplifies it, and provides the modified signal to the excitation coil, so that the frequency required by the system is increased. At the resonant frequency, the loop gain is greater than 1, and when the phase shift is 0, the sensor will start automatically at the correct frequency.

[0048] The other parts of this embodiment are the same as those of Embodiment 1, and thus will not be described in detail.

[0049] Embodiment 4:

[0050] This embodiment is further optimized on the basis of embodiment 1. In this embodiment, the noise from the amplifier provides a small signal, which is amplified by times around the loop, and the amplitude continues to grow until it is limited by the amplifier and reaches a stable state. In order to achieve density measurement, the system must measure the resonant time period that maintains the amplifier output and apply the calibration equation. The time period measurement is averaged over multiple sensor output periods to reduce noise and improve resolution. This period is the reference clock, and the positive feedback loop can provide a reference clock with high stability and accuracy, thereby improving the accuracy of density measurement.

[0051] The other parts of this embodiment are the same as those of Embodiment 1, and thus will not be described in detail.

[0052] Embodiment 5:

[0053] This embodiment also provides a frequency-selective gain conversion circuit, such as Figure 2 As shown, in this conversion circuit, it includes a power supply circuit, a bandpass filter circuit, a high-pass filter circuit, an amplification gain circuit and a comparator circuit. In this embodiment, the noise generated by the amplifier in the amplification gain circuit generates a pulse signal through the excitation coil and forms a pulsation, so that the vibration tube in the density sensor vibrates at a small amplitude resonant frequency and generates a sine wave frequency signal. After the vibration pickup element captures the vibration, an induced potential is generated. After the amplifier amplifies the potential, it is positively fed back to the excitation coil, so that the vibration tube vibrates at a large amplitude resonant frequency. The above positive feedback mode can make the vibration tube maintain oscillation at a relatively large amplitude. The sine wave frequency signal enters the measurement circuit and is converted into a square wave signal. After passing through the frequency selection gain, the microprocessor performs frequency measurement to obtain the fuel density.

[0054] Embodiment 6:

[0055] This embodiment is further optimized on the basis of embodiment 5. In this embodiment, stage 1 and stage 2 constitute the functional components of the feedback amplifier. Stage 1 is a bandpass filter, which also produces a phase shift. This stage outputs a sine wave during startup and steady-state operation. Stage 2 has additional high-pass filtering and gain. This stage introduces additional phase shift. During the startup process, the output of this stage is a sine wave until the output of the U2 amplifier is limited. Under steady-state conditions, the output is approximately a square wave that swings between 1-11V. This is used to provide current to the sensor drive coil through resistor R10. The output of U2 is also provided to the comparator, which squares the signal to provide a clean square wave with the accurate time of the mutation edge, making it more suitable for sensor clock cycle measurement. LK1 is a measurement point. The circuit is closed under steady-state conditions. During the calibration process, if the signal amplitude at this point changes significantly to a low potential, it indicates that there are bubbles in the liquid.

[0056] The falling edge of the square wave output by the comparator is used to latch the counter value, giving a count of sensor cycles and clock samples, where the sensor clock cycle is (us), Nc is the cycle count of the reference clock, Fc is the reference clock frequency, and Ns is the cycle count of the sensor; the processor determines the liquid density after measuring the sensor cycle. The formula for determining the liquid density is D=K0+K2T 2 , where K0 and K2 are sensor coefficients, which are determined by the internal calibration resistors of the sensor, and T is the sensor clock period in microseconds.

[0057] The other parts of this embodiment are the same as those of Embodiment 1, and thus will not be described in detail.

[0058] Embodiment 7:

[0059] This embodiment is further optimized on the basis of embodiment 5. In this embodiment, the positive feedback mode can make the vibration cylinder maintain oscillation with a relatively large amplitude. The sine wave frequency signal enters the measurement circuit and is converted into a square wave signal. After the frequency selection gain is passed, the microprocessor performs frequency measurement to obtain the fuel density.

[0060] The other parts of this embodiment are the same as those of Embodiment 5, and thus will not be described in detail.

[0061] Embodiment 8:

[0062] This embodiment is further optimized on the basis of Embodiment 5. In this embodiment, the amplifier in the gain amplification circuit generates a pulse signal and forms pulsation through the excitation coil, so that the vibration tube in the density sensor vibrates at a small amplitude resonant frequency to generate a sinusoidal wave frequency signal.

[0063] The other parts of this embodiment are the same as those of Embodiment 5, and thus will not be described in detail.

[0064] Embodiment 9:

[0065] This embodiment is further optimized on the basis of Embodiment 5. In this embodiment, the signal from the vibration tube is captured and amplified, and provided to the excitation coil, so that the vibration tube vibrates at a large amplitude resonant frequency. The above positive feedback mode can enable the vibration tube to maintain oscillation at a relatively large amplitude.

[0066] The other parts of this embodiment are the same as those of Embodiment 5, and thus will not be described in detail.

[0067] Embodiment 10:

[0068] This embodiment is further optimized on the basis of Embodiment 5. In this embodiment, the sinusoidal wave frequency signal is converted into a square wave signal after entering the measurement circuit, and the microprocessor performs frequency measurement to obtain the fuel density.

[0069] The other parts of this embodiment are the same as those of Embodiment 5, and thus will not be described in detail.

[0070] The above are only preferred embodiments of the present invention and are not intended to limit the present invention in any form. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention fall within the protection scope of the present invention.

Claims

1. A frequency-selective gain conversion circuit, characterized in that: The conversion circuit includes a power supply circuit, a band-pass filter circuit, a high-pass filter circuit, an amplifying gain circuit and a comparator circuit, and the power supply circuit, the band-pass filter circuit, the high-pass filter circuit, the amplifying gain circuit and the comparator circuit are connected in sequence; The bandpass filter circuit constitutes stage 1, and the high-pass filter circuit constitutes stage 2; The noise generated by the amplifier in the gain amplification circuit generates a pulse signal through the excitation coil and forms pulsation, so that the vibration tube in the density sensor vibrates at a small amplitude resonance frequency and generates a sine wave frequency signal. The vibration pickup element captures the vibration and generates an induced potential. The amplifier amplifies the induced potential and then positively feeds it back to the excitation coil, so that the vibration tube vibrates at a large amplitude resonance frequency. The sine wave frequency signal enters the conversion circuit and is converted into a square wave signal. After the frequency selection gain is obtained, the microprocessor measures the frequency to obtain the fuel density. The comparator is used to perform a square operation on the signal to provide a clean square wave and the accurate time of the mutation edge, making it more suitable for the sensor clock cycle measurement. Phase 1 generates phase shift and outputs a sine wave; Stage 2 introduces additional phase shift, outputting a sine wave at startup until the amplifier limits. The square wave output by the sensor gives a count of sensor cycles and clock samples. The sensor clock cycle is: ， Where Nc is the cycle count of the reference clock, Fc is the reference clock frequency, Ns is the cycle count of the sensor; The processor measures the sensor cycle to determine the liquid density. The formula for determining the liquid density is: D=K0+K2T 2 , Among them, K0 and K2 are sensor coefficients, which are determined by the internal calibration resistor of the sensor. T is the sensor clock period in microseconds.

2. A frequency-selective gain conversion circuit according to claim 1, characterized in that: include: Based on positive feedback, the vibration cylinder maintains oscillation at a relatively large amplitude.

3. A frequency-selective gain conversion circuit according to claim 1, characterized in that: include: The amplifier in the gain amplification circuit generates a pulse signal and forms pulsation by exciting the coil. After the pulsation is formed, the vibration tube in the density sensor vibrates at a small amplitude resonance frequency to generate a sinusoidal wave frequency signal.

4. A frequency-selective gain conversion circuit according to claim 1, characterized in that: include: The conversion circuit captures and amplifies the signal from the vibration cylinder and provides it to the excitation coil, causing the vibration cylinder to vibrate at a large-amplitude resonant frequency. The positive feedback mode allows the vibration cylinder to maintain oscillation.

5. The frequency-selective gain conversion circuit according to claim 1, characterized in that: include: The sine wave frequency signal enters the conversion circuit and is converted into a square wave signal. The microprocessor measures the frequency to obtain the fuel density.

Images