Resonant tuning fork densimeter detection circuit

Abstract

The utility model discloses a resonant tuning fork densimeter detection circuit, which relates to the technical field of electronic circuits and comprises a tuning fork transducer, a self-resonant circuit, a tuning fork power supply enabling circuit, an MCU (Microprogrammed Control Unit) control circuit, a shaping circuit, a driving circuit and an analog switch circuit, the tuning fork transducer is connected with the self-resonance circuit and the driving circuit; the self-resonance circuit is connected with the analog switch circuit and the shaping circuit; the MCU control circuit is connected with the analog switch circuit, the tuning fork enabling circuit and the shaping circuit; the analog switch circuit is connected with the driving circuit; the self-resonance circuit comprises a first signal amplification circuit, a second signal amplification circuit and a band-pass filter circuit. The tuning fork densimeter has the beneficial effects that rapid oscillation starting of the tuning fork can be realized, and the influence of heating and bubble generation on a density measurement value can be reduced, so that the measurement precision and reliability of the tuning fork densimeter are ensured.

Description

TECHNICAL FIELD

[0001] The utility model relates to electronic circuit technical field more specifically, relate to a kind of resonance tuning fork densimeter detection circuit. BACKGROUND

[0002] Tuning fork densimeter is a kind of instrument for measuring liquid density, its principle is that the vibration frequency value generated by tuning fork is different in different density solution, the density value of liquid is calculated by the difference of vibration frequency value.Tuning fork densimeter plays an important role in petroleum and natural gas, chemical industry, food and beverage, pharmaceutical, water treatment and environmental protection, papermaking and pulp paper, mining and metal processing, energy, oceanography, and the vibration of tuning fork densimeter tuning fork relies on transducer to convert electrical energy into mechanical energy, transducer can be divided into electromagnetic transducer and piezoelectric transducer, piezoelectric transducer is widely used because of low power consumption and high conversion efficiency.

[0003] In prior art, piezoelectric transducer is composed of piezoelectric ceramic stack, and the piezoelectric ceramic has inherent mechanical oscillation frequency, which is limited by volume, and the inherent frequency is high, and there is a large difference with the inherent frequency of tuning fork, so the tuning fork transducer is easy to enter the inherent frequency of piezoelectric ceramic under the drive of excitation circuit, and self-excitation is generated, energy cannot be effectively transmitted to tuning fork, leading to difficulty in tuning fork vibration; tuning fork power is large, which is easy to cause self-heating and heating of power supply and driving circuit, affect temperature compensation measurement, thereby leading to low density measurement accuracy and large overall power consumption; most of the current tuning fork densimeters include tuning fork liquid level switch, which keeps the tuning fork working continuously after the equipment is powered on, and the tuning fork immersed in liquid is easy to produce bubbles in continuous working state, which seriously affects the resonance frequency of tuning fork in liquid and leads to the decline of measurement accuracy.

[0004] Therefore, the utility model provides a kind of resonance tuning fork densimeter detection circuit, which can realize the rapid vibration of tuning fork, reduce the influence of heating and bubble generation on density measurement value, and ensure the measurement accuracy and reliability of tuning fork densimeter. UTILITY MODEL CONTENT

[0005] In order to overcome the shortcomings of the prior art, the utility model provides a kind of resonance tuning fork densimeter detection circuit, which can realize the rapid vibration of tuning fork, reduce the influence of heating and bubble generation on density measurement value, and ensure the measurement accuracy and reliability of tuning fork densimeter.

[0006] The utility model discloses a technical scheme that solves its technical problem is: a resonance formula tuning fork densimeter detection circuit, its improvement lies in, resonance formula tuning fork densimeter detection circuit includes tuning fork transducer, self resonance circuit, tuning fork power enable circuit, MCU control circuit, shaping circuit, drive circuit and analog switch circuit, tuning fork transducer is connected with self resonance circuit, drive circuit, self resonance circuit is connected with analog switch circuit, shaping circuit, MCU control circuit is connected with analog switch circuit, tuning fork enable circuit and shaping circuit, analog switch circuit is connected with drive circuit,

[0007] Self resonance circuit includes first signal amplification circuit, second signal amplification circuit and band pass filter circuit, first signal amplification circuit is connected with tuning fork transducer, second signal amplification circuit is connected with analog switch circuit, shaping circuit, band pass filter circuit is connected between first signal amplification circuit and second signal amplification circuit.

[0008] In the above structure, MCU control circuit includes main control chip U10, reset chip U1, capacitor C43, resistance R48 and crystal oscillator X1, main control chip U10 is connected with crystal oscillator X1, resistance R48, reset chip is connected between resistance R48 and capacitor C43.

[0009] In the above structure, analog switch circuit includes analog switch chip U17, resistance R29, resistance R37, resistance R39 and resistance R40, analog switch chip U17 includes NO pin, COM pin, NC pin, IN pin, V+ pin and GND pin, NC pin is connected with one end of resistance R37, COM pin is connected with one end of resistance R29 and drive circuit, NO pin resistance R29 the other end, one end of resistance R39 and one end of resistance R40 are connected, GND pin is grounded, V+ pin is connected with 3.3V voltage, IN pin is connected with main control chip U10, the other end of resistance R37 is connected with main control chip U10, the other end of resistance R39 is grounded, the other end of resistance R40 is connected with self resonance circuit.

[0010] In the above structure, the first signal amplification circuit comprises an operational amplifier U61, an operational amplifier U62, a resistor R24, a resistor R35, a resistor R36, a resistor R70, a resistor R71, a capacitor C37 and a capacitor C60; the positive input terminal of the operational amplifier U61 is connected with one end of the resistor R71, the negative input terminal and the output terminal of the operational amplifier U61 are connected with one end of the resistor R36; the positive input terminal of the operational amplifier U62 is connected with one end of the resistor R24, the negative input terminal of the operational amplifier U62 is connected with one end of the resistor R35, the output terminal of the operational amplifier U62 is connected with the other end of the resistor R35; the capacitor C60 is connected between the other end of the resistor R36 and one end of the resistor R35; the capacitor C37 is connected in parallel with the resistor R35; the other end of the resistor R34 is connected with a 16V voltage; the other end of the resistor R71 is connected with one end of the resistor R70 and the tuning fork transducer; the other end of the resistor R70 is connected with the tuning fork transducer and grounded.

[0011] In the above structure, the band-pass filter circuit comprises an operational amplifier U63, a resistor R23, a resistor R28, a resistor R31 and a capacitor C32; the positive input terminal of the operational amplifier U63 is connected with one end of the resistor R31, the negative input terminal is connected with one end of the resistor R23 and one end of the capacitor C32, the output terminal is connected with the other end of the resistor R23, one end of the capacitor C27 and the second signal amplification circuit; the other end of the capacitor C32 is connected with the other end of the capacitor C27, one end of the resistor R25 and one end of the resistor R28; the other end of the resistor R28 is connected with the output terminal of the operational amplifier U62; the other end of the resistor R25 is connected with a 16V voltage.

[0012] In the above structure, the second signal amplification circuit comprises an operational amplifier U64, a resistor R26, a resistor R32, a resistor R33, a capacitor C25, a capacitor C26, a capacitor C30 and a capacitor C35; the resistor R33 and the capacitor C35 are both connected in parallel between the negative input terminal and the output terminal of the operational amplifier U64; the capacitor C25 and the capacitor C26 are connected in parallel, one end of which is connected with the positive power input terminal of the operational amplifier and connected with a 32V voltage, and the other end is grounded; the resistor R26 is connected between the output terminal of the operational amplifier U63 and the positive input terminal of the operational amplifier U64; one end of the capacitor C30 is connected with a 16V voltage, and the other end is connected with the positive input terminal of the operational amplifier U64; one end of the resistor R32 is connected with a 16V voltage, and the other end is connected with the negative input terminal of the operational amplifier U64; the negative power input terminal of the operational amplifier U64 is grounded, and the output terminal is connected with the other end of the resistor R40 and the shaping circuit.

[0013] In the above structure, the shaping circuit includes an operational amplifier U67, resistors R16, R17, R20, R21, R22, capacitor C21, and capacitor C61. Resistor R17 and capacitor C61 are connected in parallel, with one end grounded and the other end connected to the positive input terminal of amplifier chip U66. Resistor R20 is connected between the positive input terminal of operational amplifier U67 and the output terminal of operational amplifier U64. One end of resistor R21 is connected to the negative input terminal of operational amplifier U67, and the other end is connected to a 3.3V voltage. One end of resistor R22 is connected to the negative input terminal of operational amplifier U67, and the other end is grounded. One end of capacitor C21 is grounded, and the other end is connected to a 3.3V voltage and connected to the positive power supply input terminal of operational amplifier U67. One end of resistor R16 is connected to the output terminal of operational amplifier U67 and the main control chip U10, and the other end is connected to a 3.3V voltage. The negative power supply input terminal of operational amplifier U67 is grounded.

[0014] In the above structure, the tuning fork power enable circuit includes MOSFETs Q1 and Q3, resistors R10, R12, R13, and R14, a boost converter chip U2, resistors R6, R7, R8, and R11, inductor L2, diode D2, capacitors C9, C12, C15, C16, C58, and C60; the boost converter chip U2 includes CII, VCC, IPX, DC, GND, TC, SE, and SC pins; resistor R12 is connected between the gate of MOSFET Q1 and the drain of MOSFET Q3; resistor R10 is connected between the gate and source of MOSFET Q1; one end of resistor R13 is connected to the drain of MOSFET Q1, and the other end is connected to the main control chip U10; one end of resistor R14 is connected to the main control chip U10. The gate of S-channel transistor Q3 is connected, and the other end is grounded; the drain of MOSFET Q1 is connected to the VCC pin and one end of resistor R8; the source of MOSFET Q3 is grounded; the other end of resistor R8 is connected to the IPX pin; one end of resistor R7 is connected to the CII pin and one end of resistor R6, and the other end of resistor R7 is grounded; capacitors C12, C15, C16, C58, and C60 are connected in parallel, with one end connected to the other end of resistor R6 and the cathode of diode D2 and connected to a 32V voltage, and the other end grounded; the anode of diode D2 is connected to the SC pin and one end of inductor L2; the other end of inductor L2 is connected to one end of resistor R11 and the IPX pin; the other end of resistor R11 is connected to the DC pin; one end of capacitor C9 is connected to the TC pin, and the other end is grounded; the SE pin is grounded.

[0015] In the above structure, the driving circuit includes amplifier chip U65, amplifier chip U66, resistors R60, R61, R62, and R63, capacitor C29, and capacitor C55. The positive input terminal of amplifier chip U65 is connected to the COM pin of analog switch chip U17, the negative input terminal is connected to one end of resistor R60 and one end of resistor R61, and the output terminal is connected to one end of capacitor C29 and one end of resistor R62. The positive input terminal of amplifier chip U66 is connected to a 16V voltage, the negative input terminal is connected to the other end of resistor R62 and one end of resistor R63, and the output terminal is connected to the other end of resistor R63 and one end of capacitor C55. The other ends of capacitors C29 and C55 are both connected to a tuning fork transducer. The other end of resistor R61 is connected to a 3.3V voltage. The other end of resistor R60 is grounded.

[0016] The beneficial effects of this invention are as follows: This invention outputs a strong drive signal to the drive circuit via the MCU control circuit, and then sends the strong drive signal to the tuning fork transducer. The tuning fork transducer converts the electrical energy of the strong drive signal into mechanical energy to achieve rapid oscillation of the tuning fork. After the tuning fork starts oscillating, the strong drive signal is turned off, and the circuit switches to a self-resonant circuit to ensure that the tuning fork maintains a self-resonant state. Since the self-resonant circuit has a bandpass filter circuit, the center frequency is the inherent resonant frequency of the tuning fork, effectively filtering out interference from the tuning fork transducer and other abnormal frequencies, and preventing the circuit from entering the self-excited resonance of the tuning fork transducer. In addition, the tuning fork power enable circuit can keep the tuning fork in an intermittent working state, reducing the impact of heat generation and bubble generation on the density measurement value. Therefore, this invention can achieve rapid oscillation of the tuning fork and reduce the impact of heat generation and bubble generation on the density measurement value, so as to ensure the measurement accuracy and reliability of the tuning fork density meter. Attached Figure Description

[0017] Figure 1 This is an overall block diagram of a resonant tuning fork density meter detection circuit according to the present invention;

[0018] Figure 2 This is a schematic diagram of the MCU control circuit of a resonant tuning fork density meter detection circuit according to the present invention.

[0019] Figure 3 This is a schematic diagram of the analog switching circuit of a resonant tuning fork density meter detection circuit according to the present invention;

[0020] Figure 4 This is a schematic diagram of the first signal amplification circuit of a resonant tuning fork density meter detection circuit according to the present invention;

[0021] Figure 5This is a schematic diagram of the bandpass filter circuit of a resonant tuning fork density meter detection circuit according to the present invention;

[0022] Figure 6 This is a schematic diagram of the second signal amplification circuit of a resonant tuning fork density meter detection circuit according to the present invention;

[0023] Figure 7 This is a schematic diagram of the shaping circuit of a resonant tuning fork density meter detection circuit according to the present invention.

[0024] Figure 8 This is a schematic diagram of the tuning fork power supply enable circuit of a resonant tuning fork density meter detection circuit according to this utility model.

[0025] Figure 9 This is a schematic diagram of the driving circuit of a resonant tuning fork density meter detection circuit according to the present invention. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] The following will clearly and completely describe the concept, specific structure, and technical effects of this utility model in conjunction with embodiments and accompanying drawings, so as to fully understand the purpose, features, and effects of this utility model. Obviously, the described embodiments are only a part of the embodiments of this utility model, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are all within the scope of protection of this utility model. Furthermore, all connections / linkages involved in the patent do not simply refer to direct contact between components, but rather to the ability to form a better connection structure by adding or reducing connecting accessories according to specific implementation conditions. The various technical features in this utility model can be combined interactively without contradicting each other.

[0028] Reference Figure 1As shown, this utility model discloses a resonant tuning fork density meter detection circuit. The resonant tuning fork density meter detection circuit includes a tuning fork transducer, a self-resonant circuit, a tuning fork power enable circuit, an MCU control circuit, a shaping circuit, a driving circuit, and an analog switch circuit. The tuning fork transducer is connected to the self-resonant circuit and the driving circuit. The self-resonant circuit is connected to the analog switch circuit and the shaping circuit. The MCU control circuit is connected to the analog switch circuit, the tuning fork enable circuit, and the shaping circuit. The analog switch circuit is connected to the driving circuit. The self-resonant circuit includes a first signal amplification circuit, a second signal amplification circuit, and a bandpass filter circuit. The first signal amplification circuit is connected to the tuning fork transducer, and the second signal amplification circuit is connected to the analog switch circuit and the shaping circuit. The bandpass filter circuit is connected between the first signal amplification circuit and the second signal amplification circuit.

[0029] It should be noted that, in this embodiment, a tuning fork arm is fixedly installed on the outer side of the tuning fork transducer. The tuning fork arm is used to receive specific frequency energy from the tuning fork transducer and generate mechanical vibration. The tuning fork transducer is internally equipped with a pickup piezoelectric ceramic and an excitation piezoelectric ceramic. The excitation piezoelectric ceramic is used to convert electrical energy into mechanical energy to facilitate rapid oscillation of the tuning fork. The excitation piezoelectric ceramic is used to convert the mechanical energy of the tuning fork vibration into electrical energy and send it to subsequent circuits for detection. The self-resonant circuit is used to process the electrical signal sent by the tuning fork transducer. Specifically, the self-resonant circuit includes a first signal amplification circuit, a bandpass filter circuit, and a second signal amplification circuit. The first signal amplification circuit is used to initially amplify the electrical signal sent by the tuning fork transducer to facilitate subsequent removal of noise in the electrical signal. The circuit includes a bandpass filter circuit for filtering out noise from the initially amplified electrical signal, preserving the inherent resonant frequency of the tuning fork, preventing self-excitation of the tuning fork transducer, and preventing noise from affecting the tuning fork frequency acquisition. The second signal amplification circuit further amplifies the filtered electrical signal to ensure it is effectively transmitted to subsequent circuits. The analog switch circuit enables switching between the drive signal and the resonant signal. The drive circuit converts the drive signal sent by the MCU control circuit into a signal capable of driving the tuning fork to vibrate. The tuning fork power enable circuit controls the power supply to the tuning fork. The shaping circuit converts the electrical signal sent by the self-resonant circuit into a square wave of the corresponding frequency. The MCU control circuit manages and controls the switching of the tuning fork power enable circuit and the analog switch circuit.In the specific implementation of this utility model, after the tuning fork product is powered on, the MCU control circuit controls the tuning fork power enable circuit to open and the switch to close by outputting a high level. At this time, the tuning fork power enable circuit supplies power to the self-resonant circuit and the drive circuit, and the MCU control circuit controls the analog switch circuit to switch to the strong drive signal terminal and sends a strong drive signal to the drive circuit. This signal then passes through the drive circuit to the piezoelectric ceramic at the excitation terminal of the tuning fork transducer, driving the tuning fork fork arm to vibrate, thereby achieving rapid oscillation of the tuning fork. After the tuning fork arm vibrates, the piezoelectric ceramic at the transducer pickup terminal converts the received vibration signal into a voltage signal for output. The self-resonant circuit amplifies and filters the voltage signal to filter out interference from the tuning fork transducer and other abnormal frequencies, preventing the circuit from entering the transducer's self-resonance. A portion of the signal after passing through the self-resonant circuit enters the integrated circuit. The waveform is converted into a standard square wave by the shaping circuit, which is then input to the MCU control circuit for frequency acquisition. Simultaneously, the frequency value is converted into a density value for output. Another portion of the signal enters the drive circuit via an analog switch and reaches the piezoelectric ceramic at the excitation end of the tuning fork transducer, driving the tuning fork arm to vibrate. After the tuning fork has been working for a period of time, the MCU control circuit outputs a low level to control the tuning fork power enable circuit to close, the switch opens, and the tuning fork power enable circuit disconnects the power supply to the self-resonant circuit and drive circuit, stopping the tuning fork from working. This reduces the impact of circuit heating and bubble formation on the density measurement value. After a period of time, it reopens, repeating the switching state. Therefore, it can achieve rapid tuning fork oscillation while minimizing the impact of heating and bubble formation on the density measurement value, ensuring the measurement accuracy and reliability of the tuning fork density meter.

[0030] Reference Figure 2 As shown, the MCU control circuit includes a main control chip U10, a reset chip U1, a capacitor C43, a resistor R48, and a crystal oscillator X1; the main control chip U10 is connected to the crystal oscillator X1 and the resistor R48; the reset chip is connected between the resistor R48 and the capacitor C43.

[0031] It should be noted that, in this embodiment, the main control chip U10 is model GD32F303CGT6, which is mainly responsible for acquiring the frequency value generated by the tuning fork and controlling the switching of the tuning fork drive unit; the crystal oscillator X1 is 8MHz, which is used to provide a suitable operating frequency for the main control chip U10; the signal of the reset chip U1 is MAX809S, which is mainly used to ensure that the main control chip U10 starts running from a known safe state when powered on or when a fault occurs; the capacitor C43 is used to cooperate with the reset chip U1 to provide a stable reset process; the resistor R48 is used to adjust the current to ensure stable circuit operation.

[0032] Reference Figure 3As shown, the analog switch circuit includes an analog switch chip U17, resistors R29, R37, R39, and R40. The analog switch chip U17 includes a NO pin, a COM pin, an NC pin, an IN pin, a V+ pin, and a GND pin. The NC pin is connected to one end of resistor R37, the COM pin is connected to one end of resistor R29 and the drive circuit, the other end of resistor R29, one end of resistor R39, and one end of resistor R40 are connected to the NO pin, the GND pin is grounded, the V+ pin is connected to a 3.3V voltage, and the IN pin is connected to the main control chip U10. The other end of resistor R37 is connected to the main control chip U10. The other end of resistor R39 is grounded. The other end of resistor R40 is connected to the self-resonant circuit.

[0033] It should be noted that in this embodiment, the analog switch circuit consists of an analog switch chip U17 and resistors R29, R37, R40, and R50. When the tuning fork is powered on, the MCU control circuit controls the tuning fork power enable circuit to open through the main control chip U10. The MCU control circuit outputs a strong drive signal through the main control chip U10 to the NC pin of the analog switch circuit via resistor R37. At this time, the analog switch chip U17 is controlled by the MCU control circuit to connect and conduct the NC pin and COM pin. This signal passes through the analog switch chip... The output is from the COM pin of U17. Within 3 seconds of powering on the tuning fork or after the tuning fork stops vibrating, the tuning fork needs to be forcibly driven. The frequency of the forced drive signal is basically the same as the natural resonant frequency of the tuning fork. The MCU control circuit inputs a low level to the IN pin of the analog switch chip U17. When the IN pin is low, the NC pin and COM pin of the analog switch chip U17 are conducting. At other times, the IN pin is high, and the COM pin and NO pin are conducting, switching to the tuning fork self-resonance drive state. In addition, the model of the analog switch chip U17 is RS2103.

[0034] Reference Figure 4As shown, the first signal amplification circuit includes operational amplifier U61, operational amplifier U62, resistors R24, R35, R36, R70, R71, capacitor C37, and capacitor C60. The positive input terminal of operational amplifier U61 is connected to one end of resistor R71, and the negative input terminal of operational amplifier U61 is connected to its output terminal and one end of resistor R36. The positive input terminal of operational amplifier U62 is connected to one end of resistor R24, the negative input terminal of operational amplifier U62 is connected to one end of resistor R35, and the output terminal of operational amplifier U62 is connected to the other end of resistor R35. Capacitor C60 is connected between the other end of resistor R36 and one end of resistor R35. Capacitor C37 is connected in parallel with resistor R35. The other end of resistor R34 is connected to a 16V voltage. The other end of resistor R71 is connected to one end of resistor R70 and a tuning fork transducer. The other end of resistor R70 is connected to the tuning fork transducer and grounded. (Refer to...) Figure 5 As shown, the bandpass filter circuit includes operational amplifier U63, resistors R23, R28, R31, and capacitor C32. The positive input terminal of operational amplifier U63 is connected to one end of resistor R31, the negative input terminal is connected to one end of resistor R23 and one end of capacitor C32, and the output terminal is connected to the other end of resistor R23, one end of capacitor C27, and the second signal amplification circuit. The other end of capacitor C32 is connected to the other end of capacitor C27, one end of resistor R25, and one end of resistor R28. The other end of resistor R28 is connected to the output terminal of operational amplifier U62. The other end of resistor R25 is connected to a 16V voltage. (Refer to...) Figure 6 As shown, the second signal amplification circuit includes an operational amplifier U64, resistors R26, R32, and R33, and capacitors C25, C26, C30, and C35. Resistor R33 and capacitor C35 are both connected in parallel between the negative input and output terminals of operational amplifier U64. Capacitors C25 and C26 are connected in parallel, with one end connected to the positive power input terminal of the operational amplifier and connected to a 32V voltage, and the other end grounded. Resistor R26 is connected between the output terminal of operational amplifier U63 and the positive input terminal of operational amplifier U64. One end of capacitor C30 is connected to a 16V voltage, and the other end is connected to the positive input terminal of operational amplifier U64. One end of resistor R32 is connected to a 16V voltage, and the other end is connected to the negative input terminal of operational amplifier U64. The negative power input terminal of operational amplifier U64 is grounded, and its output terminal is connected to the other end of resistor R40 and the shaping circuit.

[0035] It should be noted that, in this embodiment, after the tuning fork starts oscillating, the piezoelectric ceramic at the pickup end of the tuning fork transducer converts the received mechanical energy into electrical energy. The electrical signal is amplified and filtered by a self-resonant circuit. The self-resonant circuit consists of a signal amplification circuit and a bandpass filter circuit. The signal amplification circuit is composed of a first signal amplification circuit and a second signal amplification circuit. The first signal amplification circuit amplifies the electrical signal output by the pickup piezoelectric ceramic, increasing its amplitude to facilitate driving subsequent circuits. The bandpass filter circuit filters out noise from the tuning fork signal after passing through the first signal amplification circuit. This filter is a Chebyshev bandpass filter, with its center frequency being the natural resonant frequency of the tuning fork. It effectively filters out interference from the transducer and other abnormal frequencies, preventing the circuit from entering the transducer's self-resonance and also preventing external signals from affecting the signal frequency acquisition. The signal amplitude after passing through the bandpass filter is relatively small, and then it is amplified by a second signal amplification circuit, which is a non-inverting proportional amplifier circuit. After passing through the self-resonant circuit, part of the output signal enters the analog switching circuit and then the driving circuit to drive the tuning fork's self-resonance, while the other part enters the shaping circuit.

[0036] Reference Figure 7 As shown, the shaping circuit includes operational amplifier U67, resistors R16, R17, R20, R21, R22, capacitor C21, and capacitor C61. Resistor R17 and capacitor C61 are connected in parallel, with one end grounded and the other end connected to the positive input terminal of amplifier chip U66. Resistor R20 is connected between the positive input terminal of operational amplifier U67 and the output terminal of operational amplifier U64. One end of resistor R21 is connected to the negative input terminal of operational amplifier U67, and the other end is connected to a 3.3V voltage. One end of resistor R22 is connected to the negative input terminal of operational amplifier U67, and the other end is grounded. One end of capacitor C21 is grounded, and the other end is connected to a 3.3V voltage and connected to the positive power input terminal of operational amplifier U67. One end of resistor R16 is connected to the output terminal of operational amplifier U67 and the main control chip U10, and the other end is connected to a 3.3V voltage. The negative power input terminal of operational amplifier U67 is grounded.

[0037] It should be noted that, in this embodiment, the shaping circuit is used to shape the output signal of the self-resonant circuit, turning the signal into a standard square wave. Specifically, the signal output by the self-resonant circuit is compared with a fixed voltage value after being divided by resistors R17 and R20. After comparison, the amplitude of the output signal is 3.3V, and the frequency is the frequency of the tuning fork vibration. The output signal is sent to the main control chip U10 of the MCU control circuit for frequency acquisition and frequency-density value conversion.

[0038] Reference Figure 8As shown, the tuning fork power enable circuit includes MOSFETs Q1 and Q3, resistors R10, R12, R13, and R14, a boost converter chip U2, resistors R6, R7, R8, and R11, inductor L2, diode D2, capacitors C9, C12, C15, C16, C58, and C60; the boost converter chip U2 includes CII, VCC, IPX, DC, GND, TC, SE, and SC pins; resistor R12 is connected between the gate of MOSFET Q1 and the drain of MOSFET Q3; resistor R10 is connected between the gate and source of MOSFET Q1; one end of resistor R13 is connected to the drain of MOSFET Q1, and the other end is connected to the main control chip U10; one end of resistor R14 is connected to the MOSFET... The gate of Q3 is connected, and the other end is grounded; the drain of the MOSFET Q1 is connected to the VCC pin and one end of the resistor R8; the source of the MOSFET Q3 is grounded; the other end of the resistor R8 is connected to the IPX pin; one end of the resistor R7 is connected to the CII pin and one end of the resistor R6, and the other end of the resistor R7 is grounded; capacitors C12, C15, C16, C58, and C60 are connected in parallel, with one end connected to the other end of the resistor R6 and the cathode of the diode D2 and connected to a 32V voltage, and the other end grounded; the anode of the diode D2 is connected to the SC pin and one end of the inductor L2; the other end of the inductor L2 is connected to one end of the resistor R11 and the IPX pin; the other end of the resistor R11 is connected to the DC pin; one end of the capacitor C9 is connected to the TC pin, and the other end is grounded; the SE pin is grounded.

[0039] It should be noted that, in this embodiment, the tuning fork power enable circuit consists of two parts. The first part consists of MOSFET Q1, MOSFET Q3, resistors R10, R12, R13, and R14, forming a switch that controls the power input. When the power needs to be turned on, a high level can be output from the pin of the main control chip U10 to resistor R13 to turn it on; when the power needs to be turned off, a low level can be output from the pin of the main control chip U10 to resistor R13 to turn it off. The second part consists of boost converter chip U2, resistors R6, R7, R8, and R11, inductor L2, diode D2, capacitors C12, C15, C16, and C58, and capacitor... C60 forms a DC-DC boost circuit. When the tuning fork needs to work, the main control chip U10 outputs a high level to resistor R13 through its corresponding control pin, turning on the switch. After the switch is turned on, the power supply goes through MOSFET Q1 to the subsequent DC-DC boost circuit to increase the voltage, boosting the input voltage to 32V to power the operational amplifier for the tuning fork signal and drive. To turn off the power, the main control chip U10 simply outputs a low level to resistor R13 through its corresponding control pin. The tuning fork power enable circuit is turned on and off intermittently during specific operation to reduce the impact of heating of the tuning fork's own power drive circuit and solution bubbles on frequency acquisition, thereby ensuring the measurement accuracy and reliability of the tuning fork density meter.

[0040] Reference Figure 9 As shown, the driving circuit includes amplifier chip U65, amplifier chip U66, resistors R60, R61, R62, and R63, capacitor C29, and capacitor C55. The positive input terminal of amplifier chip U65 is connected to the COM pin of analog switch chip U17, the negative input terminal is connected to one end of resistor R60 and one end of resistor R61, and the output terminal is connected to one end of capacitor C29 and one end of resistor R62. The positive input terminal of amplifier chip U66 is connected to a 16V voltage, the negative input terminal is connected to the other end of resistor R62 and one end of resistor R63, and the output terminal is connected to the other end of resistor R63 and one end of capacitor C55. The other ends of capacitors C29 and C55 are both connected to a tuning fork transducer. The other end of resistor R61 is connected to a 3.3V voltage. The other end of resistor R60 is grounded.

[0041] It should be noted that in this embodiment, when the signal output from the analog switch circuit reaches the drive circuit, the input signal of the drive circuit is compared with the voltage value of the voltage divider formed by resistors R60 and R61, and output by the amplifier chip U65. Since the operational amplifier U64 is powered by 32V, the waveform after comparison is a square wave with an amplitude of nearly 32V. This signal is then inverted by an inverting circuit composed of resistors R62 and R63 and amplifier chip U65. The inverted signal and the signal before inversion are respectively input to the piezoelectric ceramic plate at the excitation end of the tuning fork transducer through capacitors C55 and C29 to drive the tuning fork to vibrate. Among them, capacitors C55 and C29 are used to pass AC and block DC, and the amplifier chip U65 is model RS8414.

[0042] The above is a detailed description of the preferred embodiments of the present utility model. However, the present utility model is not limited to the described embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present utility model. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A resonant tuning fork density meter detection circuit, characterized in that, The resonant tuning fork density meter detection circuit includes a tuning fork transducer, a self-resonant circuit, a tuning fork power enable circuit, an MCU control circuit, a shaping circuit, a drive circuit, and an analog switch circuit; the tuning fork transducer is connected to the self-resonant circuit and the drive circuit; the self-resonant circuit is connected to the analog switch circuit and the shaping circuit; the MCU control circuit is connected to the analog switch circuit, the tuning fork enable circuit, and the shaping circuit; and the analog switch circuit is connected to the drive circuit. The self-resonant circuit includes a first signal amplification circuit, a second signal amplification circuit, and a bandpass filter circuit. The first signal amplification circuit is connected to a tuning fork transducer, and the second signal amplification circuit is connected to an analog switch circuit and a shaping circuit. The bandpass filter circuit is connected between the first signal amplification circuit and the second signal amplification circuit.

2. The resonant tuning fork density meter detection circuit according to claim 1, characterized in that, The MCU control circuit includes a main control chip U10, a reset chip U1, a capacitor C43, a resistor R48, and a crystal oscillator X1; the main control chip U10 is connected to the crystal oscillator X1 and the resistor R48; the reset chip is connected between the resistor R48 and the capacitor C43.

3. The resonant tuning fork density meter detection circuit according to claim 2, characterized in that, The analog switch circuit includes an analog switch chip U17, resistors R29, R37, R39, and R40. The analog switch chip U17 includes a NO pin, a COM pin, an NC pin, an IN pin, a V+ pin, and a GND pin. The NC pin is connected to one end of resistor R37; the COM pin is connected to one end of resistor R29 and the drive circuit; the other end of resistor R29, one end of resistor R39, and one end of resistor R40 are connected to the NO pin; the GND pin is grounded; the V+ pin is connected to 3.3V; and the IN pin is connected to the main control chip U10. The other end of resistor R37 is connected to the main control chip U10; the other end of resistor R39 is grounded; and the other end of resistor R40 is connected to the self-resonant circuit.

4. The resonant tuning fork density meter detection circuit according to claim 3, characterized in that, The first signal amplification circuit includes operational amplifier U61, operational amplifier U62, resistors R24, R35, R36, R70, R71, capacitor C37, and capacitor C60. The positive input terminal of operational amplifier U61 is connected to one end of resistor R71, and the negative input terminal of operational amplifier U61 is connected to its output terminal and one end of resistor R36. The positive input terminal of operational amplifier U62 is connected to one end of resistor R24, the negative input terminal of operational amplifier U62 is connected to one end of resistor R35, and the output terminal of operational amplifier U62 is connected to the other end of resistor R35. Capacitor C60 is connected between the other end of resistor R36 and one end of resistor R35. Capacitor C37 is connected in parallel with resistor R35. The other end of resistor R34 is connected to a 16V voltage. The other end of resistor R71 is connected to one end of resistor R70 and a tuning fork transducer. The other end of resistor R70 is connected to the tuning fork transducer and grounded.

5. The resonant tuning fork density meter detection circuit according to claim 4, characterized in that, The bandpass filter circuit includes an operational amplifier U63, resistors R23, R28, and R31, and a capacitor C32. The positive input terminal of the operational amplifier U63 is connected to one end of resistor R31, the negative input terminal is connected to one end of resistor R23 and one end of capacitor C32, and the output terminal is connected to the other end of resistor R23, one end of capacitor C27, and the second signal amplification circuit. The other end of capacitor C32 is connected to the other end of capacitor C27, one end of resistor R25, and one end of resistor R28. The other end of resistor R28 is connected to the output terminal of operational amplifier U62. The other end of resistor R25 is connected to a 16V voltage.

6. The resonant tuning fork density meter detection circuit according to claim 5, characterized in that, The second signal amplification circuit includes an operational amplifier U64, resistors R26, R32, and R33, and capacitors C25, C26, C30, and C35. Resistor R33 and capacitor C35 are both connected in parallel between the negative input and output terminals of operational amplifier U64. Capacitors C25 and C26 are connected in parallel, with one end connected to the positive power input terminal of the operational amplifier and connected to a 32V voltage, and the other end grounded. Resistor R26 is connected between the output terminal of operational amplifier U63 and the positive input terminal of operational amplifier U64. One end of capacitor C30 is connected to a 16V voltage, and the other end is connected to the positive input terminal of operational amplifier U64. One end of resistor R32 is connected to a 16V voltage, and the other end is connected to the negative input terminal of operational amplifier U64. The negative power input terminal of operational amplifier U64 is grounded, and its output terminal is connected to the other end of resistor R40 and the shaping circuit.

7. The resonant tuning fork density meter detection circuit according to claim 6, characterized in that, The shaping circuit includes an operational amplifier U67, resistors R16, R17, R20, R21, R22, capacitor C21, and capacitor C61. Resistor R17 and capacitor C61 are connected in parallel, with one end grounded and the other end connected to the positive input terminal of amplifier chip U66. Resistor R20 is connected between the positive input terminal of operational amplifier U67 and the output terminal of operational amplifier U64. One end of resistor R21 is connected to the negative input terminal of operational amplifier U67, and the other end is connected to a 3.3V voltage. One end of resistor R22 is connected to the negative input terminal of operational amplifier U67, and the other end is grounded. One end of capacitor C21 is grounded, and the other end is connected to a 3.3V voltage and connected to the positive power input terminal of operational amplifier U67. One end of resistor R16 is connected to the output terminal of operational amplifier U67 and the main control chip U10, and the other end is connected to a 3.3V voltage. The negative power input terminal of operational amplifier U67 is grounded.

8. The resonant tuning fork density meter detection circuit according to claim 2, characterized in that, The tuning fork power enable circuit includes MOSFETs Q1 and Q3, resistors R10, R12, R13, and R14, a boost converter chip U2, resistors R6, R7, R8, and R11, inductor L2, diode D2, capacitors C9, C12, C15, C16, C58, and C60. The boost converter chip U2 includes CII, VCC, IPX, DC, GND, TC, SE, and SC pins. Resistor R12 is connected between the gate of MOSFET Q1 and the drain of MOSFET Q3. Resistor R10 is connected between the gate and source of MOSFET Q1. One end of resistor R13 is connected to the drain of MOSFET Q1, and the other end is connected to the main control chip U10. One end of resistor R14 is connected to MOSFET Q3. The gate of transistor Q3 is connected, and the other end is grounded; the drain of transistor Q1 is connected to the VCC pin and one end of resistor R8; the source of transistor Q3 is grounded; the other end of resistor R8 is connected to the IPX pin; one end of resistor R7 is connected to the CII pin and one end of resistor R6, and the other end of resistor R7 is grounded; capacitors C12, C15, C16, C58, and C60 are connected in parallel, with one end connected to the other end of resistor R6 and the cathode of diode D2 and connected to a 32V voltage, and the other end is grounded; the anode of diode D2 is connected to the SC pin and one end of inductor L2; the other end of inductor L2 is connected to one end of resistor R11 and the IPX pin; the other end of resistor R11 is connected to the DC pin; one end of capacitor C9 is connected to the TC pin, and the other end is grounded; the SE pin is grounded.

9. The resonant tuning fork density meter detection circuit according to claim 3, characterized in that, The driving circuit includes amplifier chip U65, amplifier chip U66, resistors R60, R61, R62, and R63, capacitor C29, and capacitor C55. The positive input terminal of amplifier chip U65 is connected to the COM pin of analog switch chip U17, the negative input terminal is connected to one end of resistor R60 and one end of resistor R61, and the output terminal is connected to one end of capacitor C29 and one end of resistor R62. The positive input terminal of amplifier chip U66 is connected to a 16V voltage, the negative input terminal is connected to the other end of resistor R62 and one end of resistor R63, and the output terminal is connected to the other end of resistor R63 and one end of capacitor C55. The other ends of capacitors C29 and C55 are both connected to a tuning fork transducer. The other end of resistor R61 is connected to a 3.3V voltage. The other end of resistor R60 is grounded.

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