CN110006505B - Ultrasonic liquid level detection method - Google Patents

Ultrasonic liquid level detection method Download PDF

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Publication number
CN110006505B
CN110006505B CN201910129847.2A CN201910129847A CN110006505B CN 110006505 B CN110006505 B CN 110006505B CN 201910129847 A CN201910129847 A CN 201910129847A CN 110006505 B CN110006505 B CN 110006505B
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resistor
module
capacitor
ultrasonic
power supply
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CN110006505A (en
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徐冬
荣磊
汪寅波
陈定游
李山
周凯
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Hangzhou Supmea Automation Co ltd
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Hangzhou Supmea Automation Co ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
    • G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
    • G01F23/296—Acoustic waves
    • G01F23/2962—Measuring transit time of reflected waves

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Electromagnetism (AREA)
  • Thermal Sciences (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Amplifiers (AREA)
  • Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)

Abstract

The invention discloses an ultrasonic liquid level detection method. The ultrasonic liquid level meter in the current market has the problems of complex structure, inconvenience in use and low measurement precision. The invention relates to an ultrasonic liquid level meter which comprises a power supply module, a control module, a sensor, an ultrasonic transmitting module, an ultrasonic receiving module, a temperature compensation module and piezoelectric ceramics. The power supply module supplies power to the control module, the ultrasonic transmitting module, the ultrasonic receiving module, the temperature compensation module and the output module through the first voltage stabilizer, the second voltage stabilizer, the switching voltage stabilizer and the ultra-low voltage stabilizer. The temperature compensation module detects the ambient temperature through the temperature sensor and transmits the ambient temperature to the control module. The control module sends an ultrasonic control signal to the ultrasonic transmitting module through the singlechip; the ultrasonic transmitting module boosts the ultrasonic control signal through a high-frequency transformer and transmits the boosted ultrasonic control signal to the piezoelectric ceramics. The invention can avoid the problem of inaccurate measurement caused by blind areas.

Description

Ultrasonic liquid level detection method
Technical Field
The invention belongs to the technical field of liquid level detection, and particularly relates to an ultrasonic liquid level meter and a liquid level detection method thereof.
Background
Along with the development of science and technology, the technical scheme of distance measurement is more and more diversified, especially the distance measurement technique of being applied to the measurement thing position, and the principle of surveying the thing position at present mainly includes contact and non-contact, and non-contact is because the characteristics of indirect and medium contact, convenient to use has unique advantage under some special operating modes, and non-contact is again based on the ultrasonic wave principle. However, the ultrasonic liquid level meter in the current market has the disadvantages of complex structure, inconvenient use and low measurement precision, and is difficult to meet the requirements of the broad market.
Disclosure of Invention
The invention aims to provide an ultrasonic liquid level meter and a liquid level detection method thereof.
The invention relates to an ultrasonic liquid level meter which comprises a power supply module, a control module, a sensor, an ultrasonic transmitting module, an ultrasonic receiving module, a temperature compensation module and piezoelectric ceramics. The power supply module supplies power to the control module, the ultrasonic transmitting module, the ultrasonic receiving module, the temperature compensation module and the output module through the first voltage stabilizer, the second voltage stabilizer, the switching voltage stabilizer and the ultra-low voltage stabilizer. The temperature compensation module detects the ambient temperature through the temperature sensor and transmits the ambient temperature to the control module. The control module sends an ultrasonic control signal to the ultrasonic transmitting module through the singlechip; the ultrasonic transmitting module boosts the ultrasonic control signal through a high-frequency transformer and transmits the boosted ultrasonic control signal to the piezoelectric ceramics.
The ultrasonic receiving module comprises a dual operational amplifier and a triode. The dual operational amplifier includes a first amplifier and a second amplifier. The base of the triode is connected with one end of the resistor R17 and the resistor R18. The other end of the resistor R17 is connected with one end of the nonpolar capacitor C14. The other end of the nonpolar capacitor C14 is connected to the cathode of the diode D9, the anode of the diode D8 and one end of the resistor R16. The other end of the resistor R16 is connected with one end of the nonpolar capacitor C13. The other end of the non-polar capacitor C13 is connected with the signal end of the piezoelectric ceramic. The cathode of the diode D8 and the anode of the diode D9 are both grounded. The emitter of the triode is connected with one end of a resistor R20. The other end of the resistor R20 is connected to ground. The collector of the triode is connected with the resistor R19, one end of the nonpolar capacitor C16 and the end of the resistor R18 far away from the base of the triode. The other end of the resistor R19 is connected to one end of the non-polar capacitor C15 and the third power supply output end of the power supply module. The other end of the non-polar capacitor C15 is grounded. The other end of the non-polar capacitor C16 is connected with one end of a resistor R21. The other end of the resistor R21 is connected to one end of the resistor R22, the non-polar capacitor C17 and the non-polar capacitor C18. The other end of the resistor R22 is connected to ground. The other end of the non-polar capacitor C18 is connected to one end of the resistor R23 and the inverting input terminal of the second amplifier. The other ends of the non-polar capacitor C17 and the resistor R23 are connected to the non-polar capacitor C20, one end of the non-polar capacitor C21 and the output end of the second amplifier. The other end of the non-polar capacitor C20 is grounded. The other end of the non-polar capacitor C21 is connected with one end of a resistor R26. The other end of the resistor R26 is connected with one end of the nonpolar capacitor C22, the resistor R27 and one end of the nonpolar capacitor C23. The other end of the resistor R27 is connected to ground. The other end of the non-polar capacitor C22 is connected to one end of the resistor R28 and the inverting input terminal of the first amplifier. The other end of the non-polar capacitor C23 is connected with the other end of the resistor R28, the non-polar capacitor C24, one end of the non-polar capacitor C25 and the output end of the first amplifier. The other end of the non-polar capacitor C24 is grounded. The other end of the nonpolar capacitor C25 is connected to the anodes of the diode D10 and the diode D11. The cathode of diode D10 is connected to ground. The cathode of the diode D11 is connected to one end of the resistor R30, the nonpolar capacitor C27 and the resistor R31. The other ends of the resistor R30 and the non-polar capacitor C27 are both grounded. The other end of the resistor R31 is connected with the ultrasonic signal input end of the control module. The reverse supply terminal of the first amplifier is grounded. The non-inverting input terminal of the second amplifier is connected to one terminal of the non-polar capacitor C19, the resistor R24, the resistor R25, and the non-inverting input terminal of the first amplifier. The other ends of the non-polar capacitor C19 and the resistor R25 are grounded. The other end of the resistor R24 is connected with the positive electrode of the electrolytic capacitor CD8, one end of the nonpolar capacitor C26, one end of the resistor R29 and the positive power supply end of the first amplifier. The negative electrode of the electrolytic capacitor CD8 and the other end of the nonpolar capacitor C26 are both grounded. The other end of the resistor R29 is connected with the third power supply output end of the power module.
Further, the model of the dual operational amplifier is OPA2335 AIDR.
Furthermore, the ultrasonic transmitting module comprises a second logic chip, a field effect transistor and a high-frequency transformer. The model of the second logic chip is MC74HC04 ADG. The 14 pins of the second logic chip are connected with a resistor R11, a non-polar capacitor C10, one end of the non-polar capacitor C11 and the cathode of a diode D5. The other end of the resistor R11 is connected with the 1 pin of the second logic chip and the ultrasonic emission control end MCUSSP of the control module. The other ends of the non-polar capacitor C10 and the non-polar capacitor C11 are both grounded. The anode of the diode D5 is connected to the cathode of the diode D4. The anode of the diode D4 is connected to the cathode of the diode D3. The anode of the diode D3 is connected with the third power supply output end of the power module. The second logic chip has pin 7 connected to ground and pin 2 connected to one end of resistor R12. The other end of the resistor R12 is connected with one end of the resistor R13 and the grid of the field effect transistor. The drain of the field effect transistor and the other end of the resistor R13 are both grounded. The source of the field effect transistor is connected with one terminal of the primary coil in the high-frequency transformer. The other connection terminal of the primary coil in the high-frequency transformer is connected with the anode of the electrolytic capacitor CD7, one end of the resistor R14 and the second power supply output terminal of the power supply module. The negative electrode of the electrolytic capacitor CD7 and the other end of the resistor R14 are both grounded. One connection of the secondary coil in the high-frequency transformer is connected with the anode of the diode D6 and the cathode of the diode D7. The cathode of the diode D6 is connected with the anode of the diode D7, one end of the nonpolar capacitor C12, one end of the resistor R15 and the signal end of the piezoelectric ceramic. The other terminal of the secondary coil in the high-frequency transformer is connected to the other terminal of the nonpolar capacitor C12 and the resistor R15 and is grounded. The ground wire end of the piezoelectric ceramic is grounded.
Further, the power supply module comprises a first voltage stabilizer, a second voltage stabilizer, a switching voltage stabilizer, an ultra-low voltage stabilizer, a first voltage-regulator tube, a second voltage-regulator tube, a third voltage-regulator tube and a fourth voltage-regulator tube. The first and second voltage regulators are each of type LM 317. The switching regulator is of the type MAX1836EUT 5. The model of the ultra-low voltage stabilizer is LP2980IM 5X-5.0. The 2 pin of the first voltage stabilizer is connected with external +24V voltage. The 1 pin of the first voltage stabilizer is connected with the first voltage stabilizer, the negative electrode of the second voltage stabilizer, the positive electrode of the electrolytic capacitor CD1, the non-polar capacitor C2, one end of the resistor R1 and the 3 pins of the switching voltage stabilizer. The other end of the resistor R1 is connected with the 3 pin of the first voltage stabilizer. The anode of the first voltage regulator tube is connected with the nonpolar capacitor C1, one end of the resistor R2 and the 5 pins of the switching regulator. The anode of the second voltage regulator tube, the cathode of the electrolytic capacitor CD1, the nonpolar capacitor C1, the resistor R2, the other end of the nonpolar capacitor C2 and the 2 pin of the switching regulator are all grounded. The 1 pin of the switching regulator is connected with one end of a resistor R3 and one end of a resistor R4. The other end of the resistor R4 is connected to ground. The 4-pin of the switching regulator is connected with one end of an inductor CL1 and the negative electrode of a diode D1. The other end of the inductor CL1 is connected with the other end of the resistor R3, the electrolytic capacitor CD2, the anode of the electrolytic capacitor CD3, the cathode of the third voltage-regulator tube and the cathode of the fourth voltage-regulator tube and one end of the nonpolar capacitor C3. And 6 pins of the switching regulator are connected with the anode of the diode D1, the cathode of the electrolytic capacitor CD2, the cathode of the electrolytic capacitor CD3, the anode of the third voltage-regulator tube and the fourth voltage-regulator tube, and the other end of the nonpolar capacitor C3 and grounded.
The 2 pin of the second voltage stabilizer is connected with the external +24V voltage, and the 1 pin is connected with the cathode of the diode D2, the anode of the electrolytic capacitor CD4, the resistor R5 and one end of the resistor R6. The anode of the diode D2 and the cathode of the electrolytic capacitor CD4 are both grounded. The 3 pin of the first voltage stabilizer is connected with the other end of the resistor R5. The other end of the resistor R6 is connected with the 1 pin of the ultra-low voltage regulator and the anode of the electrolytic capacitor CD 5. The 4 pins of the ultra-low voltage stabilizer are connected with the anode of an electrolytic capacitor CD 6. The negative electrodes of the electrolytic capacitor CD5 and the electrolytic capacitor CD6 and the 2-pin of the ultra-low voltage stabilizer are all grounded. The end of the inductor CL1 away from the switching regulator is the first power supply output end of the power supply module. The end of the resistor R5 away from the second regulator is the second power supply output end of the power supply module. And 4 pins of an ultra-low voltage stabilizer of the ultra-low voltage stabilizer are third power supply output ends of the power module, and 3 pins are control input ends of the power module.
Further, the control module comprises a single chip microcomputer, a first logic chip and a crystal oscillator. The model of the singlechip is ATMEGA 1284P. The model of the first logic chip is MC74HC04 ADG. The 4-pin of the singlechip is connected with one end of a resistor R7 and a non-polar capacitor C4. The other end of the resistor R7 is connected with a first power supply output end of the power supply module. The other end of the non-polar capacitor C4 is grounded. The 5 pins of the singlechip are connected with the first power supply output end of the power module, the 6 pins are grounded, the 7 pins are connected with one end of the nonpolar capacitor C5 and one end of the crystal oscillator, and the 8 pins are connected with one end of the nonpolar capacitor C6 and the other end of the crystal oscillator. The other ends of the non-polar capacitor C5 and the non-polar capacitor C6 are both grounded. The 12 pin of the singlechip is connected with one end of a resistor R9 and a1 pin of the first logic chip, and the 14 pin is connected with one end of a resistor R10 and a 5 pin of the first logic chip. The other ends of the resistor R9 and the resistor R10 are both grounded. The 6-pin of the first logic chip is connected with the control input end of the power module, the 7-pin is grounded, and the 14-pin is connected with one end of the nonpolar capacitor C9 and the first power supply output end of the power module. The other end of the non-polar capacitor C9 is grounded. Pins 17 and 38 of the singlechip are connected with a first power supply output end of the power module, pins 18, 28 and 39 are grounded, pin 27 is connected with one end of a resistor R8 and a non-polar capacitor C8, and pin 29 is connected with one end of a non-polar capacitor C7. The other end of the resistor R8 is connected with a first power supply output end of the power supply module. The other ends of the non-polar capacitor C7 and the non-polar capacitor C8 are both grounded. The 31 pin of the singlechip is the temperature signal input end of the control module, the 30 pin is the ultrasonic signal input end of the control module, and the 16 pin is the ultrasonic emission control end MCUSSP of the control module. And the 2 pins of the first logic chip are liquid level signal output ends of the control module.
Further, the temperature compensation module comprises a temperature sensor. The model of the temperature sensor is DS18B 20. The VDD pin of the temperature sensor is connected with one end of a resistor R32, a non-polar capacitor C28 and a first power supply output end of the power module, the DQ pin is connected with the other end of the resistor R32 and one end of a resistor R33, and the GND pin is grounded. The other end of the non-polar capacitor C28 is grounded. The other end of the resistor R33 is connected with one end of the resistor R34 and one end of the nonpolar capacitor C29. The other end of the resistor R34 is connected with one end of the nonpolar capacitor C30 and the temperature signal input end of the control module. The other ends of the non-polar capacitor C29 and the non-polar capacitor C30 are both grounded.
Furthermore, the ultrasonic liquid level meter also comprises an output module. The output module includes a third amplifier. The third amplifier has a model number OP07 CDR. The positive power supply end of the third amplifier is connected with one end of the nonpolar capacitor C31 and the first power supply output end of the power supply module. The other end of the non-polar capacitor C31 is grounded. The reverse power supply terminals of the third amplifiers are all grounded. The non-inverting input of the third amplifier is connected to one end of a resistor R38. The other end of the resistor R38 is connected with one end of the resistor R39. The other end of the resistor R39 is connected with one end of the resistor R40 and one end of the nonpolar capacitor C32. The other end of the resistor R40 is connected with one end of the resistor R41 and one end of the nonpolar capacitor C33. The other end of the resistor R41 is connected with one end of the resistor R42 and one end of the nonpolar capacitor C34. The other ends of the non-polar capacitor C32, the non-polar capacitor C33 and the non-polar capacitor C34 are all grounded. The other end of the resistor R42 is connected with the liquid level signal output end of the control module. The inverting input terminal of the third amplifier is connected with one end of the resistor R35, the resistor R36 and the resistor R37. The other end of the resistor R36 is connected with the output end of the third amplifier. The other end of the resistor R35 is connected with the external +24V voltage. The other end of the resistor R37 is connected to ground.
The liquid level detection method of the ultrasonic liquid level meter comprises the following specific steps:
step one, the power supply module is electrified, and the single chip microcomputer in the control module continuously transmits an interval power supply control signal to the power supply module. The interval power supply control signal is a PWM wave with the period of 1 second and the duty ratio of 30%. After the power supply module receives the interval power supply control signal, a third power supply output end of the power supply module outputs interval power supply voltage. And e, sequentially executing the steps from two to five, namely 1,2,3 and … ….
And step two, after the interval power supply control signal in the control module is changed from the low level to the high level for 0.1s, transmitting an ultrasonic control signal to the ultrasonic transmitting module. The ultrasonic control signal has a frequency equal to f and a time length equal to aiF 49 KHz. If si-1< 0.5m, then ai3; if si-1Is not less than 0.5m, then ai10. Get s00.5 m. Meanwhile, the singlechip in the control module records the time t when the ultrasonic control signal starts to be transmitted1,i。
And a high-frequency transformer in the ultrasonic transmitting module boosts the ultrasonic transmitting signal and then sends the boosted ultrasonic transmitting signal to the piezoelectric ceramic. The piezoelectric ceramic emits ultrasonic waves to the liquid surface. The ultrasonic emission signal is a signal obtained by superposing the interval power supply voltage and the ultrasonic control signal.
And step three, the piezoelectric ceramic converts the ultrasonic waves reflected by the liquid level into ultrasonic feedback signals and transmits the ultrasonic feedback signals to the ultrasonic receiving module.
And step four, filtering the part with the frequency f in the ultrasonic feedback signal by the ultrasonic receiving module, filtering and rectifying the part, and transmitting the part as a distance analog signal to the control module.
And step five, the control module draws the distance analog signals into a voltage curve in a coordinate system taking time as an abscissa and a voltage value as an ordinate. The maximum value of the ordinate of the voltage curve is Umax. The ordinate on the voltage curve is 2/3. UmaxThe point with the smallest abscissa among the points of (a) is a distance signal feature point. Recording the time t corresponding to the characteristic point of the distance signal2,i。
Step six, the temperature compensation module detects the current temperature Ti. The control module calculates the current liquid level hi＝l-(t2,i-t1,i)vTi. Wherein l is the distance between the piezoelectric ceramic and the bottom of the liquid to be measured; v. ofTi＝v0+0.6Ti，v0＝331m/s。
The invention has the beneficial effects that:
1. the echo cannot be collected during the transmission of the ultrasonic wave, so that a blind zone is formed during the period. The invention transmits different numbers of square waves according to the measured distance, and reduces the transmitting number of the square waves when the measured distance is smaller, thereby reducing the time for transmitting ultrasonic waves and avoiding the problem of inaccurate measurement caused by blind areas.
2. The invention has obvious effects in the aspects of low power consumption, stability, anti-interference performance and the like.
3. The boosting inverter circuit adopted in the ultrasonic transmitting module has the characteristics of high output energy, low high-voltage and low-current, low power consumption and the like.
4. According to the invention, the ultrasonic control signal sent by the control module is subjected to phase reversal to obtain the reverse square wave, so that the load capacity of the square wave is increased.
5. The diode D3, the diode D4, the diode D5, the capacitor C10 and the capacitor C11 play a role in stabilizing input voltage, and therefore stability and accuracy of the input voltage are improved.
6. The invention enables the calculated liquid level value to be more accurate through temperature compensation.
Drawings
FIG. 1 is a block diagram of the system of the present invention;
FIG. 2 is a diagram of a power module of the present invention;
FIG. 3 is a schematic diagram of the module of the single chip microcomputer of the present invention;
FIG. 4 is a circuit diagram of an ultrasonic transmitter module of the present invention;
FIG. 5 is a circuit diagram of an ultrasonic receiving module according to the present invention;
FIG. 6 is a circuit diagram of a temperature compensation module according to the present invention;
fig. 7 is a circuit diagram of an output module according to the present invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
As shown in fig. 1, an ultrasonic liquid level meter includes a power module 1, a control module 2, a sensor, an ultrasonic transmitting module 3, an ultrasonic receiving module 4, a temperature compensation module 5, an output module 6 and a piezoelectric ceramic 7. The power supply module 1 converts 24V voltage accessed from the outside into power for the control module 2, the ultrasonic transmitting module 3, the ultrasonic receiving module 4, the temperature compensation module 5 and the output module 6 through the first voltage stabilizer, the second voltage stabilizer, the switching voltage stabilizer and the ultra-low voltage stabilizer. The control module 2 transmits an ultrasonic control signal to the ultrasonic transmitting module through the singlechip, so that the transmitting frequency of the ultrasonic transmitting module is controlled; the ultrasonic wave emitting module 3 boosts the ultrasonic control signal into 49KHz and 200-300V high-voltage alternating current through a high-frequency transformer, and the 49KHz and 200-300V high-voltage alternating current excites the piezoelectric ceramic 7 to generate ultrasonic waves. The ultrasonic wave receiving module 4 converts the ultrasonic feedback signal generated by the piezoelectric ceramic 7 due to the reception of the ultrasonic wave into a distance analog signal through a dual operational amplifier and a triode Q1 and transmits the distance analog signal to the control module 1. The temperature compensation module 5 detects the ambient temperature through a temperature sensor and transmits the ambient temperature to the control module 1. The control module 2 calculates the liquid level through the singlechip and transmits the liquid level to the output module 6 in the form of PWM signals. The output module 6 converts the PWM signal transmitted by the singlechip into a 4-20mA current signal through a third amplifier and outputs the signal.
As shown in fig. 2, the power module 1 includes a first regulator U1, a second regulator U2, a switching regulator U3, an ultra low voltage regulator U4, a first regulator tube Z1, a second regulator tube Z2, a third regulator tube Z3, and a fourth regulator tube Z4. The first regulator U1 and the second regulator U2 are both LM 317. The switching regulator U3 is model MAX1836EUT 5. The ultra-low voltage regulator U4 is in the model of LP2980IM 5X-5.0. The first zener tube Z1 is model 1N 4739A. The second zener tube Z2 is model 1N 4742A. The third and fourth stabilivolt tubes Z3 and Z4 are each ZMM5V 6. Pin 2 of the first voltage regulator U1 is connected to the external +24V voltage. A pin 1 of the first voltage stabilizer U1 is connected with a pin 3 of a first voltage stabilizer Z1, a negative electrode of a second voltage stabilizer Z2, a positive electrode of an electrolytic capacitor CD1, a non-polar capacitor C2, a resistor R1 and a switching regulator U3. The other end of the resistor R1 is connected with pin 3 of the first voltage stabilizer U1. The anode of the first voltage regulator tube Z1 is connected with the nonpolar capacitor C1, one end of the resistor R2 and the 5 th pin of the switching regulator U3. The anode of the second voltage regulator tube Z2, the cathode of the electrolytic capacitor CD1, the nonpolar capacitor C1, the resistor R2, the other end of the nonpolar capacitor C2 and the pin 2 of the switching regulator U3 are all grounded. The 1 pin of the switching regulator U3 is connected to one end of a resistor R3 and a resistor R4. The other end of the resistor R4 is connected to ground. The 4 th pin of the switching regulator U3 is connected to one end of the inductor CL1 and the negative terminal of the diode D1. The other end of the inductor CL1 is connected with the other end of the resistor R3, the electrolytic capacitor CD2, the anode of the electrolytic capacitor CD3, the cathode of the third voltage-regulator tube Z3 and the fourth voltage-regulator tube Z4, and one end of the nonpolar capacitor C3. And a pin 6 of the switching regulator U3 is connected with the anode of the diode D1, the cathode of the electrolytic capacitor CD2, the cathode of the electrolytic capacitor CD3, the anode of the third voltage-regulator tube Z3 and the fourth voltage-regulator tube Z4, and the other end of the nonpolar capacitor C3, and is grounded.
The second voltage stabilizer U2 has 2 pins connected to external +24V voltage, 5 pins suspended, and 1 pin connected to the cathode of diode D2, the anode of electrolytic capacitor CD4, one end of resistor R5 and one end of resistor R6. The anode of the diode D2 and the cathode of the electrolytic capacitor CD4 are both grounded. The 3 pin of the first voltage stabilizer U1 is connected with the other end of the resistor R5. The other end of the resistor R6 is connected with pin 1 of the ultra-low voltage regulator U4 and the anode of the electrolytic capacitor CD 5. The 4 pins of the ultra-low voltage stabilizer U4 are connected with the anode of the electrolytic capacitor CD 6. The negative electrodes of the electrolytic capacitor CD5 and the electrolytic capacitor CD6 and the 2 pins of the ultra-low voltage stabilizer U4 are all grounded. The end of the inductor CL1 away from the switching regulator U3 is the first power supply output terminal VCC of the power supply module. The end of the resistor R5 away from the second regulator U2 is a second power supply output terminal VCC6 of the power supply module. The 4 pins of the ultra low voltage regulator U4 of the ultra low voltage regulator U4 are the third power supply output terminal VCC5 of the power module, and the 3 pins are the control input terminal VCC5_ CON of the power module.
As shown in fig. 3, the control module 2 includes a single chip U5, a first logic chip U6, and a crystal oscillator Y1. The model of the singlechip U5 is ATMEGA 1284P. The first logic chip U6 is model MC74HC04 ADG. The crystal oscillator Y1 adopts a passive crystal oscillator with the frequency of 6 MHz. The 4-pin of the singlechip U5 is connected with one end of a resistor R7 and a non-polar capacitor C4. The other end of the resistor R7 is connected to a first power supply output terminal VCC of the power module. The other end of the non-polar capacitor C4 is grounded. The 5 pin of the singlechip U5 is connected with the first power supply output end VCC of the power module, the 6 pin is grounded, the 7 pin is connected with one end of the nonpolar capacitor C5 and one end of the crystal oscillator Y1, and the 8 pin is connected with one end of the nonpolar capacitor C6 and the other end of the crystal oscillator Y1. The other ends of the non-polar capacitor C5 and the non-polar capacitor C6 are both grounded. The 12 pin of the singlechip U5 is connected with one end of a resistor R9 and the 1 pin of the first logic chip U6, and the 14 pin is connected with one end of a resistor R10 and the 5 pin of the first logic chip U6. The other ends of the resistor R9 and the resistor R10 are both grounded. The pin 6 of the first logic chip U6 is connected to the control input terminal VCC5_ CON of the power module, the pin 7 is connected to ground, and the pin 14 is connected to one terminal of the non-polar capacitor C9 and the first power supply output terminal VCC of the power module. The other end of the non-polar capacitor C9 is grounded. Pins 17 and 38 of the single chip are connected with a first power supply output terminal VCC of the power module, pins 18, 28 and 39 are grounded, pin 27 is connected with one end of a resistor R8 and a non-polar capacitor C8, and pin 29 is connected with one end of a non-polar capacitor C7. The other end of the resistor R8 is connected to a first power supply output terminal VCC of the power module. The other ends of the non-polar capacitor C7 and the non-polar capacitor C8 are both grounded. The 31 pin of the single chip microcomputer is a temperature signal input end Temp of the control module, the 30 pin is an ultrasonic signal input end Sig _ Out of the control module, and the 16 pin is an ultrasonic emission control end MCUSSP of the control module. The 2 pin of the first logic chip U6 is a liquid level signal output end mAPWM of the control module. The other pins of the singlechip U5 and the first logic chip U6 are all suspended.
As shown in fig. 4, the ultrasonic transmission module 3 includes a second logic chip U7, a field effect transistor Q2, and a high-frequency transformer CL 2. The model of the second logic chip U7 is MC74HC04 ADG. The model of the field effect transistor Q2 is 2N 7002. The 14 th pin of the second logic chip U7 is connected with a resistor R11, a non-polar capacitor C10, one end of the non-polar capacitor C11 and the cathode of a diode D5. The other end of the resistor R11 is connected with the 1 pin of the second logic chip U7 and the ultrasonic emission control end MCUSSP of the control module. The other ends of the non-polar capacitor C10 and the non-polar capacitor C11 are both grounded. The anode of the diode D5 is connected to the cathode of the diode D4. The anode of the diode D4 is connected to the cathode of the diode D3. The anode of the diode D3 is connected to the third power output terminal VCC5 of the power module. The second logic chip U7 has pin 7 connected to ground and pin 2 connected to one end of a resistor R12. The other end of the resistor R12 is connected with one end of the resistor R13 and the grid of the field effect transistor Q2. The drain of the field effect transistor Q2 and the other end of the resistor R13 are both grounded. The source of the field effect transistor Q2 is connected to one terminal of the primary coil in the high-frequency transformer CL 2. The other connection terminal of the primary coil in the high-frequency transformer CL2 is connected with the anode of the electrolytic capacitor CD7, one end of the resistor R14 and the second power supply output terminal VCC6 of the power module. The negative electrode of the electrolytic capacitor CD7 and the other end of the resistor R14 are both grounded. One connection terminal of the secondary coil in the high-frequency transformer CL2 is connected to the anode of the diode D6 and the cathode of the diode D7. The cathode of the diode D6 is connected to the anode of the diode D7, the non-polar capacitor C12, one end of the resistor R15 and the signal terminal TRANS of the piezoelectric ceramic 7. The other terminal of the secondary coil in the high-frequency transformer CL2 is connected to the other terminal of the nonpolar capacitor C12 and the resistor R15 and to ground. The ground terminal of the piezoelectric ceramic 7 is grounded. The remaining pins of the second logic chip U7 are all floating.
As shown in fig. 5, the ultrasonic wave receiving module 4 includes a dual operational amplifier and a transistor Q1. The model of the dual operational amplifier is OPA2335 AIDR. The transistor Q1 adopts a 9013 chip. The dual operational amplifier includes a first amplifier U8A and a second amplifier U8B. The base of the transistor Q1 is connected to one end of the resistor R17 and the resistor R18. The other end of the resistor R17 is connected with one end of the nonpolar capacitor C14. The other end of the nonpolar capacitor C14 is connected to the cathode of the diode D9, the anode of the diode D8 and one end of the resistor R16. The other end of the resistor R16 is connected with one end of the nonpolar capacitor C13. The other end of the non-polar capacitor C13 is connected to the signal terminal TRANS of the piezoelectric ceramic 7. The cathode of the diode D8 and the anode of the diode D9 are both grounded. The emitter of the transistor Q1 is connected to one end of the resistor R20. The other end of the resistor R20 is connected to ground. The collector of the transistor Q1 is connected to the resistor R19, one end of the non-polar capacitor C16 and the end of the resistor R18 away from the base of the transistor Q1. The other end of the resistor R19 is connected to one end of the non-polar capacitor C15 and the third power output terminal VCC5 of the power module. The other end of the non-polar capacitor C15 is grounded. The other end of the non-polar capacitor C16 is connected with one end of a resistor R21. The other end of the resistor R21 is connected to one end of the resistor R22, the non-polar capacitor C17 and the non-polar capacitor C18. The other end of the resistor R22 is connected to ground. The other end of the non-polar capacitor C18 is connected to one end of the resistor R23 and the inverting input terminal of the second amplifier U8B. The other ends of the non-polar capacitor C17 and the resistor R23 are connected to the non-polar capacitor C20, one end of the non-polar capacitor C21 and the output end of the second amplifier U8B. The other end of the non-polar capacitor C20 is grounded. The other end of the non-polar capacitor C21 is connected with one end of a resistor R26. The other end of the resistor R26 is connected with one end of the nonpolar capacitor C22, the resistor R27 and one end of the nonpolar capacitor C23. The other end of the resistor R27 is connected to ground. The other end of the non-polar capacitor C22 is connected to one end of the resistor R28 and the inverting input terminal of the first amplifier U8A. The other end of the non-polar capacitor C23 is connected with the other end of the resistor R28, the non-polar capacitor C24, one end of the non-polar capacitor C25 and the output end of the first amplifier U8A. The other end of the non-polar capacitor C24 is grounded. The other end of the nonpolar capacitor C25 is connected to the anodes of the diode D10 and the diode D11. The cathode of diode D10 is connected to ground. The cathode of the diode D11 is connected to one end of the resistor R30, the nonpolar capacitor C27 and the resistor R31. The other ends of the resistor R30 and the non-polar capacitor C27 are both grounded. The other end of the resistor R31 is connected with the ultrasonic signal input end Sig _ Out of the control module. The reverse supply terminal of the first amplifier U8A is connected to ground. The non-inverting input terminal of the second amplifier U8B is connected to one terminal of the non-polar capacitor C19, the resistor R24, the resistor R25, and the non-inverting input terminal of the first amplifier U8A. The other ends of the non-polar capacitor C19 and the resistor R25 are grounded. The other end of the resistor R24 is connected with the positive electrode of the electrolytic capacitor CD8, the non-polar capacitor C26, one end of the resistor R29 and the positive power supply end of the first amplifier U8A. The negative electrode of the electrolytic capacitor CD8 and the other end of the nonpolar capacitor C26 are both grounded. The other end of the resistor R29 is connected to a third power output terminal VCC5 of the power module.
As shown in fig. 6, the temperature compensation module 5 includes a temperature sensor U8. The temperature sensor U8 is model DS18B 20. The VDD pin of the temperature sensor is connected with one end of a resistor R32, a non-polar capacitor C28 and a first power supply output end VCC of the power module, the DQ pin is connected with the other end of the resistor R32 and one end of a resistor R33, and the GND pin is grounded. The other end of the non-polar capacitor C28 is grounded. The other end of the resistor R33 is connected with one end of the resistor R34 and one end of the nonpolar capacitor C29. The other end of the resistor R34 is connected with one end of the nonpolar capacitor C30 and the temperature signal input end Temp of the control module. The other ends of the non-polar capacitor C29 and the non-polar capacitor C30 are both grounded.
As shown in fig. 7, the output module 6 includes a third amplifier U9. The third amplifier U9 has a model OP07 CDR. The forward power supply of the third amplifier U9 is connected to one end of the non-polar capacitor C31 and the first power supply output terminal VCC of the power supply module. The other end of the non-polar capacitor C31 is grounded. The reverse supply terminals of the third amplifiers U9 are all connected to ground. The non-inverting input terminal of the third amplifier U9 is connected to one terminal of a resistor R38. The other end of the resistor R38 is connected with one end of the resistor R39. The other end of the resistor R39 is connected with one end of the resistor R40 and one end of the nonpolar capacitor C32. The other end of the resistor R40 is connected with one end of the resistor R41 and one end of the nonpolar capacitor C33. The other end of the resistor R41 is connected with one end of the resistor R42 and one end of the nonpolar capacitor C34. The other ends of the non-polar capacitor C32, the non-polar capacitor C33 and the non-polar capacitor C34 are all grounded. The other end of the resistor R42 is connected with a liquid level signal output end mAPWM of the control module. The inverting input terminal of the third amplifier U9 is connected to one end of the resistor R35, the resistor R36 and the resistor R37. The other end of the resistor R36 is connected with the output end of the third amplifier U9. The other end of the resistor R35 is connected with the external +24V voltage. The other end of the resistor R37 is connected to ground.
The liquid level detection method of the ultrasonic liquid level meter comprises the following specific steps:
step one, the power supply module is electrified, and the single chip microcomputer in the control module continuously transmits an interval power supply control signal to the power supply module. The interval power supply control signal is a PWM wave with the period of 1 second and the duty ratio of 30%. After the power supply module receives the interval power supply control signal, the second power supply output terminal VCC6 and the third power supply output terminal VCC5 of the power supply module all output interval power supply voltage, so that the ultrasonic wave emitting module is intermittently powered. And e, sequentially executing the steps from two to five, namely 1,2,3 and … …. The power consumption of the ultrasonic transmitting module can be reduced through the intermittent power supply mode of the ultrasonic transmitting module.
And step two, after the interval power supply control signal of the singlechip in the control module is changed into high-level 0.1s, the singlechip in the control module transmits an ultrasonic control signal to the ultrasonic transmitting module. The ultrasonic control signal has a frequency equal to f and a time length equal to aiF 49 KHz. If si-1< 0.5m, then ai3; if si-1Is not less than 0.5m, then ai＝10。si-1The distance between the last detected piezoelectric ceramic 7 and the liquid level; during the first detection, s is taken00.5 m. Meanwhile, the singlechip in the control module records the time t at the moment1,i。
The high-frequency transformer CL2 in the ultrasonic transmitting module boosts the ultrasonic transmitting signal into high-voltage alternating current with 49KHz frequency and 200-300V voltage effective value and then sends the alternating current to the piezoelectric ceramic 7. The piezoelectric ceramics 7 emit ultrasonic waves to the liquid surface. The ultrasonic emission signal is a signal obtained by superposing the interval power supply voltage and the ultrasonic control signal.
And step three, the piezoelectric ceramic 7 converts the ultrasonic waves reflected back by the liquid level into ultrasonic feedback signals and transmits the ultrasonic feedback signals to the ultrasonic receiving module 4.
And step four, filtering the part with the frequency of 49KHz in the ultrasonic feedback signals by the ultrasonic receiving module 4, filtering and rectifying the part, and transmitting the part as a distance analog signal to a singlechip in the control module.
And step five, drawing the distance analog signals into a voltage curve in a coordinate system taking time as an abscissa and a voltage value as an ordinate by a singlechip in the control module. The maximum value of the ordinate of the voltage curve (the maximum voltage value from the analog signal) is Umax. The ordinate on the voltage curve is 2/3. UmaxThe point with the smallest abscissa among the points of (a) is a distance signal feature point. Recording the time t corresponding to the characteristic point of the distance signal2,i。
Step six, the temperature compensation module 5 detects the current temperature Ti. Calculating the current liquid level hi＝l-(t2,i-t1,i)vTi. Wherein l is the distance between the piezoelectric ceramic 7 and the bottom of the liquid to be detected (if the piezoelectric ceramic 7 is placed above the liquid level of the reservoir, l is the distance between the piezoelectric ceramic 7 and the bottom of the reservoir); v. ofTiFor ultrasonic waves at temperature TiVelocity of, expression vTi＝v0+0.6Ti，v0The sound velocity at 0 ℃ in air is 331 m/s.
The singlechip in the control module outputs h to the output moduleiCorresponding PWM signal. Output module outputs single chip microcomputerThe PWM signal is converted into a current signal of 4-20mA to be output.

Claims (7)

1. An ultrasonic liquid level detection method adopts a liquid level meter which comprises a power supply module, a control module, an ultrasonic transmitting module, an ultrasonic receiving module, a temperature compensation module and piezoelectric ceramics; the method is characterized in that: the power supply module supplies power to the control module, the ultrasonic transmitting module, the ultrasonic receiving module, the temperature compensation module and the output module through the first voltage stabilizer, the second voltage stabilizer, the switching voltage stabilizer and the ultra-low voltage stabilizer; the temperature compensation module detects the ambient temperature through a temperature sensor and transmits the ambient temperature to the control module; the control module sends an ultrasonic control signal to the ultrasonic transmitting module through the singlechip; the ultrasonic transmitting module boosts the ultrasonic control signal through a high-frequency transformer and transmits the boosted ultrasonic control signal to the piezoelectric ceramic;
the ultrasonic receiving module comprises a dual operational amplifier and a triode; the dual operational amplifier comprises a first amplifier and a second amplifier; the base of the triode is connected with one end of a resistor R17 and a resistor R18; the other end of the resistor R17 is connected with one end of the nonpolar capacitor C14; the other end of the nonpolar capacitor C14 is connected with the cathode of the diode D9, the anode of the diode D8 and one end of the resistor R16; the other end of the resistor R16 is connected with one end of the nonpolar capacitor C13; the other end of the nonpolar capacitor C13 is connected with the signal end of the piezoelectric ceramic; the cathode of the diode D8 and the anode of the diode D9 are both grounded; the emitter of the triode is connected with one end of a resistor R20; the other end of the resistor R20 is grounded; the collector of the triode is connected with the resistor R19, one end of the nonpolar capacitor C16 and the end of the resistor R18 far away from the base electrode of the triode; the other end of the resistor R19 is connected with one end of the nonpolar capacitor C15 and the third power supply output end of the power supply module; the other end of the non-polar capacitor C15 is grounded; the other end of the nonpolar capacitor C16 is connected with one end of a resistor R21; the other end of the resistor R21 is connected with one end of a resistor R22, a nonpolar capacitor C17 and a nonpolar capacitor C18; the other end of the resistor R22 is grounded; the other end of the nonpolar capacitor C18 is connected with one end of the resistor R23 and the inverting input end of the second amplifier; the other ends of the nonpolar capacitor C17 and the resistor R23 are connected with one end of the nonpolar capacitor C20, one end of the nonpolar capacitor C21 and the output end of the second amplifier; the other end of the non-polar capacitor C20 is grounded; the other end of the nonpolar capacitor C21 is connected with one end of a resistor R26; the other end of the resistor R26 is connected with one end of the nonpolar capacitor C22, the resistor R27 and one end of the nonpolar capacitor C23; the other end of the resistor R27 is grounded; the other end of the nonpolar capacitor C22 is connected with one end of the resistor R28 and the inverting input end of the first amplifier; the other end of the nonpolar capacitor C23 is connected with the other end of the resistor R28, one end of the nonpolar capacitor C24, one end of the nonpolar capacitor C25 and the output end of the first amplifier; the other end of the non-polar capacitor C24 is grounded; the other end of the nonpolar capacitor C25 is connected with the anodes of the diode D10 and the diode D11; the cathode of the diode D10 is grounded; the cathode of the diode D11 is connected with one end of the resistor R30, the nonpolar capacitor C27 and the resistor R31; the other ends of the resistor R30 and the nonpolar capacitor C27 are grounded; the other end of the resistor R31 is connected with the ultrasonic signal input end of the control module; the reverse power supply end of the first amplifier is grounded; the positive phase input end of the second amplifier is connected with one end of the nonpolar capacitor C19, the resistor R24 and the resistor R25 and the positive phase input end of the first amplifier; the other ends of the nonpolar capacitor C19 and the resistor R25 are grounded; the other end of the resistor R24 is connected with the positive electrode of the electrolytic capacitor CD8, one end of the nonpolar capacitor C26, one end of the resistor R29 and the positive power supply end of the first amplifier; the negative electrode of the electrolytic capacitor CD8 and the other end of the nonpolar capacitor C26 are both grounded; the other end of the resistor R29 is connected with a third power supply output end of the power module;
the ultrasonic liquid level detection method comprises the following specific steps:
step one, a power supply module is electrified, and a single chip microcomputer in a control module continuously transmits an interval power supply control signal to the power supply module; the interval power supply control signal is a PWM wave with the period of 1 second and the duty ratio of 30 percent; after the power supply module receives the interval power supply control signal, a third power supply output end of the power supply module outputs the interval power supply control signal; repeating the second to the fifth steps;
step two, after the interval power supply control signal in the control module is changed from low level to high level for 0.1s, transmitting an ultrasonic control signal to the ultrasonic transmitting module; the ultrasonic control signal has a frequency equal to f and a time length equal to aiF is 49 KHz; if si-1< 0.5m, then ai3; if si-1Is not less than 0.5m, then ai＝10；si-1The distance between the last detected piezoelectric ceramic and the liquid level; get s00.5 m; meanwhile, the singlechip in the control module records the time t when the ultrasonic control signal starts to be transmitted1,i；
A high-frequency transformer in the ultrasonic transmitting module boosts the ultrasonic transmitting signal and then sends the boosted ultrasonic transmitting signal to the piezoelectric ceramic; the piezoelectric ceramics transmit ultrasonic waves to the liquid level; the ultrasonic emission signal is a signal obtained by superposing the interval power supply control signal and the ultrasonic control signal;
step three, the piezoelectric ceramic converts the ultrasonic waves reflected back by the liquid level into ultrasonic feedback signals and transmits the ultrasonic feedback signals to the ultrasonic receiving module;
filtering out the part with the frequency f in the ultrasonic feedback signal by the ultrasonic receiving module, filtering and rectifying the part with the frequency f, and transmitting the part as a distance analog signal to the control module;
step five, the control module draws the distance analog signal into a voltage curve in a coordinate system taking time as an abscissa and a voltage value as an ordinate; the maximum value of the ordinate of the voltage curve is Umax(ii) a The ordinate on the voltage curve is 2/3. UmaxThe point with the smallest abscissa among the points of (a) is a distance signal characteristic point; recording the time t corresponding to the characteristic point of the distance signal2,i；
Step six, the temperature compensation module detects the current temperature Ti(ii) a The control module calculates the current liquid level hi＝l-(t2,i-t1,i)vTi(ii) a Wherein l is the distance between the piezoelectric ceramic and the bottom of the liquid to be measured; v. ofTi＝v0+0.6Ti，v0＝331m/s。
2. An ultrasonic liquid level detection method according to claim 1, wherein: the model of the double operational amplifier is OPA2335 AIDR.
3. An ultrasonic liquid level detection method according to claim 1, wherein: the ultrasonic transmitting module comprises a second logic chip, a field effect tube and a high-frequency transformer; the model of the second logic chip is MC74HC04 ADG; the 14-pin of the second logic chip is connected with a resistor R11, a non-polar capacitor C10, one end of the non-polar capacitor C11 and the cathode of a diode D5; the other end of the resistor R11 is connected with a1 pin of the second logic chip and an ultrasonic emission control end MCUSSP of the control module; the other ends of the nonpolar capacitor C10 and the nonpolar capacitor C11 are grounded; the anode of the diode D5 is connected with the cathode of the diode D4; the anode of the diode D4 is connected with the cathode of the diode D3; the anode of the diode D3 is connected with the third power supply output end of the power module; the 7 pin of the second logic chip is grounded, and the 2 pin is connected with one end of a resistor R12; the other end of the resistor R12 is connected with one end of the resistor R13 and the grid of the field effect transistor; the drain electrode of the field effect transistor and the other end of the resistor R13 are grounded; the source electrode of the field effect transistor is connected with one wiring terminal of a primary coil in the high-frequency transformer; the other wire of the primary coil in the high-frequency transformer is connected with the anode of the electrolytic capacitor CD7, one end of the resistor R14 and the second power supply output end of the power supply module; the negative electrode of the electrolytic capacitor CD7 and the other end of the resistor R14 are both grounded; one wire of a secondary coil in the high-frequency transformer is connected with the anode of the diode D6 and the cathode of the diode D7; the cathode of the diode D6 is connected with the anode of the diode D7, one end of the nonpolar capacitor C12, one end of the resistor R15 and the signal end of the piezoelectric ceramic; the other terminal of the secondary coil in the high-frequency transformer is connected with the other terminals of the nonpolar capacitor C12 and the resistor R15 and is grounded; the ground wire end of the piezoelectric ceramic is grounded.
4. An ultrasonic liquid level detection method according to claim 1, wherein: the power supply module comprises a first voltage stabilizer, a second voltage stabilizer, a switching voltage stabilizer, an ultra-low voltage stabilizer, a first voltage-stabilizing tube, a second voltage-stabilizing tube, a third voltage-stabilizing tube and a fourth voltage-stabilizing tube; the first voltage stabilizer and the second voltage stabilizer are both LM 317; the switching regulator is of a type MAX1836EUT 5; the model of the ultra-low voltage stabilizer is LP2980IM 5X-5.0; the 2 pin of the first voltage stabilizer is connected with external +24V voltage; a pin 1 of the first voltage stabilizer is connected with a first voltage stabilizer tube, a negative electrode of the second voltage stabilizer tube, a positive electrode of an electrolytic capacitor CD1, a non-polar capacitor C2, one end of a resistor R1 and a pin 3 of the switching voltage stabilizer; the other end of the resistor R1 is connected with the 3 pin of the first voltage stabilizer; the anode of the first voltage-regulator tube is connected with the nonpolar capacitor C1, one end of the resistor R2 and the 5 pins of the switching regulator; the anode of the second voltage regulator tube, the cathode of the electrolytic capacitor CD1, the nonpolar capacitor C1, the resistor R2, the other end of the nonpolar capacitor C2 and the 2 pin of the switching regulator are all grounded; a1 pin of the switching regulator is connected with one ends of a resistor R3 and a resistor R4; the other end of the resistor R4 is grounded; the 4-pin of the switching regulator is connected with one end of an inductor CL1 and the negative electrode of a diode D1; the other end of the inductor CL1 is connected with the other end of the resistor R3, the electrolytic capacitor CD2, the anode of the electrolytic capacitor CD3, the cathode of the third voltage-regulator tube and the cathode of the fourth voltage-regulator tube and one end of the nonpolar capacitor C3; 6 pins of the switching regulator are connected with the anode of the diode D1, the cathode of the electrolytic capacitor CD2, the cathode of the electrolytic capacitor CD3, the anode of the third voltage-regulator tube and the fourth voltage-regulator tube and the other end of the nonpolar capacitor C3 and are grounded;
the 2 pin of the second voltage stabilizer is connected with external +24V voltage, and the 1 pin is connected with the cathode of a diode D2, the anode of an electrolytic capacitor CD4, a resistor R5 and one end of a resistor R6; the anode of the diode D2 and the cathode of the electrolytic capacitor CD4 are both grounded; the 3-pin of the first voltage stabilizer is connected with the other end of the resistor R5; the other end of the resistor R6 is connected with a1 pin of the ultra-low voltage stabilizer and the anode of the electrolytic capacitor CD 5; the 4 pins of the ultra-low voltage stabilizer are connected with the anode of an electrolytic capacitor CD 6; the negative electrodes of the electrolytic capacitor CD5 and the electrolytic capacitor CD6 and the 2 pins of the ultra-low voltage stabilizer are grounded; the end of the inductor CL1 far away from the switching regulator is a first power supply output end of the power supply module; the end of the resistor R5 far away from the second voltage stabilizer is the second power supply output end of the power supply module; and 4 pins of an ultra-low voltage stabilizer of the ultra-low voltage stabilizer are third power supply output ends of the power module, and 3 pins are control input ends of the power module.
5. An ultrasonic liquid level detection method according to claim 1, wherein: the control module comprises a singlechip, a first logic chip and a crystal oscillator; the type of the singlechip is ATMEGA 1284P; the model of the first logic chip is MC74HC04 ADG; the 4 pins of the singlechip are connected with a resistor R7 and one end of a non-polar capacitor C4; the other end of the resistor R7 is connected with a first power supply output end of the power supply module; the other end of the non-polar capacitor C4 is grounded; a 5 pin of the singlechip is connected with a first power supply output end of the power module, a 6 pin of the singlechip is grounded, a 7 pin of the singlechip is connected with one end of a non-polar capacitor C5 and one end of the crystal oscillator, and an 8 pin of the singlechip is connected with one end of a non-polar capacitor C6 and the other end of the crystal oscillator; the other ends of the nonpolar capacitor C5 and the nonpolar capacitor C6 are grounded; the 12 pin of the singlechip is connected with one end of a resistor R9 and a1 pin of the first logic chip, and the 14 pin is connected with one end of a resistor R10 and a 5 pin of the first logic chip; the other ends of the resistor R9 and the resistor R10 are grounded; the 6 pin of the first logic chip is connected with the control input end of the power module, the 7 pin is grounded, and the 14 pin is connected with one end of the nonpolar capacitor C9 and the first power supply output end of the power module; the other end of the non-polar capacitor C9 is grounded; pins 17 and 38 of the singlechip are connected with a first power supply output end of the power module, pins 18, 28 and 39 are grounded, pin 27 is connected with one end of a resistor R8 and a non-polar capacitor C8, and pin 29 is connected with one end of a non-polar capacitor C7; the other end of the resistor R8 is connected with a first power supply output end of the power supply module; the other ends of the nonpolar capacitor C7 and the nonpolar capacitor C8 are grounded; a 31 pin of the singlechip is a temperature signal input end of the control module, a 30 pin is an ultrasonic signal input end of the control module, and a 16 pin is an ultrasonic emission control end MCUSSP of the control module; and the 2 pins of the first logic chip are liquid level signal output ends of the control module.
6. An ultrasonic liquid level detection method according to claim 1, wherein: the temperature compensation module comprises a temperature sensor; the model of the temperature sensor is DS18B 20; a VDD pin of the temperature sensor is connected with one end of a resistor R32, a non-polar capacitor C28 and a first power supply output end of the power module, a DQ pin is connected with the other end of the resistor R32 and one end of a resistor R33, and the GND pin is grounded; the other end of the non-polar capacitor C28 is grounded; the other end of the resistor R33 is connected with one end of a resistor R34 and a non-polar capacitor C29; the other end of the resistor R34 is connected with one end of the nonpolar capacitor C30 and the temperature signal input end of the control module; the other ends of the non-polar capacitor C29 and the non-polar capacitor C30 are both grounded.
7. An ultrasonic liquid level detection method according to claim 1, wherein: the device also comprises an output module; the output module comprises a third amplifier; the model of the third amplifier is OP07 CDR; the positive power supply end of the third amplifier is connected with one end of the nonpolar capacitor C31 and the first power supply output end of the power supply module; the other end of the non-polar capacitor C31 is grounded; the reverse power supply ends of the third amplifiers are all grounded; the non-inverting input end of the third amplifier is connected with one end of a resistor R38; the other end of the resistor R38 is connected with one end of the resistor R39; the other end of the resistor R39 is connected with one end of a resistor R40 and a non-polar capacitor C32; the other end of the resistor R40 is connected with one end of a resistor R41 and a non-polar capacitor C33; the other end of the resistor R41 is connected with one end of a resistor R42 and a non-polar capacitor C34; the other ends of the nonpolar capacitor C32, the nonpolar capacitor C33 and the nonpolar capacitor C34 are all grounded; the other end of the resistor R42 is connected with the liquid level signal output end of the control module; the inverting input end of the third amplifier is connected with one end of the resistor R35, the resistor R36 and the resistor R37; the other end of the resistor R36 is connected with the output end of the third amplifier; the other end of the resistor R35 is connected with the external +24V voltage; the other end of the resistor R37 is connected to ground.
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