CN115235582A

CN115235582A - Method for measuring small blind area and large measuring range ultrasonic liquid level

Info

Publication number: CN115235582A
Application number: CN202210771652.XA
Authority: CN
Inventors: 施华健; 陈春盛; 郑金荣; 鲍小华; 沈睿汀
Original assignee: Fuzhou Probest Intelligent Technology Co ltd
Current assignee: Fuzhou Probest Intelligent Technology Co ltd
Priority date: 2022-06-30
Filing date: 2022-06-30
Publication date: 2022-10-25

Abstract

The invention relates to a method for measuring a small blind area and a large measuring range of ultrasonic liquid level. The measuring method comprises the following specific steps: the CPU converts the signals received by the ultrasonic transducer into sound wave signals for processing and amplifying; the signal is processed and output to the CPU; the CPU judges whether the signal receives a correct normal echo or not; if normal echo is received, calculating the distance; and restarting the next measurement; if no normal echo is received, entering a multi-pulse mode, judging whether a normal echo is received again, and if no normal echo is received, increasing a gain coefficient; judging whether the maximum gain coefficient is exceeded or not; if the maximum gain coefficient is exceeded, intelligently adjusting the number of pulses; judging whether the maximum pulse number is exceeded; if the pulse number exceeds the maximum pulse number, re-measuring; and if the maximum pulse number is not exceeded, the initial signal value of the variable gain amplifying circuit returns to enter the multi-pulse mode to start running. The invention enlarges the measuring range of the ultrasonic liquid level and reduces the blind area on the basis of not reducing the measuring range of the ultrasonic liquid level.

Description

Method for measuring small blind area and large measuring range ultrasonic liquid level

Technical Field

The invention relates to a method for measuring the height of a non-gaseous material, in particular to a method for measuring the ultrasonic liquid level in a small blind area and a large measuring range.

Background

The ultrasonic liquid level meter and the ultrasonic liquid level difference meter in the market at present have obvious defects, and are mainly reflected on the blind area distance and the measuring range. The dead zone of the product with large measuring range is correspondingly increased, the unification of the small dead zone and the large measuring range cannot be realized, and the practical application of liquid level measurement is influenced. In addition, in a severe environment such as a closed container, the installation and adjustment process in a narrow space can cause great troubles.

Disclosure of Invention

The invention aims to: provides a method for measuring the ultrasonic liquid level with small blind area and large measuring range.

The invention is realized by the following technical scheme: a method for measuring the ultrasonic liquid level in a small blind area and a large measuring range is implemented based on the following measuring systems:

the measuring system comprises a CPU, a driving circuit, a variable gain amplifying circuit, a band-pass filter circuit, a rectifying circuit and an ultrasonic transducer;

the CPU is connected with the driving circuit to control the driving circuit to output an excitation signal;

the driving circuit is connected with the ultrasonic transducer and used for converting the excitation signal into an acoustic signal through the ultrasonic transducer and transmitting and receiving the acoustic signal;

the CPU is connected with the variable gain amplifying circuit to control the gain coefficient;

the ultrasonic transducer is also connected with the CPU through the variable gain amplifying circuit, the band-pass filtering circuit and the rectifying circuit in sequence, so that the CPU processes and calculates the received sound wave signals to obtain a liquid level distance;

the measuring method comprises the following specific steps:

s1: the CPU sends a single pulse to the driving circuit, the ultrasonic transducer converts a sound wave signal, then sends and receives the sound wave signal, converts the received sound wave signal into an electric signal, and simultaneously controls the variable gain amplifying circuit to output minimum gain to amplify the converted electric signal;

s2: the amplified electric signal in the S1 is processed by a band-pass filter circuit, converted by a rectifying circuit and output to a CPU;

s3: the CPU processes the signal processed by the S2 and judges whether a correct normal echo is received;

s4: if normal echo is received, calculating the distance; re-entering the step 1 to start the next measurement;

s5: if no normal echo is received, entering a multi-pulse mode, and intelligently adjusting the number of pulses;

s6: the CPU sends a plurality of pulses to the driving circuit, converts sound wave signals into ultrasonic signals through the ultrasonic transducer, sends and receives the sound wave signals into electric signals, and controls the variable gain amplifying circuit to output minimum gain to amplify the received electric signals; then repeating S2, S3 and S4, and judging whether a correct normal echo is received; if normal echo is received, calculating the distance; re-entering the step 1 to start the next measurement;

s7: if S6 normal echo is not received, the CPU controls to increase the gain coefficient of the variable gain amplifying circuit;

s8: judging whether the maximum gain coefficient is exceeded or not;

s9: if the maximum gain coefficient is exceeded, intelligently adjusting the number of pulses;

s10: it is determined whether the maximum number of pulses is exceeded.

S11: if the pulse number exceeds the maximum pulse number, the step 1 is re-entered to start the next measurement;

s12: if the maximum pulse number is not exceeded, the variable gain amplifier circuit starts the operation by returning to S6.

Compared with the prior art, the invention has the beneficial effects that:

1. the gain amplification coefficient of the variable gain amplification circuit can be controlled to be minimum, and the blind area is reduced on the basis of not reducing the liquid level range of the ultrasonic wave; the ultrasonic liquid level measuring device has the advantages that the plurality of pulse control driving circuits are used for outputting signals to the ultrasonic transducer to transmit high-energy ultrasonic signals, the number of pulses is reduced when the ultrasonic liquid level is measured in a short distance, the number of pulses is increased when the ultrasonic liquid level is measured in a long distance, the gain amplification coefficient of the variable gain amplification circuit is intelligently controlled, stable wave sending and receiving of ultrasonic waves at each time are guaranteed, and the precision and the stability of ultrasonic liquid level measurement are improved. And the ultrasonic liquid level measurement with wide range ratio is realized.

2. The ultrasonic liquid level measuring process is that the transducer emits high-frequency ultrasonic pulses, and the sound waves are reflected by the surface of a measured medium, and then are partially reflected and received by the same transducer, and are converted into electric signals. The ultrasonic pulse propagates at the speed of sound wave, and the distance between the transducer and the surface of the measured medium can be calculated through the time difference between the emission and the reception. Because the non-contact measuring method is adopted, the medium to be measured is not limited, and the method can be widely used for measuring the height of various liquid and solid materials.

3. When ultrasonic waves propagate in the air, the attenuation is very large, the ultrasonic echo obtained in a wide-range measurement is very weak, in order to enable a receiving circuit of the ultrasonic waves to obtain a reliable ultrasonic echo, an ultrasonic transducer needs to obtain a high-energy excitation signal, and in order to perform good processing, amplification processing needs to be performed. Therefore, it is necessary to control the output signal of the driving circuit by a plurality of pulses, and it is necessary to control the gain amplification factor of the variable gain amplifier circuit to be maximum. The invention realizes the measurement of a large range by a multi-pulse large-gain amplification factor.

4. In order to expand the measurement range of the ultrasonic liquid level, the blind area is reduced on the basis of not reducing the range of the ultrasonic liquid level, when the measurement distance is close, the energy of an echo is large, a single pulse is required to be adopted to control a driving circuit to output a signal, and the gain amplification factor of a variable gain amplification circuit is required to be controlled to be minimum. The invention realizes the measurement of the small blind area by the single pulse small gain amplification factor.

Drawings

FIG. 1 is a flow chart of a measurement method of the present invention;

FIG. 2 is a diagram of the connection relationship of the basic circuit of the measurement method of the present invention;

FIG. 3 is a circuit diagram of the CPU of the present invention;

FIG. 4 is a circuit diagram of the driving circuit of the present invention;

FIG. 5 is a circuit diagram of a variable gain amplifier circuit according to the present invention;

FIG. 6 is a circuit diagram of a bandpass filter circuit according to the present invention;

FIG. 7 is a circuit diagram of a rectifier circuit according to the present invention.

FIG. 8 is a schematic diagram of determining normal echo according to the present invention

Detailed Description

The invention is described in detail below with reference to the following description of the drawings:

a method for measuring the ultrasonic liquid level in a small blind area and a large measuring range is implemented based on the following measuring systems:

as shown in fig. 2: the measuring system comprises a CPU, a driving circuit, a variable gain amplifying circuit, a band-pass filter circuit, a rectifying circuit and an ultrasonic transducer;

the ultrasonic transducer is also connected with the CPU through a variable gain amplifying circuit, a band-pass filter circuit and a rectifying circuit in sequence, so that the CPU processes and calculates the received sound wave signal to obtain a liquid level distance;

the measuring method comprises the following specific steps as shown in figure 1:

step 1, as shown, the CPU sends a single pulse to the PWM of the driving circuit of fig. 4 through the pin PD12 of fig. 3, converts an acoustic signal by the ultrasonic transducer, sends and receives an acoustic signal, and converts the received acoustic signal into an electrical signal, and controls the DAC initial signal value of the variable gain amplifying circuit of fig. 5 through the pin PA4 of fig. 3 to amplify the received electrical signal TRANS with minimum gain.

Here, the CPU sends a single pulse to the driving circuit, the driving circuit generates an excitation signal of 1000 +/-50 Vpp to drive the ultrasonic transducer, and the ultrasonic transducer generates an acoustic wave signal to be propagated outwards; the sound wave signal is reflected by an obstacle and is transmitted back to the ultrasonic transducer to generate an electric signal; the electric signal converted by the ultrasonic transducer passes through the variable gain amplifying circuit, and the CPU outputs a voltage signal to control the variable gain amplifying circuit to amplify the received electric signal with the minimum gain.

Step 2, the signal single1 in fig. 5 is processed by the band-pass filter circuit in fig. 6 and then output to the single2 in fig. 6, and is output to the AD _ OUT of the CPU after passing through the rectifier circuit in fig. 7.

In step 2, the electrical signal amplified in step 1 is processed by a band-pass filter circuit to remove interference signals except effective frequencies so as to have strong anti-interference capability, and then the electrical signal (sine wave signal) is converted into a direct current pulse signal by a rectifier circuit and is output to a CPU for detection.

And 3, processing and judging whether a correct normal echo is received or not after the AD _ OUT of the CPU in the figure 3 receives the signal.

And 4, receiving normal echo and calculating the distance. Re-enter step 1 to start the next measurement.

And 5, entering a multi-pulse mode when no normal echo is received, and intelligently adjusting the number of pulses.

And 6, sending n pulses to PWM of the driving circuit in the figure 4 through a PD12 pin in the figure 3, converting an acoustic signal through an ultrasonic transducer, sending and receiving the acoustic signal and converting the acoustic signal into an electric signal, and controlling a DAC of the variable gain amplifying circuit in the figure 5 through a PA4 pin in the figure 3 to amplify the received signal TRANS by minimum gain. And repeating the

steps

2, 3 and 4 to judge whether the normal waveform is received. Where n is not greater than the maximum number of pulses.

And 7, increasing the DAC signal value if no normal echo is received.

And 8, judging whether the gain coefficient exceeds the maximum gain coefficient. The maximum gain coefficient is determined by: the gain of the variable gain amplifying circuit is increased along with the increase of the output voltage of the DAC, and the available gain control voltage is 0.1-2.9V; when the DAC output voltage reaches 2.9V, no valid signal has been received, and the gain is not increased further.

And 9, intelligently adjusting the number of pulses when the gain coefficient exceeds the maximum gain coefficient, wherein the method for intelligently adjusting the number of pulses is to add 1 on the basis of the number of pulses first.

And step 10, judging whether the maximum pulse number is exceeded. Here, the maximum number of pulses is preset to 12.

And 11, if the pulse number exceeds the maximum pulse number, re-entering the step 1 to start the next measurement.

And step 12, if the maximum pulse number is not exceeded, the DAC starts to operate according to the initial signal value and returns to the step 6.

The comparison of the measuring method of the invention with the traditional ultrasonic liquid level meter is as follows:

table 1 shows the measurement parameters of a conventional ultrasonic level gauge:

traditional ultrasonic liquid level meter	Blind area	Maximum measured distance
			5 m measuring range	0.42 m	5.15 m
Measuring range of 10 meters	0.50 m	10.21 m
			Measuring range of 20 m	0.79 m	20.03 m

Table 2 shows the measurement parameters of the ultrasonic level gauge using the technique of the present invention:

ultrasonic liquid level meter using the technology of the invention	Blind area	Maximum measured distance
			5 m measuring range	0.23 m	6.37 m
Measuring range of 10 meters	0.32 m	11.52 m
			Measuring range of 20 m	0.55 m	21.14 m

The test conditions were distance measurements against a smooth wall surface. Under the same condition, the ultrasonic liquid level meter using the technology has smaller dead zone and larger measurable distance.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments or portions thereof without departing from the spirit and scope of the invention.

Claims

1. A method for measuring the liquid level of ultrasonic waves with small blind areas and large measuring range is characterized in that: it is implemented based on the following measurement system:

the measuring method comprises the following specific steps:

s1: the CPU sends a single pulse to the driving circuit, the ultrasonic transducer converts the sound wave signal, then sends and receives the sound wave signal, converts the received sound wave signal into an electric signal, and controls the variable gain amplifying circuit to output the minimum gain to amplify the converted electric signal;

s8: judging whether the maximum gain coefficient is exceeded or not;

s10: judging whether the maximum pulse number is exceeded or not;

s12: if the maximum pulse number is not exceeded, the initial signal value of the variable gain amplifying circuit returns to S6 to start operation.

2. The method for measuring the ultrasonic liquid level with small blind area and large measuring range according to claim 1, wherein the method comprises the following steps: the specific operation mode of S1 is as follows: the CPU sends a single pulse to the driving circuit, the driving circuit generates an excitation signal of 1000 +/-50 Vpp to drive the ultrasonic transducer, and the ultrasonic transducer generates a sound wave signal to be transmitted outwards; the sound wave signal is reflected by an obstacle and is transmitted back to the ultrasonic transducer to generate an electric signal; the electric signal converted by the ultrasonic transducer passes through the variable gain amplifying circuit, and the CPU outputs a voltage signal to control the variable gain amplifying circuit to amplify the received electric signal with the minimum gain.

3. The method for measuring the ultrasonic liquid level with small blind area and large measuring range according to claim 1, wherein the method comprises the following steps: in S2, the electric signal amplified in S1 is processed by a band-pass filter circuit to remove interference signals except effective frequency so as to have strong anti-interference capability, and then is converted into a direct current pulse signal by a rectifier circuit and is output to a CPU for detection.

4. The method for measuring the ultrasonic liquid level with small blind area and large measuring range according to claim 1, wherein the method comprises the following steps: in S3, the CPU compares the direct current pulse signal processed in S2 with a signal threshold, and the direct current pulse signal is considered to be a normal echo when the amplitude of the direct current pulse signal is larger than the corresponding signal threshold.

5. The method for measuring the ultrasonic liquid level with small blind area and large measuring range according to claim 1, wherein the method comprises the following steps: in S6, the number of transmitted pulses does not exceed the maximum number of pulses.

6. The method for measuring the ultrasonic liquid level with small blind area and large measuring range according to claim 1, wherein the method comprises the following steps: in S8, the criterion for determining the maximum gain coefficient is: the gain of the variable gain amplifying circuit is increased along with the increase of the output voltage of the DAC, and the available gain control voltage is 0.1-2.9V; when the DAC output voltage reaches 2.9V, no valid signal has been received, and the gain is no longer increased.

7. The method for measuring the liquid level of the ultrasonic waves with small blind area and large measuring range according to claim 1, wherein the method comprises the following steps: in S9, the method for intelligently adjusting the number of pulses is to add 1 to the number of pulses first.

8. The method for measuring the ultrasonic liquid level with small blind area and large measuring range according to claim 1, wherein the method comprises the following steps: in S10, the maximum number of pulses is preset to 12.