NL2032091A

NL2032091A - Circuit and method for measuring ultrasonic wave propagation time

Info

Publication number: NL2032091A
Application number: NL2032091A
Authority: NL
Inventors: Wang Zhongzhou; Tian Peng; Pan Zhenyu; Han Hao
Original assignee: Mezolen Instrument Changzhou Company Ltd
Priority date: 2021-07-27
Filing date: 2022-06-07
Publication date: 2023-01-31
Also published as: NL2032091B1; CN113504389A

Abstract

The present invention discloses a circuit and method for measuring ultrasonic wave propagation. time. ZX high—speed, timer‘ module is used in cooperation with a filter circuit, a peak holding circuit, a threshold comparison circuit and a zero—crossing—point comparison circuit. Finally, echo signals of an ultrasonic wave are converted, into pulse signals of a zero crossing point. By counting a time interval of two pulse signals, interval time between two pulses is calculated to be propagation time of the ultrasonic wave. Influences of a sampling frequency of ADC and FIFO of a main controller on measurement are avoided; and accurate measurement of ultrasonic wave propagation time in upstream and downstream flows is realized.

Description

CIRCUIT AND METHOD FOR MEASURING ULTRASONIC WAVE PROPAGATION TIME

TECHNICAL FIELD

The present invention belongs to the field of ultrasonic sen- sors, in particular to a circuit and method for measuring ultra- sonic wave propagation time.

BACKGROUND ART

At present, there are two common ultrasonic flowmeter tech- nologies in the market: a time transmission method and a Doppler method. Although the time transmission method started late, it is widely used and has high accuracy. The time transmission method determines a flow rate of a pipeline fluid by measuring time of downstream and upstream flows of an ultrasonic pulse traveling back and forth between two transducers. The flow rate of the fluid in the pipeline is V=C° xAT/2xL, where C is the velocity of ultra- sonic motion from a transmitter to a receiver in a static liquid;

AT is a time difference between downstream and upstream probes in a flowing liquid; and L is the distance between the two probes.

Therefore, to accurately measure the fluid flow rate in the pipe- line, it is necessary to accurately measure time values Tdu and

Tud of the upstream and downstream probes. Existing methods of measuring time differences are generally a cross-correlation algo- rithm and a software analysis algorithm, both of which need to convert an echo voltage signal into a digital signal by ADC for measurement. As a result, the measurement progress depends on the sampling frequency of ADC, which is limited by the sampling fre- quency of ADC and the FIFO size of a main controller. Therefore, measurement time performance often cannot meet requirements of ac- curate measurement.

SUMMARY

In order to solve above problems existing in the prior art for measuring ultrasonic wave propagation time, the present inven- tion provides a circuit for measuring ultrasonic wave propagation time, which comprises an MCU unit, a driving module, a timer mod- ule, a bias circuit, a filter circuit, a VGA gain adjustment cir- cuit, a peak holding and discharging circuit, a threshold compari- son circuit and a zero-crossing-point comparison circuit, wherein the driving module is connected with the timer module; the bias circuit, the filter circuit, the VGA gain adjustment circuit, the peak holding and discharging circuit, the threshold comparison circuit, the zero-crossing-point comparison circuit and the timer module are connected in sequence; and the MCU unit is used for configuring the driving module and triggering the timer module.

Preferably, the driving module comprises an ultrasonic driv- ing circuit, which comprises a dual-channel gate driver and a mul- ti-channel signal switching circuit composed of a plurality of an- alog switches; and upstream and downstream ultrasonic sensors can be controlled to be in driving and receiving modes by controlling switching logics of the analog switches.

Preferably, the VGA gain adjustment circuit comprises a vari- able gain amplifier with a gain range of 80dB, which amplifies a weak signal into an echo signal with an amplitude of 500-100mV based on VCC OFFSET bias, and can dynamically adjust an amplitude of an output waveform through a GAIN pin.

Preferably, the peak holding and discharging circuit is con- nected with a diode through output of an operational amplifier, and charges two capacitors in one direction; and a peak voltage signal of an echo signal is located at an ADC PEAK network label.

Preferably, when an EN START pin is enabled, the timer module will record a count value between a START signal and a STOP sig- nal; and the START signal will be triggered when a driving pulse is sent. When a sound wave is transmitted to a downstream probe after passing through a pipeline medium, an echo signal passes through the bias circuit, the filter circuit and the VGA gain am- plification adjustment circuit. Then, after threshold comparison and zero-crossing-point comparison, a zero-point pulse signal is generated and output to a STOP pin of the timer module. The timer module records a count value between the START signal and the STOP signal, and finally calculates propagation time between the START and the STOP.

In addition, the present invention further provides a method for measuring ultrasonic wave propagation time, which comprises the following steps:

Sl; performing pulse driving of an ultrasonic sensor arranged upstream/downstream;

S2, adjusting an analog signal of an echo at a down- stream/upstream ultrasonic sensor into a pulse signal with mani- festation of time characteristics; and 33, using a timer module to calculate a count value of the pulse signal from starting of driving to the echo, and converting into time, a calculation formula of which is TIME=1/FsxCNT, where

Fs is a timing frequency of the timer module; and CNT is a count value of a timer between START and STOP signals.

Preferably, in the step S2, the step of adjusting the analog signal of the echo into the pulse signal with manifestation of time characteristics is realized by integrating piezoelectricity of the ultrasonic echo through bias, filtering, amplification, peak holding, threshold comparison and zero-crossing-point compar- ison.

Preferably, in step S2, the circuit for measuring ultrasonic wave propagation time is used to realize a processing flow of sig- nal returning.

According to the present invention, pulse driving is per- formed to the ultrasonic sensors of a ultrasonic flowmeter; the analog signal of the echo is adjusted into the pulse signal with manifestation of time characteristics by integrating piezoelec- tricity of the ultrasonic echo through bias, filtering, amplifica- tion, peak holding, the threshold comparison circuit and the zero- crossing-point comparison circuit; and the counter circuit is used to calculate the count value of the pulse signal from starting of driving to the echo, which is finally converted into time. In this way, a time difference manner of traditional software is replaced; and measured propagation time data is more accurate.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic diagram of an overall framework of a circuit according to the present invention.

Fig. 2 is a schematic diagram of an ultrasonic driving cir- cuit.

Fig. 3 is a schematic diagram of a bias circuit.

Fig. 4 is a schematic diagram of a VGA gain adjustment cir- cuit.

Fig. 5 is a schematic diagram of a peak holding and discharg- ing circuit.

Fig. 6 is a schematic diagram of a threshold comparison cir- cuit and a zero-crossing-point comparison circuit.

Fig. 7 is a schematic diagram of a timer circuit.

Fig. 8 is a waveform diagram of a driving wave.

Fig. 2 is a schematic diagram of echo signals.

Fig. 10 is a waveform diagram of peak sampling voltages.

Fig. 11 is a schematic diagram of STOP pulse signals.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiment 1

An embodiment of a circuit for measuring ultrasonic wave propagation time of the present invention comprises: an MCU unit, a driving module, a timer module, a bias circuit, a filter cir- cuit, a VGA gain adjustment circuit, a peak holding and discharg- ing circuit, a threshold comparison circuit and a zero-crossing- point comparison circuit, wherein the driving module is connected with the timer module; the bias circuit, the filter circuit, the

VGA gain adjustment circuit, the peak holding and discharging cir- cuit, the threshold comparison circuit, the zero-crossing-point comparison circuit and the timer module are connected in sequence; and the MCU unit is used for configuring the driving module and triggering the timer module.

Fig. 2 is a schematic diagram of an ultrasonic driving cir- cuit, which comprises a multi-channel signal switching circuit composed of Ull as a dual-channel gate driver and analog switches

U9, Ul0, Ul2 and U13. Upstream and downstream ultrasonic sensors can be controlled to be in driving and receiving modes by control- ling switching logics of the analog switches.

Fig. 3 a schematic diagram of a bias circuit. Ul1B, U3A, R6 and R9 constitute a bias circuit with a bias voltage of

VCC OFFSET; and UlA realizes a differential amplification circuit to realize preliminary amplification of an ultrasonic echo signal.

Fig. 4 a schematic diagram of a VGA gain adjustment circuit.

The circuit comprises a variable gain amplifier with a gain range 5 of 80dB, which amplifies a weak signal output in Fig. 3 into an echo signal with an amplitude of 500-100mV based on VCC OFFSET bi- as, and can dynamically adjust an amplitude of an output waveform through a GAIN pin of U2.

Fig. 5 is a schematic diagram of a peak holding and discharg- ing circuit. The peak holding and discharging circuit is connected with a diode D3 through output of an operational amplifier U7A, and charges two capacitors C22 and C23 in one direction; and a peak voltage signal of an echo signal is located at an ADC PEAK network label. When peak sampling in this direction is completed, the peak voltage can be discharged by a 10Q resistor of R59 through the analog switch of U8.

Fig. 6 is a schematic diagram of a threshold comparison cir- cuit and a zero-crossing-point comparison circuit. U6 is a compar- ator. An RCl echo signal is compared with a threshold comparison voltage generated by DAC of MCU. Because of use of lower THRESHOLD comparison, when the voltage value of RCl is lower than THRESHOLD,

AN output signal of OUT CLK is set to 1; and OUT CLK will enable a rising edge trigger of U5 with clearing and preset functions. At this time, EN CMP outputs a high level.

U4 is a single-supply comparator, which will be enabled by

EM CMP. Here, a zero point is a reference voltage of VCC OFFSET.

When RC1 is less than VCC OFFSET, the output Q of U4 will be at a high level; and then Q will output a zero-crossing-point pulse voltage under the lower threshold.

Fig. 7 shows a timer module. When an EN START pin is enabled, the timer Ul4 will record a count value between a START signal and a STOP signal; and the START signal will be triggered when a driv- ing pulse is sent. When a sound wave is transmitted to a down- stream probe after passing through a pipeline medium, an echo sig- nal passes through the bias circuit, the filter circuit and gain amplification. Then, after threshold comparison and zero-crossing- point comparison, a zero-point pulse signal is generated and out-

put to a STOP pin of the timer module. The timer module records a count value between the START signal and the STOP signal, and fi- nally calculates propagation time between the START and the STOP.

The ultrasonic pulse sending can be configured according to man-machine interactions of MCU; and the number of driving waves and driving frequency can be set according to a pipe diameter and field working conditions of the medium. Before sending of a driv- ing wave, the MCU will enable the START EN pin of the timer mod- ule. After a TTL signal is sent to the driving circuit, the driv- ing voltage will be adjusted to +15V; and the TTL signal will be connected with a START pin of the timer module to trigger the start signal. A waveform diagram of the driving wave is shown in

Fig. 8.

An ultrasonic signal of a probe A excited by the driving wave is received by a probe B after passing through the pipeline fluid medium. A voltage reference of the signal received by the probe B is VCC OFFSET after passing through the bias circuit. After fil- tering and gain amplification, the echo signal is shown in Channel 2 of Fig. 9.

To obtain a peak voltage of the echo signal, it is composed of a peak sampling and discharging circuit. A waveform of a peak sampling voltage is shown in Channel 1 in Fig. 10.

After the echo signal is compared with the threshold and af- ter zero-crossing-point comparison, a zero-crossing-point STOP pulse signal is output, as shown in Fig. 11.

Timing frequency of the timer module is FS; and the count value between the START signal and the STOP signal is CNT, so time between ultrasonic wave transmission and echo reception can be calculated by the following algorithm: TIME=1/FsxCNT.

Embodiment 2

An embodiment of a method for measuring ultrasonic wave prop- agation time of the present invention comprises the following steps: 81, performing pulse driving of an ultrasonic sensor arranged upstream;

S2, adjusting an analog signal of an echo at a downstream ul- trasonic sensor into a pulse signal with manifestation of time characteristics; and

S3, using a timer module to calculate a count value of the pulse signal from starting of driving to the echo, and converting into time, a calculation formula of which is TIME=1/FsxCNT, where

More specifically, in the step S2, the step of adjusting the analog signal of the echo into the pulse signal with manifestation of time characteristics is realized by integrating piezoelectrici- ty of the ultrasonic echo through bias, filtering, amplification, peak holding, threshold comparison and zero-crossing-point compar- ison.

More specifically, in step S2, the circuit for measuring ul- trasonic wave propagation time is used to realize a processing flow of signal returning.

According to the present invention, the high-speed timer mod- ule is used in cooperation with the filter circuit, the peak hold- ing circuit, the threshold comparison circuit and the zero- crossing-point comparison circuit. Finally, the echo signals of the ultrasonic wave are converted into the pulse signals of a zero crossing point. By counting a time interval of the two pulse sig- nals, interval time between two pulses is calculated to be propa- gation time of the ultrasonic wave.

Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that many changes, modifications, substitutions and variations can be made to these embodiments without departing from the prin- ciple and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

CONCLUSIONS

An ultrasonic wave propagation time measurement circuit, characterized in that it comprises an MCU unit, a control module, a timer module, a bias circuit, a filter circuit, a VGA gain adjustment circuit, a peak hold and discharge circuit, a threshold comparison circuit and a zero crossing comparison circuit, the control module being connected to the timer module; the bias circuit, the filter circuit, the VGA gain adjustment circuit, the peak hold and discharge circuit, the threshold comparator circuit, the zero crossing comparator circuit and the timer module are connected sequentially; and the MCU unit is used to configure the control module and activate the timer module.

An ultrasonic wave propagation time measurement circuit according to claim 1, characterized in that the control module comprises an ultrasonic control circuit; the ultrasonic driver circuit includes a two-channel gate driver and a multi-channel signal switching circuit composed of a plurality of analog switches; and upstream and downstream ultrasonic sensors can be controlled to be in control and receive mode by controlling the switching logic of the analog switches.

An ultrasonic wave propagation time measurement circuit according to claim 2, characterized in that the VGA gain adjustment circuit comprises a variable gain amplifier having a gain range of 80dB, which amplifies a weak signal into an echo signal having an amplitude from 500 to 100 mV based on VCC OFFSET bias, and can dynamically adjust an amplitude of an output waveform via a GAIN pin.

4. An ultrasonic wave propagation time measurement circuit according to claim 3, wherein said surge holding and discharging circuit is connected to a diode through the output of an operational amplifier, and two capacitors

tower charges in one direction; and a peak voltage signal of an echo signal is located on an ADC PEAK network tag.

An ultrasonic wave propagation time measurement circuit according to any one of claims 1 to 4, characterized in that when an AND START pin is activated, the timer module will register a count value between a START signal and a STOP signal. signal, and the START signal is activated when a control pulse is sent; when a sound wave is sent to a downstream probe after passing through a pipeline medium, an echo signal passes through the bias circuit, the filter circuit and the VGA gain adjustment circuit; then, after threshold comparison and zero crossing point comparison, a zero point pulse signal is generated and output to a STOP pin of the timer module; and the timer module registers a count value between the START signal and the STOP signal and finally calculates the propagation time between the START and the STOP.

A method of measuring the propagation time of ultrasonic waves, characterized in that it comprises the steps of: S1, performing pulse driving of an ultrasonic sensor arranged upstream/downstream; S2, adapting an analog signal of an echo at a downstream/upstream ultrasonic sensor into a pulse signal with time characteristics; and S3, calculating a count value of the pulse signal from the start of driving to the echo using a timer module, and converting it into a time, a calculation formula of which is TIME=1/FsxCNT, where Fs is a timing frequency of the timer module; and CNT is a count value of a timer between START and STOP signals.

A method of measuring the propagation time of ultrasonic waves according to claim 6, characterized in that in step S2, the step of adjusting the analog signal of the echo into the pulse signal with manifestation of time characteristics is realized by integrating piezo electricity from the ultra-

sone echo through bias, filtering, amplification, peak holding, threshold comparison and zero crossing comparison.

An ultrasonic wave propagation time measurement method according to claim 7, characterized in that in step S2, the ultrasonic wave propagation time measurement circuit according to claim 1 is used to realize a return signal processing flow .