JP2019086339A - Ultrasonic flowmeter - Google Patents

Abstract

To provide an ultrasonic flowmeter capable of measuring a correct propagation time.SOLUTION: An ultrasonic flowmeter 1 of the invention comprises: a pair of ultrasonic sensors S1,S2; an orthogonal detection processing unit 30 which takes in a receiving wave received by the ultrasonic sensor S1 and outputs each of a real number, an imaginary number, and a reference periodic pulse for obtaining an envelope wave according to the receiving wave; a peak value and arrival time detection processing unit 40 which determines a measuring point of the envelope wave; and a propagation time measurement processing unit 50 which computes a receiving wave propagation time according to the receiving wave on the basis of the measuring point of the envelope wave and the reference periodic pulse. The propagation time measurement processing unit 50 determines the propagation time taken from transmission completion of a burst wave to reception of the receiving wave on the basis of the reference periodic pulse according to the measuring point of the envelope wave determined by a zero-cross detection unit 45 and a reference clock signal corresponding to a start point of the burst wave.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an ultrasonic flowmeter which measures the flow velocity of a fluid flowing in a pipe, and in particular, calculates an instantaneous flow rate of the fluid based on the difference in propagation time of ultrasonic waves passed through the fluid.

  As disclosed in Patent Document 1, a conventional ultrasonic flowmeter is attached to a pipe through which a fluid flows, and a pair of ultrasonic sensors capable of transmitting and receiving ultrasonic waves of a predetermined cycle, and received waves received by the ultrasonic sensors An oscillator that emits a reference clock signal as a reference for measuring the propagation time of the signal and a different-phase clock signal shifted in phase by 90 degrees with respect to the reference clock signal, and a received wave received by the ultrasonic sensor The first multiplier and low-pass filter that output the real number by multiplying one of the received waves branched and output to the left and the reference clock signal, and the other phase are multiplied by the different phase clock signal to output an imaginary number , And an envelope wave of the received wave based on the real number and the imaginary number output from the first and second multipliers and the low pass filter. Calculated comprising a evaluation unit for evaluating the propagation time according to the received wave.

  The evaluation unit is configured to obtain the envelope wave based on an amplitude obtained from the sum of the square of the real number and the square of the imaginary number and the reference clock signal, and the evaluation unit is based on the centroid position of the envelope wave. The propagation time relating to the received wave can be evaluated.

  In the conventional ultrasonic flow meter configured as described above, the first propagation time of the first received wave transmitted from one ultrasonic sensor and received by the other ultrasonic sensor, and the other ultrasonic sensor Calculate the difference from the second propagation time of the second received wave emitted from one of the ultrasonic waves received by one of the ultrasonic sensors, and measure and process the flow velocity and instantaneous flow rate of the fluid based on the difference in the propagation time There is. That is, the conventional ultrasonic flowmeter is characterized in that the propagation time can be calculated based on the position of the center of gravity of the envelope wave independent of the amplitude of the reception wave or the envelope wave.

Patent No. 4904289

  However, the conventional ultrasonic flow meter collects data (corresponding to the amplitude of the received wave and the reference clock signal) until all the received waves reach the ultrasonic sensor after determining the center of gravity of the envelope wave to be obtained. We continue to calculate this huge number of collected data. Therefore, the conventional ultrasonic flowmeter has a problem that the load for the arithmetic processing is large.

  An ultrasonic flowmeter according to the present invention comprises a pair of ultrasonic sensors for transmitting burst waves of a predetermined cycle and receiving a reception wave changed from the burst wave, and a reference time for determining the propagation time of the reception wave A reference clock transmission unit for external output, a quadrature detection processing unit for taking in the received wave and the reference time, and outputting a real number, an imaginary number and a reference periodic pulse for obtaining an envelope wave corresponding to the received wave, and the quadrature detection A peak value connected to the processing unit and the reference clock transmission unit, which calculates the peak value of the envelope wave each time based on the real number and the imaginary number, and determines the measurement point of the envelope wave from the reference periodic pulse corresponding to the peak value. An arrival time detection processing unit, the peak value / measurement point of the envelope wave obtained by the arrival time detection processing unit, and the reception based on the reference periodic pulse And a propagation time measurement processing unit for calculating the propagation time of the reception wave corresponding to the peak value / arrival time detection processing unit, the memory unit storing the real number, imaginary number, and reference periodic pulse; And a peak value computing unit that computes the peak value of the envelope wave each time based on an imaginary number, and a plurality of the peak values calculated by the peak value computing unit based on the maximum peak value corresponding to one received wave. A threshold operation unit to be determined, a threshold overrun determination unit for generating a preliminary trigger signal by comparing the peak value calculated separately based on the real number, imaginary number and reference cycle pulse stored in the memory unit with the threshold, and the threshold overrun determination unit The preset trigger signal is taken in, and a real number, an imaginary number, and a reference periodic pulse corresponding to the recalculation peak value when the threshold value is exceeded are taken from the memory unit, and are set in advance. And a zero-crossing detection unit that determines and outputs measurement points of the propagation time of the envelope wave based on the input real number, imaginary number, and reference period pulse input from the memory unit, and the reference period pulse ahead of the pulse. The propagation time measurement processing unit may generate a reference periodic pulse corresponding to the measurement point of the envelope wave determined by the zero cross detection unit and a reference time generated from the reference clock transmission unit corresponding to the start point of the burst wave. The propagation time required from the transmission of the burst wave to the reception of the reception wave is determined based on Note that the peak value / arrival time detection processing unit is a gain processing unit that corrects the envelope wave to be obtained next based on the maximum peak value of the envelope wave calculated by the peak value operation unit to be the same as the peak value. The peak value detection unit is configured to calculate the peak value of the envelope wave by multiplying the sum of the square of the real number and the square of the imaginary number by a preset proportional coefficient, and the gain processing unit Preferably, the reception wave immediately before being input to the orthogonal detection processing unit is corrected so as to have the same maximum wave height value as the reception wave of the previous time.

  As described above, in the ultrasonic flowmeter according to the present invention, after determining the measurement point to be the measurement reference of the propagation time of the envelope wave, the peak value and the phase position of the envelope wave are stored in the memory unit. Since calculation can be performed based on data, there is an advantage that the propagation time of the envelope wave can be accurately measured. Also, as described above, the ultrasonic flow meter according to the present invention calculates the propagation time after calculating the data after reaching the threshold without calculating all of the wave height values of the envelope wave, so that the ultrasonic flow meter is compared to the prior art. There is also an advantage that the number of operations can be reduced and the load on the operations can be reduced.

  Further, in the ultrasonic flowmeter according to the present invention, the peak value calculator calculating the amplitude of the envelope wave each time by multiplying the sum of the square of the real number and the square of the imaginary number by a predetermined proportional coefficient Since the gain processing unit stores the gain for adjusting the maximum amplitude of the envelope wave to be measured next time based on the maximum peak value to be equal, the propagation time is adjusted after the levels of received waves are made the same. There is also an advantage that it can measure accurately.

BRIEF DESCRIPTION OF THE DRAWINGS It is a general view of the ultrasonic flowmeter based on this invention, (a) shows the state in which the burst wave emitted from one ultrasonic sensor is propagated along the flow direction of a fluid, (b) is the other. The state which the burst wave emitted from the ultrasonic sensor is propagated against the flow direction of the fluid is shown. It is a block diagram of an ultrasonic flowmeter concerning the present invention. It is a block diagram of a quadrature detection processing part concerning the present invention. It is a block diagram of a peak value and arrival time detection processing unit according to the present invention.

  The ultrasonic flowmeter 1 according to the present invention transmits a burst wave of a predetermined cycle and receives a reception wave changed from the burst wave as shown in FIGS. 1 (a), 1 (b) and 2). It comprises a pair of ultrasonic sensors S1 and S2, and an ultrasonic processing unit 10 that generates a signal for generating the burst wave and collects the received wave to measure the propagation time of the received wave.

  The ultrasonic sensors S1 and S2 are attached to the outer periphery of a pipe 90 for flowing a fluid, and are attached at positions away from each other in the length direction of the pipe 90, respectively. The ultrasonic sensors S1 and S2 are both configured to transmit the burst wave or receive the reception wave, and receive a command from the ultrasonic processing unit 10 to transmit the burst wave and receive the reception wave. It is configured to be able to switch.

  The ultrasonic processing unit 10 constantly transmits a signal corresponding to a universal time, and the burst to the ultrasonic sensor S1 (S2) based on the signal emitted from the reference clock transmitting unit 20. And a transmission / reception path switching control unit 22 which is connected to the burst wave generator 21 and switches transmission / reception of the ultrasonic sensors S1 and S2, and passes through the transmission / reception path switching control unit 22. The received wave passing unit 23 for passing the received wave, the gain processing unit 25 for taking in the received wave passed through the received wave passing unit 23, and outputting an analog signal based on a preset amplification factor, and the gain process An A / D converter 26 for converting the analog signal output from the unit 25 into a digital signal; Calculation of the peak value of an envelope wave connected to the quadrature detection processing unit 30 connected to the reference clock transmission unit 20, the quadrature detection processing unit 30 and the reference clock transmission unit 20 and corresponding to the reception wave, and the envelope wave And a propagation time measurement processing unit 50 connected to the peak value / arrival time detection processing unit 40 to measure the propagation time of the received wave.

  The reference clock transmission unit 20 is configured to transmit a reference clock signal for operating each unit connected thereto, and the reference clock signal is linked to obtain the propagation time of the reception wave. It is a pulse signal which is emitted continuously, which is sequentially switched to ON and OFF at the shortest time interval which is a basis of generation of a reference periodic pulse described later.

  The burst wave generator 21 outputs a pulse signal of a predetermined cycle obtained by dividing the reference clock signal emitted from the reference clock transmission unit 20 by an integer N, and this pulse signal of the predetermined cycle is the ultrasonic sensor S1. Or send to any of S2.

  The transmission / reception path switching unit 22 is a circuit for switching between transmission and reception of the ultrasonic sensors S1 and S2, and when one ultrasonic sensor S1 can receive, the other ultrasonic sensor S2 can transmit. The paths connected to these two ultrasonic sensors S1 and S2 are configured to be switched.

  The quadrature detection processing unit 30 is configured to output a real number, an imaginary number, and a reference periodic pulse for taking in the received wave and the reference clock signal and obtaining an envelope wave corresponding to the received wave, as shown in FIG. It is done. Further, the quadrature detection processing unit 30 outputs a reference phase signal set to have the same phase as the burst wave and a phase to output a different phase signal set to have a phase different by 90 degrees with respect to the reference phase signal. A signal generator 31, a real number calculation unit 32a that outputs the signal corresponding to the reception wave in parallel and adds the reference phase signal to the parallel output signal to calculate a real number 33a, and the remaining parallel output signal An imaginary number calculation unit 32b for calculating the imaginary number 33b by adding the different phase signal to the reference period pulse output unit 32c for outputting either the reference phase signal or the different phase signal as the reference period pulse 33c for the burst wave; It prepares.

  The phase signal generator 31 converts the reference clock signal of the reference clock transmission unit 20 into a reference phase signal and outputs the same, and the reference clock signal differs by 90 degrees from the phase of the reference phase signal. And an out-of-phase signal generator 31b for converting the out-of-phase signal and outputting the same.

  The real number calculation unit 32a is connected to the reference phase signal generator 31a and the A / D converter 26, and is a real number that is the result of calculation based on the digital signal output from the A / D converter 26 and the reference phase signal. It is configured to output 33a.

  The imaginary number calculation unit 32b is connected to the different phase signal generator 31b and the A / D converter 26, and outputs an imaginary number 33b that is the result of calculation based on the digital signal and the different phase signal output from the A / D converter 26. It is configured to

  The reference periodic pulse output unit 32c is connected to the phase signal generator 31, and acquires either one signal of the real number calculation unit 32a or the imaginary number calculation unit 32b and is synchronized with the acquired reference phase signal or different phase signal. A signal is output as the reference periodic pulse 33c. That is, the reference cycle pulse is a signal obtained by dividing the reference clock signal by an integer N as in the case of the burst wave generator 21 described above.

  The peak value / arrival time detection processing unit 40 is connected to the orthogonal detection processing unit 30 and the reference clock transmission unit 20 as shown in FIG. 4 and the peak value of the envelope wave is detected each time based on the real number 33a and the imaginary number 33b. It is configured to calculate and determine the measurement point of the envelope wave from the reference periodic pulse 33c corresponding to the peak value.

  Further, the peak value / arrival time detection processing unit 40 sequentially stores each information output from the real number calculation unit 32a, the imaginary number calculation unit 32b, and the reference cycle pulse output unit 32c, the real number 33a and the above A peak value calculator 42 for calculating the peak value of the envelope wave each time based on the imaginary number 33b, and the maximum peak value corresponding to one received wave is fetched from the plurality of peak values obtained by the peak value calculator 42 The threshold calculation unit 43 calculates a threshold based on the maximum peak value, and the amplitude of the envelope wave is recalculated each time from the information stored in the memory unit 41, and the threshold calculated by the threshold calculation unit 43 is compared and spared. A threshold transcend judgment unit 44 capable of outputting a trigger signal, and a preliminary trigger signal issued from the threshold transcend judgment unit 44 is taken in, and a measurement point of the propagation time of the envelope wave is set. Comprising a zero crossing detector 45 constant.

  The memory unit 41 stores the numerical values of the real number 33a, the imaginary number 33b and the reference periodic pulse 33c in the same address number from the transmission completion time of the burst wave, and repeats this each time the reference clock signal is turned on or off. Also, the memory unit 41 can store the real number, the imaginary number, and the reference periodic pulse of the next burst wave, and is preset to a capacity that can store not only the first received wave but also each information of the second received wave. It consists of

  The peak value calculator 42 performs arithmetic processing of the peak value of the envelope wave by multiplying the sum of the square of the real number and the square of the imaginary number by a preset proportional coefficient, and the peak value of the envelope wave calculated here The maximum peak value is output to the gain processing unit 25 and the threshold calculation unit 43, respectively.

  The threshold calculator 43 divides the maximum crest value output from the crest value calculator 42 by a preset peak value setting value, and calculates a threshold value obtained by multiplying the divided value by the preset threshold setting value. It is configured as described above, and the obtained threshold is input to the above-mentioned threshold transceeding determination unit 44.

  The threshold transcend judging unit 44 compares the threshold obtained in real time with the real and imaginary numbers stored in the memory unit 41 and compares the peak value of the envelope wave calculated separately and calculated It is configured to emit a preliminary trigger signal when the peak value exceeds the threshold. The preliminary trigger signal is input to the zero cross detection unit 45.

  The zero-cross detection unit 45 receives information on the preliminary trigger signal, and the real number that triggered the generation of the preliminary trigger signal and the information number stored in the memory unit 41 from the address number corresponding to the imaginary number (real number , Imaginary number, reference periodic pulse) in order of address number. In addition, the zero-cross detection unit 45 sets the number of ON (1) / OFF (0) rising of the reference periodic pulse (hereinafter referred to as the number of rising) taken in the above-mentioned order based on the preset count. It counts in order. Further, the zero cross detection unit 45 outputs the address number at the time when the rising number reaches the preset count number, and the real number and the imaginary number corresponding to the address number to the propagation time measurement processing unit 50.

  The gain processing unit 25 stores a gain storage unit 25 a that temporarily stores the maximum crest value of the envelope wave output from the crest value and arrival time detection processing unit 40 as a gain value, and stores the gain storage unit 25 a. The gain value is read out, the amplification factor is registered, and a gain amplifier 25b is provided to adjust the amplitude of the reception wave that has passed through the reception wave passage unit 23 based on the amplification factor. The analog signal adjusted by passing through the gain amplifier 25 b is converted to a digital signal by the A / D converter 26 and is input to the quadrature detection processing unit 30. The gain processing unit 25 configured as described above makes it possible to perform correction processing so that the reception wave immediately before being input to the orthogonal detection processing unit 30 has the same maximum wave height value as that of the previous reception wave.

  The propagation time measurement processing unit 50 is configured to calculate the propagation time taking into consideration the phase delay of the received wave with respect to the burst wave based on the imaginary number 33b and the real number 33a output from the zero cross detection unit 45. There is.

  Specifically, the propagation time is divided into a time from completion of transmission of the burst wave to immediately before reaching the measurement point of the envelope wave and a time from immediately before reaching the measurement point to the time of reaching the measurement point. These two times are added and determined.

  The former time is the number of times of rising of the reference periodic pulse immediately before reaching the measurement point of the envelope wave from the transmission completion time of the burst wave and the time required from ON to the next ON of the reference clock signal (hereinafter referred to as It is calculated based on the unit time of the reference clock signal, and it is a rough propagation time. On the other hand, the latter time is obtained, for example, by multiplying the integer N by the unit time of the reference clock signal, dividing this value by 2π, and further dividing this value by atan 2 (imaginary number, real number). , Has a fine propagation time. The sum of the rough propagation time and the fine propagation time obtained respectively is calculated as a propagation time taking into consideration the phase delay that is finally calculated by the propagation time measurement processing unit 50. Therefore, based on the transmission completion of the burst wave propagated into the pipe 90 as shown in FIG. 1 (a) or FIG. 1 (b), the other ultrasonic sensor S2 (S1) It is possible to detect the arrival of the received wave and to determine the propagation time of ultrasonic waves in one direction.

  The ultrasonic flowmeter 1 configured as described above measures the flow velocity of a fluid (not shown) flowing in the pipe 90. First, as shown in FIG. 1 (a), the ultrasonic wave sensor S1 transmits the burst wave to reflect the inside of the pipe 90 and convert it into a reception wave, thereby receiving the first signal by the ultrasonic wave sensor S2, and the fluid The first propagation time propagated along the flow direction of Thereafter, the transmission / reception path switching control unit 22 operates to switch the ultrasonic sensors S1 and S2 that transmit burst waves. Thereby, as shown in FIG. 1 (b), the ultrasonic wave sensor S2 transmits the burst wave, reflects the inside of the pipe 90 and changes it to a reception wave, and the ultrasonic wave sensor S1 receives the second signal, The second propagation time propagated in the direction opposite to the fluid flow direction is measured. Further, the difference between the first propagation time and the second propagation time is determined, and the instantaneous flow rate of the fluid is measured each time based on the obtained difference.

  The internal processing of the ultrasonic processing unit 10 will be described below with reference to FIG. 1 (b) and FIGS. 2 to 4. The reference clock transmission unit 20 transmits the reference clock signal to the burst wave generator 21, the quadrature detection processing unit 30, and the peak value / arrival time detection processing unit 40. In response to this, the burst wave generator 21 outputs the reference clock signal to the ultrasonic sensor S2 via the transmission / reception path switching control unit 22 for a predetermined period and the remaining period to the ultrasonic sensor S2. Mask to prevent output.

  Thus, for example, 10 cycles of the reference clock signal are input to the ultrasonic sensor S2, and the burst wave is attenuated via the fluid in the pipe 90. The attenuated received wave is eventually received by the other ultrasonic sensor S1, passes through the transmission / reception switching control unit 22 and the received wave passing unit 23 in order, and is input to the gain processing unit 25.

  The received wave input to the gain processing unit 25 is a so-called analog signal attenuated as described above, but passing through the gain processing unit 25 is amplified so that the amplitude of the analog signal becomes high. The amplified analog signal is input to the A / D converter 26 and output from the A / D converter 26 to be converted into a digital signal, and the digital signal is input to the quadrature detection processing unit 30. .

  The digital signal input to the quadrature detection processing unit 30 is input to the real number calculation unit 32a and the imaginary number calculation unit 32b.

  Similarly, when the reference clock signal input to the quadrature detection processing unit 30 is output from the phase signal generator 31, the reference phase signal and the different phase signal are converted into the reference phase signal which is a real number. The different phase signal is input to the imaginary number calculation unit 32b while being input to the calculation unit 32a.

  In addition, any one of the reference phase signal or the different phase signal output from the reference phase signal generator 31a passes through the reference periodic pulse output unit 32c and reaches the peak value and arrival as the reference periodic pulse 33c. It is input to the time detection processing unit 40.

  Further, the real number calculation unit 32a inputs the real number 33a to the peak value / arrival time detection processing unit 40 based on the digital signal and the reference phase signal. Similarly, the imaginary number calculation unit 32b inputs the imaginary number 33b to the peak value / arrival time detection processing unit 40 based on the digital signal and the different phase signal. As described above, the quadrature detection processing unit 30 continuously outputs the real number 33a and the imaginary number 33b corresponding to the received wave, and the reference periodic pulse 33c serving as the reference of the phase of the received wave.

  Next, the peak value and arrival time detection processing unit 40 sequentially stores, in the memory unit 41, the above-described real number 33a, imaginary number 33b, reference cycle pulse 33c, and reference clock signal input from the reference clock transmission unit 20. . In addition to the memory unit 41, the real number 33a and the imaginary number 33b are also input as needed to the peak value calculator.

  The peak value calculator 42 calculates the peak value of the envelope wave corresponding to the received wave using the real number 33a, the imaginary number 33b and the proportional coefficient set in advance inputted thereto. Here, the equation for obtaining the peak value is to multiply the sum of the square of the real number 33a and the square of the imaginary number 33b by the proportional coefficient. The peak value calculator 42 calculates the peak value of the envelope wave as needed and determines the maximum peak value of one envelope wave necessary to measure one propagation time and determines the maximum peak value as the threshold value. The signal is output to the calculation unit 43 and the gain processing unit 25 respectively.

  The threshold calculation unit 43 to which the maximum crest value is input divides the maximum crest value by the crest value setting value, and obtains a value (hereinafter, referred to as a threshold) obtained by multiplying the divided value by the threshold setting value. The threshold value is input to the threshold value exceeding determination unit 44.

  In response to this, the threshold value exceedance determination unit 44 calculates the amplitude of the envelope wave as needed based on the real number and the imaginary number stored at one end in the memory unit 41, and compares the calculated amplitude and the threshold value. If the amplitude exceeds a threshold, the count start signal is input to the zero cross detection unit 45.

  The zero cross detection unit 45 having received the count start signal reads out the real number and imaginary number at the time of exceeding the threshold value from the memory unit 41, and stores the address number of the real number and imaginary number sequentially to the next address number. Reads real, imaginary and reference periodic pulses. Furthermore, the zero cross detection unit 45 counts the number of rising edges of the reference periodic pulse, and the propagation time measuring process is performed on the real number and the imaginary number stored in the address number when the number of counts reaches the preset number. Output to unit 50.

  The propagation time measurement processing unit 50 calculates the sum of the time corresponding to the phase delay from the imaginary number 33b and the real number 33a, and the time from the completion of transmission of the burst wave to the time immediately before the measurement point of the envelope wave. After the ultrasonic sensor S2 completes transmitting the burst wave, the propagation time to the measurement point of the envelope wave from which the ultrasonic sensor S1 has received the reception wave is calculated. The propagation time required for propagation from the ultrasonic sensor S2 to the ultrasonic sensor S1 corresponds to the above-mentioned second propagation time.

  As described above, the ultrasonic flowmeter 1 according to the present invention determines the measurement point to be the measurement reference of the propagation time of the envelope wave, and then stores the peak value and the phase position of the envelope wave in the memory unit. Since the calculation can be performed based on the acquired data, there is an advantage that the propagation time of the envelope wave can be accurately measured. Further, as described above, the ultrasonic flowmeter 1 according to the present invention calculates the data after reaching the threshold value to calculate the propagation time without calculating all the wave height values of the envelope wave, and therefore the ultrasonic flowmeter 1 is compared to the conventional case. As a result, the number of operations can be reduced, and the load on the operations can be reduced. Moreover, the ultrasonic flowmeter 1 according to the present invention comprises the peak value calculator 42 and the peak value calculator which calculate the amplitude of the envelope wave each time by multiplying the sum of the square of the real number and the square of the imaginary number. Since the gain processing unit 25 stores and sets the gain for adjusting the maximum amplitude of the envelope wave to be measured next time to be equal based on the maximum crest value determined at 42, the level of the received wave having the same directivity is There is also an advantage that both first and second propagation times can be accurately measured after being aligned.

1 ... ultrasonic flow meter 10 ... ultrasonic processing unit 20 ... reference clock transmission unit 21 ... burst wave generator 22 ... transmission / reception path switching control unit 23 ... reception wave passing unit 25 ... gain processing unit 26 ... A / D converter 30 ... Quadrature detection processing unit 31 ... phase signal generator 31a ... reference phase signal generator 31b ... different phase signal generator 32a ... real number calculation unit 32b ... imaginary number calculation unit 32c ... reference periodic pulse output unit 33a ... real number 33b ... imaginary number 33c ... reference period Pulse 40 ... peak value / arrival time detection processing section 41 ... memory section 42 ... peak value computing section 43 ... threshold value computing section 44 ... threshold crossing section 45 ... zero cross detection section 50 ... propagation time measurement processing section 90 ... piping S1, S2 ... Ultrasonic sensor

Claims (2)

A pair of ultrasonic sensors for transmitting a burst wave of a predetermined cycle and receiving a reception wave changed from the burst wave;
A reference clock generation unit that externally outputs a reference time for determining the propagation time of the received wave;
A quadrature detection processing unit that takes in the received wave and the reference time, and outputs a real number, an imaginary number, and a reference periodic pulse for obtaining an envelope wave corresponding to the received wave;
The peak value of the envelope wave is calculated each time based on the real number and the imaginary number connected to the orthogonal detection processing unit and the reference clock transmission unit, and the measurement point of the envelope wave is determined from the reference periodic pulse corresponding to the peak value. Peak value and arrival time detection processing unit,
And a propagation time measurement processing unit for calculating the propagation time of the reception wave corresponding to the reception wave based on the measurement point of the envelope wave obtained by the peak value and arrival time detection processing unit and the reference periodic pulse. ,
The peak value / arrival time detection processing section includes a memory section for storing the real number, imaginary number, and reference periodic pulse, and a peak value operation section for calculating the peak value in the envelope wave each time based on the real number and imaginary number; A threshold operation unit for obtaining a threshold based on the maximum crest value corresponding to one received wave from the plurality of crest values calculated by the crest value operation unit; and a real number, an imaginary number, and a reference periodic pulse stored in the memory unit. A threshold transcend determination unit that generates a preliminary trigger signal by comparing the calculated peak value with the threshold, and incorporating a preliminary trigger signal issued from the threshold transcend determination unit, and the memory when the threshold is exceeded Take in a real number, an imaginary number, and a reference cycle pulse corresponding to the recalculation peak value, and input a reference cycle pulse, a real number, and an imaginary number ahead of the preset setting pulse from the memory unit. Real number, with the imaginary, and a zero-cross detector which determines and outputs a measurement point of the propagation time of the envelope wave based on the reference period pulse,
The propagation time measurement processing unit is based on a reference periodic pulse corresponding to the measurement point of the envelope wave determined by the zero cross detection unit and a reference time issued from the reference clock transmission unit corresponding to the start point of the burst wave. An ultrasonic flowmeter characterized by determining a propagation time required from transmission of the burst wave to reception of the reception wave. The peak value / arrival time detection processing unit is connected to a gain processing unit that corrects the envelope wave to be obtained next time based on the maximum peak value of the envelope wave calculated by the peak value operation unit to be the same as the peak value. It consists of
The peak value detection unit is configured by arithmetic processing of the peak value of the envelope wave by multiplying the sum of the square of the real number and the square of the imaginary number by a preset proportional coefficient.
The superimposing circuit according to claim 1, wherein the gain processing unit corrects the received wave immediately before being input to the orthogonal detection processing unit so as to have a maximum peak value equal to that of the previous received wave. Sonic flow meter.

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