JP2019028040A - Ultrasonic flowmeter - Google Patents

Abstract

To provide an ultrasonic flowmeter exhibiting high measurement accuracy by detecting a characteristic change of an ultrasonic transducer due to aged deterioration.SOLUTION: The flow speed of a fluid flowing between transducers is measured by transmitting/receiving a pulse signal between the transducers. An ultrasonic flowmeter 1 detects the temperature of the fluid by a temperature detection unit 42. A waveheight value detection unit 41 detects a measured waveheight value by the pulse signal received between the transducers and associates the temperature when the measured waveheight value is detected with the detected waveheight value. Before detecting a measured waveheight value, a reference waveheight value for each temperature is held in advance in a reference value holding unit 43. The measured waveheight value and the reference waveheight value are compared by a waveheight value determination unit 44. The waveheight value determination unit 44 searches for a reference waveheight value at a temperature corresponding to the temperature that is correlated to the measured waveheight value of a determination object and makes it a reference waveheight value.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an ultrasonic flow meter.

  The ultrasonic flow meter is a flow meter in which ultrasonic transducers are installed facing each other at a certain distance on the upstream side and the downstream side in the flow path through which the fluid flows. The ultrasonic flowmeter performs transmission and reception of ultrasonic signals between the ultrasonic transducers arranged opposite each other multiple times, and the propagation time of the forward ultrasonic signal from the upstream side to the downstream side and the downstream side Measure the propagation time of the ultrasonic signal in the reverse direction from to the upstream side. Then, the flow rate value of the fluid flowing in the flow path is measured from the time difference between the propagation time of the forward ultrasonic signal and the propagation time of the backward ultrasonic signal.

  In such an ultrasonic flow meter, the SN ratio is lowered and the resonance frequency is changed due to deterioration of the transmission / reception sensitivity of the ultrasonic vibrator due to aging and temperature change. Therefore, the temporal position of the zero cross point of the received signal that is the reception point of the propagation time changes. As a result, although the flow rate is constant, the propagation time changes, causing a problem of erroneous measurement of the flow rate.

JP-A-9-236463

  However, in the ultrasonic flowmeter, the physical property values of the piezoelectric element, the matching layer, and the like constituting the ultrasonic vibrator change due to aging deterioration and temperature change. Among these factors, a change in temperature changes the internal stress due to expansion and contraction, and the impedance of the ultrasonic transducer itself changes due to this factor. In addition, the effect on impedance due to temperature change is transient, while the effect on impedance due to aging tends to gradually become apparent, but if an error due to impedance change occurs, the cause is due to aging. It is difficult to determine whether it is a lifetime due to temperature or a transient erroneous measurement due to a temperature change, and it is difficult to quantitatively calculate the rate of occurrence of erroneous measurement.

  The embodiment of the present invention has been proposed to solve the above-described problems. An object of the embodiment is to provide an ultrasonic flowmeter with high measurement accuracy by detecting a change in characteristics of an ultrasonic transducer due to deterioration over time.

  The ultrasonic flowmeter according to the embodiment of the present invention is a temperature detection that detects the temperature of the fluid in the ultrasonic flowmeter that measures the flow velocity of the fluid flowing between the transducers by transmitting and receiving a pulse signal between the transducers. And a pulse height received from the pulse signal received between the transducer, a peak value detector associated with the temperature, and a reference peak value for each temperature are held in advance before the measurement peak value is detected. A reference value holding unit; and a peak value determining unit that compares the measured peak value with the reference peak value, the peak value determining unit corresponding to a temperature associated with the measured peak value to be determined A reference wave height value at a temperature is retrieved and set as the reference wave height value.

It is a block diagram which shows the structure of 1st Embodiment. It is a functional block diagram in the composition of a 1st embodiment. It is a graph which shows the received signal Rs of 1st Embodiment. It is a graph which shows an example of the reference value held in the temperature detection part of a 1st embodiment. It is a graph which shows an example of the reference value hold | maintained at the reference value holding | maintenance part of 1st Embodiment. It is a flowchart which shows operation | movement of the ultrasonic flowmeter of 1st Embodiment. It is a figure which shows the relationship between the transmission pulse in 1st Embodiment, a received signal, the compared received signal, and propagation time. It is a flowchart which shows operation | movement of the ultrasonic flowmeter of 1st Embodiment. It is a graph which shows the enlarged view of the received signal Rs of 1st Embodiment.

[1. First Embodiment]
[1-1. Constitution]
Below, the ultrasonic flowmeter which concerns on this embodiment is demonstrated, referring FIGS. FIG. 1 is a block diagram showing the configuration of the flow meter according to the present embodiment, and FIG. 2 is a functional block diagram showing the configuration of the ultrasonic flow meter of the present embodiment more specifically.

  As shown in FIGS. 1 and 2, the ultrasonic flowmeter 1 includes a sensor unit 2 including a pair of ultrasonic transducers 21 and 22 (see FIG. 2), and a pulse is generated between the ultrasonic transducers 21 and 22. The speed of the fluid flowing through the flow path 23 is measured by transmitting and receiving signals. In the sensor unit 2, there is a possibility that a change in physical property values such as a piezoelectric element and a matching layer constituting the ultrasonic vibrator due to aged deterioration or temperature change, or a change in internal stress due to expansion or contraction due to a temperature change may occur. When a change in physical property value or internal stress occurs, the impedance of the ultrasonic transducers 21 and 22 themselves changes, and the sensitivity of transmission and reception and the resonance frequency change. This change in transmission / reception sensitivity and resonance frequency may act as an error in measurement of the flow velocity in the ultrasonic flowmeter 1. The ultrasonic flow meter 1 detects the occurrence of an error that has occurred in the sensor unit 2, and notifies the outside when an error has occurred. The ultrasonic flowmeter 1 includes a sensor unit 2, a measurement unit 3, an error determination unit 4, an input interface (hereinafter referred to as an input IF) 5, and an output interface (hereinafter referred to as an output IF) 6.

  The sensor unit 2 includes a pair of ultrasonic transducers 21 and 22 and detects a change in the flow velocity of the fluid flowing through the flow path 23. As shown in FIG. 2, the ultrasonic transducers 21 and 22 are passive elements having the same configuration. The ultrasonic transducers 21 and 22 are installed on the upstream side and the downstream side of the flow path 23 so as to be coaxially opposed with a distance L therebetween. One of the ultrasonic transducers 21 and 22 installed opposite to each other is a transmission side and the other is a reception side. The ultrasonic transducer on the transmission side receives the transmission signal Ts as a drive signal and transmits an ultrasonic signal. The ultrasonic transducer on the reception side receives the ultrasonic signal propagated through the fluid and outputs a reception signal Rs corresponding to the sound pressure and period of the ultrasonic signal.

  The measurement unit 3 measures the flow rate value of the fluid flowing through the flow path 23. The measurement unit 3 outputs the transmission signal Ts a plurality of times to the ultrasonic transducers 21 and 22 on the transmission side. Then, the measuring unit 3 transmits and receives the ultrasonic signal a plurality of times between the ultrasonic transducers 21 and 22 arranged opposite to each other, and the propagation time of the ultrasonic signal in the forward direction from the upstream side to the downstream side is measured. T1 and the propagation time T2 of the ultrasonic signal in the reverse direction from the downstream side to the upstream side are measured. Then, the flow rate value of the fluid flowing in the flow path is measured from the time difference between the propagation time T1 of the forward ultrasonic signal and the propagation time T2 of the backward ultrasonic signal.

  The error determination unit 4 determines an error based on the reference peak value Wh-r at the temperature T of the fluid flowing through the flow path 23 and the measured peak value Wh-m at the temperature T. The reference peak value Wh-r is peak values detected in advance at a plurality of temperatures before the operation of the ultrasonic flowmeter. The temperature T is a value calculated from the propagation times T1 and T2 of the ultrasonic signal, and the error determination unit 4 determines the flow rate based on the magnitude of the reference peak value Wh-r and the measured peak value Wh-m at the temperature T. Determine the occurrence of errors in the meter. As a determination method, the reference peak value Wh-r and the measured peak value Wh-m are compared, and it is assumed that an error occurs when the measured peak value Wh-m is smaller than the reference peak value Wh-r.

  The input IF 5 includes a keyboard, a dial, a button or a touch panel that accepts user input, and an input terminal that accepts setting signals. The output IF 6 is a display unit for outputting a flow rate and various set values.

  Below, with reference to FIG. 2, the structure of the ultrasonic flowmeter of this embodiment is demonstrated more concretely.

(Measurement part)
The measurement unit 3 includes a signal generation unit 31, a transmission unit 32, a transmission / reception switching unit 33, a reception unit 34, a filter unit 35, a comparator unit 36, a propagation time detection unit 37, and a flow rate measurement unit 38.

  The signal generating unit 31 divides the high-frequency clock signal generated by the signal oscillating unit 30 and sets a condition of a pulse signal for driving the ultrasonic transducer on the transmission side. For example, the pulse signal conditions are the amplitude, frequency, and number of times of the pulse signal. The signal generator 31 sets the amplitude H and frequency τ input by the user via the input IF 5 as the amplitude H and frequency τ of the pulse signal, and sets the number of transmissions of the pulse signal to n times.

  The transmission unit 32 transmits a pulse signal having the conditions set by the signal generation unit 31 to the transmission / reception switching unit 33. A pulse signal transmitted from the transmission unit 32 is defined as a transmission signal Ts.

  The transmission / reception switching unit 33 receives the transmission signal Ts transmitted by the transmission unit 32, and alternately outputs the transmission signal Ts to the upstream and downstream ultrasonic transducers, and from the reception-side ultrasonic transducer. The reception signal Rs is output to the reception unit 34.

  The receiving unit 34 receives the received signal Rs and amplifies it.

  The filter unit 35 removes noise contained in the amplified received signal Rs.

  The comparator unit 36 converts the received signal Rs from which noise has been removed into a digital signal.

  The propagation time detection unit 37 uses the reception signal Rs converted into a digital signal and the transmission signal Ts output from the transmission unit 32 to transmit the propagation time T1 in the forward direction from the ultrasonic transducer 21 to the ultrasonic transducer 22 and the supersonic wave. The propagation time T2 in the reverse direction from the acoustic transducer 22 to the ultrasonic transducer 21 is detected.

  The flow rate measuring unit 38 calculates the flow rate of the fluid flowing in the flow path 23 by obtaining the time difference between the forward and reverse propagation times T1 and T2 detected by the propagation time detecting unit 37. The flow rate measurement unit 38 measures the propagation times T1 and T2 a plurality of times, calculates the flow velocity in the flow path 23 from the time difference between the accumulated values obtained by integrating the propagation times, and calculates the flow velocity and the cross-sectional area of the flow path 23. And the volumetric flow rate value of the fluid flowing in the flow path 23 is obtained and output as a flow rate value.

(Error judgment part)
The error determination unit 4 determines the occurrence of an error in the flow meter based on the magnitude of the reference peak value Wh-r and the measured peak value Wh-m at the temperature T, and determines whether there is an error. If it is determined that there is an error, it is notified to the outside. The error determination unit 4 includes a peak value detection unit 41, a temperature detection unit 42, a reference value holding unit 43, and a peak value determination unit 44.

  The peak value detector 41 detects a measured peak value Wh-m of a predetermined wave number of the reception signal Rs. The measured peak value Wh-m detected by the peak value detector 41 is preferably the fifth wave of the received signal Rs. The timing at which the peak value detection unit 41 detects the measured peak value Wh-m is assumed that no fluid flows (zero flow rate). FIG. 3 is a diagram illustrating a waveform of the reception signal Rs output from the filter unit 35. In FIG. 3, a received waveform Rs-E is a received waveform transmitted / received between the ultrasonic transducers 21 and 22 that is not affected by aging and does not have a decrease in transmission / reception sensitivity. The reception waveform Rs-P is a reception waveform in which the transmission / reception sensitivity is lowered and the amplitude is reduced due to aging and temperature.

  The temperature detection unit 42 specifies the propagation time at the flow rate of zero with the same propagation time from the propagation times T1 and T2 detected by the propagation time detection unit 37, and obtains the current fluid temperature from the propagation time. . As a method for obtaining the temperature from the propagation time, FIG. 4 is a graph of the propagation time measured by changing the temperature in a flow rate zero state. The temperature can be obtained by comparing the propagation time detected by the propagation time detector 37 with the propagation time shown in FIG. 4 stored in the temperature detector 42 (not shown). In the above description, the relationship between the propagation time and the temperature has been described using a graph, but it may be tabular data. Information on the temperature t calculated by the temperature detection unit 42 is input to the reference value holding unit 43.

  The reference value holding unit 43 stores a reference peak value Wh-r for each temperature. The temperature range of the stored reference wave height value Wh-r can be changed for each environment in which the ultrasonic flowmeter is used. The interval for storing the reference peak value Wh-r can be changed according to the purpose of use of the ultrasonic flowmeter. For example, the solid line Rs-E shown in FIG. 5 indicates the peak value of the fifth wave shown in FIG. 6 is a graph illustrating an example of a reference peak value Wh-r that is plotted with the voltage of Wh and is held in a reference value holding unit 43; A broken line Rs-P is a received waveform in which the transmission / reception sensitivity is lowered and the amplitude is reduced due to aging and temperature.

  The peak value determination unit 44 compares the reference peak value Wh-r at the temperature t with the measured peak value Wh-m at the temperature t to determine an error. The reference value holding unit 43 acquires the fluid temperature t from the temperature detection unit 42 and selects the reference wave height value Wh-r at the temperature t held in the reference value holding unit 43. Then, data comparison is performed between the reference peak value Wh-r and the measured peak value Wh-m at the temperature t detected by the peak value detector 41.

  As described above, the peak value data includes the peak values of the first to nth waves. Therefore, the peak value detection unit 41 detects the peak value of the fifth wave from the peak values of the first to n-th waves and sets it as the measured peak value Wh-m. The measured peak value Wh-m may be detected from the peak value of the fifth wave using a peak hold circuit (not shown).

[1-2. Action]
Below, operation | movement of the ultrasonic flowmeter 1 which concerns on this embodiment is demonstrated. The operation process of the ultrasonic flowmeter 1 is roughly divided into two processes.

  The first step is a step of storing the reference peak value Wh-r in the reference value holding unit 43. The first process is a process performed at the manufacturing stage or the setup stage of the ultrasonic flowmeter 1.

  The second step is a step of measuring the fluid flow rate with the ultrasonic flowmeter 1. In the ultrasonic flowmeter 1 according to the present embodiment, the flow rate is measured and the occurrence of an error is monitored, and if an error occurs, the user is notified. In the following description, the flow rate measurement process and the error range process will be described separately.

(Flow velocity measurement process)
FIG. 6 is a flowchart showing the operation of the ultrasonic flow meter 1 in the flow velocity measurement process. As shown in FIG. 6, in the flow velocity measurement step (S101), the pulse generated by the transmission unit 32 is applied to the ultrasonic transducer 21 via the transmission / reception switching unit 33 (S101). FIG. 7A shows the transmission signal Ts applied to the ultrasonic transducer 21. The ultrasonic transducer 21 on the transmission side outputs an ultrasonic wave having a sound pressure corresponding to the magnitude of the amplitude H of the transmission signal Ts toward the ultrasonic transducer 22 on the downstream side. The pulse width τ is the period of the resonance frequency unique to the ultrasonic transducer 21. For example, when the resonance frequency is 200 kHz, the period is 5 μs.

  The ultrasonic signal output from the ultrasonic transducer 21 reaches the ultrasonic transducer 22 on the downstream side at a propagation speed T1 determined by the sound speed and distance L determined by the type and temperature of the fluid in the flow path 23 and the flow velocity of the fluid. (S102). The ultrasonic transducer 22 receives the received ultrasonic wave and outputs a reception signal Rs shown in FIG. The reception signal Rs is amplified by the amplifier built in the reception unit 34 via the transmission / reception switching unit 33, and then the noise is removed by the filter unit 35 (S103), and the output signal is output to the comparator unit 36 and the peak value detection unit 41. To do.

  The comparator unit 36 converts the received reception signal Rs into a pulse train shown in FIG. 7C at the zero cross (S104). The converted signal is output to the propagation time detector 37.

  The propagation time detection unit 37 detects the propagation time (S105). The propagation time is detected by inputting the transmission signal Ts of the transmission unit 32 shown in FIG. 7A and the pulse train of the comparator unit 36 shown in FIG. 7C, from transmission to reception shown in FIG. 7D. The propagation time T is detected.

  In the detection of the propagation time T, the reception point in FIG. 7 (d) is the point at which the pulse of the fifth wave shown in FIGS. 7 (b) and (c) rises. The pulse train may be a rising or falling point. However, the received signal Rs after the first wave, the second wave, or the sixth wave has a smaller amplitude than the third wave, the fourth wave, and the fifth wave, and is superimposed on the slope of the signal at the zero cross point and the received signal Rs. The zero cross point fluctuates due to the minute noise that occurs, and the propagation time changes and affects the measurement accuracy.

  The propagation time T in FIG. 7D is measured a plurality of times in each of the forward direction and the reverse direction, and the flow velocity in the flow path 23 is calculated from the time difference between the integrated values respectively accumulated by the flow rate measuring unit 38 (S106). The volume flow rate value of the fluid flowing in the flow path 23 is obtained by multiplying the flow velocity by the cross-sectional area of the flow path 23 and output as a flow value.

(Error judgment process)
FIG. 8 is a flowchart showing the operation of the ultrasonic flowmeter 1 in the error determination step. As shown in FIG. 8, in the error determination step, it is confirmed that the fluid flow velocity is 0 (S111). The flow rate of the fluid is determined based on the value measured by the flow rate measurement unit 38 in the flow rate measurement process.

  Then, the fluid temperature t when the fluid flow velocity is 0 is detected (S112). The temperature t is detected by the temperature detector 42. The temperature detector 42 detects the temperature t from the propagation time of the pulse signal when the fluid flow velocity is zero.

  Next, the measured peak value of the received signal when the fluid flow velocity is 0 and the temperature is t is detected (S113). The measurement peak value is detected by the peak value detector 41, and the value of the peak value of the fifth wave of the received waveform is selected.

  Thereafter, the reference wave height value of the temperature t is selected (S114). The peak value determination unit 44 searches the reference value holding unit 43 and selects a reference peak value for the temperature t. Then, the peak value determination unit 44 compares the reference peak value with the measured peak value (S115).

  As a result of the comparison, if the measured peak value is less than the reference peak value, it is assumed that an error has occurred (YES in S116), and the occurrence of the error is notified by the notification unit (S117). On the other hand, if the measured peak value is greater than or equal to the reference peak value, no error has occurred (NO in S116). The above steps S111 to 117 are performed until the flow rate step is completed (S118).

[1-3. effect]
(1) As described above, the ultrasonic flowmeter 1 measures the flow velocity of the fluid flowing between the transducers by transmitting and receiving pulse signals between the transducers. The ultrasonic flow meter 1 detects the temperature of the fluid by the temperature detection unit 42. The peak value detection unit 41 detects the measured peak value from the pulse signal received between the transducers, and associates the measured peak value with the measured peak value when the measured peak value is detected. Moreover, the ultrasonic flowmeter 1 holds the reference wave height value for each temperature in the reference value holding unit 43 in advance before the measurement wave height value is detected. Then, the peak value determination unit 44 compares the measured peak value with the reference peak value. At this time, the peak value determination unit 44 searches the reference value holding unit 43 for a reference peak value corresponding to the temperature associated with the measured peak value to be compared, and sets it as the reference peak value. As a result, when the amplitude of the received signal Rs changes due to aged deterioration or the like and an erroneous measurement occurs, it is possible to notify the occurrence of an abnormality, so that the ultrasonic flowmeter 1 with excellent reliability and accuracy can be obtained. It can be realized.

  FIG. 9 is a diagram for explaining the transition of the zero cross point that changes depending on the amplitude of the received signal. In the received signals Rs-E and Rs-P having different amplitudes shown in FIG. 9, the slope of the signal changes due to the difference in amplitude, and the temporal position of the zero cross point Zp of the comparator changes by several ns to several tens ns. Therefore, the rising position in the comparator unit 36 also changes. Therefore, the arrival time T from the output of the transmission signal until it is converted into a digital signal at the zero cross point of the fifth wave of the reception signal Rs changes by Δt, and the flow rate measurement value changes even though the flow rate is the same. Or the result will vary. In addition, the signal-to-noise ratio is reduced due to the reduction in the amplitude of the received signal, noise superimposed on the signal shifts the zero cross point, and similarly the flow rate measurement value is erroneously measured.

  According to the present embodiment, by comparing the measured peak value with the reference peak value measured at each temperature in advance, the transmission / reception sensitivity of the ultrasonic transducer due to secular change is excluded, excluding the decrease in transmission / reception sensitivity due to temperature. Can be identified. Therefore, it is possible to accurately measure the flow rate by accurately determining the deterioration of the ultrasonic transducer and excluding the deteriorated ultrasonic transducer.

(2) In addition, the temperature of the fluid is not detected directly using a thermometer or other device provided in the pipe, but is calculated from the propagation time of the pulse signal between the vibrators for temperature detection. There is no need to prepare new equipment. As a result, it is possible to realize the ultrasonic flowmeter 1 with high reliability and high accuracy with a simple configuration.

(3) Further, the temperature detection unit 42 calculates the temperature of the fluid based on a pulse signal transmitted and received between the vibrators when the fluid flow rate is zero. When the fluid is flowing, the reception result of the pulse signal is affected. By using a pulse signal transmitted and received between the transducers when the fluid flow rate is 0, and determining the error, it is possible to measure the flow rate with high accuracy by excluding degraded ultrasonic transducers. .

(4) The reference peak value Wh-r can be a peak value measured for each temperature when the fluid flow rate is zero. When the fluid is flowing, the reception result of the pulse signal is affected. By using a pulse signal transmitted and received between the transducers when the fluid flow rate is 0, and determining the error, it is possible to measure the flow rate with high accuracy by excluding degraded ultrasonic transducers. .

(5) The peak value detector 41 detects the measured peak value from the pulse signal transmitted and received between the transducers when the fluid flow rate is zero. When the fluid is flowing, the reception result of the pulse signal is affected. By using a pulse signal transmitted and received between the transducers when the fluid flow rate is 0, and determining the error, it is possible to measure the flow rate with high accuracy by excluding degraded ultrasonic transducers. .

(6) The peak value determination unit 44 reports an abnormality when the measured peak value is smaller than the reference peak value. Thereby, with a simple configuration, it is possible to accurately determine the deterioration of the ultrasonic transducer and notify the user.

[3. Other Embodiments]
In the present specification, a plurality of embodiments according to the present invention have been described. However, these embodiments are presented as examples and are not intended to limit the scope of the invention. Specifically, various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and gist of the invention.

  (1) For example, the peak value determination unit 44 compares the reference peak value Wh-r with the measured peak value Wh-m, and if the measured peak value Wh-m is smaller than the reference peak value Wh-r, an error occurs. Although it occurred, it is not limited to this. An error may occur when the measured peak value Wh-m is different from the reference peak value Wh-r. In this case, the measured peak value Wh-m and the reference peak value Wh-r may not be equal in a strict sense. Further, if the measured peak value Wh-m is a value of the reference peak value Wh-r ± α, no error may occur.

  (2) The peak value determination unit 44 sets the peak value of the fifth wave included in the measured peak value as the measurement peak value, and the reference value holding unit 43 stores the reference based on the peak value of the fifth wave in advance. It was assumed that the peak value was retained. However, in the peak value determination unit 44, if the measured peak value and the reference peak value to be compared are the same order of peak values, the peak value other than the fifth wave is selected as the measured peak value and the reference peak value. You can also For example, the peak values of the third wave, the fourth wave, and the sixth wave can be selected as the measurement peak value and the reference peak value. That is, when a pulse wave that is an independent wave is transmitted from the ultrasonic transducer on the transmission side, it becomes a pulse wave of a plurality of cycles. The multi-cycle pulse wave has a small amplitude in the first wave and the second wave. And the peak of the magnitude | size of an amplitude comes in 3-5 waves. In such a waveform, it is possible to perform accurate detection by detecting the amplitude and period with little influence of noise or the like where the amplitude reaches a peak. On the other hand, if it is possible to detect an accurate period difference or amplitude difference, peak values based on waveforms other than 3 to 5 waves may be compared.

  Moreover, each part which comprises the ultrasonic flowmeter 1 can also be comprised with the circuit which implement | achieves the operation | movement of each part. By constituting each part with a circuit, an inexpensive and highly reliable ultrasonic flowmeter can be realized.

DESCRIPTION OF SYMBOLS 1 ... Ultrasonic flowmeter, 2 ... Sensor part, 3 ... Measurement part, 4 ... Error determination part, 5 ... Input IF, 6 ... Output IF, 21 ... Ultrasonic vibrator, 22 ... Ultrasonic vibrator, 23 ... Flow Path 30... Signal oscillating unit 31... Signal generating unit 32 .. transmitting unit 33 .. transmission / reception switching unit 34 .. receiving unit 35... Filter unit 36 .. comparator unit 37 .. propagation time detecting unit 38. Measuring unit, 41... Peak value detecting unit, 42... Temperature detecting unit, 43... Reference value holding unit, 44.

Claims (6)

In ultrasonic flowmeters that measure the flow velocity of fluid flowing between transducers by transmitting and receiving pulse signals between transducers,
A temperature detector for detecting the temperature of the fluid;
Detecting a measured peak value from a pulse signal received between the vibrators and associating with the temperature, a peak value detector;
Before the detection of the measurement peak value, a reference value holding unit that holds a reference peak value for each temperature in advance,
A peak value determination unit that compares the measured peak value with the reference peak value;
With
The ultrasonic flowmeter, wherein the peak value determination unit searches the reference value holding unit for a reference peak value corresponding to a temperature associated with a measured peak value to be compared, and sets the reference peak value as a reference peak value.   The ultrasonic flowmeter according to claim 1, wherein the temperature detection unit calculates a temperature of the fluid from a propagation time of the pulse signal between vibrators, and sets the temperature of the fluid.   The ultrasonic wave according to claim 1 or 2, wherein the temperature detection unit calculates the temperature of the fluid based on a pulse signal transmitted and received between the vibrators when the fluid flow rate is zero. Flowmeter.   4. The ultrasonic flowmeter according to claim 1, wherein the reference wave height value is a wave height value measured for each temperature when the flow rate of the fluid is 0. 5.   The said peak value detection part detects a measured peak value from the pulse signal transmitted / received between vibrator | oscillators when the flow volume of a fluid is 0, The any one of Claim 1 thru | or 4 characterized by the above-mentioned. Ultrasonic flow meter.   The ultrasonic wave according to any one of claims 1 to 5, wherein the peak value determination unit notifies an abnormality when the measured peak value is smaller than the reference peak value. Flowmeter.

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