JP2006184036A - Method and instrument for ultrasonic fluid measurement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly accurately measure the flow and concentration of a fluid under measurement by correcting error time owing to its passage through a noise-removal filter thereby correctly measuring propagation time, as to an ultrasonic fluid measurement instrument. <P>SOLUTION: A pair of ultrasonic transmitter-receivers are disposed a predetermined distance apart from each other in a flowing direction in the fluid under measurement so that they together confront acoustically. An ultrasonic signal transmitted from one transmitter-receiver propagates through the fluid and is received by the other transmitter-receiver. Based on the received signal passed through a filter, the propagation time from transmission to reception is measured respectively in regard to propagation directions that form forward flow and backward flow as to the flowing direction of the fluid under measurement. The propagation time is corrected by subtracting filter passage delay time calculated correspondingly to received frequency from the measured time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultrasonic fluid measurement technique for measuring a state quantity (flow rate, concentration) of the fluid to be measured by measuring a propagation time of ultrasonic waves in the fluid to be measured.

  Conventionally, a pair of ultrasonic transducers are arranged facing the upstream side and the downstream side of the fluid to be measured, and an ultrasonic signal is transmitted in the forward direction from the upstream ultrasonic transducer to the flow of the fluid to be measured. The first propagation time until it is received by the downstream ultrasonic transducer is measured, and the ultrasonic signal is transmitted in the opposite direction to the flow from the downstream ultrasonic transducer. A fluid measuring device that measures the second propagation time until it is received by the upstream ultrasonic transducer and detects the flow rate of the test fluid based on each measured propagation time is known. (Patent Document 1).

In this apparatus, the zero cross time that passes through the transmission level 0 point after a predetermined number of cycles (alternating frequency) from the beginning of the transmission wave and the zero cross time that passes through the reception level 0 point after a predetermined number of cycles (alternating frequency) from the beginning of the reception wave. And the time from the transmission-side zero-crossing time to the reception-side zero-crossing time is detected as the propagation time, thereby canceling the influence of an unstable frequency change at the time of rising.
Japanese Patent Application Laid-Open No. 09-026341

  By the way, in this type of ultrasonic fluid measuring device, since sound is used as a detection physical quantity, acoustic noise that travels through the pipes before and after the detection unit, and when the fluid collides with the edge A of the measurement tube 1 and peels off. Is detected by mixing in the ultrasonic reception signal. For this reason, in the process of detecting the propagation time from the received ultrasonic signal, a filter is provided for extracting only the transmitted ultrasonic frequency by removing the noise frequency component which is an error factor. This filter is indispensable for measuring a precise propagation time, but on the other hand, a time delay occurs when an ultrasonic signal passes through the filter.

The delay time due to the filter passage becomes a measurement error of the ultrasonic propagation time, and then becomes a measurement error of the fluid flow rate or the concentration.
The present invention has been made paying attention to such a conventional problem, and while removing the disturbance signal by the filter, the influence of the delay due to the passage of the ultrasonic signal through the filter is prevented, and the fluid state is more accurately detected. The purpose is to be able to measure the quantity.

  For this reason, the present invention transmits an ultrasonic signal to propagate a predetermined distance in the fluid to be measured in a direction having a propagation velocity component having a magnitude different from the fluid flow direction, and the ultrasonic wave after propagation by the filter. A disturbance signal is removed from the signal, and based on each ultrasonic signal after passing through the filter, the propagation time required for each ultrasonic signal to propagate the predetermined distance is measured, while the ultrasonic wave input to the filter Detecting the frequency of the signal, calculating a delay time correction value when the ultrasonic signal passes through the filter based on the detected frequency, correcting each propagation time of the ultrasonic signal by the delay time correction value, The state quantity of the fluid to be measured is measured based on the corrected propagation time.

  With such a configuration, the delay time of the filter passage that varies depending on the frequency of the ultrasonic signal propagated in the fluid to be measured is calculated as a delay time correction value, and the actually measured propagation time is calculated by the delay time correction value. By correcting, even if the ultrasonic frequency fluctuates during measurement, the change in the filter delay time due to the frequency fluctuation can be canceled, and the actual propagation time can be obtained with high accuracy. The state of the fluid to be measured can be measured with high accuracy based on the substantial propagation time.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram of an ultrasonic fluid measuring apparatus according to an embodiment. In the figure, Lm is the distance between the ultrasonic transducers (ultrasound transducers) 2a and 2b, Cg is the sound velocity of the fluid to be measured, Vg is the flow velocity of the fluid to be measured, and θ is the fluid to be measured. It is an angle formed by the flow direction of (for example, hydrogen gas) and the propagation direction of the ultrasonic signal.

  A pair of ultrasonic transducers 2a and 2b are disposed at a predetermined distance in an acoustically opposed relationship with a measurement tube (space) 1c through which a fluid to be measured flows. Specifically, as shown in the figure, the ultrasonic transducers 2a and 2b provided in the measurement tube 1c are arranged obliquely so as to face each other. An ultrasonic signal is transmitted from the one ultrasonic transducer 2a, and the ultrasonic signal propagated in the fluid to be measured is received by the other ultrasonic transducer 2b (ultrasonic transmission type).

Then, the ultrasonic propagation time measurement circuit 3 determines the ultrasonic propagation times t1 and t2 between the ultrasonic transducers 2a and 2b in the forward direction (2a → 2b) and the reverse direction (2b → 2a), respectively. .
Although not shown, a pair of ultrasonic transducers 2a and 2b is provided at a predetermined interval in the flow direction of the fluid to be measured, and the ultrasonic waves transmitted from one ultrasonic transducer 2a are contained in the fluid to be measured. It may be propagated, reflected by the measurement tube 1c and received by the other ultrasonic transducer 2b (ultrasonic reflection type).

Here, the relationship between the propagation time, concentration (density), flow velocity, and flow rate calculation formula will be described.
The time td1 between transmission and reception in the forward direction of the measurement fluid (ultrasonic transducer 2a → 2b) detected by the ultrasonic propagation time measuring circuit 3 (see FIG. 1) and the reverse direction (ultrasonic transducer 2b → 2a). ) Between transmission / reception times td2 is represented by the following equation (see FIG. 2).
td1 = t1 + tr1 + tc1
= Lm / (Cg + Vg × cos θ) + tr1 + tc1 (1)
td2 = t2 + tr2 + tc2
= Lm / (Cg−Vg × cos θ) + tr 2 + tc 2 (2)
The first terms t1 and t2 on the right side of the equations (1) and (2) are pure ultrasonic propagation times (hereinafter referred to as propagation times) between the ultrasonic transducers 2a and 2b. Lm is the distance between the ultrasonic transducers 2a and 2b, Cg is the sound velocity of the fluid to be measured, Vg is the flow velocity of the fluid to be measured, and θ is the angle formed by the flow direction of the fluid to be measured and the propagation direction of the ultrasonic waves. .

Tr1 and tr2 are delay times from the reception time of the reception head wave to the reception time detection time. This is a calibration that is measured in advance using a calibration fluid whose sound speed is known, that is, in a state where the propagation time is known. Value.
Further, tc1 and tc2 are period transition correction times when the reception detection time changes exceeding one period of the reception frequency with respect to the calibration time, and are values updated every time a period transition is detected during measurement.

In the equation for calculating the flow velocity, the pure ultrasonic propagation time t1 (= td1-tr1-tc1) between the ultrasonic transducers 2a, 2b is obtained by subtracting the reception detection delay times tr1, tr2 from the transmission / reception times td1, td2. , T2 (= td2-tr2-tc2), the flow velocity Vg is obtained.
Vg = [Lm / (2 × cos θ)] × {1 / (td1-tr1-tc1)
-1 / (td2-tr2-tc2)}
= [Lm / (2 × cos θ)] × (1 / t1-1 / t2) (3)
Further, as shown in the following equation, the flow rate Qv is the cross-sectional area A of the measurement pipe (space) through which the fluid to be measured flows, the flow velocity distribution correction coefficient K in the piping, and the flow velocity Vg of the fluid to be measured calculated by the equation (3). Calculate by integrating.

Qv = Vg × A × K (4)
As described above, in calculating the flow velocity Vg and the flow rate Qv, the difference in the propagation time between the forward direction and the backward direction of the fluid to be measured is calculated as shown in the equation (3). However, if the propagation times td1 and td2 are sufficiently larger than the delay times tr1 and tr2, it is negligible in practice. However, when the speed of sound such as hydrogen gas is high or a small flow meter is used. It can be understood that when the ultrasonic propagation distance Lm is short, the influence on the flow velocity and flow rate measurement accuracy cannot be ignored.

As an example, propagation distance of ultrasonic signal Lm = 100mm, sound velocity of measured fluid hydrogen (dry) Cg = 1270m / s, angle θ = 45deg between ultrasonic signal and measured fluid flow, flow velocity Vg = 0 (stop) ), The ultrasonic wave propagation time under the condition of reception detection delay time tr = 137.5 μs (5.5 cycles × 1 cycle of ultrasonic waves 25 μs) is calculated by substituting into Equations 1 and 2,
td1 = td2 ≒ 216.240μs
Next, when the flow rate measurement error is calculated when a propagation time measurement error of 1 μs occurs only at td2 under this condition, the flow rate distribution correction coefficient K = 1 and the channel cross-sectional area A = 50 mm ² are assumed. Substituting into (3) and (4),
Vg = 100mm × {1 / (216.240-137.5) −1 / (216.240 + 1.0-137.5)} / (2 × cos45) ≒ 11.3 m / s
Qv = 11.3 × 50mm ² × 1 ≒ 0.00565m ³ / s = 339 L / min
As is apparent from the result of this trial calculation, a very large flow measurement error of 300 L / min occurs with a time measurement error of only 1 μs.

When calculating the fluid concentration (density ρ), the arithmetic circuit 4 first determines the sound velocity Cg using the following equation (5), and then converts it to the molar mass M using the equation (6). Then, the concentration is obtained by calculating the ratio between the average molar mass of the fluid and the molar mass of the molecule to be measured.
Cg = (Lm / 2) × {1 / (td1-tr1) + 1 / (td2-tr2)} (5)
M = γ × R × Tg / Cg ² (6)
Here, γ is a specific heat ratio, R is a gas constant, and Tg is a gas temperature (K). In equation (6) for obtaining the thus molar mass M, the influence of the received detection delay time tr1, tr2 from substituting the square of the value Cg ² sonic Cg is in even greater relationship.

As described above, it is apparent that accurate detection of the propagation time is very important for ensuring the flow velocity and flow rate measurement accuracy, particularly when a fluid having a high sound velocity Cg is a measurement target.
In addition, the present inventor provides accurate and reliable reception time even in an environment where there is a large change in the amplitude of the received signal due to density change or noise superposition, such as hydrogen gas, which has been conventionally unsuitable. As a method of detecting and measuring the propagation time with high accuracy, a method of detecting reception of an ultrasonic wave after transmission after a predetermined elapsed time has been proposed.

  Further, in the above method, when the change in the reception detection time from the reception detection start time changes beyond one cycle of the ultrasonic frequency, the reception detection time is turned back, and the measured value of the propagation time is lost. However, this problem can be applied to a fluid whose propagation time changes by more than one period of the ultrasonic frequency by providing a folding occurrence detecting means and a period transition correcting means for correcting the amount of folding. .

In addition, the reception detection delay times tr1 and tr2 due to fluctuations in the ultrasonic frequency depending on the use environment of the ultrasonic sensor and the time variation of the period transition correction means (period correction times tc1 and tc2) are corrected to reduce measurement errors. A means to reduce was proposed.
However, as described above, when a filter is provided to remove a noise frequency component that causes an error in detecting the propagation time from the ultrasonic reception signal, a time delay occurs when the ultrasonic signal passes through the filter. . That is, as schematically shown in the time chart in FIG. 3, it should be detected at a predetermined timing of the ultrasonic wave reception signal (Wr) drawn with a dotted line, but in reality, the delay of the filter as with the solid line drawing. The signal is detected at the timing when the time dt is added. That is, this delay time dt becomes a measurement error of the ultrasonic wave propagation time, and then becomes a measurement error of the fluid flow rate or concentration.

  Here, if the filter delay time is determined only by the filter characteristics, the filter delay time is included as a fixed value in the reception detection delay times tr1 and tr2 measured at the time of calibration in advance. Although it may not be necessary, the filter delay time is not actually determined only by the filter characteristics, and in particular, since it varies greatly depending on the reception frequency, it has been found that further correction is necessary.

Therefore, the present invention proposes correction of measurement error due to the passage of the filter in order to further improve the measurement accuracy in addition to the improvement of the various measurement accuracy described above.
First, the basic processing method of the present invention will be described with reference to FIG. This is the measured value td1 (td2) of the time between transmission and reception from the time when the ultrasonic transmission signal Wt is transmitted to the predetermined reception time (here, the zero crossing point of S6 and the time point of the first wave at 5.5 cycles), and the propagation time to be obtained For t1 (t2), the propagation time is obtained by subtracting the reception detection delay correction time tr1 (tr2) and the period transition correction time tc1 (tc2) obtained in advance from the detection time td1 (td2).

  Here, in the equations (1) and (2), the reception detection delay correction time tri (i = 1, 2) is a value including the filter passage and the circuit delay time, but the filter delay time is received. Measurement error is caused by the change depending on the frequency. In the present invention, in order to correct this measurement error, an error time dt is set as a total value of frequency-dependent signal delay times in the filter unit, and the error time dt is set separately from the reception detection delay correction time tri. . As a result, the equations (1) and (2) are replaced with the following equations.

tdi = ti + tri + tci + dt (i = 1, 2) (7)
Here, the reception detection delay correction time tri (i = 1, 2) from which the error time dt is separated is expressed by the following equation.
tri = (Nri / fc) (8)
Nri is the number of periods up to the reception detection time, and is a value indicated by 5.5 periods in FIG. 2 described above. Since Nri takes a value every half period, it is expressed by the following equation.

Nri = 0.5 × INT (tri × 2 × fc) (9)
fc: Reception frequency at the time of calibration In Expression (9), the INT function is an integer obtained by rounding off the decimal part of the calculation result in parentheses to tri and fc which are real numbers including a decimal point.
Tφ is a time including the filter delay time φ (fc) at the calibration reception frequency fc and the steady delay time δ of the circuit until the reception detection time, and is expressed by the following equation.

Tφ = φ (fc) + δ (10)
Since this Tφ corresponds to dt at the time of calibration in the equation (7), dt = Tφ, and using a fluid whose propagation time ti is known, an actual measurement value is substituted into the equation (7) and obtained as the remainder of each variable. It is done. That is, it is expressed by the following formula.
Tφ = tdi− (ti + tri + tci) (11)
Tci is expressed by the following equation.

tci = Nci / fr (12)
Here, Nci is the number of times that the zero crossing of the target reception detection has shifted over one period with respect to the calibration, and at the time of calibration, Nci = 0 and the reception frequency fr = the calibration frequency fc.
From the above relationship, in the equation (7), the error time dt due to the filter passage at the time of measurement is expressed by the following equation.

dt = Tφ + Δφ (13)
Here, Δφ is obtained by time-converting the phase change difference from the reference frequency f0 (= calibration frequency fc), and is expressed by the following equation.
Δφ = {φ (fr) / (fr × 360)} − {φ (fc) / (fc × 360)} (14)
Therefore, the reception frequency (calibration frequency) fc is stored at the time of calibration, the error time Tφ at the time of calibration is calculated from the equation (11), and the reception frequency fr at the time of measurement and the calibration frequency fc are used (14 ) Is calculated from the equation (E), and these are added according to the equation (13), the error time dt due to the filter passage at the time of measurement can be calculated.

In this way, the error time dt due to the filter passage that changes depending on the reception frequency at the time of measurement is calculated, and the measurement error depending on the reception frequency and the like is eliminated as much as possible using the error time dt. The propagation time ti (i = 1, 2) can be obtained.
Based on the high-accuracy propagation time ti (i = 1, 2) obtained in this way, the flow rate / concentration calculation circuit 4 in FIG. 1 calculates the flow rate measurement value by the equations (3) and (4). Similarly, the fluid density (concentration) is calculated and output by the equations (5) and (6).

  In the above embodiment, the reception frequency at the time of calibration is set as the reference frequency, and the filter delay time is corrected for the difference in the reception frequency at the time of measurement with respect to the reception frequency fc at the time of calibration. However, a predetermined reference frequency (for example, The filter delay time may be corrected for a difference from a nominal value of 40 Hz or a median of ultrasonic sensor manufacturing variation. In this case, the correction amount is calculated by calculating the difference from the reference frequency (40 Hz or the like) during calibration as well as during measurement. In this method, since the filter delay time with respect to the reference frequency is known in advance, it is not necessary to store the reception frequency at the time of calibration. Further, as shown in FIG. 4, a map in which the filter delay time correction amount GD is directly set for the reception frequency fr or the correction amount difference ΔGD for (40 Hz) is set as the reference frequency is provided. It is also possible to obtain the correction amount by searching from. In the first embodiment in which the former map is used and the reception frequency at the time of calibration is the reference frequency, the filter delay time correction amount GD (fc) referenced from the map at the time of calibration and measurement is used instead of calculating by the equation (14). ), GD (fr) can be used to calculate Δφ by the following equation.

Δφ = GD (fr) −GD (fc) (15)
In addition, since the filter delay time changes depending on the temperature of the filter circuit, a temperature sensor for detecting the temperature of the filter circuit is provided, and the map of the filter delay time is displayed with the frequency and the filter delay for each predetermined temperature interval. A three-dimensional map in which time is associated or a plurality of two-dimensional maps at predetermined temperature intervals such as Tc1, Tc2, and Tc3 as shown in FIG. 5 may be provided. The high-precision measurement can be performed by removing the influence of.

Also, good measurement performance can always be maintained by correcting the map by performing calibration according to predetermined conditions such as a reception frequency and temperature as will be described later for each measurement or periodically. An embodiment for performing such calibration will be described below.
FIG. 6 shows a circuit configuration.

  The output of the calibration signal generation circuit 3m is input to the external frequency control input terminal of the transmission drive circuit 3a, outputs a control voltage signal for generating a single reference frequency during measurement, and also during calibration. A control voltage signal for changing the frequency is output. A voltage-controlled oscillation circuit can be applied as the frequency variable circuit of the transmission drive circuit 3a.

  Next, the calibration signal application circuit 3n switches so that the output of the transmission / reception direction selector switch 3b is guided to the ultrasonic signal extraction filter at the time of measurement, and the output of the transmission drive circuit 3a instead of the reception signal at the time of calibration. Is switched to lead to the ultrasonic signal extraction filter 3k. For the calibration signal applying circuit 3n, an element having no delay time or frequency dependency is desirable. For example, a mechanical relay switch is suitable.

Next, the filter delay time measurement circuit 3o measures the delay time between the output signal of the transmission drive circuit 3a and the output of the ultrasonic signal extraction filter 3k, and outputs it to the delay time storage circuit 3o. A time counter can be applied to the filter delay time measuring circuit 3k in the same manner as the transmission / reception time counting circuit 3e.
Further, the calibration signal generation circuit 3m is provided with an input terminal for an external event signal, and is set so as to execute calibration by the input of the external event signal.

The filter delay time measurement circuit 3o has a function of comparing the measured delay time with a limit value, and outputs a circuit abnormality alarm when a delay time exceeding the limit value is measured. Is provided.
Next, the processing sequence according to the embodiment will be described with reference to the follow chart of FIG.

This flow is started when the power is turned on. First, a temporary reception start time tg and a reception delay correction time tr are set together with initial values related to transmission / reception control and measurement of ultrasonic signals (S101).
Then, the transmission / reception direction is switched (S102), an ultrasonic drive signal is output, and counting of the time between transmission / reception is started (S103).

Then, it waits until the reception start time is reached (S104). When the reception start time is reached, the zero crossing of the reception signal is detected, the transmission / reception time count is stopped, and the count value at that time (propagation time detection time td) is read. (S105).
Next, the process branches depending on whether calibration or measurement is performed. (S106). As branch determination information at this time, assuming that the fuel cell vehicle is mounted on the fuel cell vehicle, the fuel cell power plant uses any signal such as accelerator OFF or parking brake ON indicating an idle state, so that the fluid to be measured Calibration can be performed when is in a steady state.

Next, the processing sequence when the calibration is executed based on the determination result will be described. First, instead of the reception signal, the output of the transmission drive circuit is guided to the ultrasonic signal extraction filter by the calibration signal application circuit 3n. (S107).
Next, the control voltage signal output of the calibration signal generation circuit 3m is changed, and the first calibration frequency is output from the transmission drive circuit (S108).

Next, the delay time storage circuit 3o measures the delay time of the ultrasonic signal extraction filter at the first calibration frequency, and stores the delay time at an address corresponding to the first calibration frequency (S109).
In the next calibration end determination, it is determined whether the calibration is completed up to a predetermined frequency range. If not completed, the process returns to the calibration frequency setting in S108, and the measurement and storage of the delay time by the next calibration frequency is repeatedly executed (S110). When calibration at all frequencies is completed, the calibration signal applying circuit 3n is switched so that the received signal is guided to the ultrasonic signal extraction filter 3k to prepare for fluid measurement execution.

When the fluid measurement is executed, the delay time corresponding to the reception frequency fr is read with reference to the delay time map held in the delay time storage circuit (S112).
Next, the actual propagation time t1 (t2) is calculated from the propagation time detection time td1 (td2) by the equations (1) and (2) (S113).
The propagation time calculated here is the propagation time in the direction (flow forward direction 2a → 2b = t1, flow backward direction 2b → 2a = t2) selected by the transmission / reception direction switching, and therefore the propagation time corresponding to that direction. Store in variables (t1, t2) (S114).

Next, based on the propagation times t1 and t2 obtained by processing the processes S102 to S114 twice as a set, the flow rate measurement value is calculated and output by the equations (3) and (4).
Similarly, the fluid density (concentration) is calculated and output according to equations (5) and (6). (S115).
The flowchart of FIG. 11 shows a subroutine of another form of the calibration execution sequence.

  Similarly to the above, after switching the output of the transmission drive circuit 3a to be guided to the ultrasonic signal extraction filter by the calibration signal application circuit 3n (S201), the frequency received in the latest measurement is the current delay time map. It is determined whether the frequency range is out of the input range. If it is determined that the frequency range is out of range, the frequency range is expanded to include the reception frequency, and a calibration signal in the expanded frequency range is generated. (S202). On the other hand, if it is determined that the current map is within the frequency range, the process proceeds to the next step (S203) without performing the expansion process.

  Next, while sequentially generating calibration signals at predetermined frequency intervals (S203) and measuring and storing the filter delay time (S204), the frequency of the generated calibration signal is outside the frequency range of the current map. If it is determined that the frequency is out of the range, the reception frequency axis of the filter delay time map is expanded and updated so as to include the frequency as an input frequency range that can be input (S206). If it is determined that the frequency is within the frequency range of the current map, the process proceeds to the next step (S208) without extending and updating the reception frequency axis.

Next, it is determined whether the detected filter delay time has reached a predetermined limit value (S208). If it is determined that the filter delay time has reached, it is determined that there is an abnormality in the propagation time measurement circuit, and an alarm for the abnormality is issued. (S209). If the limit value is not reached, the process proceeds to the next step (S210) without issuing an alarm.
After S210, as in the above-described embodiment, it is determined whether the calibration has been completed up to a predetermined or extended frequency range, and the processes of S203 to S209 are repeatedly executed until the calibration is completed. The signal application circuit 3n is switched so that the received signal is guided to the ultrasonic signal extraction filter 3k to prepare for the fluid measurement execution.

  In the present embodiment, the reception frequency axis of the filter delay time map is extended and updated with respect to reception frequencies outside the range. However, as described above, a three-dimensional map using the filter circuit temperature as a parameter or a predetermined value is used. When the temperature at the time of measurement is outside the temperature range that can be entered in the current map, the temperature axis of the map is expanded as in the case of the reception frequency. It is good also as a structure which updates or adds the two-dimensional map outside a range. Further, it goes without saying that the map may be expanded or added to both the frequency and the temperature.

1 is an overall configuration diagram of an ultrasonic fluid measuring apparatus according to an embodiment of the present invention. Time chart for explaining errors due to filter passage of the same device Similarly, a time chart to explain the problem The figure which shows the relationship between group delay time and phase characteristic of an ultrasonic signal extraction filter Example of delay time correction map of the same embodiment Configuration diagram of calibration execution circuit in the second embodiment The flowchart which shows an example of a calibration execution process same as the above Flow chart showing an example of map correction by executing calibration

Explanation of symbols

    DESCRIPTION OF SYMBOLS 1c ... Measuring tube, 2a, 2b ... Ultrasonic transducer, 3 ... Ultrasonic propagation time measuring circuit, 3a ... Transmission drive circuit, 3d ... Reception detection circuit, 3k ... Ultrasonic signal extraction filter circuit, 3m ... Calibration signal Generation circuit, 3n: Calibration signal application circuit (switch), 3k: Filter delay time measurement circuit, 4 ... Flow rate / concentration calculation circuit

Claims (10)

The ultrasonic signal is propagated in directions having propagation velocity components of different magnitudes with respect to the flow direction in the measured fluid, and the measured signal is based on a plurality of propagation times required to propagate a predetermined distance respectively. An ultrasonic fluid measurement method for measuring a fluid state quantity,
The disturbance signal is removed by passing the ultrasonic signal propagated through the predetermined distance through a filter,
Based on the ultrasonic signal from which the disturbance signal has been removed, each propagation time required for the ultrasonic signal to propagate a predetermined distance in the direction having the propagation velocity component of the different magnitude is measured,
Detecting the frequency of the ultrasonic signal input to the filter;
Calculate a delay time correction value when the ultrasonic signal passes through the filter based on the detected frequency,
Each propagation time of the measured ultrasonic signal is corrected by the delay time correction value,
An ultrasonic fluid measurement method, comprising: measuring a state quantity of the fluid to be measured based on the corrected propagation time.   The ultrasonic fluid measurement method according to claim 1, wherein the state quantity of the fluid to be measured is a flow rate or a concentration. An ultrasonic wave transmission / reception wave that is arranged so that it can be received after transmitting an ultrasonic signal and propagating it in a direction having a propagation velocity component of a magnitude different from the fluid flow direction in the fluid to be measured, and propagating each of them for a predetermined distance. And
A filter for removing a disturbance signal from the ultrasonic signal after propagation;
Based on the ultrasonic signal after passing through the filter, the ultrasonic signal is transmitted in a direction having a propagation velocity component having a magnitude different from the fluid flow direction in the fluid to be measured, and then propagated for a predetermined distance. Propagation time measuring means for measuring each propagation time until reception;
With
A frequency detection means for detecting the frequency of the ultrasonic signal received by the ultrasonic transducer;
A delay time correction value calculating means for calculating a delay time correction value when the ultrasonic signal passes through the filter based on the detected frequency;
Propagation time correction means for correcting each propagation time measured by the propagation time measurement means with a delay time correction value calculated by the delay time correction value calculation means;
Fluid state quantity measuring means for measuring a state quantity of the fluid to be measured based on the corrected propagation time;
An ultrasonic fluid measuring device comprising: A pair of the ultrasonic transducers are arranged so as to be acoustically opposed at a predetermined distance in the flow direction in the fluid to be measured,
The propagation time measuring means measures the propagation time until the ultrasonic signal transmitted from one of the pair of ultrasonic transducers propagates through the fluid and is received by the other ultrasonic transducer. The ultrasonic fluid measuring device according to claim 3, wherein the measurement is performed with respect to a forward flow direction and a reverse propagation direction with respect to a fluid flow direction.   The delay time correction value calculating means includes a map in which the detection value of the ultrasonic frequency or the detection value of the ultrasonic frequency and the data of the delay time correction value corresponding to the detection value of the filter temperature are set, The ultrasonic fluid measurement device according to claim 3 or 4, wherein a delay time correction value is searched from a map.   Generate a calibration signal in a predetermined frequency range to be used in the ultrasonic transducer, pass the filter, and calculate the delay time correction value data based on the time difference between the calibration signals before and after passing through the filter The ultrasonic fluid measurement apparatus according to claim 5, wherein the map data is updated with the data.   When an input data value exceeding the current input data range of the map is detected, the input data range of the map is extended by executing calibration in a state exceeding the input data range. The ultrasonic fluid measuring device according to claim 5 or 6.   8. The ultrasonic fluid measurement apparatus according to claim 6, wherein calibration is executed when a condition under which the fluid under measurement is in a steady state is detected.   9. The alarm according to any one of claims 6 to 8, wherein, when the delay time of the detected filter reaches a predetermined limit value as a result of execution of calibration, an alarm is given that an abnormality has occurred in detection of the propagation time. The ultrasonic fluid measuring device according to claim 1.   The ultrasonic fluid measurement apparatus according to claim 3, wherein the state quantity of the fluid to be measured is a flow rate or a concentration.

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