Patent Publication Number: US-2013238260-A1

Title: Ultrasonic measuring device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an ultrasonic measuring device that measures the flow speed and flow volume of a fluid by using ultrasonic waves. 
     Priority is claimed on Japanese Patent Application No. 2012-051498, filed Mar. 8, 2012, the content of which is incorporated herein by reference. 
     2. Description of the Related Art 
     All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains. 
     An ultrasonic measuring device is one conventionally known measuring device for measuring the flow speed and flow volume of a fluid flowing in piping. An advantage of this ultrasonic measuring device is that it can take measurements merely by attaching transducers for sending and receiving ultrasonic waves to the outer surface of the piping, without carrying out work such as making a hole in the piping. This ultrasonic measuring device typically uses transmission method (propagation time difference method) or reflection method (reflection correlation method). 
     An ultrasonic measuring device using transmission method sends and receives an ultrasonic signal diagonally through the fluid flowing in the piping, and measures the flow speed and the like of the fluid flowing in the piping by determining the difference between the propagation time when an ultrasonic signal was sent and received in the direction of the flow of the fluid, and the propagation time when an ultrasonic signal was sent and received in an opposite direction to the flow of the fluid. In contrast, an ultrasonic measuring device using reflection method sends a plurality of ultrasonic signals diagonally through the fluid flowing in the piping, receives a plurality of reflection signals from air-bubbles and small particles contained in the fluid, and measures the flow speed and the like from a correlation of these received signals. 
     Japanese Unexamined Patent Application, First Publication No. 2005-181268 discloses an ultrasonic measuring device that can measure using both transmission method and reflection method, the device switching between the two methods in accordance with a correlation value or the strength of a receive signal obtained by receiving an ultrasonic signal through the fluid flowing in the piping. Japanese Unexamined Patent Application, First Publication No. 2010-181326 discloses an ultrasonic measuring device that, when using transmission method to measure the flow volume, determines flow volume correction coefficients from average flow speeds measured using reflection method and transmission method, and calculates an accurate flow volume based on the average flow speed measured using transmission method and the flow volume correction coefficients. 
     While an ultrasonic measuring device using transmission method can perform measuring even if the fluid does not contain any air-bubbles, a very large volume of air-bubbles in the fluid will obstruct the ultrasonic signal and make measuring impossible. On the other hand, while an ultrasonic measuring device using reflection method can perform measuring even if there is a very large volume of air-bubbles in the fluid, when the fluid contains no air-bubbles at all, a reflection signal cannot be obtained from air-bubbles and measuring therefore becomes impossible. 
     Since the ultrasonic measuring device disclosed in Japanese Unexamined Patent Application, First Publication No. 2005-181268 can switch between measuring using transmission method and measuring using reflection method, if the measuring method is switched in accordance with the volume of the air-bubbles contained in the fluid, measuring could conceivably be performed irrespective of the volume of the air-bubbles contained in the fluid. It is difficult to achieve high precision when measuring is performed using only transmission method, or using only reflection method. For example, when measuring is performed using only reflection method, the measuring precision is adversely affected by factors such as the oscillation state of the ultrasonic waves, resonance with the piping, and reverberation near the wall of the piping. 
     Since the ultrasonic measuring device disclosed in Japanese Unexamined Patent Application, First Publication No. 2010-181326 calculates the flow volume based on the average flow speed measured using transmission method and flow volume correction coefficients determined from average flow speeds measured using reflection method and transmission method, it can achieve high measuring precision. However, the ultrasonic measuring device disclosed in Japanese Unexamined Patent Application, First Publication No. 2010-181326 can only perform measuring when the volume of air-bubbles contained in the fluid is sufficient to enable measuring by both transmission and reflection methods. 
     SUMMARY 
     An ultrasonic measuring device that measures a flow volume of a fluid by sending an ultrasonic signal to the fluid and receiving a transmission signal or a reflection signal of the ultrasonic signal obtained from the fluid, may include: a first computing unit configured to perform a calculation to a first receive signal obtained by receiving the transmission signal, and to determine a first flow volume indicating the flow volume of the fluid; a second computing unit configured to perform a correlation calculation of a second receive signal obtained by receiving the reflection signal, and to determine a second flow volume indicating the flow volume of the fluid; a storage unit configured to store a first correction coefficient, which is used in correcting the first flow volume, and a second correction coefficient, which is used in correcting the second flow volume; and a correcting unit configured to output one of the first flow volume, which is corrected by using the first correction coefficient stored in the storage unit, and the second flow volume, which is corrected by using the second correction coefficient stored in the storage unit, based on a volume of air-bubbles contained in the fluid. 
     The ultrasonic measuring device may further include: a determining unit configured to determine the volume of air-bubbles contained in the fluid by using a first correlation value, which is obtained by the first computing unit, and a second correlation value, which is obtained by the second computing unit. 
     The determining unit may include: a first determining unit configured to determine whether or not the first correlation value exceeds a first threshold that is set with consideration for the volume of air-bubbles contained in the fluid; and a second determining unit configured to determine whether or not the second correlation value exceeds a second threshold that is set with consideration for the volume of air-bubbles contained in the fluid. 
     If the first determining unit determines that the first correlation value exceeds the first threshold, then the correcting unit may output the first flow volume that has been corrected by using the first correction coefficient. If the first determining unit determines that the first correlation value does not exceed the first threshold and the second determining unit determines that the second correlation value exceeds the second threshold, then the correcting unit may output the second flow volume that has been corrected by using the second correction coefficient. 
     The ultrasonic measuring device may further include: a first calculating unit configured to calculate the first correction coefficient if the second determining unit determines that the second correlation value exceeds the second threshold; and a second calculating unit configured to calculate the second correction coefficient if the first determining unit determines that the first correlation value exceed the first threshold and the second determining unit determines that the second correlation value exceed the second threshold. 
     The first correction coefficient may indicate a ratio between the flow volume of the fluid determined from the second receive signal and a flow volume based on an average flow speed, and the second correction coefficient may indicate a ratio between the first flow volume corrected by using the first correction coefficient and the flow volume of the fluid determined from the second receive signal. 
     The ultrasonic measuring device may further include: a first transducer configured to send a first ultrasonic signal to the fluid and to receive a first reflection signal of the first ultrasonic signal from the fluid; and a second transducer configured to send a second ultrasonic signal to the fluid and to receive a second reflection signal of the second ultrasonic signal from the fluid. The second transducer may receive a first transmission signal of the first ultrasonic signal from the fluid, and the first transducer may receive a second transmission signal of the second ultrasonic signal from the fluid. 
     The first computing unit may include an average flow speed computing unit and a flow volume computing unit. The average flow speed computing unit may be configured to perform a correlation operation of a receive signal, which is obtained when the ultrasonic signal was sent and received in a direction of a flow of the fluid, and a receive signal, which is obtained when the ultrasonic signal was sent and received in an opposite direction to the flow of the fluid, and to determine an average speed of the fluid flowing in a piping by determining a time difference when a correlation value reaches its maximum. 
     The flow volume computing unit may determine the flow volume of the fluid by calculating V 1 ×πr 2 , where V 1  is the average speed of the fluid determined by the average flow speed computing unit and r is a cross-sectional area of the piping. 
     The second computing unit may include a flow volume computing unit and an average flow volume computing unit. The flow volume computing unit may determine a flow speed distribution of the fluid by performing a correlation calculation using a plurality of receive signals obtained when the ultrasonic signal was sent through the fluid at predetermined intervals of time, and use the flow speed distribution to determine the second flow volume that is the flow volume of the fluid flowing in a piping. The average flow volume computing unit may determine the flow speed distribution of the fluid by performing the correlation calculation using the plurality of receive signals obtained when the ultrasonic signal was sent through the fluid at predetermined intervals of time, and use an average speed obtained by averaging the flow speed distribution to determine the flow volume based on an average flow speed of the fluid flowing in the piping. 
     The flow volume computing unit and the average flow volume computing unit may divide the plurality of receive signals, which are obtained by sending the ultrasonic signal through the fluid, a plurality of times into a plurality of sections corresponding to their temporal positions, and perform a correlation process to each section. A time interval with a maximum correlation may be determined for every section, and the flow speed of the fluid in every section may be determined from each time interval, whereby the flow speed distribution of the fluid in a diameter direction of the piping is determined. 
     The first calculating unit may calculate the first correction coefficient Kr by performing a following calculation: 
         Kr=F 21 /F 21′  (1)
 
     where F 21  is the second flow volume calculated by the second computing unit and received from the second computing unit, and F 21 ′ is the flow volume based on an average flow speed of the fluid calculated by the second computing unit and received from the second computing unit. 
     The second calculating unit may calculate the second correction coefficient Cr by performing a following calculation: 
         Cr=F 12 /F 21  (2)
 
     where F 12  is the first flow volume corrected by the correcting unit and received from the correcting unit, and F 21  is the second flow volume calculated by the second computing unit and received from the second computing unit. 
     An ultrasonic measuring method that measures a flow volume of a fluid by sending an ultrasonic signal to the fluid and receiving a transmission signal or a reflection signal of the ultrasonic signal obtained from the fluid, may include: performing a calculation to a first receive signal obtained by receiving the transmission signal so as to determine a first correlation value and a first flow volume indicating the flow volume of the fluid; performing a correlation calculation of a second receive signal obtained by receiving the reflection signal so as to determine a second correlation value and a second flow volume indicating the flow volume of the fluid; storing a first correction coefficient, which is used in correcting the first flow volume, and a second correction coefficient, which is used in correcting the second flow volume; and outputting one of the first flow volume, which is corrected by using the first correction coefficient that has been stored, and the second flow volume, which is corrected by using the second correction coefficient that has been stored, based on a volume of air-bubbles or particles contained in the fluid. 
     The ultrasonic measuring method may further include: determining the volume of air-bubbles contained in the fluid by using the first correlation value and the second correlation value. 
     The ultrasonic measuring method may further include: determining whether or not the first correlation value exceeds a first threshold that is set with consideration for the volume of air-bubbles contained in the fluid; and determining whether or not the second correlation value exceeds a second threshold that is set with consideration for the volume of air-bubbles contained in the fluid. 
     The ultrasonic measuring method may further include: outputting the first flow volume that has been corrected by using the first correction coefficient if determined that the first correlation value exceeds the first threshold; and outputting the second flow volume that has been corrected by using the second correction coefficient if determined that the first correlation value does not exceed the first threshold and the second correlation value exceeds the second threshold. 
     The ultrasonic measuring method may further include: calculating the first correction coefficient if determined that the second correlation value exceeds the second threshold; and calculating the second correction coefficient if determined that the first correlation value exceed the first threshold and the second correlation value exceed the second threshold. 
     The first correction coefficient may indicate a ratio between the flow volume of the fluid determined from the second receive signal and a flow volume based on an average flow speed. The second correction coefficient may indicate a ratio between the first flow volume corrected by using the first correction coefficient and the flow volume of the fluid determined from the second receive signal. 
     The ultrasonic measuring method may further include: performing a correlation operation of a receive signal, which is obtained when the ultrasonic signal was sent and received in a direction of a flow of the fluid, and a receive signal, which is obtained when the ultrasonic signal was sent and received in an opposite direction to the flow of the fluid, so as to determine an average speed of the fluid flowing in a piping by determining a time difference when a correlation value reaches its maximum. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above features and advantages of the present invention will be more apparent from the following description of certain preferred embodiments taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a block diagram illustrating the constitution of primary parts of an ultrasonic measuring device in accordance with the first preferred embodiment of the present invention; 
         FIG. 2  is a block diagram illustrating the constitution of primary parts of a signal processing unit of an ultrasonic measuring device in accordance with the first preferred embodiment of the present invention; 
         FIG. 3  is a diagram illustrating one example of flow speed distribution determined using an ultrasonic measuring device in accordance with the first preferred embodiment of the present invention; 
         FIG. 4  is a diagram illustrating conditions for calculating a correction coefficient in the ultrasonic measuring device in accordance with the first preferred embodiment of the present invention; and 
         FIG. 5  is a diagram illustrating conditions for outputting a measurement signal in an ultrasonic measuring device in accordance with the first preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be now described herein with reference to illustrative preferred embodiments. Those skilled in the art will recognize that many alternative preferred embodiments can be accomplished using the teaching of the present invention and that the present invention is not limited to the preferred embodiments illustrated herein for explanatory purposes. 
     An ultrasonic measuring device in accordance with a first preferred embodiment of the invention will be described with reference to the drawings.  FIG. 1  is a block diagram illustrating the constitution of primary parts of an ultrasonic measuring device in accordance with the first preferred embodiment of the present invention. As shown in  FIG. 1 , an ultrasonic measuring device  1  in accordance with the first preferred embodiment of the present invention includes a control unit  10 , a drive signal generating circuit  11 , a send switch  12 , sending circuits  13   a  and  13   b , transducers  14   a  and  14   b , receiving circuits  15   a  and  15   b , a receive switch  16 , an A/D converter  17 , and a signal processing unit  18 , and uses ultrasonic signals to measure the flow speed and flow volume of a fluid X flowing in piping TB. 
     The ultrasonic measuring device  1  in accordance with the first preferred embodiment of the present invention can measure using transmission method (propagation time difference method) and using reflection method (reflection correlation method). When measuring with transmission method, the ultrasonic measuring device  1  sends and receives an ultrasonic signal diagonally through the fluid X flowing in the piping TB, and measures the flow volume and the like of the fluid X flowing in the piping TB by determining the difference between the propagation time when an ultrasonic signal was sent and received in the direction of the flow of the fluid X, and the propagation time when an ultrasonic signal was sent and received in an opposite direction to the flow of the fluid X. When measuring with reflection method, the ultrasonic measuring device  1  sends a plurality of ultrasonic signals diagonally through the fluid X flowing in the piping TB, receives a plurality of reflection signals from air-bubbles B contained in the fluid X, and measures the flow volume and the like of the fluid X flowing in the piping TB by executing a correlation process to the received signals. 
     The control unit  10  controls the overall operation of the ultrasonic measuring device  1 . For example, it outputs a trigger signal Tr to the drive signal generating circuit  11  and controls the sending of ultrasonic signals to the fluid X. Also, the control unit  10  outputs control signals C 1  and C 2  to the send switch  12  and the receive switch  16 , outputs a control signal C 3  to the signal processing unit  18 , and controls the switching between transmission method and reflection method described above. 
     Based on the trigger signal Tr output from the control unit  10 , the drive signal generating circuit  11  outputs a drive signal S 0  for generating an ultrasonic signal to be sent to the fluid X. The send switch  12  inputs the drive signal S 0  from the drive signal generating circuit  11 , and, based on the switch signal C 1  output from the control unit  10 , switches the output destination of the drive signal S 0  to one of the sending circuits  13   a  and  13   b.    
     The sending circuit  13   a  outputs the drive signal S 0  from the send switch  12  to the transducer  14   a , and makes it send an ultrasonic signal to the fluid X. Similarly, the sending circuit  13   b  outputs the drive signal S 0  from the send switch  12  to the transducer  14   b , and makes it send an ultrasonic signal to the fluid X. The transducers  14   a  and  14   b  are attached to the outer surface of the piping TB such that it is sandwiched between them when viewed in the direction of the flow of the fluid X (towards the right side of the page), and send and receive ultrasonic signals based on the drive signal S 0 . These transducers  14   a  and  14   b  can be attached to the piping TB without carrying out work such as making a hole in the piping TB, and, as shown in  FIG. 1 , the transducer  14   b  is attached downstream from the transducer  14   a  (downstream in the direction of the fluid X is flowing in). 
     Specifically, based on the drive signal S 0  output from the sending circuit  13   a , the transducer  14   a  sends an ultrasonic signal diagonally through the fluid X flowing in the piping TB (i.e. in the direction heading toward the transducer  14   b ), receives a transmission signal or a reflection signal of the ultrasonic signal obtained from the fluid X, and outputs a receive signal S 1 . The transmission signal is an ultrasonic signal that was sent from the transducer  14   b  and transmitted through the fluid X, while the reflection signal is an ultrasonic signal that was sent from the transducer  14   a  and reflected by air-bubbles B contained in the fluid X. 
     Based on the drive signal S 0  output from the sending circuit  13   b , the transducer  14   b  sends an ultrasonic signal diagonally through the fluid X flowing in the piping TB (i.e. in the direction heading toward the transducer  14   a ), receives a transmission signal or a reflection signal of the ultrasonic signal obtained from the fluid X, and outputs a receive signal S 2 . The transmission signal is an ultrasonic signal that was sent from the transducer  14   a  and transmitted through the fluid X, while the reflection signal is an ultrasonic signal that was sent from the transducer  14   b  and reflected by air-bubbles B contained in the fluid X. 
     The receiving circuit  15   a  amplifies the receive signal S 1  output from the transducer  14   a  with a predetermined amplification factor, and the receiving circuit  15   b  amplifies the receive signal S 2  output from the transducer  14   b  with a predetermined amplification factor. The receive switch  16  inputs the receive signals S 1  and S 2  amplified by the receiving circuits  15   a  and  15   b , and, based on the switch signal C 2  output from the control unit  10 , switches one of the receive signals S 1  and S 2  for output to the A/D converter  17 . The A/D converter  17  performs a sampling process to the receive signals S 1  and S 2  (analog signals) output from the receive switch  16 , and converts them to a receive signal S 3  (digital signal). 
     The signal processing unit  18  performs a process complying with the control signal C 3  from the control unit  10  to the receive signal S 3  output from the A/D converter  17 , measures the flow speed and the flow volume of the fluid X flowing in the piping TB, and outputs a measurement signal S 4  indicating the measurement result. In the first preferred embodiment, the signal processing unit  18  outputs a measurement signal S 4  indicating a measurement result of the flow volume of the fluid X flowing in the piping TB. 
       FIG. 2  is a block diagram illustrating the constitution of primary parts of a signal processing unit of an ultrasonic measuring device in accordance with the first preferred embodiment of the present invention. As shown in  FIG. 2 , the signal processing unit  18  includes a transmission method computing unit  21  (first computing unit), a reflection method computing unit  22  (second computing unit), an air-bubble volume determining unit  23  (determining unit), a correction coefficient computing unit  24 , a correction coefficient storage unit  25  (storage unit), and a correcting unit  26 . 
     The transmission method computing unit  21  may hereinafter be referred to as a first computing unit. The reflection method computing unit  22  may hereinafter be referred to as a second computing unit. The air-bubble volume determining unit  23  may hereinafter be referred to as a determining unit. The correction coefficient storage unit  25  may hereinafter be referred to as a storage unit. The control signal C 3  from the control unit  10  is not shown in  FIG. 2 . 
     The transmission method computing unit  21  includes an average flow speed computing unit  21   a  and a flow volume computing unit  21   b . The transmission method computing unit  21  performs a computation needed to perform measuring using the transmission method to a receive signal S 3  from the A/D converter  17 , and determines the average flow speed and the flow volume of the fluid X flowing in the piping TB. The average flow speed computing unit  21   a  performs a correlation operation of the receive signal S 3  obtained when the ultrasonic signal was sent and received in the direction of the flow of the fluid X, and the receive signal S 3  obtained when the ultrasonic signal was sent and received in an opposite direction to the flow of the fluid X, and determines the average speed of the fluid X flowing in the piping TB by determining the time difference when the correlation value reaches its maximum. 
     The flow volume computing unit  21   b  multiplies the average flow speed of the fluid X determined by the average flow speed computing unit  21   a  by the cross-sectional area of the piping TB, and thereby determines the flow volume of the fluid X flowing in the piping TB (first flow volume). Specifically, if V 1  is the average speed of the fluid X determined by the average flow speed computing unit  21   a  and  r  is the cross-sectional area of the piping TB, the flow volume computing unit  21   b  determines the flow volume of the fluid X by calculating V 1 ×πr 2 . When the flow volume of the fluid X is determined, the flow volume computing unit  21   b  outputs a flow volume signal S 11  indicating the flow volume of the fluid X. 
     The reflection method computing unit  22  includes a flow volume computing unit  22   a  and an average flow volume computing unit  22   b . The reflection method computing unit  22  performs a computation needed to perform measuring using the transmission method to a receive signal S 3  from the A/D converter  17 , and determines a flow volume of the fluid X flowing in the piping TB, and a flow volume based on an average flow speed. The flow volume computing unit  22   a  determines the flow speed distribution of the fluid X by performing a correlation calculation using a plurality of receive signals S 3  (signals obtained by receiving a reflection signal of the ultrasonic signal) obtained when an ultrasonic signal was sent through the fluid X at predetermined intervals of time (e.g. several hundred μsec), and uses the flow speed distribution to determine the flow volume of the fluid X flowing in the piping TB (second flow volume). While the average flow volume computing unit  22   b  determines the flow speed distribution of the fluid X in a similar manner to that of the flow volume computing unit  22   a , it uses an average speed obtained by averaging the flow speed distribution to determine the flow volume based on an average flow speed of the fluid X flowing in the piping TB. 
     Specifically, the flow volume computing unit  22   a  and the average flow volume computing unit  22   b  divide a plurality of receive signals S 3  obtained by sending an ultrasonic signal through the fluid X a plurality of times into a plurality of sections corresponding to their temporal positions, and perform a correlation process to each section. A time interval with the maximum correlation is determined for every section, and the flow speed of the fluid X in every section is determined from each time interval, whereby the flow speed distribution of the fluid X in the diameter direction of the piping TB is determined. 
       FIG. 3  is a diagram illustrating one example of flow speed distribution determined using an ultrasonic measuring device in accordance with the first preferred embodiment of the present invention. In  FIG. 3 , the horizontal axis is the distance (the distance in the diameter direction of the piping TB) from one of the transducers that is sending and receiving ultrasonic signals (e.g. transducer  14   a ), and vertical axis is the flow speed of the fluid X. The white circles in  FIG. 3  show the flow speed at each distance (measurement point) where a measurement was taken. As shown in  FIG. 3 , the distribution is such that the flow speed of the fluid X is higher in the center portion of the piping TB, and decreases toward the inner wall of the piping TB. 
     The flow volume computing unit  22   a  integrates the cross-sectional area of the piping TB (the cross-sectional area of the piping TB near each measurement point) over the flow speed distribution of the fluid X that was determined, and thereby determines the flow volume of the fluid X flowing in the piping TB. The average flow volume computing unit  22   b  determines an average flow speed (see  FIG. 3 ) by averaging the flow speed distribution of the fluid X that was determined, and integrates the cross-sectional area of the piping TB over this average flow speed, thereby determining a flow volume based on average flow speed of the fluid X flowing in the piping TB. Specifically, if V 2  if the average flow speed of the fluid X that was determined, and r is the radius of the piping TB, the average flow volume computing unit  22   b  determines the average flow speed of the fluid X by calculating V 2 ×πr 2 . When the flow volume of the fluid X and the flow volume based on average flow speed are determined, the flow volume computing unit  22   a  outputs a flow volume signal S 21  indicating the flow volume of the fluid X, and the average flow volume computing unit  22   b  outputs an average flow volume signal S 21 ′ indicating the flow volume based on average flow speed of the fluid X. 
     The air-bubble volume determining unit  23  includes a correlation value determining unit  23   a  (first determining unit) and a correlation value determining unit  23   b  (second determining unit), and determines the volume of the air-bubbles B contained in the fluid X flowing in the piping TB. The correlation value determining unit  23   a  may hereinafter be referred to as a first determining unit. The correlation value determining unit  23   b  may hereinafter be referred to as a second determining unit. The correlation value determining unit  23   a  determines whether the correlation value obtained by the average flow speed computing unit  21   a  of the transmission method computing unit  21  exceeds a threshold set with consideration for the volume of the air-bubbles B contained in the fluid X (first threshold), and outputs a determination signal J 1  indicating the determination result. 
     When measuring using transmission method, if the volume of the air-bubbles B contained in the fluid X becomes too large, the air-bubbles B obstruct the ultrasonic signal and measuring becomes impossible. Accordingly, the question of whether the volume of the air-bubbles B contained in the fluid X will allow measuring using transmission method is treated as a reference for setting the threshold. When the correlation value obtained by the average flow speed computing unit  21   a  has exceeded the threshold, measuring using transmission method is possible, and in that case the value of the determination signal J 1  is ‘1’. 
     The correlation value determining unit  23   b  determines whether the correlation value obtained by the flow volume computing unit  22   a  exceeds a threshold set with consideration for the volume of the air-bubbles B contained in the fluid X (second threshold), and outputs a determination signal J 2  indicating the determination result. While measuring using reflection method can be performed even if the fluid X contains a large volume of air-bubbles B, when the fluid X contains no air-bubbles B at all, no reflection signal can be obtained from air-bubbles B and measuring therefore becomes impossible. Accordingly, the question of whether the volume of the air-bubbles B contained in the fluid X will allow measuring using reflection method is treated as a reference for setting the threshold. When the correlation value obtained by the flow volume computing unit  22   a  exceeds the threshold, measuring using reflection method is possible, and in that case the value of the determination signal J 2  is ‘1’. 
     The correction coefficient computing unit  24  includes a correction coefficient calculating unit  24   a  (first calculating unit) and a flow volume comparing unit  24   b  (second calculating unit), and calculates correction coefficients for correcting the flow volume signal S 11  from the transmission method computing unit  21  and the flow volume signal S 21  from the reflection method computing unit  22 . The correction coefficient calculating unit  24   a  may hereinafter be referred to as a first calculating unit. The flow volume comparing unit  24   b  may hereinafter be referred to as a second calculating unit. The flow volume signals S 11  and S 21  are corrected to achieve highly precise measurements even under circumstances where, depending on the volume of the air-bubbles B contained in the fluid X, only measuring using transmission method is possible, or only measuring using reflection method is possible. 
     The correction coefficient calculating unit  24   a  calculates a correction coefficient Kr (first correction coefficient) based on the flow volume signal S 21  from the reflection method computing unit  22  and the average flow volume signal S 21 ′ from the transmission method computing unit  21 . This correction coefficient Kr is for correcting the flow volume signal S 11  output from the transmission method computing unit  21  when measuring is possible using both transmission method and reflection method, or when measuring is only possible using transmission method. Specifically, if F 21  is the flow volume of the fluid X indicated by the flow volume signal S 21 , and F 21 ′ is the flow volume based on average flow speed of the fluid X indicated by the average flow volume signal S 21 ′, the correction coefficient calculating unit  24   a  calculates the correction coefficient Kr by performing the following calculation: 
         Kr=F 21 /F 21′  (1)
 
     The flow volume comparing unit  24   b  compares the flow volume signal S 12  from the correcting unit  26  (the signal obtained when the correcting unit  26  corrects the flow volume signal S 11  from the transmission method computing unit  21 ) with the flow volume signal S 21  from the reflection method computing unit  22 , and calculates a correction coefficient Cr (second correction coefficient). This correction coefficient Cr is for correcting the flow volume signal S 21  output from the reflection method computing unit  22  when measuring can only be performed using reflection method. Specifically, if F 12  is the flow volume of the fluid X indicated by the flow volume signal S 12 , and F 21  is the flow volume of the fluid X indicated by the flow volume signal S 21 , the flow volume comparing unit  24   b  calculates the correction coefficient Cr by performing the following calculation: 
         Cr=F 12 /F 21  (2)
 
       FIG. 4  is a diagram illustrating conditions for calculating a correction coefficient in the ultrasonic measuring device in accordance with the first preferred embodiment of the present invention. As shown in  FIG. 4 , the volume of air-bubbles B contained in the fluid X is classified as ‘none to very small’, ‘small’, ‘large’, or ‘too large’, depending on the determination signals J 1  and J 2  output from the air-bubble volume determining unit  23 . When the volume of the air-bubbles B is ‘none to very small’, measuring can only be performed using transmission method. When the volume of the air-bubbles B is ‘small’, measuring can be performed using both transmission method and reflection method. When the volume of the air-bubbles B is ‘large’, measuring can only be performed using reflection method. When the volume of the air-bubbles B is ‘too large’, measuring cannot be performed using transmission or reflection method. 
     As shown in  FIG. 4 , the correction coefficient calculating unit  24   a  calculates the correction coefficient Kr when the determination signal J 2  output from the air-bubble volume determining unit  23  has a value of ‘1’. (when the volume of the air-bubbles B is ‘small’ or ‘large’). The flow volume comparing unit  24   b  calculates the correction coefficient Cr when determination signals J 1  and J 2  output from the air-bubble volume determining unit  23  each have a value of ‘1’ (when the volume of the air-bubbles B is ‘small’). 
     The correction coefficient storage unit  25  stores the correction coefficient Kr calculated by the correction coefficient calculating unit  24   a  of the correction coefficient computing unit  24  and the correction coefficient Cr calculated by the flow volume comparing unit  24   b . The correction coefficient storage unit  25  stores the correction coefficients Kr and Cr in combination with the average flow speed determined by the average flow speed computing unit  21   a  of the transmission method computing unit  21  and the flow volume based on average flow speed determined by the average flow volume computing unit  22   b  of the reflection method computing unit  22 . By storing them in correspondence in this manner, the correction coefficients Kr and Cr can be used over a wide range of flow speeds. 
     The correcting unit  26  includes flow volume correcting units  26   a  and  26   b , and a flow volume output unit  26   c . The correcting unit  26  uses correction coefficients Kr and Cr stored in the correction coefficient storage unit  25  to correct the flow volume signal S 11  from the transmission method computing unit  21  and the flow volume signal S 21  from the reflection method computing unit  22 , and outputs one of the corrected flow volume signals S 12  and S 22  in accordance with the volume of the air-bubbles B contained in the fluid X. The flow volume correcting unit  26   a  uses the correction coefficient Kr stored in the correction coefficient storage unit  25  to correct the flow volume signal S 11  from the transmission method computing unit  21 , and outputs the corrected flow volume signal S 12  to the flow volume output unit  26   c  and the flow volume comparing unit  24   b  of the correction coefficient computing unit  24 . The flow volume correcting unit  26   b  uses the correction coefficient Cr stored in the correction coefficient storage unit  25  to correct the flow volume signal S 21  from the reflection method computing unit  22 , and outputs the corrected flow volume signal S 22  to the flow volume output unit  26   c.    
     The flow volume output unit  26   c  inputs the flow volume signal S 12  from the flow volume correcting unit  26   a  and the flow volume signal S 22  from the flow volume correcting unit  26   b , and outputs one of them as a measurement signal S 4  in accordance with the determination signals J 1  and J 2  from the air-bubble volume determining unit  23 .  FIG. 5  is a diagram illustrating conditions for outputting a measurement signal in an ultrasonic measuring device in accordance with the first preferred embodiment of the present invention. 
     As shown in  FIG. 5 , when the determination signal J 1  has a value of ‘1’ (when the volume of the air-bubbles B is ‘little to very small’ or ‘small’), the flow volume output unit  26   c  outputs the flow volume signal S 12  as the measurement signal S 4 , and when the determination signal J 1  has a value of ‘0’ and the determination signal J 2  has a value of ‘1’ (when the volume of the air-bubbles B is ‘large’), it outputs the flow volume signal S 22  as the measurement signal S 4 . When the determination signals J 1  and J 2  both have values of ‘0’, the flow volume output unit  26   c  outputs an error signal. 
     Subsequently, the operation of the ultrasonic measuring device  1  in the constitution described above will be explained. The operation of the ultrasonic measuring device  1  (mainly, the operation of the signal processing unit  18 ) differs according to the volume of the air-bubbles B contained in the fluid X flowing in the piping TB. Therefore, an operation when the volume of the air-bubbles B is ‘small’, an operation when the volume of the air-bubbles B is ‘none to very small’, and an operation when the volume of the air-bubbles B is ‘large’ will be explained in that order. 
     Operation when the Volume of the Air-Bubbles B is ‘Small’ 
     When measuring of the fluid X flowing in the piping TB starts, measuring is performed using the transmission and reflection methods alternately, under the control of the control unit  10 . Incidentally, when the volume of the air-bubbles B is ‘none to very small’, and when it is ‘large’, measuring is performed using the transmission and reflection methods alternately, in the same manner as when the volume of the air-bubbles B is ‘small’. 
     When measuring using the transmission method starts, a process is performed to obtain a receive signal S 3  by sending and receiving an ultrasonic signal in the direction of the flow of the fluid X. Specifically, the control unit  10  outputs the switch signals C 1  and C 2 , the send switch  12  is switched such that the sending circuit  13   a  becomes the output destination of the drive signal S 0 , and the receive switch  16  is switched such that the receive signal S 2  from the receiving circuit  15   b  is output to the A/D converter  17 . Thereafter, the control unit  10  outputs a trigger signal Tr to the drive signal generating circuit  11 , which generates the drive signal S 0 . 
     The drive signal S 0  generated by the drive signal generating circuit  11  is input via the send switch  12  and the sending circuit  13   a  to the transducer  14   a , whereby the transducer  14   a  sends an ultrasonic signal to the fluid X. Of the ultrasonic signal that the transducer  14   a  sent to the fluid X, the ultrasonic signal that was transmitted through the fluid X and reached the transducer  14   b  (transmission signal) is received at the transducer  14   b , which outputs a receive signal S 2  in accordance with that transmission signal. The receive signal S 2  is amplified by the receiving circuit  15   b  and then input via the receive switch  16  to the A/D converter  17 , which converts it to a digital receive signal S 3 . This receive signal S 3  is input to the signal processing unit  18 , and stored in the average flow speed computing unit  21   a  of the transmission method computing unit  21 . 
     A process is then performed to obtain a receive signal S 3  when an ultrasonic signal is sent and received in an opposite direction to the flow of the fluid X. Specifically, the control unit  10  outputs the switch signals C 1  and C 2 , the send switch  12  is switched such that the sending circuit  13   b  becomes the output destination of the drive signal S 0 , and the receive switch  16  is switched such that the receive signal S 1  from the receiving circuit  15   a  is output to the A/D converter  17 . Thereafter, the control unit  10  outputs a trigger signal Tr to the drive signal generating circuit  11 , which generates the drive signal S 0 . 
     The drive signal S 0  generated by the drive signal generating circuit  11  is input via the send switch  12  and the sending circuit  13   b  to the transducer  14   b , whereby the transducer  14   b  sends an ultrasonic signal to the fluid X. Of the ultrasonic signal that the transducer  14   a  sends to the fluid X, the ultrasonic signal that is transmitted through the fluid X and reaches the transducer  14   a  (transmission signal) is received at the transducer  14   a , which outputs a receive signal S 1  in accordance with that transmission signal. The receive signal S 1  is amplified by the receiving circuit  15   a  and then input via the receive switch  16  to the A/D converter  17 , which converts it to a digital receive signal S 3 . This receive signal S 3  is input to the signal processing unit  18 , and stored in the average flow speed computing unit  21   a  of the transmission method computing unit  21 . 
     When the above operation ends, the average flow speed computing unit  21   a  of the transmission method computing unit  21  performs a correlation operation to the receive signal S 3  obtained when the ultrasonic signal was sent and received in the direction of the flow of the fluid X, and the receive signal S 3  obtained when the ultrasonic signal was sent and received in an opposite direction to the flow of the fluid X, determining the average flow speed of the fluid X flowing in the piping TB. The flow volume computing unit  21   b  then multiplies the average flow speed thus determined by the cross-sectional area of the piping TB and determines the flow volume of the fluid X flowing in the piping TB, and the flow volume computing unit  21   b  outputs the flow volume signal S 11 . 
     The correlation value obtained by the correlation operation of the average flow speed computing unit  21   a  is input to the correlation value determining unit  23  a of the air-bubble volume determining unit  23 , and it is determined whether this correlation value exceeds the threshold set with consideration for the volume of the air-bubbles B contained in the fluid X. Since the case being considered here is one where the volume of the air-bubbles B is ‘small’, the correlation value determining unit  23   a  determines that the correlation value exceeds the threshold, and outputs a determination signal J 1  with a value of ‘1’. (see  FIG. 4 ). 
     When measuring using the reflection method starts, a process is performed to obtain a receive signal S 3  by receiving a reflection signal when an ultrasonic signal is sent in the direction of the flow of the fluid X. Specifically, the control unit  10  outputs the switch signals C 1  and C 2 , the send switch  12  is switched such that the sending circuit  13   a  becomes the output destination of the drive signal S 0 , and the receive switch  16  is switched such that the receive signal S 1  from the receiving circuit  15   a  is output to the A/D converter  17 . Thereafter, the control unit  10  outputs a trigger signal Tr to the drive signal generating circuit  11 , which generates the drive signal S 0 . 
     The drive signal S 0  generated by the drive signal generating circuit  11  is input via the send switch  12  and the sending circuit  13   a  to the transducer  14   a , whereby the transducer  14   a  sends an ultrasonic signal to the fluid X. Of the ultrasonic signal that the transducer  14   a  sends to the fluid X, the ultrasonic signal that is reflected by the air-bubbles B contained in the fluid X (reflection signal) is received at the transducer  14   a , which outputs a receive signal S 1  in accordance with that reflection signal. The receive signal S 1  is amplified by the receiving circuit  15   a  and then input via the receive switch  16  to the A/D converter  17 , which converts it to a digital receive signal S 3 . This receive signal S 3  is input to the signal processing unit  18 , and stored in the flow volume computing unit  22   a  and the average flow volume computing unit  22   b  of the reflection method computing unit  22 . 
     A process is then performed to obtain a receive signal S 3  by receiving a reflection signal when an ultrasonic signal is sent in the opposite direction to the flow of the fluid X. Specifically, the control unit  10  outputs the switch signals C 1  and C 2 , the send switch  12  is switched such that the sending circuit  13   b  becomes the output destination of the drive signal S 0 , and the receive switch  16  is switched such that the receive signal S 2  from the receiving circuit  15   b  is output to the A/D converter  17 . 
     Thereafter, the control unit  10  outputs a trigger signal Tr to the drive signal generating circuit  11 , which generates the drive signal S 0 . 
     The drive signal S 0  generated by the drive signal generating circuit  11  is input via the send switch  12  and the sending circuit  13   b  to the transducer  14   b , whereby the transducer  14   b  sends an ultrasonic signal to the fluid X. Of the ultrasonic signal that the transducer  14   b  sends to the fluid X, the ultrasonic signal that is reflected by the air-bubbles B contained in the fluid X (reflection signal) is received at the transducer  14   b , which outputs a receive signal S 2  in accordance with that reflection signal. The receive signal S 2  is amplified in the receiving circuit  15   b  and then input via the receive switch  16  to the A/D converter  17 , which converts it to a digital receive signal S 3 . The receive signal S 3  is input to the signal processing unit  18 , and stored in the flow volume computing unit  22   a  and the average flow volume computing unit  22   b  of the reflection method computing unit  22 . 
     When the operation described above is performed a predetermined number of times, the flow volume computing unit  22   a  and the average flow volume computing unit  22   b  each divide the plurality of stored receive signals S 3  into a plurality of sections corresponding to their temporal positions, perform a correlation process to each divided section, and determine the flow speed distribution of the fluid X in the diameter direction of the piping TB. The flow volume computing unit  22   a  multiplies the flow speed distribution of the fluid X by the cross-sectional area of the piping TB (the cross-sectional area of the piping TB near each measurement point) and integrates the product, thereby determining the flow volume of the fluid X flowing in the piping TB, and the flow volume computing unit  22   a  then outputs the flow volume signal S 21 . The average flow volume computing unit  22   b  determines the average flow speed of the flow speed distribution of the fluid, multiplies the average flow speed by the cross-sectional area of the piping TB to determine a flow volume based on the average flow speed of the fluid X flowing in the piping TB, and outputs the average flow volume signal S 21 ′. 
     Incidentally, the correlation value obtained by the correlation operation of the flow volume computing unit  22   a  is input to the correlation value determining unit  23   b  of the air-bubble volume determining unit  23 , and it is determined whether it exceeds the threshold set with consideration for the volume of the air-bubbles B contained in the fluid X. Since the case being considered here is one where the volume of the air-bubbles B is ‘small’, the correlation value determining unit  23   b  determines that the correlation value exceeds the threshold and outputs a determination signal J 2  with a value of ‘1’ (see  FIG. 4 ). 
     The flow volume signal S 11  output from the transmission method computing unit  21  is input to the flow volume correcting unit  26   a  of the correcting unit  26 . The flow volume signal S 21  output from the reflection method computing unit  22  is input to the correction coefficient calculating unit  24   a  and the flow volume comparing unit  24   b  of the correction coefficient computing unit  24 , and also to the flow volume correcting unit  26   b  of the correcting unit  26 . The average flow volume signal S 21 ′ is input to the flow volume comparing unit  24   b  of the correction coefficient computing unit  24 . 
     When the flow volume signal S 21  and the average flow volume signal S 21 ′ from the reflection method computing unit  22  are input to the correction coefficient calculating unit  24   a , a correction coefficient Kr is calculated using the equation (1) and stored in the correction coefficient storage unit  25  (see  FIG. 4 ). The correction coefficient Kr is immediately read by the flow volume correcting unit  26   a , and used in correcting the flow volume signal S 11  from the transmission method computing unit  21 . A flow volume signal S 12  obtained by correcting the flow volume signal S 11  with the correction coefficient Kr is output to the flow volume output unit  26   c.    
     The flow volume signal S 12  from the flow volume correcting unit  26   a  is output to the flow volume comparing unit  24   b  of the correction coefficient computing unit  24 . When this flow volume signal S 12  and the flow volume signal S 21  output from the reflection method computing unit  22  are input to the flow volume comparing unit  24   b , a correction coefficient Cr is calculated using the equation (2) and stored in the correction coefficient storage unit  25  (see  FIG. 4 ). This correction coefficient Cr is read by the flow volume correcting unit  26   b  and used in correcting the flow volume signal S 21  from the reflection method computing unit  22 . A flow volume signal S 22  obtained by correcting the flow volume signal S 21  with the correction coefficient Cr is output to the flow volume output unit  26   c.    
     Thus the flow volume signal S 12  from the flow volume correcting unit  26   a  and the flow volume signal S 22  from the flow volume correcting unit  26   b  are input to the flow volume output unit  26   c . As shown in  FIG. 5 , when the volume of the air-bubbles B is ‘small’, determination signals J 1  and J 2  with values of ‘1’ are output from the air-bubble volume determining unit  23 , and the flow volume output unit  26   c  therefore outputs the flow volume signal S 12  from the flow volume correcting unit  26   a  (the signal obtained by using the correction coefficient Kr to correct the flow volume signal S 11  determined by the transmission method computing unit  21 ) as the measurement signal S 4 . 
     Operation when the Volume of Air-Bubbles B is ‘None to Very Small’ 
     As in the case when the volume of the air-bubbles B is ‘small’, measuring is performed using the transmission and reflection methods alternately, the transmission method computing unit  21  provided in the signal processing unit  18  outputs a flow volume signal S 11  to the flow volume correcting unit  26   a  of the correcting unit  26 , and the reflection method computing unit  22  outputs a flow volume signal S 21  to the flow volume correcting unit  26   b  of the correcting unit  26 . The flow volume signal S 21  from the reflection method computing unit  22  is also input to the correction coefficient calculating unit  24   a  and the flow volume comparing unit  24   b  of the correction coefficient computing unit  24 , and the average flow volume signal S 21 ′ is input to the flow volume comparing unit  24   b  of the correction coefficient computing unit  24 . 
     Since the case being considered here is one where the volume of the air-bubbles B is ‘none to very small’, the correlation value determining unit  23   a  of the air-bubble volume determining unit  23  determines that the correlation value exceeds the threshold, whereas the correlation value determining unit  23   b  determines that it does not exceed the threshold. As shown in  FIG. 4 , the air-bubble volume determining unit  23  therefore outputs a determination signal J 1  with a value of ‘1’ and a determination signal J 2  with a value of ‘0’. 
     When the determination signal J 1  has a value of ‘1’ and the determination signal J 2  has a value of ‘0’, the correction coefficient calculating unit  24   a  and the flow volume comparing unit  24   b  of the correction coefficient computing unit  24  do not calculate the correction coefficients Kr and Cr (see  FIG. 4 ). Consequently, the correction coefficient Kr stored in the correction coefficient storage unit  25  is read by the flow volume correcting unit  26   a  and used in correcting the flow volume signal S 11  from the transmission method computing unit  21 . 
     The flow volume signal S 12  obtained when the flow volume correcting unit  26   a  used the correction coefficient Kr to correct the flow volume signal S 11  is output to the flow volume output unit  26   c . As shown in  FIG. 5 , when the determination signal J 1  has a value of ‘1’ and the determination signal J 2  has a value of ‘0’, the flow volume signal S 12  from the flow volume correcting unit  26   a  (the signal obtained by using the correction coefficient Kr to correct the flow volume signal S 11  determined by the transmission method computing unit  21 ) is output as the measurement signal S 4 . 
     Operation when the Volume of the Air-Bubbles B is ‘Large’ 
     As in the case when the volume of the air-bubbles B is ‘small’, measuring is performed using the transmission and reflection methods alternately, the transmission method computing unit  21  provided in the signal processing unit  18  outputs a flow volume signal S 11  to the flow volume correcting unit  26   a  of the correcting unit  26 , and the reflection method computing unit  22  outputs a flow volume signal S 21  to the flow volume correcting unit  26   b  of the correcting unit  26 . The flow volume signal S 21  from the reflection method computing unit  22  is also input to the correction coefficient calculating unit  24   a  and the flow volume comparing unit  24   b  of the correction coefficient computing unit  24 , and the average flow volume signal S 21 ′ is input to the flow volume comparing unit  24   b  of the correction coefficient computing unit  24 . 
     Since the case being considered here is one where the volume of the air-bubbles B is ‘large’, the correlation value determining unit  23   a  of the air-bubble volume determining unit  23  determines that the correlation value does not exceed the threshold, whereas the correlation value determining unit  23   b  determines that it exceeds the threshold. As shown in  FIG. 4 , the air-bubble volume determining unit  23  therefore outputs a determination signal J 1  with a value of ‘0’ and a determination signal J 2  with a value of ‘1’. 
     When the determination signal J 1  has a value of ‘0’ and the determination signal J 2  has a value of ‘1’, the correction coefficient calculating unit  24   a  of the correction coefficient computing unit  24  calculates the correction coefficient Kr and stores it in the correction coefficient storage unit  25 . The flow volume comparing unit  24   b  does not calculate the correction coefficient Cr (see  FIG. 4 ). The correction coefficient Cr stored in the correction coefficient storage unit  25  is read by the flow volume correcting unit  26   a  and used in correcting the flow volume signal S 21  from the transmission method computing unit  21 . 
     The flow volume signal S 22  obtained when the flow volume correcting unit  26   b  has used the correction coefficient Cr to correct the flow volume signal S 21  is output to the flow volume output unit  26   c . As shown in  FIG. 5 , when the determination signal J 1  has a value of ‘0’ and the determination signal J 2  has a value of ‘1’, the flow volume signal S 22  from the flow volume correcting unit  26   b  the signal obtained by using the correction coefficient Cr to correct the flow volume signal S 21  determined by the reflection method computing unit  22 ) is then output as the measurement signal S 4 . 
     As described above, in the preferred embodiment, the flow volume of the fluid X is determined using each of the transmission method and the reflection method, and at least one of a flow volume obtained by using the correction coefficient Kr to correct the flow volume determined using the transmission method and a flow volume obtained by using the correction coefficient Cr to correct the flow volume determined using the reflection method is output in accordance with the volume of the air-bubbles B contained in the fluid X. This makes it possible to measure with high precision, irrespective of the volume of the air-bubbles B contained in the fluid X. For example, when measuring using only the reflection method, even if there are adverse factors such as the oscillation state of the ultrasonic waves, resonance with the piping, and reverberation near the wall of the piping, and such like, by using the correction coefficient Cr to correct flow volume, high-precision measuring can be achieved. 
     While the ultrasonic measuring device  1  in accordance with the preferred embodiment of the present invention has been described above, the invention is not limited to the preferred embodiment described above and can be freely modified within the scope of the invention. For example, to simplify the explanation of the preferred embodiment described above, the example is one where the volume of the air-bubbles B contained in the fluid X when the ultrasonic measuring device  1  starts operating is ‘small’. However, to achieve precise measuring even if the volume of the air-bubbles B when the ultrasonic measuring device  1  starts operating is ‘small’ or none to very small&#39;, predetermined fixed values can be used as initial values for the correction coefficients Kr and Cr and stored in the correction coefficient storage unit  25 . 
     In the preferred embodiment described above, the example is one where the correction coefficient Cr is calculated by comparing the flow volume determined by the transmission method computing unit  21  (more accurately, the flow volume corrected by the flow volume correcting unit  26   a  of the correcting unit  26 ) with the flow volume determined by the reflection method computing unit  22 . However, the correction coefficient Cr can also be determined by comparing the average flow speed determined by the transmission method computing unit  21  with the average flow speed determined by the reflection method computing unit  22 . 
     In the preferred embodiment described above, the example is one where the air-bubble volume determining unit  23  determines the volume of the air-bubbles using a correlation value determined by the transmission method computing unit  21  and a correlation value determined by the reflection method computing unit  22 . However, instead of using correlation values, the air-bubble volume determining unit  23  can determined the volume of the air-bubbles based on the amplitude of the receive signal S 3 . 
     The present invention provides an ultrasonic measuring device that can perform highly precise measuring, irrespective of the volume of air-bubbles contained in the fluid. 
     According to the invention, the ultrasonic measuring device determines a first flow volume indicating the flow volume of a fluid from a first receive signal obtained by receiving a transmission signal, determines a second flow volume indicating the flow volume of the fluid from a second receive signal obtained by receiving a reflection signal, and, in accordance with the volume of the air-bubbles contained in the fluid, outputs one of the first flow volume, corrected using a first correction coefficient stored in a storage unit, and the second flow volume, corrected using a second correction coefficient. 
     As used herein, the following directional terms “forward, rearward, above, downward, right, left, vertical, horizontal, below, transverse, row and column” as well as any other similar directional terms refer to those directions of an apparatus equipped with the present invention. Accordingly, these terms, as utilized to describe the present invention should be interpreted relative to an apparatus equipped with the present invention. 
     The term “configured” is used to describe a component, unit or part of a device includes hardware and/or software that is constructed and/or programmed to carry out the desired function. 
     Moreover, terms that are expressed as “means-plus function” in the claims should include any structure that can be utilized to carry out the function of that part of the present invention. 
     The term “unit” is used to describe a component, unit or part of a hardware and/or software that is constructed and/or programmed to carry out the desired function. Typical examples of the hardware may include, but are not limited to, a device and a circuit. 
     While preferred embodiments of the present invention have been described and illustrated above, it should be understood that these are examples of the present invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of the present invention. Accordingly, the present invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the claims.