JP4572546B2 - Fluid flow measuring device - Google Patents

Description

  The present invention relates to a fluid flow measuring device that measures the flow of a fluid such as gas or water using ultrasonic waves.

  A conventional fluid flow measuring apparatus of this type is generally as shown in FIG. 10 (see, for example, Patent Document 1). This apparatus includes a first ultrasonic transducer 32 and a second ultrasonic transducer 33 installed in a flow path 31 through which fluid flows, and switching means for switching between transmission and reception of the first ultrasonic transducer 32 and the second ultrasonic transducer 33. 34, transmission means 35 for driving the first ultrasonic transducer 32 and the second ultrasonic transducer 33, and a signal received by the ultrasonic transducer on the reception side and passed through the switching means 34 are amplified to a predetermined amplitude. The amplifying means 36, the reference comparing means 37 for comparing the voltage of the received signal amplified by the amplifying means 36 with the reference voltage, and the reference comparing means 37, as shown in FIG. The determination means 38 that outputs the output signal D to the repetition means 39 at the first zero cross point a of the subsequent amplified signal, the signal from the determination means 38 is counted and counted a preset number of times and from the determination means 38 A repetition means 39 for outputting a signal to the control means 42; a timing means 40 for counting the time set by the repetition means 39; and a flow rate calculation for calculating the flow rate according to the time counted by the timing means 40. The control means 42 which controls the operation | movement of the transmission means 35 in response to the means 41, the flow output calculated from the flow rate calculation means 41, the signal from the repetition means 39, the determination means 38, the repetition means 39, the time measuring means 40, the flow rate calculation It comprises means 41 and control means 42.

  In this apparatus, the transmission means 35 is operated by the control means 42 and the ultrasonic signal transmitted from the ultrasonic vibrator 32 propagates in the flow and is received by the second ultrasonic vibrator 33, and is amplified by the amplification means 36. The signal is processed by the reference comparison unit 37 and the determination unit 38, and is input to the control unit 42 through the repetition unit 39. This operation is repeated n times set in advance, and the time between them is measured by the time measuring means 40. Then, the first ultrasonic transducer 32 and the second ultrasonic transducer 33 are switched by the switching means 34, and the same operation is performed. From the upstream to the downstream of the fluid to be measured (this direction is a positive flow) and the downstream Then, the propagation time of each upstream (in this direction as a reverse flow) was measured, the flow velocity of the fluid to be measured was obtained, and the flow rate Q was obtained from Equation 1.

  Here, the effective distance in the flow direction between the ultrasonic transducers is L, the measurement time for n times from upstream to downstream is t1, the measurement time for n times from downstream to upstream is t2, and the flow velocity of the fluid to be measured is v The cross-sectional area of the flow path is S, the sensor angle is φ, and the flow rate is Q.

Q = S · v = S · L / 2 · cos φ ((n / t1) − (n / t2)) (Expression 1)
Actually, the flow rate is calculated by further multiplying Equation 1 by a coefficient corresponding to the flow rate.

  The gain of the amplifying unit 36 is adjusted so that the signal received by the ultrasonic transducer on the receiving side has a constant amplitude, and is adjusted so that the peak voltage value of the received signal falls within a predetermined voltage range. The This is the same as the number of times that the peak voltage value of the received signal falls below the lower limit of the predetermined voltage range as indicated by the received signal b shown by the dotted line in FIG. As indicated by the received signal c indicated by the dotted line in FIG. 12, the number of times that exceeds the upper limit of the predetermined voltage range is counted, and the gain at the next flow rate measurement is adjusted according to the magnitude. For example, if the number of times below the lower limit is large, the gain is increased so that it falls within the upper and lower limits of the voltage range as in the received signal a shown by the solid line in FIG.

Further, the reference voltage of the reference comparing means 37 for comparing with the voltage of the received signal amplified by the amplifying means 36 determines the position of the zero cross point detected by the determining means 38. Taking FIG. 11 as an example, the third wave of the received signal is determined. The zero-cross point a of the received signal is set to the midpoint voltage of the peak voltage of the two waves and three waves of the received signal so that the determination means 38 detects the zero cross point a. By doing so, even if the peak voltage of the two waves of the received signal rises for some reason or the peak voltage of the three waves decreases, a margin is provided for both, and the zero crossing point a of the third wave is stably obtained by the determination means 38. Can be detected.
JP 2003-106882 A

  However, the above conventional fluid flow measuring device uses a fixed resistor and a semi-fixed resistor as a voltage setting method of the reference voltage to be compared with the received signal amplified to a predetermined amplitude level in the reference comparing means 37, and resistance dividing voltage. It has been used a lot in setting. In this method, since the semi-fixed resistor is manually adjusted while monitoring the reference voltage so as to generate a predetermined voltage, it takes time to set the reference voltage, and there is a possibility of occurrence of an adjustment error. .

  Further, the adjustment position may change due to secular change after adjustment, mechanical vibration, thermal shock, or the like. When the sensitivity changes due to temperature change, flow rate change, aging change of the ultrasonic vibrator, etc., there is a problem that the reference voltage needs to be set again. Such a fluid flow measuring device is required to have low power consumption because it uses a battery as a power source.

  The present invention solves the above-described conventional problems, and provides a fluid flow measuring device that quickly and accurately sets a reference voltage, always maintains an optimum reference voltage, and has low power consumption. Objective.

  In order to solve the above-mentioned conventional problems, the fluid flow measuring device according to the present invention provides a peak of each wave of the received wave due to the time difference measured by the time difference measuring means when the reference voltage of the reference setting means is changed from the minimum to the maximum. The voltage position is recognized, and the reference voltage is set between specific waves of the received wave based on the peak voltage ratio.

  As a result, the reference voltage set by the reference setting means is set between the peak voltages of specific waves of the received wave based on the received wave of the ultrasonic signal, and the reference voltage that optimizes the time difference measured by the time difference measuring means is manually adjusted. Therefore, the fluid flow measuring device can be configured so that the setting operation can be performed quickly and accurately, and continuously maintained at the optimum reference voltage.

  The fluid flow measuring device of the present invention changes the reference voltage from the minimum to the maximum, and changes the reference voltage from the minimum to the maximum among a plurality of inflection points where the time difference measured by the time difference measuring means changes greatly. The peak voltage of each wave of the received wave is recognized from a plurality of inflection points where the time difference measured by the time difference measuring means at that time changes greatly, and between the peak voltage of specific two waves or three waves from the ratio of the peak voltage By using the reference setting means that automatically sets the reference voltage at the midpoint voltage or an arbitrary point, it is the most stable against the voltage fluctuation of the received signal among the received waves of ultrasonic waves. Can be set to a voltage that can detect the arrival time of the sound wave signal, and the time difference measured by the time difference measuring means during flow measurement deviates from the predetermined time difference determined based on the time difference when the reference voltage is set The reference voltage is reset Divide.

  Accordingly, there is an effect that the reference voltage can be quickly set without human intervention, and the fluid flow measuring device can be configured so that the reference voltage can be maintained at an optimum voltage during flow rate measurement after the setting.

  The first invention includes a first vibrator and a second vibrator that are provided in the fluid pipe line and transmit and receive an ultrasonic signal, a transmission unit that drives the vibrator, a switching unit that switches transmission and reception of the vibrator, Amplifying means for amplifying the received signal of the vibrator, time measuring means for measuring the accumulated time of transmission / reception of the ultrasonic signal, and flow rate calculating means for calculating a flow velocity and / or a flow rate based on the time measured by the time measuring means, Ultrasonic wave from the reference comparison means for comparing the voltage of the reception signal of the reception-side vibrator of the first vibrator and the second vibrator with the reference voltage, and the outputs of the reference comparison means and the amplification means Fluid flow comprising determination means for determining the arrival time of a signal, time difference timing means for measuring a time difference between outputs of the reference comparison means and the determination means, and reference setting means for setting a reference voltage of the reference comparison means Measuring equipment , The peak voltage position of each wave of the received wave is recognized by the time difference counted by the time difference measuring means when the reference voltage is changed from the minimum to the maximum, and the specific wave of the received wave is determined based on this peak voltage ratio. By using a fluid flow measuring device as a reference setting means for setting a reference voltage between them, the reference voltage can be set quickly and accurately and the most stable reference voltage against fluctuations in the received ultrasonic signal It can be set as the fluid flow measuring device which can be set up.

  According to a second aspect of the present invention, there is provided time difference storage means for storing the time difference measured by the time difference measurement means when adjusting the fluid flow measuring device main body, and the reference setting means uses the time difference stored in the time difference storage means as a reference after measuring the flow rate. By using the fluid flow measuring device according to item 1, which is the target value of the time difference used when setting the voltage, the reference voltage is automatically corrected and the fluid flow which can always be maintained at the optimum reference voltage. It can be set as a measuring device.

  According to a third aspect of the invention, the reference setting means limits the setting range of the reference voltage between the peak voltages of the specific waves when the reference voltage is set between the specific waves of the received wave when adjusting the fluid flow measuring device body. By adopting the fluid flow measuring device according to Item 2, it is optimal to reset the reference voltage by detecting that the magnitude relationship with the reference voltage has broken due to fluctuations in the received signal of the ultrasonic wave during flow rate measurement. It is possible to provide a fluid flow measuring device that can maintain a constant reference voltage.

  According to a fourth aspect of the present invention, the reference setting means sets the reference voltage in an interval of a predetermined ratio between the peak voltages of specific waves when the reference voltage is set between specific waves of the received wave when adjusting the fluid flow measuring device body. By using the fluid flow measuring device according to claim 2 that limits the range, it is possible to provide a fluid flow measuring device that can always keep the optimum reference voltage more quickly.

  According to a fifth aspect of the present invention, the reference setting means does not perform the reference voltage adjustment operation until the flow rate calculated by the flow rate calculation means exceeds a predetermined flow rate. Therefore, it is possible to provide a fluid flow measuring device that can always maintain an optimum reference voltage.

  According to a sixth aspect of the present invention, when the flow rate calculated by the flow rate calculation unit returns from the state where the flow rate calculation unit is equal to or higher than the flow rate to zero, the reference setting unit receives the received wave if the flow rate is different from the reference voltage position at the previous flow rate zero. 6. The direction of ultrasonic signal transmission / reception by the influence of the flow rate of the fluid flowing through the flow path by reinitializing the reference voltage set during the specific wave Separately, the reference voltage is reset by detecting that the magnitude relationship between the received ultrasonic signal and the reference voltage has collapsed and changing the amplification level of the amplification means according to the transmission / reception direction of the ultrasonic signal. The fluid flow measuring device can keep the reference voltage of the means optimal.

  In the seventh invention, when the flow rate calculated by the flow rate calculation unit returns from the state where the flow rate calculation unit is equal to or higher than the predetermined flow rate to zero, the reference setting unit is within a predetermined value compared with the reference voltage position at the previous flow rate zero. 8. The fluid flow measuring device according to claim 7, wherein the reference voltage adjustment operation is not performed until the flow rate again exceeds a predetermined flow rate, so that the ultrasonic wave is transmitted and received in the direction of ultrasonic signal transmission / reception due to the influence of the flow rate of the fluid flowing through the flow path. When the magnitude relationship between the received signal and the reference voltage is broken, the reference voltage of the reference comparison means is set for each direction of ultrasonic signal transmission / reception, so that the reference voltage of the reference comparison means can be kept optimal. It can be a flow measuring device.

  According to an eighth aspect of the present invention, in the reference setting means, the reference voltage adjustment operation is performed when the flow rate calculated by the flow rate calculation means moves in a flow rate range among a plurality of preset flow rate ranges. By using a fluid flow measurement device, it is possible to reliably determine the inflection point of the time difference measured by the time difference measuring means, and use the voltage at the midpoint of the inflection point or any point as the reference voltage. Thus, a fluid flow measuring device capable of maintaining the reference voltage of the reference comparison means optimally can be obtained.

  According to a ninth aspect of the present invention, the reference setting means is the fluid flow measuring device according to the first to eighth aspects of the invention, wherein the reference voltage is changed after adjusting the amplification degree of the amplifying means, whereby the time difference inflection measured by the time difference measuring means. A fluid flow measuring device that can reliably determine the point and can maintain the reference voltage of the reference comparison means optimally by using the voltage at the middle point of the inflection point or an arbitrary point as the reference voltage; I can do it.

  A tenth invention is a program for causing a computer to function as all or part of the means of the fluid flow measuring device according to any one of the first to ninth inventions. Since it is a program, a part or all of the flowmeter side device of the present invention can be easily realized by using a microcomputer or the like, and changes in characteristics or operations such as changes in ultrasonic transducers or changes over time can be realized. The setting conditions and constants can be changed flexibly. Further, the program can be easily distributed by recording it on a recording medium or distributing the program using a communication line.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows a block diagram of a fluid flow measuring apparatus according to Embodiment 1 of the present invention. 2 and 5 are operation explanatory views of the fluid flow measuring apparatus of the first embodiment, and FIGS. 3 and 4 are the flowcharts.

  In FIG. 1, a first ultrasonic transducer 2 (first transducer) that transmits ultrasonic waves in the middle of a flow path 1 and a second ultrasonic transducer 3 (second transducer) that receives ultrasonic waves are in the flow direction. Arranged at an angle φ. 5 is a transmission means to the first ultrasonic transducer 2, 4 is a switching means for switching between transmission and reception of the first ultrasonic transducer 2 and the second ultrasonic transducer 3, and 6 is an ultrasonic transducer on the receiving side. Amplifying means 7 amplifies the received signal with a gain according to an instruction from the control means 12, and 7 is a reference comparing means for comparing the signal amplified by the amplifying means 6 with a reference voltage and outputting a signal.

  8 is a judging means for judging the arrival time of the ultrasonic wave from the output of the reference comparing means 7 and the signal amplified by the amplifying means 6, and 9 is a control means 12 which counts the signal of the judging means 8 and counts a preset number of times. It is a repeating means for outputting a repeating signal. Reference numeral 10 denotes a time counting means for counting the time counted in advance by the repeat means 9, and 11 detects the flow velocity of the fluid according to the time measured by the time measuring means 10, and further the size and flow of the pipe line. It is a flow rate calculation unit (calculation unit) that calculates the flow rate in consideration of the state.

  A control unit 12 receives signals from the flow rate calculation unit 11 and the repetition unit 9 and controls operations of the transmission unit 5 and the amplification unit 6. 13 is a time difference timing means for measuring the time difference between the output of the reference comparison means 7 and the output of the determination means 8, and 14 is for setting the reference voltage of the reference comparison means 7 and storing the peak voltage values of 2 and 3 waves. Reference setting means 15 is a time difference storage means for storing the time difference measured by the time difference measuring means 13 after the reference setting means 14 sets the reference voltage.

  The operation and action of the fluid flow measuring apparatus configured as described above will be described below.

  First, the control means 12 starts operation in the following manner in a mode dedicated to the manufacturing process during the manufacturing process by an input for mode switching (not shown). After the power is turned on, the control means 12 sets a temporary reference voltage for gain adjustment (step 1 in FIG. 3). For example, as shown in FIG. 2, the gain adjustment is performed by adjusting the gain so that the peak voltage value of five waves, which is the maximum amplitude of the received wave, becomes a predetermined voltage value, and the reference voltage at this time is one wave. Any value can be used as long as it is higher than the peak voltage and lower than the peak voltage of the five waves. The reference voltage is fixed during gain adjustment. This is to prevent the reference voltage from becoming higher than the peak voltage of five waves by changing the reference voltage, or from being lower than the peak voltage of one wave, so that the reference comparison means 7 and the determination means 8 do not operate correctly.

  Since the gain adjustment of the fluid flow measuring device is the same as that of the conventional example, the description thereof is omitted in the present embodiment.

First, after adjusting the gain so that the signal received by the second ultrasonic transducer 3 on the receiving side has a constant amplitude (step 2), the reference setting unit 14 sets the reference voltage to the minimum voltage in the setting range ( Step 3).

  After setting the lowest reference voltage, the control means 12 sets the number of repetitions of the repetition means 9 to 1 and operates the transmission means 5 to transmit an ultrasonic signal from the first ultrasonic transducer 2 (step 4). .

  The ultrasonic signal transmitted from the first ultrasonic transducer 2 propagates through the flow path 1, is received by the second ultrasonic transducer 3, is amplified by the amplification means 6, It is output to the determination means 8. FIG. 2 shows the state of the received signal after amplification. That is, as shown in FIG. 2, the reference comparing means 7 compares the output (received signal A) of the amplifying means 6 with the reference voltage (step 5 in FIG. 3), and the time difference when the magnitude relationship is inverted (timing c). An output signal C is output to the time measuring means 13 and the determination means 8.

  The time difference timing means 13 starts timing when the output signal C from the reference comparison means 7 is input (step 6). In the determination means 8, the sign of the output of the amplifying means 6 after the timing c is changed from positive to negative. The zero cross point a is determined as an ultrasonic arrival point (step 7), and the output signal D is output to the repetition means 9 and the time difference timing means 13. When receiving the output signal D from the determination means 8, the time difference timing means 13 ends the time measurement (step 8) and outputs the time difference Td measured to the reference setting means 14. The reference setting means 14 increases the reference voltage by one control unit (for example, 2 mV) in the reference voltage variable range (step 9). Since the number of repetitions set in the repetition unit 9 is one, the control unit 12 inputs a signal indicating that the repetition operation has been completed from the repetition unit 9, operates the transmission unit 5 again, and the first ultrasonic vibration An ultrasonic signal is transmitted from the child 2. Until the reference setting unit 14 sets the reference voltage to the maximum voltage in the reference voltage setting range, the above operation is repeated.

When the reference setting unit 14 finishes setting up to the maximum reference voltage, the reference setting unit 14 greatly changes the time difference counted by the time difference counting unit 13 when the reference voltage is changed from the minimum voltage to the maximum voltage in the setting range. (For example, is it changed 1.3 times or more compared to the previous time difference?) There are a plurality of inflection points.

This inflection point will be described with reference to FIGS. FIG. 5 is a diagram showing the time difference measured by the time difference measuring means 13 when the reference setting means 14 changes the reference voltage from the minimum voltage to the maximum voltage in the setting range . As shown in FIG. 2, the time difference measured by the time difference measuring means 13 is the time difference between the outputs of the reference comparing means 13 and the judging means 8, so that the peak of each wave (1 wave, 2 waves, 3 waves ...) of the received signal is obtained. When there is a reference voltage in the vicinity of the voltage (in FIG. 6, p1, p2, p3,...), The time difference is minimum (p1, p2, p3,... Corresponding to p1, p2, p3,. The value is about 1/4 of the period of the ultrasonic wave (500 ns when the drive frequency is 500 KHz).

  When the reference voltage is increased from that point and exceeds the peak voltage of each wave, the time difference measured by the time difference measuring means 13 suddenly increases, and as shown in FIG. 5, the inflection points of the time difference (Tp1, Tp2 having the minimum time difference). , Tp3 ...). For example, when the reference voltage is near the peak p2 of two waves (but does not exceed p2) and exceeds the peak voltage p2 of two waves, the inflection point is Tp2. This means that the reference voltage that becomes the inflection point of the time difference becomes a voltage near the peak voltage of each wave of the received signal.

  It has been experimentally confirmed that the ratio of these peak voltages is almost constant depending on the flow path and the sensor. For example, as shown in FIG. 6, the ratio of the peak voltage p1 of one wave to the peak voltage p2 of two waves p2 / p1≈2.5, the ratio of the peak voltage p2 of two waves to the peak voltage p3 of three waves p3 / p2≈1. .8, and the ratio of the peak voltage p3 of 3 waves to the peak voltage p4 of 4 waves, p4 / p3≈1.3.

  Thus, since the ratio of the peak voltage of each wave shows a constant value, it is possible to recognize each wave of the received wave. In other words, the peak voltage at which the ratio of a certain peak voltage to the previous peak voltage (one before the lower reference voltage) is about 2.5 times is a peak voltage of two waves, about 1.8 times. Is the peak voltage of three waves. The reference setting unit 14 confirms the peak voltage ratio as described above, recognizes the peak voltage of a specific wave (2 waves and 3 waves) of the received wave based on the peak voltage ratio, and determines the specific wave (2 waves, A reference voltage is set to Vref at the midpoint of the peak voltage of (three waves) (step 11 in FIG. 3).

  Then, the time difference storage means 15 stores the time difference measured by the time difference timing means 13 after setting the reference voltage to the midpoint Vref of the peak voltage of this specific wave (2 waves, 3 waves), and the peak of the two waves The reference setting means stores the voltage and the peak voltage of three waves (reference voltage setting range) (step 12), and the mode dedicated to the manufacturing process is terminated.

  By storing the peak voltage of two waves and the peak voltage of three waves, it is possible to detect a point for detecting the arrival time of the ultrasonic signal during the manufacturing process (for example, the three-wave negative zero-cross point a in FIG. 2). The settable range of the reference voltage is stored.

  The intent of setting the reference voltage between 2 and 3 waves is to set each reference signal within the reference voltage range (the peak voltage range of 2 waves and 3 waves in FIG. 6) with the widest peak voltage. For example, in FIG. 5, if the reference voltage is set to Vref at the midpoint of the peak voltage of 2 waves and 3 waves in FIG. 5, the peak voltage of 2 waves and 3 waves is set. This is because a large margin can be taken between the reference voltage and the determination means 8 can detect the arrival time of the ultrasonic reception signal most stably with respect to the voltage fluctuation of the reception signal.

  After setting the reference voltage in the manufacturing process, when the power is turned on after the control means 12 is switched to the normal mode by an input for mode switching (not shown) at the installation site of the fluid flow measuring device, the following operation is performed. To start. After adjusting the gain so that the signal first received by the ultrasonic transducer on the receiving side has a constant amplitude (step 21 in FIG. 4), the control means 12 sets the repeat means 9 to be the repeat count once and sets the reference voltage. Start the confirmation operation. The operation of the reference setting unit 14 after starting the operation will be described with reference to FIG. When the operation is started, the control unit 12 operates the transmission unit 5 to transmit an ultrasonic signal from the first ultrasonic transducer 2 (step 22), and is received by the second ultrasonic transducer 3 amplified by the amplification unit 6. The ultrasonic signal is output to the reference comparison means 7 and the determination means 8, and the reference comparison means 7 compares the received signal with the reference voltage (step 23), and the time difference counting means 13 measures the time from when the magnitude relationship is reversed. Until the first negative zero cross point at which the sign of the output of the amplification means 6 changes from positive to negative is detected by the determination means 8 (steps 25 and 26).

  The time difference measured by the time difference timing means 13 is compared with the time difference stored in the time difference storage means 15 (step 27), and if it is equal to or greater than a predetermined value, the reference voltage is set again (step 28). If it is within a predetermined value (for example, ± 20%), the reference voltage is not changed, and the flow proceeds to flow velocity measurement and flow rate calculation processing. That is, if there is no change in conditions such as the characteristics of the fluid to be measured and the component parts when stored in the time difference storage means 15 at the time of manufacture, there is no change in the relationship between the gain-adjusted received wave and the reference voltage, and the time difference storage means The time difference stored in 15 is the same as the time difference measured by the time difference measuring means 13 in step 26. However, if the two time differences differ by a predetermined value or more for some reason, the reference voltage is set again. FIG. 7 shows the flow rate measurement process.

  The control unit 12 sets a regular number of repetitions (for example, 256 times) in the repetition unit 9 and starts measuring the flow rate. When the flow rate measurement is started, the control unit 12 operates the transmission unit 5 to transmit an ultrasonic signal from the first ultrasonic transducer 2 (step 32 in FIG. 7), and the second ultrasonic transducer amplified by the amplification unit 6. 3 is output to the reference comparison means 7 and the determination means 8, and the reference comparison means 7 compares the received signal with the reference voltage (step 33), and measures the time difference from the time when the magnitude relationship is inverted. Time measurement is started by the means 13 (step 34), and the time difference is measured until the first negative zero cross point at which the sign of the output of the amplification means 6 changes from positive to negative by the determination means 8 (steps 35 and 36). . After the zero crossing point (ultrasonic arrival point) is detected by the determination unit 8, the control unit 12 operates the transmission unit 5 again to transmit an ultrasonic signal from the ultrasonic transducer 2. This series of operations is repeated 256 times preset (step 31), and after the predetermined number of repetitions, the reference setting means 14 calculates the average value of the time differences counted by the time difference counting means 13 for the number of repetitions (step 31). 37) Based on this, the flow rate is calculated by the flow rate calculation means 11 to calculate the flow rate.

  It is determined whether or not the flow rate calculated by the flow rate calculation unit 11 is equal to or higher than a predetermined flow rate (for example, 400 L / h). If the flow rate is equal to or higher than the predetermined flow rate (step 38), the average value of the time differences calculated by the reference setting unit 14 is Comparison with a predetermined value set in advance (for example, 120% of the time difference measured by the time difference measuring means 13 when the reference voltage set at the time of manufacture is at the midpoint between the two waves of the received wave and the third wave) (step 39). . If it is equal to or greater than the predetermined value, it is determined whether or not the current reference voltage exceeds the upper limit of the reference voltage setting range stored at the time of manufacture (three-wave peak voltage during the manufacturing process) (step 43). If so, the flow rate measurement is terminated. If the upper limit of the setting range is not exceeded, the reference voltage is increased by one control unit (2 mV) (step 44).

  Further, the average value of the time difference calculated by the reference setting means 14 and another predetermined value which is preset and different from step 24 (for example, when the reference voltage set at the time of manufacture is at the midpoint between the two waves of the received wave and the three waves) (Step 40), the flow rate measurement is terminated if it is not less than the predetermined value. When it is less than the predetermined value, it is determined whether or not the current reference voltage falls below the lower limit of the reference voltage setting range stored at the time of manufacture (two-wave peak voltage during the manufacturing process) (step 41). If not, the reference voltage is decreased by one control unit (2 mV) (step 42).

  If the lower limit of the set range is not reached, the flow rate measurement is terminated. That is, when the average value of the time difference calculated by the reference setting means 14 is within 80 to 120% of the time difference at the time of setting the reference voltage at the time of manufacture at a predetermined flow rate (400 L / h) or more, the reference voltage remains as it is. When the average value of the time difference is 120% or more, the reference voltage is increased for each flow measurement within a range where the reference voltage does not exceed the peak voltage of the three waves during the manufacturing process. In addition, when the average value of the time difference when setting the reference voltage at the time of manufacture is less than 80%, the reference voltage should be decreased for each flow measurement within the range where the reference voltage does not fall below the peak voltage of the two waves during the manufacturing process. become.

  As described above, after the predetermined number of repetitions, the reference voltage is changed according to the situation. Further, the time from the start of the flow measurement to the end of the predetermined number of repetitions is measured by the time measuring means 10, and the first ultrasonic vibrator 2 and the second ultrasonic vibrator 3 are switched by the switching means 4, and the same operation is performed. Then, the respective propagation times from the upstream to the downstream and the downstream to the upstream of the fluid to be measured are measured, and the flow rate calculation unit 11 determines the flow rate value in consideration of the size of the flow path and the flow state from these time differences.

  It should be noted that the average value of the time difference calculated by the reference setting means 14 in step 43 in FIG. 7 is a predetermined value set in advance (for example, the reference voltage set at the time of manufacture is at the midpoint between the two waves of the received wave and the third wave). The current reference voltage exceeds the upper limit of the reference voltage setting range stored at the time of manufacture (three-wave peak voltage during the manufacturing process) when the time difference of the time difference measuring means 13 is 120% or more) In order to determine whether or not 90% of the upper limit of the setting range has been exceeded, the lower limit of the reference voltage setting range stored at the time of manufacture in step 41 (during the manufacturing process) In this case, it may be determined whether or not the value is lower than 10% of the lower limit, and in this case, the reference set by the reference setting means 14 is determined. Voltage is 2 during manufacturing process Stably it would be set between 10% and 90% between the peak voltage and the third waveform of the peak voltage.

  Further, the flow rate calculation means 11 detects the flow velocity of the fluid, and further calculates the flow rate in consideration of the size of the pipe line and the flow state. However, even when the flow rate is not calculated, the obtained flow velocity of the fluid is calculated. Therefore, it is possible to determine the change in the flow velocity, and it is possible to detect the leakage of the fluid.

(Embodiment 2)
Further, another operation of the reference setting unit 14 will be described with reference to FIG.

  FIG. 8 is a flowchart for explaining another operation of the reference setting means 14.

  In FIG. 8, the operation from step 31 to step 37 until the average value of the time difference is calculated after finishing the predetermined number of repetitions is the same as the operation of FIG. Give an explanation. When the reference setting unit 14 calculates the average value of the time differences counted by the time difference counting unit 13 for the number of repetitions, it is determined whether or not the flow rate calculated by the flow rate calculation unit 11 is 0 L / h (step 51). If it is / h, the difference between the current reference voltage and the reference voltage set at the time of manufacture is determined (step 52). If the difference is more than a preset value, the reference voltage setting operation performed in the initial setting operation is performed. Is executed again (step 53). If it is within the predetermined value, the reference voltage is not changed and the process is terminated. If the flow rate determination at step 51 is not 0 L / h, the reference voltage is set by the procedure after step 39 described above.

(Embodiment 3)
Furthermore, another operation | movement of the reference | standard setting means 14 is demonstrated using FIG.

  FIG. 9 is a flowchart for explaining another operation of the reference setting means 14.

  In FIG. 9, the operation from step 31 to step 37 after the operation of a predetermined number of repetitions is completed and the average value of the time difference is calculated is the same as the operation of FIG. Give an explanation. When the reference setting means 14 calculates the average value of the time differences counted by the time difference counting means 13 corresponding to the number of repetitions, a plurality of flow zones are divided by the flow rate calculated by the flow rate calculation means 11 (step 61 in FIG. 9).

  For example, the flow rate is divided into three zones of 0 to less than 400 L / h, 400 to less than 1000 L / h, and 1000 L / h or more, the operation is repeated a predetermined number of times, and the flow rate calculated by the flow rate calculation unit 11 is measured last time. If it is the same as that in the flow rate flow zone (step 62), the reference voltage is not changed and the processing is terminated.

  If the flow rate measured this time is different from the flow rate zone measured last time, the processing after step 39 is performed. Step 39 and subsequent steps are the same as those in FIG.

  That is, if the current measurement time is 100 L / h and the current measurement time is 300 L / h, the same flow rate zone is maintained, so the reference voltage remains unchanged, and the previous measurement is 100 L / h and the current measurement time is 500 L / h. Since the flow rate zone is different, the reference voltage changing process after step 39 is performed.

  In the present embodiment, the reference point is the midpoint between the inflection points of specific waves (2 wave and 3 wave peak voltages) among a plurality of inflection points where the time difference measured by the time difference measuring means 13 changes greatly. Although the voltage is set, there is a characteristic in the direction (increase or decrease) of the voltage fluctuation of the received signal. For example, if the voltage fluctuation of the received signal does not increase but only decreases, the reference voltage is changed by the time difference. Setting a voltage lower than the midpoint between the inflection points can provide a larger margin with respect to the reference voltage against voltage fluctuation (decrease) in the received signal. In such a case, for example, the reference voltage that is set to be 1/3 between the inflection points of the maximum interval of time difference may be set to an arbitrary point according to the voltage fluctuation of the received signal.

  At the time of manufacture, the fluid to be measured (LPG etc.) is injected into the fluid flow measurement device, and the reference voltage is automatically set to the midpoint of the specific wave (between 2 waves and 3 waves) according to the peak voltage ratio of each wave of the received waveform By setting to, the correct reference voltage is set even if the fluid to be measured is not filled in the fluid flow measuring device at the installation site, and the reference voltage is changed by automatic adjustment of the reference voltage after the operation starts. However, it is possible to prevent an incorrect voltage from being set by limiting the change range to a specific wave interval (between 2 waves and 3 waves) at the time of manufacture.

As described above, in the present embodiment, the reference voltage is changed from the minimum voltage of the setting range to the maximum voltage at the initial setting in the manufacturing process or the like, and the time difference measured by the time difference measuring means 13 at that time is a plurality of changes. Recognize the peak voltage of each wave of the received waveform from the inflection point, and reference the wave of the received waveform based on the ratio of the peak voltage, for example, the midpoint voltage between the peak voltages of two specific waves or three waves, or any point By using the reference setting means 14 for automatically setting the voltage, two waves that can detect the arrival time of the ultrasonic signal most stably against the voltage fluctuation of the received signal in the ultrasonic reception waveform, The reference voltage can be set reliably and automatically between the peak voltages of the three waves. Also, after setting the reference voltage at the time of manufacturing, the characteristics of the parts change for some reason until the flow rate is measured at the installation site, and the time difference is stored. Stored in means 15 Time difference and the time difference counting means 13 during manufacture to reset the reference voltage Different larger than the time difference counting you are. If the two time differences are the same, flow measurement is started without resetting the reference voltage. Further, the reference voltage is reset when the time difference measured by the time difference measuring means 13 at the time of flow rate deviates from a predetermined time difference determined based on the time difference when the reference voltage is set.

  As a result, the reference voltage can be set quickly without human intervention, and the fluid flow measuring device can maintain the reference voltage at an optimum voltage during flow rate measurement even after the setting. Furthermore, since the reference voltage is not reset more than necessary, such as less than a predetermined flow rate or the same flow rate zone, the flow rate can be measured with low power consumption.

  Further, by using a recording medium storing a program for executing the operation of the fluid flow measuring device of the present embodiment, set values such as a predetermined ratio of the control means 12 and the reference setting means 14 and the number of repetitions of the repetition means 9 It is possible to flexibly cope with changes in the ultrasonic wave, changes in the ultrasonic vibrator, or changes over time.

  As described above, the fluid flow measuring device according to the present invention can quickly and accurately set the reference voltage, and thus can be applied to the measurement of the flow velocity and flow rate of fluid such as gas and water.

1 is a block diagram of a fluid flow measuring device according to a first embodiment of the present invention. Diagram explaining the operation of the device Flow chart of the device Flow chart of the device Diagram explaining the operation of the device Diagram explaining the operation of the device Flow chart of the device Flow chart explaining other operations of the apparatus Flow chart explaining other operations of the apparatus Block diagram of a conventional fluid flow measurement device Operation explanatory diagram of a conventional fluid flow measuring device Operation explanatory diagram of the amplifying means of the conventional fluid flow measuring device

Explanation of symbols

1 channel 2 first ultrasonic transducer (first transducer)
3 Second ultrasonic transducer (second transducer)
4 switching means 5 transmitting means 6 amplifying means 7 reference comparing means 8 determining means 9 repeating means 10 timing means 11 flow rate calculating means (calculating means)
12 Control means 13 Time difference counting means 14 Reference setting means 15 Time difference storage means

Claims (3)

A first vibrator and a second vibrator that are provided in the fluid conduit and transmit and receive ultrasonic signals ;
Transmitting means for driving the first vibrator and the second vibrator ;
Switching means for switching between transmission and reception of the first vibrator and the second vibrator ;
Amplifying means for amplifying the received signals of the first vibrator and the second vibrator ;
Time measuring means for measuring the accumulated time of transmission and reception of the ultrasonic signal ;
Calculation means for calculating the flow velocity and / or flow rate based on the time measured by the time measuring means ;
A reference comparing means for comparing the voltage of the received signal output from the amplifying means with a reference voltage and outputting a signal when the magnitude relationship is inverted ;
A determination means for outputting a signal at the time of determining the first negative zero cross point at which the voltage of the reception signal output from the amplification means changes from positive to negative after receiving the signal output from the reference comparison means ;
Time difference timing means for timing the time difference between signals output from the reference comparison means and the determination means ;
When the reference voltage is changed from the minimum voltage of the setting range to the maximum voltage, a plurality of values in which the time difference measured by the time difference measuring means changes rapidly are recognized as peak voltages, and any of the plurality of peak voltages is recognized. Reference setting means for setting an intermediate value between the first peak voltage and the second peak voltage as the reference voltage when a ratio between the one peak voltage value and the second peak voltage value becomes a predetermined value ;
A time difference storing means for storing a time difference measured by the time difference measuring means when setting the reference voltage ;
In a fluid flow measuring device comprising:
If the difference between the value measured by the time difference timing means after setting the reference voltage and the value stored in the time difference storage means is greater than or equal to a predetermined value , the reference setting means sets the reference voltage again, and the reference If the difference between the value measured by the time difference measuring means after setting the voltage and the value stored in the time difference storage means is less than a predetermined value, the flow rate is measured, and the flow rate calculated by the flow measurement is equal to or greater than the predetermined value. The reference voltage is changed in the case of
Fluid flow measuring device. The flow rate wherein the reference setting means calculates said calculation means, a plurality of preset the reference voltage adjusting operation fluid flow measuring device according to claim 1 to perform when moved a flow rate region in the flow rate range . The reference setting means the reference voltage fluid flow measuring device according to claim 1 for changing the after adjusting the amplification degree of said amplifying means.

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