JPH08226836A - Kalman vortex flowmeter - Google Patents

Abstract

PURPOSE: To provide a Kalman vortex flowmeter which prevents a wrong flow- rate measured result from being output when a 'pulse omission' is generated by a method wherein a front cycle buffer region used to store the specific number or higher of measured output values is installed in a RAM. CONSTITUTION: In a transmission part 2, at the beginning of the start of respective sampling cycles, cycle measured values of output pulse signals from a Kalman vortex flow-rate detection part 1 are stored, in the order of their measurements, in front cycle buffer regions TB(1), TB(2),... TB(n) whose number has been set in a RAM 7. That is to say, a plurality of, i.e., three of higher of, measured output values of a pulse cycle measuring counter 6 are stored in the buffer regions TB(1) to TB(n) in the order of their outputs. A cycle reference value which is decided on the basis of the stored values is compared with the cycle values which have been measured by the counter 6. Only when the measured cycle values do not exceed the cycle reference value, the cycle measured values and the number of transmissions of a Kalman vortex signal are integrated and processed. As a result, data is removed in the cycle measured values and the integrated value of the number of transmissions of pulse signals when a 'pulse omission' is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate calculation output control means in a Karman vortex flowmeter for measuring the flow rate of air or water.

[0002]

2. Description of the Related Art In a Karman vortex flowmeter, when a columnar obstacle is placed in a fluid flow, vortices are alternately generated from both ends of the obstacle orthogonal to the flow direction at a frequency proportional to the flow velocity of the fluid. This is a flow meter that utilizes the phenomenon of The Karman vortex flowmeter has a flow rate detection part that amplifies the weak signal output by the Karman vortex sensor and a Karman vortex sensor that consists of a piezoelectric element that captures slight pressure fluctuations in the fluid when vortices are generated by an obstacle. A waveform shaping circuit that outputs a pulse signal having a constant waveform when this value exceeds a certain value is provided, and a Kalman pulse signal having a frequency corresponding to the flow rate of the fluid is transmitted from the flow rate detection unit.

In the transmission section for detecting the Kalman pulse signal and calculating and outputting the flow rate, conventionally, between the Karman pulse signals input from the Karman vortex flow rate detection section to the transmission section within a predetermined fixed sampling period. Measure the total number of cycles and the total number of pulse signals, divide the total number of pulse signals by the total number of cycles between pulse signals to obtain the frequency of the Kalman pulse signal in the sampling cycle, and convert this frequency value into a flow rate value. By doing so, the flow rate of the fluid is measured and output.

[0004]

The flow rate detecting portion of the Karman vortex flowmeter amplifies the weak signal output by the Karman vortex sensor and outputs a shaped pulse signal of a constant waveform when this value exceeds a certain value. Therefore, the "fluctuation" of the fluid flow
Due to factors such as the above, the output signal value of the Karman vortex sensor drops and the shaped pulse signal is not transmitted.
May occur.

When this "pulse omission" occurs, the transmission unit according to the prior art counts the total number of input pulse signals by the amount of "pulse omission", so the frequency obtained by the calculation is lower than the actual Kalman pulse frequency. It becomes a low frequency and causes a large error in the flow rate measurement output value. Therefore, the transmission section is provided with an area in the RAM for storing and storing the output values in the order of output each time the cycle between the Kalman pulse signals input from the vortex flow rate detection section is detected and measured. In the processing procedure to calculate the flow rate by calculating the frequency when counting up,
A reference cycle in the sampling period is determined based on the value of the measurement cycle stored in the measurement cycle counter area set in the RAM, and the value of the reference cycle is compared with each cycle measurement value stored in the measurement cycle counter area in order. However, when a cycle measurement value with a deviation of a predetermined value or more from a reference value is detected, a process of excluding this cycle measurement value and the count of pulses that give this cycle measurement value from the integration target data in the sampling period is performed. If this is provided, even if a “pulse dropout” in which a shaped pulse signal is not generated and a value with a longer cycle than the normal pulse cycle is stored in the measurement cycle counter area, this value is used to calculate the frequency and flow rate. It is possible to obtain the correct frequency and flow rate values by excluding them from the data used for It requires large-capacity storage area as a storage means for storing, not realistic.

According to the present invention, when the "pulse dropout" occurs, the process of calculating and outputting the flow rate value based on the frequency value is invalidated, and a small capacity storage area in which an erroneous flow rate measurement result is not output is provided. It is an object of the present invention to improve the reliability of flow rate measurement by the Karman vortex flowmeter by providing a transmission section of the Karman vortex flowmeter configured.

[0007]

[Means for Solving the Problems] When a "pulse omission" of one pulse occurs in the Karman vortex flowmeter, the pulse count value during the sampling period is reduced by one count, and when the "pulse omission" occurs, it is adjacent to the pulse count value. The period between pulses is measured as about twice as long as when there is no "pulse omission", but in normal fluid flow, even if there is a drastic change in the flow rate, the measurement result of the adjacent period is 2 times.
It's not twice as different.

Therefore, in order to prevent the occurrence of an error due to "pulse omission" in the Karman vortex flowmeter, in the present invention, the transmission section of the Karman vortex flowmeter performs step processing of calculation and output at the timing given by the system clock. A microcomputer, a reference cycle timer for giving a sampling cycle for executing an arithmetic output process, a pulse cycle measurement counter for measuring a time interval between pulse signals transmitted by the Karman vortex flow rate detection unit, and a measurement output of the pulse cycle measurement counter. A head cycle buffer area for storing a plurality of values of 3 or more in the order of output and an area for temporarily storing a count value and a mantissa value generated in the course of arithmetic processing executed in a microcomputer are set. RAM and
It is composed of a ROM that stores the procedure of the arithmetic processing and an output unit that outputs the result of the arithmetic processing. When the Karman vortex flow rate detection unit transmits the Karman vortex signal, it is involved in the cycle measurement called by the microcomputer from the ROM. In the program, check the number of measurement cycle values stored in the head cycle buffer area set in RAM. When the number of stored data reaches a predetermined number, the cycle in the sampling period is determined based on the stored value of the measurement cycle. Every time the Karman vortex flow rate detection unit transmits a Karman vortex signal, the reference value is determined, and this cycle reference value is compared with the value of the cycle measured by the pulse cycle measurement counter, and the value of the measurement cycle is the cycle reference value. Only when the predetermined ratio is not exceeded, a processing procedure is added to integrate this cycle measurement value and the number of Karman vortex signal transmissions, and the reference cycle timer performs sampling. When you count up the period, RO
Processing for dividing the integrated value of the number of Karman vortex signal transmissions by the integrated value of the period measurement values obtained above into the transmission frequency of the Karman vortex flow rate detection unit in the sampling period in the flow rate calculation program called from M Establish a procedure.

[0009]

In the transmission section of the Karman vortex flowmeter according to the present invention, the cycle measurement value between the output pulse signals of the Karman vortex flow rate detection section is measured in the preset number of head cycle buffers at the beginning of each sampling cycle. When the cycle measurement value is stored in the first cycle buffer, the cycle reference value for this sampling period is set based on the stored value of the measurement cycle during the process of the cycle measurement program. Whenever the detection unit transmits the Karman vortex signal, the cycle reference value is compared with the value of the cycle measured by the pulse cycle measurement counter, and the value of the measurement cycle does not exceed a predetermined constant ratio of the cycle reference value. Only this cycle measurement value and the number of Karman vortex signal transmissions are integrated, so when the reference cycle timer counts up the sampling cycle, the cycle measurement value The integrated value of the pulse signal originating number and thus being excluded data when the "missing pulse" occurs.

[0010]

FIG. 1 shows a schematic structure of an embodiment of the Karman vortex flowmeter according to the present invention. In FIG. 1, reference numeral 1 denotes a Karman vortex flow rate detection unit including a Karman vortex sensor that generates a signal in a cycle that is inversely proportional to the flow velocity of a fluid, and a waveform shaping circuit that amplifies and outputs the signal of the Karman vortex sensor. Reference numeral 2 denotes a transmission unit composed of the following 3 to 9 components which counts the Karman vortex pulse signal transmitted from the flow rate detection unit 1 for each predetermined sampling period and calculates and outputs the flow rate value. .

In the transmission unit 2, reference numeral 3 is a microcomputer that receives the output pulse signal of the Karman vortex flow rate detection unit 1, calculates the flow rate, and outputs it. Step operation at timing. Reference numeral 5 is a reference cycle timer (SCT) that determines the execution cycle of the measurement calculation processing performed by receiving the output pulse signal of the Karman vortex flow rate detection unit 1, and 6 is triggered by the pulse signal transmitted by the flow rate detection unit 1. When it is started, the time interval until the next pulse signal is input is measured, and when the next pulse signal is input and the measured value up to this time is transferred to the microcomputer 3, the measured value is cleared to zero, Is a pulse cycle measuring counter for restarting the measurement of the time interval until the arrival of the pulse, and the output signal of the flow rate detecting unit 1 passes through the interrupt input terminal INT2 related to the pulse frequency measurement of the microcomputer 3 to the pulse cycle measuring counter 6 Entered in.

The ROM 8 is a read-only storage means in which the operating process of the microcomputer 3 is stored, and the storage program includes an interrupt request signal INT in which the reference cycle timer 5 counts up the sampling cycle.
When 1 is input to the microcomputer 3, a flow rate calculation program (82) that is called to perform processing, and when the flow rate detection unit 1 emits a pulse, this is generated by an interrupt signal INT.
The cycle measurement program (81) started as No. 2 is included.

The RAM 7 is a storage means capable of writing and reading at any time for temporarily storing a code (flag) and a count value indicating a state in which temporary storage is required during the execution process of the arithmetic processing of the microcomputer 3. In the storage area of the RAM 7, a pulse number counter (NP) that counts the pulses output by the Karman vortex flow rate detection unit 1 in each sampling cycle, and a cycle measurement between successive pulses that the pulse cycle measurement counter 6 measures and outputs. A head cycle buffer (TB (1) to TB (n)) that stores and stores a predetermined number n of values in order of output, and a pulse cycle measurement counter 6 after the cycle measurement value stored in the head cycle buffer The measurement cycle counter (TF (r)) that temporarily stores the cycle measurement value sent by the device until the next cycle measurement value is output, and the integration cycle counter (TT that accumulates and stores the measurement cycle value
C) is secured, and the pulse number counter (NP) and the integration period counter (TTC) are stored in respective counters for temporarily holding the values stored in the respective counters during execution of the arithmetic output processing. Corresponding buffer areas NB and TTB are secured. Then, in the RAM 7, when the integrated value TTC of the pulse period integration counter exceeds a predetermined upper limit value MTC, a measurement end flag (ED) indicating the end of integration for ending the integration of the pulse interval measurement results.
F) and a period measurement flag (PT) indicating whether the process of measuring and integrating the pulse interval is being executed or is waiting to be executed.
Areas for storing F) and are also secured and set.

Further, the RAM 7 has a reference period timer 5
Is provided with a sampling time counter (STC) that stores a count value to be counted in determining the flow rate measurement cycle. This sampling time counter (STC)
As the value of the sampling cycle set to, the time is set to be sufficiently longer than the cycle of the output pulse transmitted by the vortex flow rate detection unit in the range in which the time variation of the flow rate can be followed in order to maintain the measurement accuracy of the flow rate.

Next, FIGS. 2 to 5 show the flow of one embodiment of the arithmetic processing program executed by the microcomputer 3 based on the first invention of the present application, and the Karman vortex flow rate of the present invention will be described below with reference to these drawings. The operation of the shape will be described.
The Karman vortex flow type transmission unit 2 according to the present invention illustrated in FIG.
When the initial condition is set and the system is on standby, the interrupt from the reference cycle timer 5 is set as the higher order and the reference cycle timer 5
Enters an interrupt standby state in which an interrupt due to an output pulse of the flow rate detection unit 1 that occurs at a shorter time interval than the sampling period determined by the set value of the sampling time counter (STC) that is counted is lower.

First, the interrupt process by the output pulse of the Karman vortex flow rate detection unit 1 which has a high interrupt frequency will be described. When the output pulse of the Karman vortex flow rate detection unit 1 is input to the interrupt request terminal 1NT2 of the microcomputer 3,
The cycle measuring program (81) of the flow of FIG. 2 is called from the ROM 8 and the processing is executed (P0).

When there is an interrupt due to the output pulse of the Karman vortex flow rate detecting unit 1, the period measuring program (81) temporarily masks the interrupt due to the detecting unit output pulse and checks the state of the period measuring flag PTF (P1 , P2), PTF
Is 0, indicating that the pulse interval is not being measured,
In order to measure the period from this input pulse to the next input pulse, the count value PPC of the pulse period measurement counter 6 is initialized and activated (P3), and the pulse number counter NP and the pulse period integration counter TTC are initialized. Later (P
4) The period measurement flag PTF is set to 1 indicating that the measurement is in progress (P5), the interruption by the output pulse of the Karman vortex flow rate detection unit 1 is permitted (P6), and the interruption is restored.

On the other hand, when the period measurement flag PTF indicates 1 being measured, the stored value N of the pulse number counter
P is incremented (P7), and it is checked whether or not this value has reached a predetermined numerical value SP of 3 or more as the number of cycle measurement data for obtaining the reference cycle (P8). The measured value PCC is stored in the NP-th cycle measurement buffer TB (NP) to initialize the cycle measurement counter 6 (P9), and the transferred measurement cycle counter value TB
After adding (NP) to the stored value TTC of the pulse period integration counter (P10), the calculation process for obtaining the reference period is performed based on a predetermined program (P11), and the stored value NP of the pulse number counter exceeds SP. In this case, the measured value PCC of the pulse cycle measurement counter 6 is set to the measurement cycle counter TF.
Stored in (r) and initialized (P12), add the transferred measurement cycle counter value TF (r) to the stored value TTC of the pulse cycle integration counter (P13), and then determine the missing pulse based on a predetermined program. Correction processing is performed (P14).

When the above reference period calculation or pulse drop discrimination correction processing is completed, the stored value of the stored value TTC of the pulse period integration counter is compared with a predetermined upper limit set value MTC of the pulse period integrated value (P15), and TTC is set. Does not exceed the MTC, the interrupt by the output pulse of the Karman vortex flow rate detection unit 1 masked earlier is allowed (P6) and the interrupt is restored (P17), and the pulse cycle integration TTC is set to the upper limit set value MTC. If it exceeds, the measurement end flag EDF
The end of measurement is set to 1 (P16) and the interrupt is restored without interrupt permission (P17).

Next, the number SP of data used to determine the period reference value is used for the period reference value calculation processing program called in the period measurement program started by the interrupt by the output pulse of the Karman vortex flow rate detecting unit 1. The flow of one embodiment in the case of being realized as No. 3 will be described with reference to FIG. The reference period calculation processing program of the embodiment of FIG. 3 is called when the count number NP of the pulse number counter is 3 or less which is set as the value of the initial sampling data number SP in the step P11 of the period measurement program. The count number NP of the pulse number counter is S
It is judged whether or not the value of P reaches 3 (R1), and if it is not 3, it immediately returns to the calling period measurement program (R10), but when it is equal to 3, the first 3 data of the pulse period measurement result. Period measurement buffers TB (1), TB as
(2), and the period measurement values stored in TB (3) are compared with each other, and the average value TR of the remaining two data excluding the maximum value data TM is obtained and set as the period reference value TR (R
2 to R7).

By the way, when one pulse is missing, the pulse period is doubled. Therefore, the value C × TR obtained by multiplying the cycle reference value TR obtained by the above by a constant coefficient C less than 2 and the first three data TB (1), T of the cycle measurement result
The maximum value TM of B (2) and TB (3) is compared and inspected, and C ×
When the value of TR is exceeded, the occurrence of "pulse omission" is recognized, so the cumulative cycle counter holding value TTC added with the incorrect measurement cycle value at this time is replaced with 3xTR as an approximate value of the correct value ( R9) to return to the calling cycle measurement program. It should be noted that 2 in the above processing
The value of the constant C, which is less than, is set to, for example, 1.5 so that the loss of one pulse can be detected reliably and reliably.

Next, in the period measurement program, the count number NP of the pulse number counter exceeds the value SP of the number of data used to determine the period reference value, and the reference period value T
This will be described with reference to FIG. 4 showing a flow of one embodiment of the pulse omission determination correction processing program that is called in the processing when the output pulse of the Karman vortex flow rate detection unit 1 is input after R is determined.

The pulse missing determination correction processing program, when called, first sets the period value TF (r) measured by the output pulse of the Karman vortex flow rate detection unit 1 at this time to a reference period value TR of a constant value of less than 2. Value C x T multiplied by the coefficient C of
Compared with R (E1), if the measurement period TF (r) is less than this value, it immediately returns to the calling source (E3), but if it exceeds, the occurrence of "pulse omission" is recognized. Accumulation period counter hold value TT to invalidate the measurement result of
While subtracting the value TF (r) of this measurement cycle from C,
After subtracting 1 count from the count number NP of the pulse number counter (E2), the process returns to the calling source (E3). The value of the constant C less than 2 in the above process is set to, for example, 1.5 so that the loss of one pulse can be detected reliably and reliably, as in the reference period calculation process.

According to the period measuring program described above, the period reference value T excluding "pulse omission" is excluded by using a plurality of period measuring data obtained at the beginning of the sampling period.
When R is set, when there is an interrupt due to the output pulse of the Karman vortex flow rate detection unit 1, data in which a pulse omission occurs based on this value is excluded, and when the sampling cycle ends, the pulse number counter is stored. As the value NP and the stored value TTC of the integration cycle counter, data excluding "pulse missing" is obtained.

When the reference cycle timer 5 counts up the sampling cycle counter STC, an interrupt occurs, and the sampling cycle ends, the stored value NP of the pulse number counter and the stored value TTC of the integration cycle counter are used in this sampling cycle. The flow of one embodiment of the flow rate calculation program (82) for obtaining the value of the flow rate will be described with reference to FIG.

As shown in FIG. 5, when the flow rate calculation program (82) is activated by an interrupt from the reference period timer 5, it first temporarily masks the interrupt due to the output pulse of the Karman vortex flow rate detector 1. Then, the state of the measurement end flag (EDF) is checked (S1, S2). When the measurement end flag (EDF) is 1 and the end of the pulse period measurement is indicated, the measurement values stored in the pulse number counter (NP) and the integration period counter (TTC) are measured during the flow rate value calculation process. In order to hold it, the buffers (NB, TT) provided corresponding to the respective counters are held.
The transfer is retracted to B) (S3). On the other hand, when the measurement end flag (EDF) is 0, indicating that the measurement has not ended, the pulse number buffer (NPB) and the integration period buffer (TTB) are cleared to zero to end the pulse period measurement. The standby state is maintained (S4).

When the processing based on the above measurement end flag (EDF) inspection result is completed, the measurement end flag (EDF)
And the pulse period measurement flag (PTF) are set to 0 to indicate that the period measurement of the output pulse signal of the Karman vortex flow rate detection unit 1 is in the unstarted and unfinished state (S5). Interruption by the output pulse of the flow rate detection unit 1 masked in (1) is permitted (S6). Therefore, when this process ends, the transmission unit 2 returns to the interrupt standby state by the output pulse of the flow rate detection unit 1.

Subsequently, the value stored in the pulse number buffer NB is checked (S7), and when the value is 0, the flow rate value Q is directly set to 0 (S9). When the value stored in the NB is not 0, The value NB of the pulse number buffer is divided by the value TTB of the integration cycle buffer to obtain the value of the frequency FRB, and the value is multiplied by the conversion coefficient K to obtain the flow rate value Q (S8). After executing the output process of the flow rate value Q (S10), the process returns from the interrupt (S11).

By the way, when the pulse height discrimination setting value of the waveform shaping circuit of the Karman vortex flow rate detecting section 1 is properly adjusted, the pulse omission occurs accidentally and independently. Therefore, the average value of three or more of the period measurement results of the output pulse signal of the Karman vortex flow rate detection unit 1 measured by the period measurement program is twice the value of the period when no pulse omission occurs. It usually does not exceed. The flow of the embodiment of the reference period calculation program based on the second invention for determining the value of the reference period by utilizing this is shown in FIG. 6, and this embodiment will be described. For the sake of simplification of description, the number of data SP used to determine the cycle reference value is also 3 in this embodiment.

When called, the reference period calculation processing program of the embodiment shown in FIG. 6 first determines whether or not the count number NP of the pulse number counter has reached the value 3 of SP (K
1) If it is not 3, it immediately returns to the calling period measurement program (K10), but if it is equal to 3, the period measurement buffers TB (1), TB (2), TB (2), as the first 3 data of the pulse period measurement result. And the average value of the cycle measurement values stored in TB (3) is calculated and used as the value T of the temporary reference cycle.
Let it be RI (K2). Then, the value TR of this temporary reference period
The value C × TRI obtained by multiplying I by a constant coefficient C less than 2 and the cycle measurement value TB (i) (i = 1,2,3) stored in the cycle measurement buffer are sequentially compared, and TB (i) If the value exceeds the above discriminant value and a pulse dropout is recognized, the cycle measurement value TB (i) when this pulse dropout is subtracted from the stored integrated value TTC of the integration cycle counter, and the value is replaced by a temporary value close to the true value. The reference cycle value TRI is added to obtain a new integration cycle value TTC (K3 to 8).

When the above-described pulse omission detection and correction processing by comparing the cycle measurement values is completed, the value obtained by dividing the value TTC of the correction integration cycle by the value 3 of the number of detected pulses is taken as the value TR of the reference cycle, and the caller is called. Return to the cycle measurement program of (K10). Furthermore, when a "pulse omission" occurs during measurement of the period that determines the reference period of the first Karman vortex signal pulse in each sampling period, the measurement result is deleted until a correct measurement value that does not include "pulse omission" is obtained. The flow of the embodiment of the reference period calculation program by the processing based on the third invention for repeating the measurement is shown in FIG. 7, and this embodiment will be described. For the sake of simplification of description, the number of data SP used to determine the cycle reference value is also 3 in this embodiment.

In the reference period calculation processing program of the embodiment shown in FIG. 7, each time a Karman vortex signal pulse is input from the Karman vortex flow rate detection unit 1, the value TB (i) (i) of the measurement period measured by the signal pulse is measured. = 1,2,3) is the value T of the measurement period measured by the previous Karman vortex signal pulse input
The replacement process is performed so that the measured values are arranged in order of magnitude compared to B (i) (for example, in ascending order) (T1 to T8). Value C x TB (1) multiplied by the coefficient C of and the maximum period measurement value T
B (3) is compared (T10), and if the value of TB (3) does not exceed the above discriminant value and "pulse omission" is not recognized, the minimum value TB of the cycle measurement values replaced in ascending order After the average value of (1) and the next larger value TB (2) is set to the value TR of the reference period (T11), the process returns from the reference period calculation (T14).

On the other hand, the value of TB (3) is the above discriminant value C × T.
If it exceeds B (1), "pulse omission" is recognized. Therefore, in order to invalidate the measurement result, subtract the value TB (3) of the third measurement cycle from the accumulated cycle counter holding value TTC and pulse. After subtracting 1 count from the count number NP of the number counter (T9), the value TB of the second measurement cycle
Regarding (2), after performing the same inspection processing (T12), the operation returns from the reference cycle calculation (T14).

According to the processing of the flow of FIG. 7 explained above, when the pulse omission is detected, the count number NP of the pulse number counter is decremented, so that the correct period measurement without the pulse omission is performed a predetermined number of times. In the example, it will be repeated 3 times.

[0035]

In the transmission section of the Karman vortex flowmeter according to the present invention, it is not possible to store all measurement values in the measurement cycle counter area in which the measurement value output value of the pulse cycle measurement counter is stored. Set a narrow area where only data can be stored, and when a predetermined number of pulse period measurement values are obtained, determine the reference period in the sampling period based on the obtained pulse period measurement values. Each time the pulse period of the output pulse of the detector is measured by the pulse period measurement counter, this measured value is compared with the value of the reference period, and only when the value of the measurement period does not exceed a predetermined fixed ratio of the value of the reference period. Since the period measurement value and the generation of one Karman vortex signal are integrated in the integration period counter and the pulse number counter, "pulse omission" occurs when the sampling period ends. Since the measured value from which the influence is excluded remains in the integration period counter and the pulse number counter and the flow rate can be directly calculated by this value, the correct frequency can be obtained even if "pulse omission" occurs using a small RAM. -The effect that a Karman vortex flowmeter that outputs the flow rate value can be obtained is obtained.

Then, when a predetermined number of, for example, three data are obtained as the period measurement result, the average value is obtained as a temporary reference period, and the temporary reference period value and each period measurement value are sequentially compared to obtain a pulse. The process of subtracting the cycle measurement value TB (i) when the omission occurs from the value of the integration cycle and instead adding the temporary reference cycle value TRI that is close to the true value to obtain a new integration cycle value is as follows:
Since the simple processing is repeated, the processing speed is fast, and the time-dependent fluctuation of the flow rate is great, and the sampling cycle is effectively adapted to the target to be set.

On the other hand, each time the Karman vortex signal pulse is input, the value of the measurement cycle measured by the signal pulse is compared with the value of the measurement cycle measured by the previous Karman vortex signal pulse input, and the measured value After performing the replacement process so that the lines are arranged in the order of magnitude, inspect for missing pulses,
When a pulse dropout is recognized, the reference period calculation program that subtracts the measurement result from the accumulated period counter holding value and the count number of the pulse number counter to invalidate the measurement result ensures that the pulse dropout will not occur. Since the period measurement for obtaining the reference period is repeated until a predetermined number of non-period measurement data is obtained, an accurate reference period value can be obtained with certainty, and the streamline distribution is unstable and causes pulse dropout. It is possible to obtain the effect that it can be effectively applied to a measurement target or the like in which noise is easily generated.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a Karman vortex flowmeter according to the present invention.

FIG. 2 is a flow chart of a cycle measurement program activated by an output pulse interrupt of a flow rate detection unit.

FIG. 3 is a flow chart of a program for obtaining a reference period.

FIG. 4 is a flow chart of a pulse missing determination correction program.

FIG. 5 is a flow chart of a flow rate calculation program activated by a reference period timer interrupt.

FIG. 6 is a flow chart of a program of another embodiment for obtaining a reference cycle.

FIG. 7 is a flow chart of a program of another embodiment for obtaining a reference cycle.

[Explanation of symbols]

 1 Karman Vortex Flow Rate Detection Unit 2 Transmission Unit 3 Microcomputer 4 System Clock 5 Reference Period Timer 6 Pulse Period Measurement Counter 7 RAM PTF Period Measurement Flag EDF Measurement End Flag NP Pulse Number Counter NB Pulse Number Buffer TB (i) Head Period Buffer ( i = 1,2, n) TF (r) Measurement cycle counter TTC Integration cycle counter TTB Integration cycle buffer STC Sampling cycle counter TR Reference cycle TRI Temporary reference cycle TM Maximum measurement cycle value MTC 8 ROM 81 Cycle measurement program 82 Flow rate calculation program 9 Output signal converter

Claims (3)

[Claims] 1. A Karman vortex flow rate comprising a Karman vortex flow rate detection section having a Karman vortex sensor as a flow rate detection end, and a transmission section for performing calculation and output processing for measuring the output pulse signal of the flow rate detection section to obtain the flow rate. The transmission unit includes a microcomputer that performs a step process of calculation and output at a timing given by a system clock, a reference period timer that gives a sampling period for performing a calculation output process, and the Karman vortex flow rate detection unit. A pulse cycle measurement counter for measuring the time interval between transmitted pulse signals, a head cycle buffer area for storing and storing a plurality of three or more measured output values of the pulse cycle measurement counter in order of output, and a microcomputer. A RAM in which an area for temporarily storing the count value and the mantissa value generated in the process of arithmetic processing is set, and It comprises a ROM that stores the procedure of arithmetic processing and an output unit that outputs the result of arithmetic processing. When the Karman vortex flow rate detection unit emits a Karman vortex signal, the microcomputer calls and executes it from the ROM. In the cycle measurement program, the number of measurement cycle values stored in the head cycle puffer area set in the RAM is checked, and when the number of stored data reaches a predetermined number, sampling is performed based on the stored value of the measurement cycle. Every time the Karman vortex flow rate detector sends a Karman vortex signal, the cycle reference value is compared with the cycle value measured by the pulse cycle measurement counter, and the value of the measurement cycle is the cycle. Only when the predetermined fixed ratio of the reference value is not exceeded, a processing procedure for integrating the cycle measurement value and the number of Karman vortex signal transmissions is provided. When the sampling cycle is counted up, a flow rate calculation program called by the microcomputer from the ROM is divided into a flow rate value in the sampling period by dividing the integrated value of the Karman vortex signal transmission number by the integrated value of the cycle measurement values obtained as described above. Karman vortex flowmeter, characterized in that a processing procedure for obtaining 2. The process of the reference period calculation performed in the process of executing the period measurement program, whether or not the count number of the pulse number counter has reached a preset value as the number of measurement period values used for the reference period calculation. If it is equal to the set value, the average value of the cycle measured values stored in the head cycle buffer is calculated and calculated. Is set as the value of the temporary reference cycle, and 2 is added to this temporary reference cycle value.
If the discriminant value obtained by multiplying by a constant coefficient less than and the cycle measured value stored in the head cycle buffer are sequentially compared, and the value of the head cycle buffer exceeds the above discriminant value and pulse omission is recognized, the integration cycle The measured cycle value when this pulse dropout is subtracted from the accumulated value stored in the counter, and instead the temporary reference cycle value close to the true value is added to obtain a new integrated cycle value. When the processing for missing detection correction is completed, the value obtained by dividing the value of the correction integration cycle by the value of the number of detection pulses is set as the value of the reference cycle, and the process returns to the calling cycle measurement program. The Karman vortex flowmeter according to claim 1. 3. The process of the reference period calculation performed in the process of executing the period measurement program is such that, every time a Karman vortex signal pulse is input from the Karman vortex flow rate detection unit, the period measurement value measured by the signal pulse is up to the previous time. Of the Karman vortex signal pulse is compared, and the replacement process is performed so that the measured values are arranged in order of magnitude, for example, in ascending order. When the replacement process is completed, the minimum period measured value is less than 2 The discriminant value obtained by multiplying by a constant coefficient of is compared with the maximum period measurement value at the end of the permutation.If the period measurement maximum value does not exceed the above discrimination value and pulse omission is not recognized, the ascending order When the minimum value of the cycle measurement values replaced with and the average value of the next largest measurement value are used as the reference cycle value, the operation returns from the reference cycle calculation, and the cycle measurement maximum value exceeds the above determination value. Is measured The period measurement maximum value is subtracted from the accumulated period counter holding value to invalidate the result, and 1 count is subtracted from the count number NP of the pulse number counter, and then the same inspection process is performed on the next period measured value. The Karman vortex flowmeter according to claim 1, which is a process of returning from the reference period calculation after the operation.