JP3147648B2 - Karman vortex flowmeter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[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 perpendicular to the flow direction at a period inversely proportional to the flow velocity of the fluid. This is a flow meter that utilizes the phenomenon that occurs. The flow detector of this Karman vortex flowmeter has a Karman vortex sensor consisting of a piezoelectric element that captures the slight pulse-like pressure fluctuation of the fluid when an eddy is generated by an obstacle, and a weak pulse output by a piezoelectric element. A waveform shaping circuit is provided for amplifying and shaping the signal, and a pulse signal having a frequency corresponding to the flow rate of the fluid is transmitted from the flow detecting unit. The flow rate of the fluid is measured and output by measuring and calculating the frequency or period of the fluid.

[0003]

Since the flow rate detecting section of the Karman vortex flowmeter includes a Karman vortex sensor composed of a piezoelectric element or the like for detecting pulse-like minute pressure fluctuations,
If accidental shock vibration is applied to the flow detection unit or a pipe connected close to the flow detection unit, this shock vibration is transmitted to the piezoelectric element of the Karman vortex sensor and is equivalent to the Karman vortex generated by the flow of fluid. Signal is generated. For this reason, from the transmission unit configured according to the prior art that measures the pulse signal output by the Kalman vortex sensor, converts it to a flow value, and outputs it, when the fluid should be stopped and the flow rate should be zero, The pulse generated by the impact vibration is measured, and a flow rate signal as if a fluid is flowing may be transmitted.

[0004] The present invention has been made in view of the above-mentioned problems in the Karman vortex flowmeter according to the prior art,
When the fluid is stopped and the flow rate is zero, the Karman vortex flowmeter provides a transmission section that does not output a false flow rate output signal even if shock vibration is applied to the flow rate detection section or the piping connected to it, providing a Karman vortex flowmeter. An object is to improve the reliability of flow measurement by a vortex flowmeter.

[0005]

In order to achieve the above object,
According to the present invention, the transmission unit of the Kalman vortex flowmeter is provided with a microcomputer that performs step processing of calculation and output at a timing given by a system clock, a reference cycle timer that provides a basic unit of a cycle for performing calculation output processing, A pulse interval measurement counter for measuring a time interval between pulse signals transmitted by the detection unit, a ROM storing a procedure of calculation and processing executed by a microcomputer, and a count value and a mantissa value generated in a process of the calculation process. RA temporarily stored
M, and the count-up signal of the reference period timer and the output signal of the Kalman vortex flow rate detection unit are used as interrupt signals, and the flow rate detection unit is called by the microcomputer and stored in the ROM. The frequency of each sampling cycle determined by the reference cycle timer of the output pulse is measured and the flow rate is calculated, and when a non-zero flow rate is detected following the zero sampling cycle, a predetermined delay time is set. In the meantime, a process of continuously outputting an output signal of zero flow rate is performed, and a measured value obtained in a new sampling cycle is output after a lapse of a delay time.

[0006]

Each time the flow rate detector sends a pulse signal, the pulse interval measurement counter uses this as an interrupt signal to restart the time interval measurement operation and measure the time interval until the next pulse input. The value of the time interval between the pulses measured by the interval measurement counter until the restart point is added to the pulse interval integrated value storage area provided in the RAM, and the count value of the number of pulses also provided in the RAM The number of input pulses is counted using the storage area.

When the reference period timer counts up, the microcomputer uses this as an interrupt signal and outputs
The sampling program stored in M is called to check whether a preset sampling time has elapsed. If the sampling time has not elapsed, the process returns to the interrupt standby state. The stored output processing program is called, and the result R of the interrupt processing by the output signal of the flow rate detection unit is obtained.
Using the pulse interval integrated value stored in the AM and the value of the number of input pulses, the value of the frequency of the pulse output by the flow rate detection unit 1 during the sampling period is obtained.

When the value of the pulse frequency obtained by the above calculation is zero, the calculation of the flow rate value is immediately executed from the pulse frequency value, and the flow rate value corresponding to the pulse frequency value of zero is output. . On the other hand, if the pulse frequency obtained by the calculation is not zero, the value of the pulse frequency obtained in the previous sampling cycle stored in the RAM is checked, and if the stored value is not zero, the value of the calculation result is Performs a process of outputting a flow rate value determined by the frequency, and if the stored value is zero, during a predetermined delay period,
A process for continuously outputting an output signal of zero flow rate is performed, and a flow rate value determined by a pulse frequency measured in a new sampling period after the delay period has elapsed is output.

[0009]

FIG. 1 shows a schematic configuration 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 pulse signal at a period inversely proportional to the flow velocity of a fluid, and a waveform shaping circuit that amplifies and shapes the pulse signal of the Karman vortex sensor and outputs the amplified signal. It is.

Reference numeral 2 denotes a transmission unit including the following 3 to 8 components for calculating and outputting a flow value by using a Karman vortex pulse signal transmitted from the flow detection unit 1 as an input signal. In the transmission measuring unit 2, a microcomputer 3 receives the output pulse signal of the Karman vortex flow detecting unit 1, performs a calculation for obtaining the flow rate, and performs a process of outputting the calculation. Step operation.

Reference numeral 5 denotes a unit time ST of the measurement calculation processing performed by receiving the output pulse signal of the Karman vortex flow rate detection unit 1,
This is a reference period timer generated from the clock signal of the system clock 4, and the execution time of each step of the measurement operation is determined as an integral multiple of the unit time ST given by the timer. 6 is activated by using a pulse signal transmitted from the flow rate detection unit 1 as a trigger, measures a time interval until a next pulse signal is input, and inputs a next pulse signal, and measures a value up to this time. Is transferred to the microcomputer 3, the measurement value is cleared to zero, and the measurement of the time interval until the next pulse arrives is a pulse interval measurement counter. The output signal of the flow rate detection unit 1 is Interrupt input terminal INT related to frequency measurement
The signal is input to the pulse interval measurement counter 6 via the line 2.

The ROM 8 is a read-only storage unit in which the operation process of the microcomputer 3 is stored. In the storage program, the reference cycle timer 5 counts up and the interrupt request signal INT1 is input to the microcomputer 3. A sampling program (81) for calling and processing, a frequency calculation program (82) activated when the flow rate detector 1 transmits a pulse as an interrupt signal INT2, and a reference cycle timer 5 An output processing program (83) that is started when the number of interrupts from the server exceeds a preset sampling period set value MTS is included.

The RAM 7 temporarily stores codes (flags) indicating the states indicated by the codes in parentheses below and the count values that need to be temporarily stored in the course of execution of the arithmetic processing of the microcomputer 3. Possible storage means. In the storage area of the RAM 7, a pulse interval integration counter (PTC) for integrating the count value (PCC) of the pulse interval measurement counter 6, a pulse interval integration buffer (PTB) for temporarily storing the integrated value, a flow rate detection Each time the unit 1 emits an output pulse, an area for a pulse number counter (NPC) for counting the output pulse and an area for a pulse number buffer (NPB) for temporarily storing the count value are secured and set. The RAM 7 stores the integrated value PTC of the pulse interval integrating counter as the predetermined upper limit value MP.
When the integration of the pulse interval measurement result is terminated because T has been exceeded, a measurement end flag (EDF) indicating this and a pulse indicating whether the pulse interval measurement integration process is being executed or waiting for execution An interval measurement flag (PTF);
Is also set and secured.

Further, the RAM 7 has a frequency register (FRQ) used for calculating and calculating a frequency value based on the values stored in the pulse interval accumulation buffer PTB and the pulse number buffer NPB, and temporarily stores the value. A frequency buffer (FRB) to be stored, a sampling time counter (STC) for counting the number of interrupts for each interrupt from the reference cycle timer 5, and a frequency measurement value in the previous sampling cycle being zero and the next sampling cycle. A delay time counter (DEC) that performs a timer operation when the output value is kept at zero, which is the previous measurement value, for a preset delay time when the frequency measurement value at the time becomes a non-zero value; An area for storing the set value DES, such as the set number of times of delay time (DES), is reserved and set.

Next, FIG. 2 is a timing chart showing the operation sequence of the main components of the Karman vortex flowmeter illustrated in FIG. 1, and the flow of a program related to FIGS. 3 to 5 is shown below. The operation of the Karman vortex flowmeter of the present invention will be described with reference to these drawings. The transmission unit 2 of the Karman vortex flowmeter according to the present invention illustrated in FIG. 1 sets an interrupt from the reference period timer 5 as an upper rank and an interrupt from the output of the flow rate detector 1 as a lower rank when an initial condition is set and the apparatus is in a standby state. And enters an interrupt waiting state.

The reference period timer 5 counts up the unit time ST, and the reference time pulse
Is input to the interrupt request terminal INT1, the sampling program (81) of the flow shown in FIG. (S
1) As shown in FIG. 3, the sampling program (81) first increments the count value of the sampling time counter STC (S2), and uses the incremented STC value as a unit set in advance as the sampling time. The value is compared with a value MTS representing a multiple of the time ST (S3),
When it is determined that the STC has not reached the MTS, that is, when it is within the sampling time, the process immediately returns from the interrupt (S10).

On the other hand, when STC becomes equal to MTS, that is, when the sampling time has elapsed, the count value STC of the sampling time counter is cleared to zero in preparation for the start of the next sampling cycle (S4), and the measurement end flag EDF is set. (S5), and when the EDF indicates that the measurement of the pulse interval and the integration of the result have been completed, the counts of the pulse interval integration counter PTC and the pulse number counter NPC are respectively compared with the pulse interval integration buffer PTB and the pulse. Transfer to the number buffer NPB (S
6) When the measurement end flag EDF indicates that the measurement integration process of the pulse interval is not completed, the pulse interval integration buffer PTB and the pulse number buffer NPB are cleared to zero (S7).

When the data transfer to the pulse interval accumulation buffer PTB and the pulse number buffer NPB or the zero clear processing is completed, the pulse interval accumulation counter PTC and the pulse number counter NPC are cleared to zero in order to restart the pulse interval measurement. And the measurement end flag ED
F is set to zero indicating that the measurement is not completed, and zero is set to the pulse interval measurement flag PTF to indicate that the measurement is in standby. (S8) After the above processing is completed, the processing shifts to the output processing program 83 of the flow shown in FIG. 5 (S9), and the output processing program 83
Is completed, the process returns from the interrupt by the reference period timer (S
10), the state of waiting for the interruption from the reference cycle timer 5 is returned again.

Next, prior to the description of the output processing step, an interruption step by an output pulse of the flow rate detection unit 1 will be described. When the output pulse of the flow rate detector 1 is input to the interrupt request terminal 1NT2 of the microcomputer 3, the frequency measurement program 82 in the flow of FIG. 4 is called out and the processing is performed. (P1) When the frequency measurement program 82 is interrupted by the output pulse of the flow rate detector 1, the pulse interval measurement flag PTF
(P2), and if the PTF indicates that the pulse interval is not being measured, the PTF is started to start the pulse interval measurement by the next output pulse from the flow rate detection unit 1.
TF is set to the display during measurement, and the pulse interval integration counter PTC and the pulse number counter NPC are cleared to zero (P
4) After that, the counting start of the pulse interval measurement counter PCC of 6 is started. (P8) When the pulse interval measurement flag PTF indicates that measurement is in progress, the stored value of the pulse number counter NPC is incremented (P3), and the pulse interval measurement counter PC of 6 is incremented.
The count value of C is added to the stored value of the pulse interval integration counter PTC to obtain a new stored value of PTC (P5). Then, the stored value of the new PTC is compared with a predetermined upper limit set value MPT of the pulse interval integrated value (6), and when the stored value of the PTC does not exceed the MPT, the pulse interval measurement counter PCC of 6 is started ( P8) and return from the interrupt. (P9) On the other hand, when the value stored in the pulse interval integration counter PTC exceeds the upper limit set value MPT of the pulse interval integration value, it is determined that the pulse interval measurement has ended, and the pulse interval measurement end flag EDF is displayed as an end display. Interval measurement flag PT
Display F during non-measurement (P7) and return from interrupt.
(P9) By the above processing, each time an interrupt is generated by the pulse signal from the flow rate detector 1, the time interval between successive pulses is measured by the pulse interval measurement counter PCC, and the value is sent to the pulse interval integration counter PTC. The number of pulses transmitted from the flow rate transmitter is stored in the pulse counter NPC that has been integrated.

Next, an output processing program of the flow of FIG. 5 executed at the end of the sampling period will be described. According to the processing of the frequency measurement program 82 activated by the interruption by the output pulse of the flow rate detector 1 described above, when the flow rate detector 1 does not transmit any pulse signal during the sampling period, the pulse interval accumulation buffer PTB And the number zero is stored in the pulse number buffer NPB. Therefore, in the output processing program,
First, the value stored in the pulse interval accumulation buffer PTB is checked, and the processing in the subsequent steps is selected. (O2) When the value stored in the pulse interval accumulation buffer PTB is zero, zero is stored as the value of the Kalman frequency in the frequency register FRQ (O3), the delay time counter DEC is cleared to zero (O9), and then stored in the frequency register FRQ. Transfer the value to the frequency buffer FRB. (O10) On the other hand, if the value stored in the pulse interval accumulation buffer PTB is not zero, the equation (1) is calculated by dividing the value stored in the pulse number accumulation buffer NPB by the value stored in the pulse interval accumulation buffer PTB. The value of the Kalman frequency in the period is obtained, and this value is stored in the frequency register FRQ (O4).

[0021]

FRQ = NPB / PTB (1) Next, the value of the Kalman frequency measured and calculated in the previous sampling cycle stored in the frequency buffer FRB is checked (O5). If this value is zero, the delay is determined. The time counter DEC is incremented (O6), and the incremented DEC value is compared with a preset delay time set count DES as a multiple of the sampling time MTS (O7). Store zero in FRB. (O8) In the above process, when the value of the Kalman frequency in the previous sampling cycle stored in the frequency buffer FRB is not zero (O5), and the count value of the delay time counter DEC does not exceed the delay time set number DES. In this case, the value stored in the frequency register FRQ is transferred to the frequency buffer FRB after the delay time counter DEC is cleared to zero (O9), similarly to the case where zero is stored as the value of the Kalman frequency in the frequency register FRQ (O3). . (O10) By the above processing, the value of the Kalman frequency for obtaining the flow rate value is stored in the frequency buffer FRB.
Output calculation processing is executed using this stored value (O11), and the process returns from the output processing step. (O12) According to the output processing described above, if a new non-zero Kalman frequency FRQ is obtained when the measured flow rate output is zero, the flow rate value determined by the non-zero frequency is immediately output. Instead, the flow rate measurement output keeps a zero value during the predetermined delay time DES, and a flow rate signal corresponding to the Kalman frequency measured and calculated in a new sampling cycle after the delay time DES elapses.

[0022]

In the transmission section of the Karman vortex flowmeter according to the present invention, a single microcomputer for performing the measurement and calculation processing, a reference cycle timer for providing a basic unit of the cycle for performing the calculation output processing, and a flow detection section are provided. A pulse interval measurement counter that measures a time interval between pulse signals to be transmitted is provided, and a reference period timer and an output signal of the flow rate detection unit are used as an interrupt source, and the output of the Karman vortex flow rate detection unit is set every predetermined sampling period. A measurement calculation process for acquiring a signal and outputting a flow value is performed.In the measurement calculation process, when a new non-zero Kalman frequency is obtained when the measured flow output is zero, a predetermined delay is set. During the time, the flow measurement output keeps zero value, and when the non-zero Kalman frequency is obtained after the delay time has elapsed, Corresponding flow rate signal is to be outputted. For this reason, even if a shock or the like is applied to the flow rate detector and a suspicious output signal is generated when the flow rate measurement value indicates zero, a delay time longer than the shock vibration decay time should be set. As a result, the zero flow output value before the impact is applied is held until the shock vibration is attenuated, so that even when the flow rate is zero, a stable and highly reliable measurement value which is not disturbed by noise is obtained. This effect can be obtained by a transmission unit having a simple configuration using a single microcomputer.

[Brief description of the 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 timing chart for explaining the operation of the flow meter of FIG. 1;

FIG. 3 is a flowchart of a measurement reference period timer interrupt process;

FIG. 4 is a flowchart of a flow detection unit output pulse interrupt processing;

FIG. 5 is a flowchart of an output process.

[Explanation of symbols]

 1 Karman vortex flow detector 2 Transmitter 5 Reference period timer 6 Pulse interval measurement counter 3 Microcomputer 4 System clock 7 RAM PTF Pulse interval measurement flag EDF measurement end flag PTC Pulse interval integration counter PTB Pulse interval integration value buffer NPC pulse number counter NPB pulse number buffer FRQ frequency register FRB frequency buffer STC sampling time counter DEC delay time counter DES delay time setting times 8 ROM 81 sampling program 82 frequency calculation program 83 output processing program

Claims (1)

(57) [Claims] 1. A Karman vortex flow rate detector comprising a Karman vortex sensor having a flow rate detection end as a flow rate detector, and a transmission section for performing a calculation and an output process for calculating a flow rate by measuring an output pulse signal of the flow rate detector. Wherein the transmission unit is a microcomputer that performs step processing of computation and output at a timing given by a system clock that is a component, a fixed-period timer that provides a unit time of a cycle for performing computation output processing, A pulse interval measurement counter for measuring a time interval between pulse signals transmitted by the flow rate detection unit, a ROM storing procedures of calculations and processes performed in the microcomputer, and a count value generated in a process of the calculation process RA that temporarily stores and a mantissa
M, a count-up signal of the reference period timer, and an output signal of the flow rate detection unit as an interrupt signal by a processing procedure called by the microcomputer from the ROM,
The frequency of the pulse output by the flow rate detector is measured for each sampling cycle determined by the reference cycle timer, and the flow rate is obtained by calculation. In the sampling cycle following the zero sampling rate, the non-zero flow rate is detected and measured. Then, during a predetermined delay time, a process of continuously outputting an output signal of zero flow rate is performed, and a measurement value obtained in a new sampling cycle after the delay time has elapsed is output. A Karman vortex flowmeter characterized in that: