JP4828745B2 - Vortex flow meter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vortex flowmeter, and more particularly, to a vortex flowmeter configured to monitor the presence or absence of abnormality in flow measurement to prevent erroneous measurement.
[0002]
[Prior art]
As a conventional vortex flowmeter using ultrasonic waves, for example, as shown in FIGS. 1 and 2, a vortex generator 2 that generates Karman vortices in a flow path 1a of a flowmeter main body 1 through which a fluid to be measured flows, The ultrasonic transmitter 3a that transmits ultrasonic waves to the fluid to be measured flowing downstream of the vortex generator 2, and the ultrasonic reception that receives the ultrasonic waves that have passed through the fluid to be measured in the flow path 1a and outputs a reception signal A phase comparator 8 for generating a vortex signal corresponding to the frequency of the Karman vortex by comparing the phases of the transmitter 3b and the transmission signal input to the ultrasonic transmitter 3a with the reception signal output from the ultrasonic receiver 3b. And have.
[0003]
A transmission signal from the transmitter 4 is amplified by the amplifier 5 and supplied to the ultrasonic transmitter 3a. The reception signal output from the ultrasonic receiver 3 b is amplified by the amplifier 6, shaped by the waveform shaping circuit 7, and input to the phase comparator 8.
[0004]
In the vortex flowmeter, the ultrasonic wave transmitted from the ultrasonic transmitter 3a is propagated in the fluid, and the modulated wave from the Karman vortex is received by the ultrasonic receiver 3b, and amplified and shaped in waveform. By comparing the phases of the obtained reception signal and transmission signal, a vortex signal proportional to the frequency of the alternating Karman vortex generated downstream of the vortex generator 2 was obtained.
[0005]
The phase comparator 8 compares the phases of the transmission signal output from the transmitter 4 and the reception signal output from the ultrasonic receiver 3 b and outputs a vortex signal obtained from the phase difference to the amplifier 9. The vortex signal amplified by the amplifier 9 is subjected to waveform shaping by the waveform shaping circuit 10 and input to the control circuit 11 to be converted into a flow rate measurement value.
[0006]
The vortex signal amplified by the amplifier 9 is also input to the amplitude monitoring circuit 12, the amplitude monitoring circuit 12 monitors the change in amplitude, and the presence or absence of abnormality is supplied to the control circuit 11. In the control circuit 11, when an amplitude abnormality of the vortex signal occurs, the vortex signal integration process is stopped to prevent a measurement error from occurring.
[0007]
The transmission signal output from the transmitter 4 has a constant period. On the other hand, the ultrasonic wave propagated in the fluid to be measured is subjected to phase modulation (Doppler effect) from the Karman vortex generated alternately. Therefore, when the phase comparator 8 compares the phase of the transmission signal and the reception signal, the phase difference changes according to the generation of vortices.
[0008]
It is known that the Karman vortex has a higher frequency in proportion to the increase in the flow velocity, and the magnitude of the modulation (vortex signal amplitude value) that the ultrasonic wave receives by the Karman vortex increases in accordance with the flow velocity. Therefore, the vortex flowmeter calculates the flow rate by measuring the frequency of the Karman vortex generation. The pulse of the vortex signal output from the waveform shaping circuit 10 has a duty of 50%.
[0009]
However, in the vortex flowmeter configured as described above, due to the influence of pressure pulsation caused by other equipment on the pipe through which the fluid to be measured flows and the turbulence of the flow in the high flow area, In some cases, a flow signal (vortex signal) is output even though there is no flow.
[0010]
In this case, it is known that the proportional relationship between the frequency and the amplitude value of the vortex signal is lost, and the duty of the pulse does not become 50%. When there is an abnormality, the output of the vortex signal is stopped or an alarm is output for notification.
[0011]
Also, when an abnormality occurs in the electrical circuit that processes the above-mentioned signals, the output may also become abnormal. For this, the presence or absence of abnormality is monitored by monitoring the signal amplitude value of the transmission signal and reception signal. Has been detected.
[0012]
The reception signal output from the ultrasonic receiver 3b is amplified by the amplifier 6 and then subjected to waveform shaping by the waveform shaping circuit 7 and input to the phase comparator 8. The ultrasonic transmitter 3a and the ultrasonic receiver 3b When an abnormality occurs in the reception amplifier circuit (amplifier 6 and waveform shaping circuit 7) including the received signal, the reception signal is not input to the phase comparator 8, and as a result, the output of the phase comparator 8 becomes abnormal.
[0013]
Therefore, in the prior art, as shown in FIG. 3, the second amplitude monitoring circuit 13 averages whether the output value of the receiving amplifier 6 is an amplitude value sufficient to be pulsed by the waveform shaping circuit 7. Monitoring. Similarly, the third amplitude monitoring circuit 14 monitors whether the transmission signal from the transmitter 4 is also transmitted to the ultrasonic transmitter 3a with a specified signal amplitude value.
[0014]
In addition, as shown in FIG. 3, the above-described monitoring is performed in all cases, and the transmission signal, the reception signal, the vortex signal, the electric circuit and the flow state of the fluid to be measured (presence of pulsation due to pressure fluctuation) are constantly monitored. It was.
[0015]
Note that the transmission signal and reception signal determination method depends on the configuration of the amplitude monitoring circuits 13 and 14, but the transmission / reception signal is converted into a smooth voltage signal by the smoothing circuit and monitored by the A / D converter of the control circuit 11. And a voltage comparison IC.
[0016]
[Problems to be solved by the invention]
However, the conventional vortex flowmeter has a circuit configuration as shown in FIG. 3 in order to monitor Karman vortex detection abnormality and electric circuit failure, and always monitors the signals of all the monitoring circuits at regular intervals. As a result, there is a problem that the processing load of the control circuit 11 that performs the monitoring process becomes heavy and the calculation process of the flow rate measurement is delayed.
[0017]
Therefore, conventionally, if the circuit configuration is the same, the processing capacity of the control circuit 11 is lowered, leading to a decrease in flow rate measurement performance. Moreover, in the conventional vortex flowmeter, in order to improve the flow measurement performance of the control circuit 11, it is necessary to improve the performance of the CPU used in the control circuit 11, and the cost of the CPU increases.
[0018]
Therefore, an object of the present invention is to provide a vortex flowmeter that solves the above problems.
[0019]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has the following features.
The invention according to claim 1 includes a vortex generator that generates a Karman vortex in a flow path through which the fluid to be measured flows, an ultrasonic transmitter that transmits ultrasonic waves to the fluid to be measured flowing downstream of the vortex generator, An ultrasonic receiver that receives an ultrasonic wave that has passed through the fluid to be measured in the flow path and outputs a reception signal; a transmission signal that is input to the ultrasonic transmitter; and a reception signal that is output from the ultrasonic receiver. A phase comparator that generates a vortex signal corresponding to the cycle of the Karman vortex, a first monitoring unit that monitors whether the vortex signal is abnormal, and a second monitoring unit that monitors the transmission signal When the abnormality of the vortex signal is detected by the third monitoring means for monitoring the received signal and the first monitoring means, the transmission signal is monitored by the second monitoring means, and the vortex signal is detected by the first monitoring means. When an abnormality is detected, the third monitoring means switches to monitor the received signal. And vortex signal monitoring for monitoring the flow state of the fluid to be measured (Karman vortex presence / absence) and transmission / reception signal monitoring for monitoring the state of the transmission / reception circuit can be performed at the same time. Detects whether the error is caused by a flow or circuit abnormality to prevent erroneous measurement.
[0020]
According to a second aspect of the present invention, there is provided a vortex generator that generates a Karman vortex in a flow path through which a fluid to be measured flows, an ultrasonic transmitter that transmits ultrasonic waves to the fluid to be measured that flows downstream of the vortex generator, and An ultrasonic receiver that receives an ultrasonic wave that has passed through the fluid to be measured in the flow path and outputs a reception signal; a transmission signal that is input to the ultrasonic transmitter; and a reception signal that is output from the ultrasonic receiver. A phase comparator that generates a vortex signal corresponding to the cycle of the Karman vortex, a first monitoring unit that monitors whether the vortex signal is abnormal, and a second monitoring unit that monitors the transmission signal The third monitoring means for monitoring the received signal and the presence or absence of abnormality of the transmission signal are monitored. When the abnormality of the transmission signal is detected, the transmission signal is monitored by the second monitoring means regardless of the state of the vortex signal. And monitor the reception signal for abnormalities and detect abnormalities in the reception signal. And control means for switching so that the received signal is monitored by the third monitoring means regardless of the signal state, and the transmission / reception signal is monitored according to the state of the vortex signal, so that the control circuit operates efficiently. The monitoring function can be added without degrading the result measurement performance.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 4 is a block diagram showing an embodiment of the vortex flowmeter according to the present invention. In FIG. 4, the same parts as those in FIGS. 1 to 3 described above are denoted by the same reference numerals, and the description thereof is omitted.
[0022]
As shown in FIG. 4, the control circuit 21 of the vortex flowmeter 20 of the present invention only monitors the vortex signal in the normal state for the purpose of efficiently monitoring the vortex signal and the transmission / reception signal. When an abnormality is detected in the vortex signal, a control program (control means) for monitoring transmission / reception signals is stored in order to narrow down the cause.
[0023]
In the present embodiment, a smoothing circuit is employed as the first amplitude monitoring circuit (first monitoring means) 22 for monitoring the amplitude value of the vortex signal, and a voltage signal proportional to the signal amplitude is input to the A / D input of the control circuit 21. The data is taken into the cover 28 and monitored by the control circuit 21. The configuration of the amplitude monitoring circuit 22 is such that an AC component is extracted by the coupling capacitor 25 and then a smoothed signal voltage is extracted by the resistor 26 and the capacitor 27.
[0024]
Although not shown in FIG. 4, the second amplitude monitoring circuit (second monitoring means) 24 for the transmission signal and the third amplitude monitoring circuit (third monitoring means) 23 for the reception signal are also connected to the cup. The configuration is the same as the configuration of the amplitude monitoring circuit 12 having a smoothing circuit including a ring capacitor 25, a resistor 26, and a capacitor 27.
[0025]
Next, the monitoring operation of the monitoring means of the present embodiment will be described with reference to FIGS.
Now, it is assumed that there is no failure in the vortex flowmeter 20 and no abnormality (pulsation due to pressure fluctuation) has occurred in the flow of the fluid to be measured. At this time, the control circuit 21 normally only monitors the vortex signal output from the amplifier 9 at a constant interval t1.
Here, as shown in FIG. 5A, when an abnormality is detected in the vortex signal at the timing of monitoring A, until the monitoring timing (monitoring B) of the next vortex signal, FIG. ), The transmission signal and the reception signal are monitored at a constant interval t2.
[0026]
Next, another monitoring timing will be described with reference to FIGS. As shown in FIG. 6A, when an abnormality is detected in the vortex signal at the timing of monitoring A and the transmission / reception signal is monitored, it is determined that the transmission signal is abnormal. In this case, as shown in FIG. 6B, the monitoring of the transmission signal is continued at a constant interval t2 regardless of the state of the vortex signal.
[0027]
On the other hand, since the reception signal is normal, as shown in FIG. 6C, after monitoring only from monitoring A to monitoring B, the monitoring operation is stopped again. Further, when an abnormality is detected in the vortex signal in the monitoring C, the monitoring of the received signal is resumed as in the case of FIG.
[0028]
Next, regarding the arithmetic processing executed by the control circuit 21 to realize the monitoring method (see FIGS. 5 and 6), refer to the flowcharts of FIGS. 7 to 11, FIG. 13, and the state transition matrix of FIG. To explain.
[0029]
FIG. 7 is a control program for interrupting for a certain period of time for actual monitoring, FIG. 8 is a control program for performing vortex pulse rising interrupt, and FIG. 9 is a vortex pulse falling interrupt processing. The control program is classified as follows. Further, FIG. 10 is classified into a control program for monitoring a vortex signal by a predetermined time interruption routine, and FIG. 11 is classified into a control program for monitoring a received signal and a control program for performing a transmission signal monitoring routine (not shown).
[0030]
First, interrupt processing for a certain period of time will be described with reference to FIG.
As shown in FIG. 7, this fixed time interrupt processing uses the timer counter interrupt function of the control circuit 21 and is activated at predetermined time intervals (for example, at 100 msec intervals or 1 sec intervals).
[0031]
In step S1 of FIG. 7 (hereinafter, “step” is omitted), when a predetermined time has elapsed, the control circuit 21 reads a counter that measures the time for taking in the vortex pulse.
[0032]
In the next S2, it is checked whether the eddy pulse capturing time (counter value) has elapsed. When the vortex pulse capturing time (counter value) has elapsed in S2, the process proceeds to S3, and the vortex signal monitoring routine (vortex signal monitoring program) is started.
[0033]
In S2, when the vortex pulse capturing time (counter value) has not elapsed, the process proceeds to S4 without starting the eddy signal monitoring routine, and the received signal monitoring routine (received signal monitoring program) is started.
[0034]
Subsequently, a transmission signal monitoring routine (transmission signal monitoring program) is started in S5. Thus, the current process is terminated, and thereafter, the process after S1 is executed again after a predetermined time has elapsed.
[0035]
Next, the vortex pulse rising interrupt routine and the vortex pulse falling interrupt routine will be described with reference to FIGS.
[0036]
The vortex pulse is input to the input port of the control circuit 21, and the interrupt programs shown in FIGS. 8 and 9 are started in synchronization with the rise and fall of the vortex pulse.
[0037]
First, when the rising signal of the eddy pulse is inputted, the eddy pulse rising interruption program shown in FIG. 8 is started, and at S7, it is first confirmed whether it is the first pulse by the flow rate flag.
[0038]
In S7, in the case of the first pulse, that is, in the case where the flag is in the reset state, the process proceeds to S8 and the flow rate flag is set. Thereafter, the process proceeds to S12, where the timer counter is reset and started. In S13, the pulse number counter for storing the pulse number is incremented, and the current eddy pulse rising interrupt program is terminated.
[0039]
If it is not the first pulse in S7, that is, if the flag is set, the process proceeds to S9 to read the current timer counter value. In the next S10, the read timer counter value is stored in the memory as time t2 when the vortex pulse was at the low level. In S11, the pulse high level time t1 is read from the memory, and duty = t1 / (t1 + t2) is calculated and stored in the memory.
[0040]
In S12, the timer counter is reset and started in order to measure the pulse width (the time during which the vortex pulse is at a high level). In the next S13, the pulse number counter is incremented, and the current eddy pulse rising interrupt program is terminated.
[0041]
When the pulse falling signal is input, the control circuit 21 activates the pulse falling interrupt program shown in FIG. 9, and reads the timer counter value at that time in S14. In the next S15, the read timer counter value is stored as a pulse high level time. Subsequently, in S16, the timer counter is reset and started in order to measure the time during which the vortex pulse is at the low level, and the current pulse falling interrupt program is terminated.
[0042]
Next, the vortex signal monitoring process will be described with reference to FIG.
As shown in FIG. 10, when the eddy signal monitoring routine is started, the control circuit 21 first reads out the pulse number counter and, in S17, sets the value obtained by dividing the value by the acquisition time as the measurement frequency f0 and stores the memory of the control circuit 21. To remember. In the next S18, the pulse number counter is reset to zero in order to measure the frequency during the next acquisition time. In step S19, it is confirmed whether the measurement frequency f0 is equal to or lower than the monitoring method switching frequency f1.
[0043]
In S19, if f0 ≦ f1, the process proceeds to S20, where the current vortex signal amplitude v0 is measured and stored in the memory. Further, in S21, the theoretical value v1 of the vortex signal amplitude value at the measurement frequency f0 is calculated using an approximate expression showing the relationship between the vortex signal frequency f and the vortex signal amplitude v stored in advance in the program.
[0044]
In the next S22, the above v0 and v1 are compared to check whether vO is −n% or less of v1. In S22, if vO is −n% or less of v1, the process proceeds to S24, and it is determined that the vortex signal is abnormal.
[0045]
In S22, if vO is larger than -n% of v1, the process proceeds to S23, and it is checked whether vO is greater than + n% of v1. In S23, when vO is + n% or more of v1, the process proceeds to S24 and it is determined that the vortex signal is abnormal. In S23, when vO is less than + n% of v1, the process proceeds to S25 and it is determined that the vortex signal is normal.
[0046]
In S19, if f0> f1, the process proceeds to S26, where the aforementioned duty is read from the memory of the control circuit 11, and it is confirmed whether the duty is -m% or less. In S26, when the duty is -m% or less, the process proceeds to S28, and it is determined that the vortex signal is abnormal. In S26, if the duty is larger than -m%, the process proceeds to S27, and it is confirmed whether the duty is + m% or more.
[0047]
In S27, when the duty is + m% or more, it is determined in S28 that the vortex signal is abnormal. In S27, when the duty is less than + m%, the process proceeds to S29 and it is determined that the vortex signal is normal.
[0048]
Next, the received signal monitoring process will be described with reference to FIG.
As shown in FIG. 11, in the received signal monitoring process, the processing content is selected according to the state of the received signal amplitude. When the current state is state 1, the normal state, when it is state 2, the inspection state, and state 3 Is in an abnormal state.
[0049]
In S30, when the vortex signal is in a normal state, the state 1 is selectively activated, and the process proceeds to S31 to check whether there is an abnormality in the vortex signal. For example, the vortex signal monitoring result (not shown) Check with flags.
[0050]
If the vortex signal is normal as a result of monitoring the vortex signal in S31, the current process is terminated. If the vortex signal is abnormal as a result of monitoring the vortex signal in S31, the process proceeds to S32, and the output voltage signal of the received signal amplitude value smoothed by the amplitude monitoring circuit 13 is converted to the A / D of the control circuit 11. Obtained from the incoming port (not shown). Subsequently, the process proceeds to S33, where the received signal amplitude value is compared with a preset specified value.
[0051]
The specified value is determined from the circuit configuration, and is set to a smooth voltage value corresponding to an amplitude value necessary for pulsing by the waveform shaping circuit 7.
[0052]
If the received signal amplitude value is equal to or less than the specified value in S33, the process proceeds to S34, the counter for counting the continuous occurrence is set to 1, the state is changed to state 2, and the current process is terminated. Thus, at the next start-up, the state 2 is selected and processed in S30.
[0053]
If the received signal amplitude value is greater than or equal to the specified value in S33, the process proceeds to S35, the counter for counting continuous occurrence is reset, and the current process is terminated. As a result, at the next start-up, the state 1 (normal state) is selected and processed in S30.
[0054]
Next, state 2 (monitoring state) will be described.
State 2 corresponds to the inspection time t1 in FIGS. 5 and 6, and is a process for monitoring the state of the received signal during the time t1 at a constant period t2.
[0055]
When the state 2 (monitoring state) is selected in S30, the process proceeds to S36, and the output voltage signal of the received signal amplitude value smoothed by the amplitude monitoring circuit 13 is input to the A / D input port (not shown) of the control circuit 11. )). Subsequently, the process proceeds to S37, where the received signal amplitude value is compared with a preset specified value.
[0056]
If the received signal amplitude value is equal to or smaller than the specified value in S37, the process proceeds to S38, and 1 is added to the counter for counting the occurrence of continuity, and in S39, it is checked whether or not the abnormality of the received signal is continuous n times or more. In S39, when the reception signal abnormality is continuous n times or more, the process proceeds to S40, it is determined that there is an abnormality in the reception circuit, a reception circuit abnormality alarm is output, the continuous occurrence counter is reset, and the state Is changed to state 3 (abnormal state). In S39, when the abnormality of the received signal is not continuous n times or more, the current process is terminated without performing the process of S40.
[0057]
If the received signal amplitude value is greater than or equal to the specified value in S37, the process proceeds to S42 to check whether the inspection time t1 has elapsed. If the inspection time t1 has not elapsed in S42, the process proceeds to S43 and the state is changed to state 1. In S42, when the inspection time t1 has elapsed, since the reception signal abnormality did not occur n times during the inspection time, it is determined that there is no abnormality in the receiving circuit, and an alarm is not output and the current time is not output. The process ends.
[0058]
Next, state 3 (abnormal state) will be described.
State 3 is a monitoring process performed between the monitoring B and the monitoring C shown in FIG. 6, and monitoring is performed at a constant time interval t2 regardless of the state of the vortex signal because there is an abnormality in the received signal. It is.
[0059]
When the state 3 is selected in S30, the process proceeds to S44, and the output voltage signal of the received signal amplitude value smoothed by the amplitude monitoring circuit 13 is obtained from the A / D input port (not shown) of the control circuit 11. To do. Subsequently, the process proceeds to S44a, where the received signal amplitude value is compared with a preset specified value.
[0060]
In S44a, when the received signal amplitude value is less than or equal to the specified value (abnormal), in order to continue monitoring the received signal, the current process is terminated without resetting the continuous occurrence counter and changing the state.
[0061]
If the received signal amplitude value is greater than or equal to the specified value in S44a, the process proceeds to S46, and 1 is added to the counter that counts continuous occurrences, and in S47, it is checked whether the received signal is normal n times or more. . In S47, when the normality of the received signal is continuous n times or more, the process proceeds to S48, it is determined that the receiving circuit has returned to normal, the receiving circuit abnormality alarm is canceled, and the continuous occurrence counter is reset, And the state is changed to state 1 (normal state), and the current process is terminated.
[0062]
FIG. 12 is a state transition matrix showing the contents of the flowchart of FIG.
In FIG. 12, the state (status) of the received signal is shown in the row direction, and the situation (event) occurring at that time is shown in the column direction. Note that “-” shown in FIG. 12 means to be ignored. Further, regarding the transmission signal monitoring, the same processing as in FIG.
[0063]
Next, a modified example of the monitoring process will be described with reference to FIG.
In the above embodiment, the condition for determining the abnormality of the receiving circuit is the case where the abnormality occurs continuously n times, but in this modification, the condition is determined by the average value of the smoothed voltage values measured during the inspection time. The method will be described.
[0064]
In FIG. 13, when the state 1 (normal state) is selected in S30, the process proceeds to S31 and it is checked whether or not an abnormality has occurred in the vortex signal. If there is an abnormality in the vortex signal in S31, the process proceeds to S32, and the output voltage signal of the received signal amplitude value smoothed by the amplitude monitoring circuit 23 is input to the A / D input port (not shown) of the control circuit 21. Get from.
[0065]
In the next S49, the output voltage value of the acquired received signal amplitude value is recorded in the memory of the control circuit 21. Subsequently, in S50, the number of stored data is set to one. In the next S51, the state is changed to state 2 and the current process is completed.
[0066]
In S31, when there is no abnormality in the vortex signal, the current process is terminated in order to continue the state 1 without changing the state.
[0067]
When the state 2 (monitoring state) is selected in S30, the process proceeds to S36, and the output voltage signal of the received signal amplitude value smoothed by the amplitude monitoring circuit 23 is output to the A / D input port of the control circuit 21. (Not shown).
[0068]
In the next S52, the output voltage value of the acquired received signal amplitude value is recorded in the memory of the control circuit 11. Subsequently, in S53, 1 is added to the number of stored data.
[0069]
In the next S41, it is checked whether or not the inspection time t1 has elapsed. If the inspection time t1 has not elapsed in S41, the current process is terminated in order to continue the state 3 without changing the state in order to continue the state 2 monitoring state.
[0070]
When the inspection time t1 has elapsed in S41, the process proceeds to S54, and an average voltage value is obtained from a plurality of smoothed voltages stored in the memory and the number of stored data. In next S55, it is checked whether or not the average voltage value is equal to or less than a reference value. In S55, when the average voltage value is less than or equal to the reference value, the process proceeds to S56, where it is determined that an abnormality has occurred in the receiving circuit, an alarm is output, and the state is changed to state 3 (abnormal state).
[0071]
When the state 3 is selected in S30, the process proceeds to S44, and the output voltage signal of the received signal amplitude value smoothed by the amplitude monitoring circuit 23 is output from the control circuit 21 as in the case of the states 1 and 2. Acquired from A / D input port (not shown).
[0072]
In the next S58, the output voltage value of the acquired reception signal amplitude value is recorded in the memory of the control circuit 21. Subsequently, in S59, 1 is added to the number of stored data.
[0073]
In the next S60, it is checked whether or not a predetermined time t1 has elapsed. If the predetermined time t1 has not elapsed in S60, the current process is terminated in order to continue the state 3 without changing the state.
[0074]
In S60, when the predetermined time t1 has elapsed, an average voltage value is obtained from a plurality of smoothed voltages stored in the memory and the number of stored data. In next step S62, it is checked whether or not the average voltage value is equal to or less than a reference value. In S62, when the average voltage value is less than or equal to the reference value, the process proceeds to S63, where it is determined that the receiving circuit has returned to normal, the alarm output is canceled, and the state is changed to state 1 (normal state). End the process.
[0075]
【The invention's effect】
As described above, according to the first aspect of the present invention, the vortex generator that generates the Karman vortex in the flow path through which the fluid to be measured flows, and the ultrasonic wave that transmits ultrasonic waves to the fluid to be measured that flows downstream of the vortex generator. An ultrasonic transmitter, an ultrasonic receiver that receives an ultrasonic wave that has passed through the fluid to be measured in the recording channel and outputs a reception signal, and a transmission signal that is input to the ultrasonic transmitter and an output from the ultrasonic receiver A phase comparator that generates a vortex signal corresponding to the cycle of the Karman vortex by comparing the phase with the received signal, a first monitoring means that monitors whether the vortex signal is abnormal, and a first that monitors the transmission signal When the abnormality of the vortex signal is detected by the second monitoring means and the first monitoring means, the third monitoring means for monitoring the received signal and the second monitoring means monitor the transmission signal, and the first monitoring When the vortex signal abnormality is detected by the means, the received signal is monitored by the third monitoring means. And a control means for switching, so that the vortex signal monitoring for monitoring the flow state of the fluid to be measured (the presence or absence of Karman vortex) and the transmission / reception signal monitoring for monitoring the state of the transmission / reception circuit can be performed simultaneously. Detects whether the current output is due to flow or circuit abnormality to prevent erroneous measurement. In addition, since it is not necessary to constantly monitor the reception signal and the transmission signal, it is possible to reduce the burden on the control circuit and suppress an increase in cost.
[0076]
According to the invention of claim 2, the vortex generator for generating Karman vortices in the flow path through which the fluid to be measured flows, and the ultrasonic transmission for transmitting the ultrasonic waves to the fluid to be measured flowing downstream of the vortex generator. , An ultrasonic receiver that receives the ultrasonic wave that has passed through the fluid to be measured in the flow path and outputs a reception signal, a transmission signal that is input to the ultrasonic transmitter, and a reception that is output from the ultrasonic receiver A phase comparator that generates a vortex signal corresponding to the cycle of the Karman vortex by comparing the phase with the signal, a first monitoring means that monitors whether the vortex signal is abnormal, and a second monitor that monitors the transmission signal Means, a third monitoring means for monitoring the received signal, and the presence or absence of abnormality in the transmission signal. When the abnormality in the transmission signal is detected, the transmission signal is transmitted by the second monitoring means regardless of the state of the vortex signal. Is monitored, whether there is an abnormality in the received signal, and an abnormality in the received signal is detected. Includes control means for switching so that the third monitoring means monitors the reception signal regardless of the state of the vortex signal. Therefore, the transmission / reception signal is monitored according to the state of the vortex signal. Can be efficiently operated, and as a result, a monitoring function can be added without degrading measurement performance. Further, when the reception signal and the transmission signal always return to normal, by canceling the monitoring process, it is possible to reduce the burden on the control circuit and suppress an increase in cost.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a conventional example 1 of a vortex flowmeter.
FIG. 2 is a configuration diagram showing a conventional example 2 of a vortex flowmeter.
FIG. 3 is a configuration diagram showing a conventional example 3 of a vortex flowmeter.
FIG. 4 is a block diagram showing an embodiment of a vortex flowmeter according to the present invention.
FIG. 5 is a timing chart for explaining a monitoring operation by a monitoring unit.
FIG. 6 is a timing chart for explaining another example of the monitoring operation by the monitoring means.
FIG. 7 is a flowchart for explaining interrupt processing for a fixed time for actual monitoring.
FIG. 8 is a flowchart for explaining eddy pulse rising interrupt processing;
FIG. 9 is a flowchart for explaining eddy pulse falling interrupt processing;
FIG. 10 is a flowchart for explaining vortex signal monitoring processing;
FIG. 11 is a flowchart for explaining received signal monitoring processing;
12 is a state transition matrix showing the contents of the flowchart of FIG.
FIG. 13 is a flowchart for explaining a modified example of the monitoring process;
[Explanation of symbols]
1 Flow meter body
2 Vortex generator
3a Ultrasonic transmitter
3b Ultrasonic receiver
4 Transmitter
5,6,9 amplifier
7,10 Waveform shaping circuit
8 Phase comparator
20 Vortex flowmeter
21 Control circuit
22 First amplitude monitoring circuit
23 Third amplitude monitoring circuit
24 Second amplitude monitoring circuit
25 Coupling capacitor
26 Resistance
27 Capacitor

Claims (2)

A vortex generator for generating Karman vortices in the flow path through which the fluid to be measured flows;
An ultrasonic transmitter for transmitting ultrasonic waves to a fluid to be measured flowing downstream of the vortex generator;
An ultrasonic receiver that receives the ultrasonic wave that has passed through the fluid to be measured in the flow path and outputs a reception signal;
A phase comparator that generates a vortex signal corresponding to a cycle of the Karman vortex by comparing the phase of the transmission signal input to the ultrasonic transmitter and the reception signal output from the ultrasonic receiver;
First monitoring means for monitoring the presence or absence of abnormality of the vortex signal;
Second monitoring means for monitoring the transmission signal;
Third monitoring means for monitoring the received signal;
When the abnormality of the vortex signal is detected by the first monitoring means, the transmission signal is monitored by the second monitoring means, and when the abnormality of the vortex signal is detected by the first monitoring means, the third Control means for switching so as to monitor the received signal by the monitoring means,
A vortex flowmeter characterized by comprising: A vortex generator for generating Karman vortices in the flow path through which the fluid to be measured flows;
An ultrasonic transmitter for transmitting ultrasonic waves to a fluid to be measured flowing downstream of the vortex generator;
An ultrasonic receiver that receives the ultrasonic wave that has passed through the fluid to be measured in the flow path and outputs a reception signal;
A phase comparator that generates a vortex signal corresponding to a cycle of the Karman vortex by comparing the phase of the transmission signal input to the ultrasonic transmitter and the reception signal output from the ultrasonic receiver;
First monitoring means for monitoring the presence or absence of abnormality of the vortex signal;
Second monitoring means for monitoring the transmission signal;
Third monitoring means for monitoring the received signal;
Whether or not the transmission signal is abnormal is monitored, and when the transmission signal is abnormal, the transmission signal is monitored by the second monitoring means regardless of the state of the vortex signal, and the abnormality of the reception signal is detected. Control means for monitoring the presence or absence of the received signal and switching the received signal to be monitored by the third monitoring means regardless of the state of the vortex signal;
A vortex flowmeter characterized by comprising:

Images