JPS5836296B2 - Flowmeter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flowmeter, and in particular includes an abnormality detection section that detects an abnormality in a flow rate measurement value, and an abnormality detection signal from the abnormality detection section that is counted and subjected to preset discrimination. A flow rate comprising an abnormality counter that determines an abnormality by comparing it with a standard, and an output holding section that maintains the flow velocity measurement value during the abnormality at the measurement value before the abnormality occurrence based on the abnormality determination output from the abnormality counter. It is related to the meter.

The prior art will be explained with reference to FIGS. 1 to 3.

Figure 1 is a block diagram for explaining the overall configuration of a flowmeter that is equipped with an abnormality counting function and an output holding function that maintains the flow velocity measurement value at the value measured immediately before the abnormality occurs when an abnormality occurs. Block diagram showing details of the abnormality counting section in the figure, No. 3
The figure is a time chart of signals of each part for explaining the operation of FIG. 2.

Probes 2 and 3 are attached to a tube 1 through which fluid flows.

For example, an ultrasonic transducer is used as the probe.

The flow velocity measuring section 4 processes the signals sent from the probes 2 and 3 to measure the flow velocity.

In the case of a flow meter that uses ultrasonic waves, the ultrasonic waves will be interrupted if there is foreign matter, such as dust or air bubbles, in the ultrasonic propagation path.

If the ultrasonic wave is interrupted, flow velocity measurement cannot be performed.

However, the flow velocity measurement unit 4 outputs some value as the flow velocity even while the ultrasonic waves are interrupted.

This flow velocity value is different from the true flow velocity.

This is because the ultrasonic signals received by the probes 2 and 3 are themselves scattered by foreign objects.

Therefore, it is determined whether the ultrasonic waves are propagating normally or not, and if there is an abnormality, the flow velocity output from the flow velocity measuring section 4 is maintained at the value before the abnormality occurred, or an alarm is issued, and the user A device is required to notify of abnormalities.

The abnormality detection section 5 looks at the ultrasonic reception signals from the probes 2 and 3 in the flow rate measurement section 4 and determines whether the ultrasonic waves are propagating normally.

When an abnormality is detected, the signal holding section 7 is caused to hold the flow velocity output immediately before the abnormality occurred.

Further, the abnormality counting section 6 counts and processes the abnormality detection signal from the abnormality detection section 5.

FIG. 2 shows the configuration.

The third factor is the time chart of the respective signals.

The abnormality detection signal from the abnormality detection section 5 becomes an enable signal 11 and a reset signal 13 for the counter 10, and the
0 counts clock signal 12 from clock 15.

The enable signal 11 from the abnormality detection unit 5 is abnormal (ABN
), the counter 10 performs counting operation, and when the enable signal 11 returns to normal (N), the counter 1
0 is reset.

When the count value of the counter 10 reaches a value equal to or greater than a preset value, an output 14 is generated.

This output 14 becomes a set signal for the flip-flop 16, and the output 23 of the flip-flop 16 is inverted.

Further, the output from the abnormality detection section 5 passes through a sign inverting circuit 17, and the signals whose sign is inverted become an enable signal 19 and a reset signal 21 for the counter 18.

The operation of the counter 18 is similar to that of the counter 10, in that it counts the clock signal 20 from the clock 15, and when the counted value exceeds a set value, an output 22 is generated.

This output 22 becomes a reset signal for the flip-flop 16, and the output 23 of the flip-flop 16 is inverted again.

In this way, the output 23 of the abnormality counting section 6 is
When the output is abnormal (ABN) and the period exceeds a certain set value, it is inverted, and conversely, when it is normal (N) and the period exceeds a certain set value, it is inverted again.

By applying this output 23 to the signal holding section 7 in FIG. 1, the signal holding section 7 is caused to hold the flow velocity output immediately before the occurrence of the abnormality.

The input to the signal holding unit 7 is the output from the abnormality detection unit 5,
Although the output 23 from the abnormality counting section 6 overlaps with the output 23, the output from the abnormality counting section 6 corresponds to an abnormality with a longer period, resulting in a double output holding mechanism.

In addition, the alarm output 9 is the output 23 of the abnormality counter 6 which has a long cycle.
Make it work.

However, the conventional output holding and alarm signal output mechanism described above has the following disadvantages.

The interruption of ultrasonic propagation is thought to be due to the influence of foreign matter, as described above.

Therefore, particularly in highly turbid liquids and sewage, ultrasonic propagation is frequently interrupted due to the influence of foreign substances.

In this case, with the conventional output holding and alarm signal output mechanism, the abnormality counting section 6 cannot respond to the rapid output change from the abnormality detection section 5.

For example, no matter how many times an abnormality (ABN) that is shorter than the set period occurs, the output of the abnormality counter 6 will not be reversed, so it is assumed that the normal state continues. No matter how many times N) appears, the output of the abnormality counter 6 will not be reversed again and it will be considered that the abnormality continues.

That is, conventional flow meters cannot quickly respond to abnormalities and normal conditions.

The purpose of the present invention is to eliminate the above-mentioned disadvantages of the prior art, and to distinguish between normal and abnormal according to the ultrasonic propagation situation even in cases where it is easily affected by foreign substances such as highly turbid liquid or sewage. The purpose of the present invention is to provide a flow meter that can discriminate and measure a stable flow rate.

The feature of the present invention is to determine the proportion of the period during which ultrasonic propagation is normal and to determine that the proportion exceeds a certain value as normal, and to determine that the following cases are abnormal. During a preset first cycle, the abnormality detection signal from The abnormality counter is configured to determine an abnormality in a measured flow velocity value based on whether or not the measured value exceeds a set determination reference value.

An embodiment of the present invention will be described below with reference to FIGS. 4 and 5.

What has been largely changed in the present invention is the structure and function of the abnormality counting section 6, and FIG. 4 shows its block structure.

FIG. 5 is a time chart of signals of each part for explaining the operation of FIG. 4.

The output 38 from the abnormality detection section 5 is input to the AND gate 31 together with the clock signal 34 from the clock 30, and the output of the AND gate 31 is used as the clock signal 35 of the counter 32.

The period of clock signal 34 will be referred to as the second period.

Further, the clock signal from the clock 30 is inputted to the time width setter 33, where a reset signal 36 having a preset period (first period) is generated.

The output of the counter 32 passes through a latch 37 and becomes the output 39 of the abnormality counter.

When the output 38 from the abnormality detection section 5 fluctuates as shown in FIG. 5, the clock power 35 generated by sampling this with the clock signal 34 is applied to the counter 32.

The measurement period of the counter 32 is the first period of the reset signal 36.
The period is

During each of these first cycles, if there is a clock force 35 greater than the set value of the counter 32, the output of the abnormality counter 3
9 is reversed.

The signal holding unit 7 (FIG. 1) receives this abnormality counter output 39 and holds the flow velocity measurement value at the value before the abnormality occurred.

Further, the abnormality counter output 39 becomes the alarm output 9 (FIG. 1).

In this manner, in the embodiment shown in FIG. 4, abnormality is determined based on the percentage of abnormality or normality during the first period.

The present invention can be realized not only by a hardware circuit configuration but also by software using a microcomputer or the like.

FIG. 6 is a flow diagram when the present invention is implemented by software.

When a reset is applied with a signal corresponding to the reset signal 36 having the first period, the memory i is set to zero.

Thereafter, each time there is a timer interrupt corresponding to the clock signal 34 having the second period, it is determined whether or not the abnormality detection section output 38 is abnormal. ″ increases.

When the content of the memo IJi becomes equal to a preset value N, a final output corresponding to the abnormality counter output 39 is set, and this final output is sent to the output holding unit 7 and the alarm output 9.

In this way, when the present invention is implemented using software, the hardware configuration can be simplified, and the ratio that is the standard for abnormality determination can be changed by a simple program change.

According to the present invention, even when susceptible to the influence of foreign substances such as highly turbid liquid or sewage, the
It is possible to create a flowmeter that can distinguish between normal and abnormal and can measure stable flow rate.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the overall structure of a flowmeter to which the present invention is applied, Fig. 2 is a block diagram of a conventional abnormality counter, Fig. 3 is a time chart of signals of each part in Fig. 2, and Fig. 4 5 is a block diagram of an abnormality counter showing one embodiment of the present invention, FIG. 5 is a time chart of signals of each part in FIG. 4, and FIG. 6 is a flow diagram for explaining another embodiment of the present invention. 2, 3... Probe, 4... Flow velocity measuring section, 5... Abnormality detection section, 6... Abnormality counting section, 7...・Output holding unit, 30...Clock, 32...Counter, 33...
Time width setting section, 37... Latch, 38...
... Abnormality detection section output, 39... Abnormality counter output.

Claims (1)

[Claims] 1. An abnormality detection section that detects an abnormality in the flow velocity measurement value, an abnormality counting section that determines an abnormality by counting the abnormality detection signal from this abnormality detection section and comparing it with a preset discrimination standard, and an abnormality counting section. In the flowmeter, the abnormality counting section is configured to output the abnormality detection signal from the abnormality detection signal to a preset value. During the first cycle, sampling and counting are performed in a second cycle that is set shorter than the first cycle, and whether the counted value within the first cycle exceeds a preset discrimination reference value. 1. A flowmeter characterized by having an abnormality counter that determines whether a flow velocity measurement value is abnormal based on whether or not the flow rate is abnormal.