JPH0120651Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a pulse detection circuit, and is applied, for example, to detecting flow rate pulses in a flowmeter, and is used to detect failures in flowmeters and their peripheral equipment through which fluid with relatively large flow rate fluctuations passes. The present invention relates to a pulse detection circuit that can detect pulses.

Generally, in a metered liquid supply device, a desired amount of liquid to be supplied is preset in a preset counter, and when the fluid passes through a flow meter after the start of liquid supply, the flow rate pulses that are sequentially transmitted from a flow rate pulse generator are sent to the preset counter. Some devices count the amount of liquid, and when the counted value matches the preset value, the liquid supply pump is stopped and a fixed amount of liquid is supplied. However, this method has the problem that it cannot deal with defects in the equipment itself, such as a defect in the flow rate pulse generator or a disconnection in the transmission line, and the fluid continues to flow and overflows.

Therefore, the present applicant previously proposed a patent application No. 50-131048 entitled "Abnormality Detection Circuit for Flow Meter", in which a counting circuit connected to a flow meter receives a constant number of clock pulses emitted within a set time from an oscillator circuit and performs counting. At the same time, the flow pulse from the flow pulse generator is input to the counting circuit at a cycle smaller than the above set time, and when the fluid flows normally, a clock pulse is generated by inputting the flow pulse every time the above set time is repeated. It is reset to zero before the counted value reaches the above-mentioned certain number, so that an alarm will not be generated.
On the other hand, even if the fluid is flowing normally, if the flow rate pulse is not transmitted due to a defective pulse transmitter, transmission line failure, etc., the counter will not be reset to zero and will count the clock pulses up to the above fixed value, causing an alarm. We have proposed a system that detects the above failure and prevents overflow. That is, according to this, since the above-mentioned monitoring setting time and the number of clock pulses during that time are each constant values, the above-mentioned case where the fluid inherently flows without large flow rate fluctuations, that is, when the flow rate pulse cycle is approximately constant, It detects failures in pulse generators, transmission lines, etc.

However, if the fluid inherently flows with relatively large flow rate fluctuations, that is, with large fluctuations in the flow rate pulse period, it is difficult to set the above-mentioned monitoring time corresponding to this fluctuation period, and monitoring is not performed. The drawback was that it was not possible.

The present invention eliminates the above-mentioned drawbacks by variably setting successive monitoring times in response to relatively large fluctuations in the flow rate of fluid passing through a flowmeter and monitoring the presence or absence of flow rate pulses. Its configuration consists of an output circuit that outputs the detection pulse from the detector at variable intervals, an oscillation circuit that oscillates a clock pulse with a predetermined cycle, and a clock pulse that outputs the clock pulse at a predetermined cycle. a counting circuit that counts the number of clock pulses or its corresponding number as a first count value; and a counting circuit that counts the number of clock pulses or its corresponding number as a first count value;
a matching circuit (preset counter) that sequentially counts the counted value of the first and second counted values and outputs a predetermined signal when the first and second counted values match; and a matching circuit (preset counter) that resets the counted value of the counting circuit to zero every cycle of the detected pulse. A reset circuit is used to detect an abnormality in the detector based on the predetermined signal.

Next, one example will be explained.

FIGS. 1 and 2 are a circuit diagram and a time chart, respectively, when one embodiment of the pulse detection circuit according to the present invention is applied to monitoring the flow rate of a flowmeter.
In Fig. 1, 1 is a measurement signal input terminal, 2 is an input terminal for flow rate pulses from a flow pulse generator, 3 is an AND gate, 4 and 5 are mono multivibrators, 6 and 8 are flip-flop circuits, and 7 is an or gate.

Reference numeral 9 denotes an oscillator circuit which oscillates a clock pulse having a frequency sufficiently higher than the flow rate pulse frequency. 10 is a frequency division counter circuit which counts pulses by varying the frequency division ratio N arbitrarily by an external setting switch 11, and oscillates pulses having a frequency of 1/N of the clock pulse from the oscillator circuit 9. 12 and 13 are mono multivibrators, respectively, and 14 and 15 are AND gates, respectively.

A readout counter 21 counts and reads out the clock pulses of the oscillator circuit 9 corresponding to one period of the flow rate pulse that has passed through the AND gate 14.

22 is a preset counter which takes in (loads) and stores the number of clock pulses from the readout counter 21 when the mono multivibrator 12 outputs the one shot load signal;
From this value, a frequency division counter circuit 10 corresponding to one cycle of the next circulating pulse that has passed through the AND gate 15
subtracts the number of frequency-divided pulses, and outputs an alarm signal when the subtracted value becomes zero.

23 is a time counter whose set value is varied by the setting switch 24, which monitors the time from when the metering signal is input until when the first flow rate pulse is input, and when this time exceeds the set value, it outputs an alarm signal. Output. 25 is an OR gate, 26 is a flip-flop circuit, and 27 is an alarm signal output terminal.

Further, 28 is an inverter, and 29 is an AND gate, which generates an alarm if a flow rate pulse is input when no metering signal is output.

Next, the operation of the pulse detection circuit will be explained. In FIG. 1, when the measuring signal 1a shown in FIG. 2A is input to the terminal 1, the flip-flop circuit 6
is triggered by the signal 1a and outputs a signal 6a- ₁ as shown in C in the figure from the Q terminal. signal 6a
- ₁ is the output signal 4a of mono multivibrator 4
At the same time, the output signal 7a reaches the OR gate 7, and the OR gate output signal 7a as shown in FIG. Therefore, the flip-flop circuit 8 outputs a signal 8a- ₁ as shown in FIG. On the other hand, the clock pulse 9a as shown in FIG.
- ₁ opens the AND gate 14 and N in the same figure.
The clock pulse 9a- ₁ is sequentially inputted to the readout counter 21 and the time counter 23, and counting is started from zero as a numerical value _X1 .

On the other hand, the signal 8a- ₁ reaches the AND gate 15 at the same time, and together with the signal 6a- ₂ from the terminal of the flip-flop circuit 6, opens the AND gate 15.
A frequency-divided pulse 10a from a frequency-divided counter circuit 10 as shown in FIG. Furthermore, frequency division counter circuit 1
If the frequency division ratio N of 0 is 2, the number of divided pulses 10a is 1/2 of the number of clock pulses 9a within the same time, so the number of clock pulses 9a- ₂ is set to 100, for example.
(-X ₂ ), the frequency divided pulse 10a- ₂ during this period
The number of is 50(−x ₂ ).

Here, if no flow rate pulse is input from the input terminal 2 even after a certain period of time has elapsed after the input of the measuring signal 1a, the time counter 23 continues to count the clock pulses 9a- ₁ , and this counted value becomes the above-mentioned value. When it matches the set value set by the setting switch 24, that is, when it counts up, an alarm signal is output and the flip-flop circuit 26 is triggered via the OR gate 25. Therefore, the flip-flop circuit 26 holds the alarm signal and continuously outputs the alarm signal from the terminal 27 to warn that the first flow rate pulse 2a shown in FIG. 2B does not reach. Here, the set value of the setting switch 24 can be varied, and the initial monitoring time until the first flow rate pulse 2a is reached can be arbitrarily set variably.

However, if the first flow rate pulse 2a as shown in figure B is input before the time counter 23 counts up, the AND gate 3 opens and the signal 3a as shown in figure H is output to the mono multivibrator 4, respectively. 5 is input. Therefore, _the output signal 4a of the mono multivibrator 4 becomes _low level for a short time as shown in FIG. , signal 5
A- ₁ resets the flip-flop circuits 6 and 8, respectively, and makes the signals 6a- ₁ and 8a- ₁ low as shown in FIG. The reading is stopped when X ₁ pieces have been read during the time t ₁ up to that point. Also, when the flip-flop circuit 8 is reset, the signal 8b- ₁ is output from the terminal as shown in G in the figure, so the mono multivibrator 12 outputs the one-shot signal 1 as shown in M in the figure.
2a is output and inputted to the L terminal of the preset counter 22 as a load signal. Therefore, the count value _X1 of the clock pulse 9a counted as described above by the readout counter 21 is the preset counter 2.
2 via terminal D and stored. Furthermore, the rise of the one-shot signal 5b- ₁ from the terminal of the mono-multivibrator 5 triggers the mono-multivibrator 13 as shown in FIG.

In this way, preparations for sequentially detecting the flow rate pulses 2a, 2b, 2c, . . . and issuing an alarm for failure of the flow rate pulse transmitter or the like are completed.The meaning of the period of the flow rate pulses will now be explained. Between each rising point of the flow rate pulses 2a and 2b (i.e., in one period of the flow rate pulse in Fig. 2B)
The flow rate (denoted as T ₁ ) is the following flow rate pulse 2b, 2
It is equal to the flow rate between each rising point of c (that is, one cycle of the next flow rate pulse, indicated by T ₂ in B in the same figure), and therefore, if the next cycle is infinite compared to the previous cycle, then This means that the above-mentioned failure has occurred, and an alarm is issued to warn you. However, in reality, it is impossible to detect the infinity of the next cycle, so the presence or absence of the next flow rate pulse is detected within the monitoring time set based on the first cycle, and if there is no flow pulse, It is confirmed that the above failure occurred. Here, since oil is not supplied during the time t ₁ from when the measuring signal 1a is input to when the first flow pulse 2a is input, from the second flow pulse 2b, that is, from the time T ₁ to T ₂ The above-mentioned monitoring time detection work shall be performed sequentially in this order.

The output signal 4a of the mono multivibrator 4 has become low level due to the first flow rate pulse 2a.
rises to a high level after a short period of time as shown in Figure 2D, and at this time triggers the flip-flop circuit 8 again via the OR gate 7, causing
The signal 8a- ₂ is output from the terminal, and the output of the signal 8b- ₁ from the terminal is stopped. This signal 8
a- ₂ reaches the AND gates 14 and 15, and the readout counter 21 starts reading the clock pulse 9a- ₂ as shown at N in the figure as a value _X2 from zero. Further, the preset counter 22 is supplied with a frequency-divided pulse 10a- ₂ as shown in FIG. Here, in the preset counter 22, the count value X _a-1 (a
-2, 3,...), the above frequency divided pulse 1 is read out sequentially.
The work of successively subtracting the counted value x _a (a=2, 3,...) of 0a- ₂ starts at the same time, and the above memorized value x _a-1
continues to decrease until it reaches zero by successively continuing the calculation (X _a-1 −x _a ), and the time during this is the monitoring time.

Therefore, if the flow rate pulse transmitter continues to operate normally, a signal is sent to terminal 2 as described below before the monitoring time elapses, that is, before the (X _{a -1} - x _a ) value becomes zero. The second flow rate pulse 2b as shown in FIG. 2B is input and no alarm signal is generated.

However, due to a defect in the flow pulse generator, a failure in the transmission line, etc., the second flow pulse 2b is output to terminal 2.
If the input is not input or there is a large delay, the above monitoring time will pass and the above (X _a-1 - x _a ) value will become zero, and at the time it reaches zero, the preset counter 22 will issue an alarm signal. An alarm signal is continuously outputted via the OR gate 25 and the flip-flop circuit 26, and the above-mentioned failure is detected and an alarm is issued.

Here, the clock pulse 9a and the frequency division pulse 10
Since the frequency ratio of a is N:1 based on the frequency division ratio N (N-2 in this case) set by the setting switch 11, the number of clock pulses loaded above is N times the time required for counting. It is equal to the number of frequency-divided pulses input within. Therefore, roughly speaking, if the current cycle (time T ₁ ' in this case) is within N times the previous cycle of the flow rate pulse (time t _{1 in this case), the above failure detection alarm will not be generated, but if the current cycle (time T 1} ' in this case) is within N times, If the flow rate exceeds this value, the above-mentioned alarm will be issued, and this comparison will be repeated every time a flow rate pulse is input thereafter. Therefore, the above-mentioned N times period, that is, the monitoring time, is successively set variably in response to fluid flow rate fluctuations, and even when fluid flow rate fluctuations are large, failures of the flowmeter and its peripheral equipment can be prevented. Accurate detection and effective monitoring can be performed.

Next, before the alarm is issued from the terminal 2 as described above, a second flow rate pulse 2 as shown in FIG. 2B is generated.
If b is input, the mono multivibrator 5 is triggered in the same way as in the above case, so the readout counter 21 and preset counter 22 are reset by resetting the flip-flop circuit 8 and stopping the signal 8a- ₂ . Counting of the clock pulse 9a- ₂ and frequency division pulse 10a- ₂ is stopped, and the monomultivibrator 12 is stopped.
The clock pulse count value _X2 of the readout counter 21 is loaded and stored in the preset counter 22 in place of the count value _X1 by the one shot signal 12b. At the same time, one shot signal 5b- ₂ of mono multivibrator 5 is generated in the same manner.
When the terminal rises, the one-shot signal 13b is output, and the lead-out counter 21 and time counter 23 are reset to zero.

Subsequently, in the same way as in the above case, the rise of the signal 4a of the mono multivibrator 4 causes the flip-flop circuit 8 to output the signal 8a- ₃ , and the readout counter 21 receives the clock pulse 9a-3.
Start reading ₃ as the number X ₃ from zero. Here, in the same manner, the count value of the frequency division pulse 10a- ₃ is calculated from the memory count value _X2 using the preset counter 22.
The work of successively subtracting x ₃ is started, and the above memorized value is
X ₂ continues to decrease as the calculation of (X ₂ −x ₃ ) continues. Therefore, in the same way, the flow rate pulse generator continues to operate normally, and before the above (X ₂ −x ₃ ) value becomes zero, the third flow rate pulse 2c as shown in FIG. 2B is input to the terminal 2. Similarly, a new clock pulse count value _X3 is stored in the preset counter 22, and this operation is repeated every time a flow rate pulse is input.

As shown in FIGS. 2A and 2B, if there is a flow rate pulse 2n after the metering signal 1a disappears, the AND gate 3 does not open, and the signal 28a output from the inverter 28 and the signal 28a output from the inverter 28 as shown in FIG. As a result, the AND gate 29 is opened and a signal 29a as shown in J in the figure passes through, and the OR gate 25 and the flip-flop circuit 2
6 and issues an alarm to warn of an abnormality.

As described above, according to the pulse detection circuit of the present invention, the count value of the clock pulse corresponding to the current detection pulse is set and stored based on the count value of the clock pulse corresponding to the detection pulse one cycle before, that is, within the monitoring time. Since it is designed to monitor, it can be applied, for example, to detect abnormalities such as failure of a flow meter, and the monitoring time can be variably set according to the current flow rate even if the fluid flow rate fluctuation is relatively large. The above-mentioned failures can be detected accurately and effectively, and the range of application of abnormality detection can be greatly expanded, which is convenient. Also, the monitoring time can be set to the cycle of the detection pulse (flow rate pulse) one cycle before. Since it is automatically varied accordingly, there is no need for the operator to perform troublesome work such as setting the monitoring time variably according to the flow rate, thereby reducing the number of man-hours.

[Brief explanation of the drawing]

FIG. 1 and FIGS. 2A to 2P are a circuit diagram and a time chart, respectively, when one embodiment of the pulse detection circuit according to the present invention is applied to monitoring the flow rate of a flowmeter. 4, 5, 12, 13... Mono multivibrator, 6, 8, 26... Flip-flop circuit, 9
... Oscillator circuit, 10 ... Frequency division counter circuit, 11, 24 ... Setting switch, 21 ... Readout counter, 22 ... Preset counter, 23 ... Time counter.

Claims (1)

[Claims for Utility Model Registration] 1. An output circuit that outputs detection pulses from a detector at variable cycles, an oscillation circuit that oscillates clock pulses with a predetermined cycle, and an output circuit that outputs the clock pulses at a given cycle of the detection pulses. a counting circuit that counts the corresponding number as a first count value; It consists of a coincidence circuit that outputs a predetermined signal when the first and second count values match, and a reset circuit that resets the count value of the counting circuit to zero every cycle of the detection pulse, and the predetermined signal causes the detector to A pulse detection circuit configured to detect abnormalities in. 2. The matching circuit has a frequency dividing/counting circuit, and the first count value, which is the number of clock pulses, and the number of clock pulses are divided and counted by the frequency dividing/counting circuit at a predetermined frequency division ratio. 2. The pulse detection circuit according to claim 1, wherein the pulse detection circuit is configured to output the predetermined signal when the counted value of .