JPH03242514A - Detecting system for flow rate - Google Patents

Abstract

PURPOSE:To prevent an erroneous detection of the abnormality of the flow rate by detecting the number of pulses from when a start instruction to start measuring of a frequency is received to when an end signal to inform completion of the measurement is input from a timer means, outputting the number of pulses outside and converting the output number as an input to the flow rate. CONSTITUTION:When a program is started to be executed, detection of a frequency by a frequency detecting means 10 and counting by a timer means 12 are started. A flow rate calculating means 14 detects whether the counting by the timer means is completed. If the counting is not completed, detection of the frequency is continued. If the counting is finished, the detected frequency is converted to the flow rate. If the flow rate is not smaller than a regulated minimum flow rate, the value of the flow rate is output. If the detected flow rate is smaller than the regulated minimum rate, abnormality of the flow rate is output.

Description

[Detailed Description of the Invention] ', Industrial Application Field 2 The present invention is a Klk for measuring the flow rate of a fluid flowing in a pipe, etc.
to the detection system.

[Conventional technology]

A detector as shown in FIG. 5 has conventionally been used as a flow rate detector for measuring the flow rate of fluid flowing in a pipe or the like. In FIG. 5, 2 is a pipe through which fluid flows, and 20
1 is an orifice flowmeter.

This flowmeter allows part of the fluid flowing through the pipe 2 to flow into the internal glass pipe 205, and floats 2 inside the glass pipe 20S.
02 is floated by the flow of fluid. The position of this float 202 in the glass tube 205 is
5, that is, the flow rate of the fluid flowing through the pipe 2. Therefore, by knowing the position of the float 202, the flow rate in the g2 can be known. Also, a magnet is prepared inside the float 202 (not shown).
. 203 is a fluid abnormality detector that detects changes in the magnetic field. 206 is a flow abnormality detection position. Here, when the float 202 crosses the flow abnormality detection position 206 according to the flow rate, the change in the magnetic field at this position from N to S or from S to N is detected by the flow 1 abnormality detector 203, and the float 202
It is possible to know whether the flow rate is above or below the flow rate abnormality detection position 206, that is, whether the flow rate is in a normal region or an abnormal region. In addition, the flow rate abnormality detector 203
02 is above or below the flow rate abnormality detection position 206, that is, whether the flow rate is normal or abnormal, the control unit 204 performs necessary processing as appropriate when an abnormality occurs.

[Problem to be solved by the invention]

The conventional flow rate detector described above has the following drawbacks.

Since the flow rate value must be visually read, it is not possible to input the flow rate value as data into the control unit and perform some processing (for example, digital display of the flow rate value, etc.). Also, since flow rate abnormality detection relies on changes in the magnetic field, when the earth's magnetism and surrounding magnetic fields are installed on the flow rate abnormality detector side,
Is it necessary to perform adjustment operations to cancel during maintenance, etc.?
In addition, orifice-type flowmeters have narrow internal channels, which can easily cause clogging and false detection of flow rate abnormalities.

The purpose of the present invention is to solve the above problems and provide a flow rate detection system that uses a Karman vortex flow rate detector as a flowmeter and digitally processes the output of this detector to obtain the flow rate. It is in.

[Means to solve the problem]

In order to achieve the above object, the flow rate detection system according to the present invention includes: a flow rate detector that outputs a pulse with a frequency proportional to the flow rate; a means for instructing the start of frequency measurement and measurement at an arbitrary fixed time; a timer means having a function of receiving an instruction to start the measurement and transmitting the end of the measurement for a certain period of time to an external device; and a timer means having the pulse as an input and receiving a start instruction from the frequency measurement start instruction means, and then starting the measurement from the timer means. The apparatus includes a means for measuring the number of pulses while inputting the end notification and outputting the pulse number to the outside, and a flow rate calculation means having a function of inputting the pulse number output and converting it into a flow rate.

〔Example〕

Next, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a tR function block diagram showing one embodiment of the present invention.

In the figure, ■ is a Karman vortex flow rate detector, and 4 is a probe for this detector. 2 is a pipe through which fluid flows. The operating principle of the Karman vortex flow rate detector 1 is as follows. That is, when the probe 4 is placed in a fluid perpendicular to the flow, a number of vortices (so-called Karman vortices) are generated downstream of the probe 4 in proportion to the flow rate. The number of these vortices is detected by a pick-up tube, and the Karman vortex flow rate detector 1 outputs a pulse with a frequency corresponding to the number of vortices. Reference numeral 10 denotes a frequency detection means, which detects the rising edge of a pulse. When the flow rate is below a certain standard, the pulses have a frequency proportional to the flow rate, and the pulses intersect with each other, and finally the pulse becomes less likely to occur. This situation is shown in FIGS. 3(a), (b), and (c). Normally, pulses are output correctly as shown in Figure 3 (a), but when the flow rate drops below the specified level, pulses are no longer output correctly as shown in Figure 3 (b), and finally, as shown in Figure 3 (C). As shown, it does not come out at all.

Therefore, if the pulse is not output correctly, the frequency detection means 1
If it is 0, the frequency cannot be detected correctly. Therefore, find in advance the minimum flow rate that will output pulses correctly.
Let the pulse frequency at that time be n. 11 is a frequency detection start instructing means, which instructs the frequency detecting means 10 to start detection. At the same time, the frequency detection start instructing means 11 instructs the timer means 12 to start time measurement.

The timer means 12 measures for one second, and when the measurement ends, notifies the frequency detection section 10 that the measurement has ended. At this point, the frequency detection means 10 stops detecting the rising edge of the pulse. Thereafter, the frequency detection means 10 transmits the counted number of pulse rises to the flow rate calculation means 14. This flow rate calculation means 1
4 has a function to calculate the flow rate from the number of pulses obtained per second, and a function to calculate the measurement pulse from the specified number of pulses obtained per second corresponding to the lower limit flow rate that can correctly detect the flow rate using the Karman vortex flow detector 1. It has a function of determining whether the number is large or small, that is, whether the pulse frequency is larger or smaller than the above n. If the number of measured pulses is equal to or greater than the specified number of pulses, the flow rate calculation means 14 outputs the obtained flow rate value to the flow I value output line 50. If the number of measured pulses is less than the specified number of pulses, the flow rate calculation means 14 outputs a flow rate abnormality to the flow rate abnormality output line 51. When the flow rate calculation means 14 completes the process, it notifies the initialization means 13 that the process has ended. Thereafter, the initialization means 13 sends an initialization signal to the frequency detection means 10, the frequency detection start instruction means 11, and the timer means 12. Thereafter, the frequency detection start instructing unit 11 instructs the start of pulse detection again.

FIG. 2 is a block diagram of the flow rate detection system of this embodiment constructed using a microcomputer. This microcomputer system consists of a CPU 71 with a built-in timer and an R O that stores the programs necessary for measurement.
M72, R for storing data necessary for measurement and judgment;
AM73, input port door 0 that receives pulse input from the Karman vortex flow rate detector l, outputs the flow rate value or flows! It consists of an output port door 4 that outputs abnormalities. CPU 71 controls the entire measurement. The input ports I to 70 receive pulse inputs, and the CP 71 detects and counts the rising edge of the pulse through the input port 0 during an internal timer measurement period. When the measurement is completed, the above-mentioned processing is performed and the flow rate abnormality or flow rate value is outputted from the output port door 4. This control is performed according to a software program. FIG. 4 is a flowchart of this program. When the program starts running (
Step 100 ), start frequency detection (measurement of pulse rise) and timer count (time measurement) (
Step 101). It is determined whether or not the timer count has ended (step 102); if not, the frequency detection is continued (step 103); if it has ended, the detected frequency is converted to a flow rate (step 1).
04). If the obtained flow rate is equal to or higher than the specified minimum flow rate (step 105), the flow rate value is outputted (step 106).
), if the flow rate is smaller than the specified minimum flow rate, a flow rate abnormality is output (step 107). After that, the frequency detection means, the frequency detection start instruction means, and the timer means are initialized.
108), return to step 101.

In this example, the measurement time is set to 1 second, or any other arbitrary time may be used. Also, here, a Karman vortex flow rate detector or another pulse output type detector may be used.

〔Effect of the invention〕

As explained above, since the flow rate detection system of the present invention processes and detects all flow rates as digital signals, the detected flow rate values can be freely used as data, and there is no need to make adjustments like in conventional systems. There is no possibility of false detection, and the probability of false detection is -11 (lower than 0).

[Brief explanation of drawings]

Fig. 1 is a process diagram showing an embodiment of the present invention, Section 2 is a process diagram showing an example of realizing this embodiment using a microcomputer system, and Figs.
b), (C) are diagrams showing an example of the output form of a Karman vortex flow rate detector, and Figure 4 is the microcontroller shown in Figure 2;
Chiyae, Figure 5 C, conventional? There is a diagram showing the amount detection method. 1... Karman vortex flow rate detector 4... Probe 10... Frequency detection means 1
1...Frequency detection start instruction means 12...Timer means 14...Flow rate calculation means

Claims (1)

[Claims] (1) A flow rate detector that outputs a pulse with a frequency proportional to the flow rate, a means for instructing the start of frequency measurement and measurement for a given period of time, and an external device that receives the instruction to start the measurement and ends the measurement for a certain period of time. a timer means having a function of transmitting a signal to the user; and a timer means which takes the pulse as an input and measures the number of pulses during a period between receiving a start instruction from the frequency measurement start instruction means and inputting a measurement end notification from the timer means; A flow rate detection system comprising means for outputting a pulse number to the outside, and a flow rate calculation means having a function of inputting the pulse number output and converting it into a flow rate.