JPH03239916A - Wrong piping detection system of differential flow rate measuring instrument - Google Patents

Abstract

PURPOSE:To detect the wrong connection of piping automatically by feeding liquid to a series of pipes by one pump and monitoring a differential flow rate measured values in a transient period from the start of the liquid feeding to the convergence of the differential flow rate measured value on a constant value. CONSTITUTION:The flow directions in measurement pipes 1 and 2 are normal, but the measurement pipe 1 for inflow rate detection and the measurement pipe 2 for outflow rate detection are inverted in roll. In this case, the single pump is used to supply the liquid at the same flow rate to the measurement pipes 1 and 2 for the zero-point adjustment of the differential flow rate. The measurement pipe on the upstream side and the measurement pipe on the downstream side have a propagation time difference in flow velocity right after the liquid begins to flow. When the measurement pipe 2 and measurement pipe 1 are inverted in roll, the differential flow rate is inverted momentarily until a stationary value 0 is reached. For the purpose, the polarity of the differential flow rate right after the liquid begins to flow into the respective measurement pipes at the same flow rate is decided to detect the wrong connection of the pipes. Consequently, the detection output is sent out of a warning output circuit 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an electromagnetic differential flow rate measuring device having a function of automatically detecting incorrect piping connections.

(Prior Art) Two electromagnetic flowmeters are used in this type of differential flow rate measuring device. This electromagnetic flowmeter is an instrument for measuring the flow rate of conductive fluid using Faraday's law.

When a fluid to be measured is caused to flow at a flow rate V in a measuring tube having a cross-sectional area S and multiplied by a magnetic flux density B perpendicular to the direction of the flow velocity, an electromotive force E is generated in a direction perpendicular to each of the flow velocity and the magnetic flux.

At this time, there is a proportional relationship between each parameter: Emk-v·B (1) where k is a proportionality constant. That is, when the flow velocity V increases or decreases, the electromotive force E increases or decreases linearly.

Furthermore, by paying attention to the polarity of the electromotive force E, it is also possible to detect a backflow (corresponding to v<Q in equation (4)).

By the way, in a differential flow rate measuring device, when measuring a minute flow rate (for example, blood, etc.) where the fluid pressure is not so high, a resin tube may be used to connect the flowmeter to the flow meter. This is because it is easier to remove when cleaning or replacing pipes frequently. Since this type of differential flow rate measuring device uses two electromagnetic flowmeters, it is necessary to connect four tubes.

(Problems to be Solved by the Invention) As mentioned above, in this type of differential flow rate measuring device, two
Since a stand-alone electromagnetic flowmeter is used, it is necessary to connect four tubes, and as a result, there is a problem in that it is easy to connect the piping incorrectly.

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a differential flow rate measuring device having a function of automatically detecting a connection error in piping.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a system in which piping is connected so that a system inlet fluid and a system outlet fluid, which are objects of differential flow rate measurement, respectively pass through. A differential flow rate measurement device comprising: two measuring tubes, an electromagnetic flow rate measuring section that measures the flow rate passing through each of the measuring tubes, and a calculation means that outputs the difference between the measured values of the side flow rate measuring section as a differential flow rate. In the device, after the piping connections to the four ports of the measurement tube have been completed, one pump supplies fluid to the series of piping, and after the fluid supply starts, the differential flow rate measurement value is constant. This method is characterized by monitoring the differential flow rate measurement value during the transition period until it converges to the value, and detecting incorrect piping for the measurement pipe based on the polarity of the differential flow rate measurement value.

(Function) After the piping connections to the four ports of the measurement tube are completed, if fluid is supplied to the series of piping by one pump, if the piping is connected correctly, two pumps will be connected. The electromagnetic flowmeter produces a measured output with a predetermined time difference.

Therefore, when observing the difference between these measured values, a peak output that swings to a predetermined polarity is observed during the transition period from the start of fluid feeding until the flow rate of both measuring tubes reaches a steady state, and based on this, piping connections are made. It is possible to judge the quality of the product.

(Example) FIG. 1 is a block diagram schematically showing the hardware configuration of an electromagnetic differential flow rate measuring device according to the present invention.

As shown in the figure, the electromagnetic differential flow rate measuring device of this embodiment includes a measuring tube 1 for detecting the inflow flow rate, a measuring tube 2 for detecting the outflow flow rate, and a measuring tube 2 for detecting the inflow flow rate, and a detection electrode of the oil J fixed pipe l. A buffer amplifier 3 that amplifies the signal, a buffer amplifier 4 that amplifies the signal from the detection electrode of the measurement tube 2, and outputs a signal that is aimed at the difference between the detected flow rate of the measurement tube 1 and the detection flow rate of the measurement tube 2. an A/D converter 6 that digitizes the output of the buffer amplifier 3, an A/D converter 7 that digitizes the output of the differential amplifier 5, and an A/D converter 6゜7. A signal output circuit 9 outputs a differential flow rate signal processed by the microprocessor 8, and an alarm circuit 10 having a contact output using an open collector, for example. .

In addition to the normal differential flow rate calculation process, the microprocessor 8 detects incorrect connection of pipes by executing the process shown in the flowchart of FIG. 2 (steps 201 and 202). .

FIG. 3<a) is an explanatory diagram showing a normal piping connection state and collar for the differential flow rate measuring device 100.

As shown in the figure, the outlet 0U of the external system S1
The liquid flowing out from the TI flows into the measuring tube 1 from the inlet A of the differential flow rate measuring device 100 via the pipe P1, and flows out from the outlet B. At this time, the flow rate of measuring tube 1 is Ql
shall be.

The liquid flowing out from the outlet B flows into the inlet IN2 of the external system S2 via the pipe P2.

Similarly, the liquid flowing out from the outlet 0UT2 of the external system S2 passes through the pipe P3 to the differential flow rate measuring device 10.
0 flows into the measuring tube 2 from the inlet C, and flows out from the outlet. The flow rate of the measuring tube 2 at this time is assumed to be Q2.

The liquid flowing out from the outlet flows into the inlet INI of the external system S1 via the pipe P4.

At this time, the differential flow rate ΔQ is obtained as ΔQ−Ql−Q2 (2).

On the other hand, the cases shown in FIGS. 3(b) to 3(h) may be considered as incorrect piping connections.

Among these incorrect piping connections, Fig. 3(e) to Fig. 3(h)
), the inlet and outlet are reversed in the external system, causing problems such as flow not flowing as planned, and incorrect piping can be easily discovered.

Therefore, the cases shown in FIGS. 3(b) to 3(h) will be described below.

First, the case shown in FIG. 3(b) will be explained.

In this piping connection state, the flow directions in each of the measurement tubes 1 and 2 are normal, but the roles of the measurement tube 1 for inflow flow rate detection and the measurement tube 2 for outflow flow rate detection are reversed.

In such a case, in order to adjust the zero point of the differential flow rate, a single pump is used to flow the same flow rate to the measurement tube 1 for inflow flow rate detection and the measurement tube 2 for outflow flow rate detection.

Immediately after the flow starts, a difference in transmission time occurs in the change in flow velocity between the measurement pipe located on the upstream side and the measurement pipe located on the downstream side.

The fourth approximation of the change in flow rate in each measurement pipe using an exponential function
Shown in Figure (a). Here, Ql represents the flow rate in the measuring tube 1 for detecting the inflow flow rate, Q2 represents the flow rate in the measuring tube 2 for detecting the outflow flow rate, and Ql-V [1-EXP (-t/τ)]2-0 ( However, 0<t<T) Q2-v [1-EXP ((T-t)/τ) (however, t>T) ■, steady flow rate T Two fluids flow out from the measuring tube 1 for inflow flow rate detection This is a time constant of 12 times the transmission time required to reach the measuring tube 2 for flow rate detection.

The differential flow rate ΔQ when the pipes are connected normally can be found from equation (2).

ΔQ-Q 1-02 -V [1-EXP (-t/τ)] (However, O<t<T) -V*EXP (T/τ)*EXP(-t/τ) (However, t/ T) becomes. This is shown in FIG. 4(b). The differential flow rate is the steady value O
The flow becomes positive instantaneously.

On the other hand, as shown in FIG. 3(b), when the roles of the measurement tube for detecting the outflow flow rate and the measurement tube for detecting the inflow flow rate are reversed, g 2-V [1-E X P (-t/r)
]Q 1-0 (0<t<T) Ql-V [1-EXP ((T-t)/r)](
However, since t>T), ΔQ-Ql-Q2 -V [1-EXP (-t/τ)] (however, 0<t
<T) w−v*EXP (T/τ)*EXP(-t/τ) (where t/T). This is shown in FIG. 4(c). Differential flow rate is steady value 0
By the time this happens, the amount of flow becomes instantaneously reversed.

From the above, it is possible to detect incorrect connection of the pipes by determining the polarity of the differential flow rate immediately after the same flow rate starts flowing into each measurement pipe. This is output from the alarm output circuit 10 to the outside.

Next, the cases of FIG. 3(C) and FIG. 3(d) will be explained.

In order to adjust the zero point of the differential flow rate, the same flow rate is made to flow through the measurement pipe 1 for detecting the inflow flow rate and the measurement pipe 2 for detecting the outflow flow rate. At this time, the direction of fluid flow is of opposite polarity compared to the normal case.

Therefore, since the signal detected by the inflow flow rate detection measuring tube 1 also has the opposite polarity, incorrect piping can be detected. This is output from the alarm output circuit 10 to the outside.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, when the same flow rate is caused to flow through the measurement tube for inflow flow rate detection and the measurement tube for outflow flow rate detection for zero point calibration of differential flow rate, that is, preparation for measurement of differential flow rate. At this stage, incorrect connection of piping can be detected without any particular increase in cost.

[Brief explanation of drawings]

Fig. 1 is a block diagram schematically showing the hardware configuration of the embodiment device, Fig. 2 is a flowchart showing erroneous piping detection processing in the embodiment device, Fig. 3 is an explanatory diagram showing the piping connection mode, and Fig. 4 is a graph showing changes over time in the flow rate of each city's fixed pipe and the finally obtained differential flow rate. 1...Measurement tube for inflow flow rate detection 2...Measurement tube for outflow flow rate detection 3.4...Buffer amplifier 5...Differential amplifier 6.7...A/D converter 8... Microprocessor 9...Signal output circuit 10...Alarm output circuit

Claims (1)

[Claims] (1) Two measuring pipes to be connected so that the system inlet fluid and the system outlet fluid to be measured for the differential flow rate respectively pass therethrough, and an electromagnetic flow measuring section that measures the flow rate passing through each of the measuring pipes. , a calculation means for outputting the difference between the measured values of the two flow rate measurement sections as a differential flow rate, wherein after the piping connections to the four ports of the measurement pipe are temporarily completed, the series of piping Fluid is supplied by one pump to A method for detecting incorrect piping for a differential flow rate measuring device, which is characterized by detecting incorrect piping for a differential flow rate measuring device.