JPH03142323A - Differential flow rate measuring instrument - Google Patents

Abstract

PURPOSE:To easily and quickly execute zero point calibration by providing the measure ment mode where relations between a detected flow rate and a differential flow rate measurement error stored in the teaching mode are referred to correct the differential flow rate measured value every time the value is obtd. CONSTITUTION:A first detector 1 is attached to an inflow passage, and a second detector 2 is attached to an outflow passage. Respective outputs of detectors 1 and 2 are amplified by amplifiers 3 and 4. A differential amplifier 5 outputs the differential voltage between output voltages of amplifiers 3 and 4, namely, a voltage corresponding to the difference flow rate. The voltage is converted by an A/D converter 6 and is fetched into a signal processing part 7 as a differential flow rate (y). The output of the amplifier 3 is converted by an A/D converter 8 and is fetched into the processing part 7 as a detected flow rate F1. The processing part 7 is provided with the teaching mode and the measurement mode. In the teaching mode, plural sets of relations be tween the detected flow rate F1 and a difference flow rate measurement error DELTAy are obtained and are stored in an EEPROM 9. In the measurement mode, relations between the detected flow rate F1 and the measurement error DELTAy stored in the teaching mode are referred to correct the difference flow rate measured value (y) every time the value (y) is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a differential flow rate measuring device using two electromagnetic flow rate detectors.

(Prior Art) An electromagnetic flow rate detector is an instrument for measuring the flow rate of a conductive fluid using Faraday's law.

When a non-1 m$1 constant fluid is caused to flow at a flow rate V in a measuring tube with a cross-sectional area S, and a magnetic flux density B is applied perpendicular to the flow velocity direction, an electromotive force meter is generated in a direction perpendicular to the flow velocity and the speed.

At this time, the distance between each parameter is E=kvB (however, k
is a proportionality constant), and as the flow velocity V increases or decreases, the electromotive force E increases or decreases linearly.

By the way, to control the cooling water used in steel rolling, etc., the inflow flow rate and the outflow flow rate are controlled by lI? The differential flow rate may be monitored.

FIG. 5 is a block diagram showing a conventional example of such a left-side AN setting device.

As shown in the figure, this device includes two electromagnetic flow rate detectors, namely a first detector 1 and a second detector 2.

The output voltages of these detectors 1.2 are each amplified by amplifiers 3 and 4, and then a differential voltage between the two is determined by a differential amplifier 5.

The differential voltage obtained in this way is digitized by an A/D converter 6, and then taken into a signal processing section 7 composed of a microprocessor or the like.

The signal processing unit 7 performs predetermined calculations based on the differential voltage read from the A/D converter 6 to obtain data corresponding to the differential flow rate, and displays this on a display (not shown) or as measured data. It is output to the outside.

Here, the zero point that serves as the basis for measuring the differential flow rate is
This is the point where the inflow capacity and outflow capacity are equal.

To adjust this zero point, if there is a large amount of kneading with a differential flow rate (
For example, the flow rate is converted to 0. In the case of 3 ml s e cli degree), it is sufficient to set an appropriate inflow flow rate at one point and adjust the amplifier gain etc. so that the differential flow rate output at that time becomes zero.

The reason for this is that, as shown in Fig. 6, the relationship between the inflow flow rate This is because it can be regarded as almost a straight line.

(Problem to be Solved by the Invention) However, in such a conventional differential flow measuring device, when measuring a minute differential flow y, the inflow flow aX
The relationship between F1 and each detector output Fl, F2 can no longer be regarded as a straight line, and the zero point changes depending on the inflow flow mx.

Therefore, in the zero point calibration using only - points, it is difficult to obtain the correct zero point of the differential flow rate, and there is a problem that the zero point calibration is time-consuming and, in some cases, it is not possible to obtain the correct zero point.

This invention has been made in view of the above-mentioned problems, and its main purpose is to provide a differential flow rate measuring device using this type of electromagnetic flow rate detector to measure minute differential flow rates. The purpose of this invention is to easily and quickly perform so-called zero point calibration.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention detects the difference between two flow paths based on signals from two electromagnetic flow rate detectors installed in each target flow path. A teaching mode in which a plurality of sets of relationships between the detected flow rate in either one of the flow paths and the differential flow rate measurement error between the two flow paths are memorized with different detected flow rates in a differential flow rate measuring device that determines the flow rate by 1Ill; Every time a differential flow rate measurement value is obtained, refer to the relationship between the detected flow rate and the arrival flow rate m1lF1 constant error stored in the teaching mode. It is characterized by comprising:

(Function) According to such a configuration, by setting to the teaching mode, zero point calibration can be performed easily and quickly, while by setting to the M1 constant mode, even if there is a minute difference in flow rate. This can be measured accurately.

(Embodiment) FIG. 1 is a block diagram showing a major embodiment of an incoming Wk ill device according to the present invention.

In the figure, a first detector 1 is attached to the inflow channel, and a second detector 2 is attached to the outflow channel.

The output of each of these detectors 1.2 is amplified by an amplifier 3,41.

The differential amplifier 5 outputs a voltage difference between the output voltage of the amplifier 3 and the output voltage of the amplifier 4, that is, a voltage corresponding to the differential flow rate.

The voltage corresponding to this differential flow rate is converted to A by the A/D converter 6.
After being changed to /D, it is taken into the signal processing section 7 as the arrival my.

On the other hand, the output of the amplifier 3 is converted into A/D by the A/D converter 8, and then taken into the signal processing section 7 as the detection flow ff1F1 by the first detector 1.

The signal processing section 7 has a teaching mode and a measurement mode, as will be described later.

Then, in the teaching mode, a plurality of sets of relationships between the detected flow rate F1 by the first detector 1 and the differential flow rate measurement error Δy are obtained in a piping state where the inflow flow rate and the outflow flow rate are matched,
This is stored in EEPROM9.

In addition, in the 1I-1 constant mode, each time the differential flow rate measurement value y is obtained, the detected flow rate 1 stored in the teaching mode is
The left applied ff1llI11 constant value y is corrected by referring to the relationship between nF1 and the differential flow ffi 71111 constant error Δy.

In FIG. 2, while keeping the inflow flow rate and the outflow flow rate the same, the inflow flow rate is changed to xi, x2. x3゜x4. x5. x
The detected flow of each detector 1.2 is changed in order of ff1F1.6. It is a graph showing the state of F2.

As shown in the figure, in a region where the differential flow rate is minute, each of the detected flow rates Fl and F2 changes non-linearly with respect to the inflow flow rate. Therefore, each inlet flow mx1, x2 . x3. x4
．． x5. Differential flow rate measurement error Δyt at x6, ΔY2
．． Δy3. ΔY4. Δy5. Δy6 differs individually.

FIG. 3 is a flowchart schematically showing the configuration of a control program executed by the microprocessor of the signal processing section 7. As shown in FIG.

The operation of the apparatus of this embodiment will be explained below with reference to this flowchart. In the figure, when the program is started, various flags and
After initializing registers (step 301),
The operating mode is read (step 302).

Here, if the operation mode is set to the teaching mode by a predetermined switch or the like (step 3o3), the above-mentioned teaching mode is executed.

In this teaching mode, while increasing the pointer n sequentially from 1 (steps 304, 309), each time the operator waits for the inflow flow rate = outflow flow m - x n (steps 305, 306 YES), and The process of reading the detected current ff1F1 by the detector and the differential current 11 ill constant error Δy obtained from the differential amplifier 5 at that time and storing them as a pair in the EEPROM 9 is repeated (steps 307 and 308).

On the other hand, if the operation mode is determined to be 11-1 constant mode (
Step 303), the detected flow rate F1 and the differential flow rate y are read through the A/D converter 6 and A/D 8 (steps 311 and 312).

Thereafter, using Δy1 to Δy6 registered in the teaching mode, the differential flow rate measurement error Δy corresponding to the detected flow rate F1 by the first detector 1 is determined by linear interpolation (step 313
).

That is, in the teaching mode mentioned above, since multiple sets of relationships between Fl and Δyn are stored, the one with the closest detected flow ff1F1 is found among them, and the corresponding differential flow measurement error Δy is calculated by linear interpolation. That's what I'm asking for.

Next, the differential flow QJl constant value is corrected by adding the corresponding differential flow rate measurement error Δy to the differential flow rate measurement value y at that time (step 314).

After that, the corrected flow m measured value y is displayed and output.

Alternatively, it is output to the outside as a control output (
step 315).

As described above, according to the device of this embodiment, the piping condition is set in advance so that no differential flow rate flows between the inflow channel and the outflow channel, and while maintaining this state, the inflow flow rate is adjusted as shown in Fig. 2. As shown, the relationship between the differential flow measurement errors Δy1 to Δy6 and the detected flow ff1F1 of the first detector 1 in that state is stored in advance, and in the actual measurement stage, the left Each time the ffi measurement value y is obtained, the differential flow rate measurement value y is corrected with reference to the relationship between the detected flow rate F1 and the differential flow rate measurement errors Δy1 to Δy6.

As explained in Fig. 2, in a region where the differential flow rate is small, the detector output does not necessarily vary linearly with the inflow flow rate, but this is because the physical pattern of the fluid flowing through the detection section changes depending on the flow rate. This is because the electromotive force fluctuates.

Although this variation in the physical pattern of the fluid is related to the structure of the detection unit and the structure of the piping system, it is almost constant, and it is considered that the pattern of change in the output of the detector is also constant.

Therefore, although the zero points of the differential flow rate (indicated by Δy1 to Δy6 in the figure) also change depending on the inflow flow rate, the pattern of the change is always constant.

Therefore, in the teaching mode mentioned above, Fl and Δy1
If the relationship .about.Δy6 is memorized, accurate sleeve correction can be performed in the 11?1 constant mode.

In the above embodiment, the differential flow rate was calculated by the differential amplifier 5, but as shown in FIG. 4, the detected flow mF1. Of course, the signal processing unit 7 may directly read F2 and perform the difference calculation using software.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, in a differential flow rate measuring device using two electromagnetic flow rate detectors of this type, zero point calibration in differential flow rate measurement can be performed quickly and accurately. In addition, since there is no need to adjust the gain of the J-width amplifier, it is possible to reduce the number of parts such as trimmer capacitors, and this has the effect of reducing costs and improving reliability. .

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the differential flow rate measuring device according to the present invention, and Fig. 2 shows the detected flow rate of each detector when the inflow flow rate is gradually changed in a piping state where no differential flow rate flows. 3 is a flowchart schematically showing the configuration of the control program executed in the signal processing section, FIG. 4 is a block diagram showing another embodiment of the present invention, and FIG. 5 is a conventional FIG. 6, which is a block diagram showing an example of the left-hand effi measuring device, is a graph showing the relationship between the inflow flow rate and the detector output within a range where the differential flow rate is relatively large. 1...First detector 2...Second detector 3...September 4...1sampler 5...Differential amplifier 6...A/D converter 7...・Signal processing unit 8...A/D converter 9...EEPROM

Claims (1)

[Claims] (1) In a differential flow rate measuring device that measures the differential flow rate between two flow paths based on signals from two electromagnetic flow rate detectors installed in each target flow path, detection in one of the flow paths is performed. a teaching mode in which a plurality of sets of relationships between the flow rate and the differential flow rate measurement error between the two flow paths are stored while varying the detected flow rate; and each time a differential flow rate measurement value is obtained, the detected flow rate stored in the teaching mode is A measurement mode for correcting the differential flow rate measurement value by referring to the relationship between the difference flow rate measurement error and the differential flow rate measurement error.