JP2589524B2 - Area flowmeter and flow measurement method using the flowmeter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to an area type flowmeter for measuring the flow rate of a sample gas in an air pollution measuring instrument or the like in order to control the flow rate of the sample gas to be constant, and the flowmeter. It relates to a flow measurement method.

(Prior Art) FIG. 7 shows a known area flow meter of this type. In FIG. 1, reference numeral 10 denotes a tapered tube made of glass or the like having a hollow conical shape, through which the sample gas whose flow rate is to be measured passes from below to above.

20 is a light-shielding float housed inside the tapered tube 10, 30 is a cylindrical outer envelope surrounding the tapered tube 10, 40
Are light-emitting elements such as light-emitting diodes mounted at the axial center position of the inner surface of the outer enclosure 30; 50a, 50b are silicon juxtaposed on the inner surface of the outer enclosure 30 so that light from the light-emitting element 40 is evenly applied. A light receiving element such as a photocell, 60 is an inverting amplifier, and 70 is a differential amplifier.

In this flow meter, when the float 20 is in front of the light emitting element 40 as shown in the figure, a part of the light blocked by the float 20 enters the light receiving surface of the same area of each of the light receiving elements 50a and 50b, Since the light receiving amounts of the elements 50a and 50b are equal, their output voltages are equal to each other. Also, for example, when the float 20 is in front of the upper light receiving element 50a, the amount of light received by the lower light receiving element 50b is larger than that of the upper light receiving element 50a, and conversely, the float 20 is provided by the lower light receiving element 50b. When it is near the front, the amount of light received by the upper light receiving element 50a is larger than that of the lower light receiving element 50b.

Therefore, by checking the balance between the output voltages of the light receiving elements 50a and 50b with the differential amplifier 70, it is possible to detect in which direction the float 20 is deviated from the center position in the vertical direction. In other words, when the envelope 30 is moved up and down and the index provided at the axial center thereof is adjusted to the desired flow rate scale attached to the tapered pipe 10, the detection is performed as described above from the deviation of the float 20 at that time. By controlling the opening and closing of a sample gas flow control valve (not shown) according to the flow rate of the sample gas,
The flow rate of the sample gas can be maintained at a constant value.

(Problems to be Solved by the Invention) However, in this area type flow meter and the flow rate measuring method using the flow meter, the two light receiving elements 50a and 50b are symmetrically arranged with respect to the light emitting element 40 and close to each other. It is necessary to arrange them, and furthermore, these light receiving elements 50a, 50b are required to have exactly the same characteristics on the above-mentioned measurement principle, so that no special order products are used as the light receiving elements 50a, 50b. However, there is a disadvantage that the cost is high.

Further, even if the two light receiving elements 50a and 50b are arranged as close as possible, the respective light receiving surfaces cannot be arranged side by side due to design restrictions. Therefore, when the relatively small float 20 is in front of the light emitting element 40, there is a possibility that a dead zone where the position of the float 20 cannot be detected accurately may occur, and there has been a problem that accurate flow rate measurement cannot be performed.

Furthermore, conventionally, the detectable range of the float 20 is determined by the light receiving area of the light receiving elements 50a and 50b,
It was only possible to detect whether the position of the float 20 was above or below the front of the light emitting element 40 as a center. In addition, the amount of light received by the light receiving elements 50a and 50b is equal both when the float 20 is in front of the light emitting element 40 and when the float 20 is above or below the detection range. Output voltage is the same,
There was a problem that the position of the float 20 could not be specified.

In addition, the output voltage balance of the light receiving elements 50a and 50b was adjusted by operating the trimmer resistor in a state where light is uniformly applied to the light receiving elements 50a and 50b. The aging of the characteristics of the element 40 and the light receiving elements 50a, 50b has made the balance adjustment work more complicated.

The present invention has been proposed in order to solve the above-mentioned problems. The purpose of the present invention is to reduce the cost by making it possible to use a standard light-receiving element, to generate a dead zone, to narrow the detection range, and to achieve a balance. It is an object of the present invention to provide an area type flowmeter capable of accurately detecting a float position and performing high-precision flow measurement while eliminating the complexity of adjustment, and a flow measurement method using the flowmeter.

(Means for Solving the Problems) In order to achieve the above object, an area type flow meter according to the present invention is firstly applied to an area type flow meter in which a light emitting element and a light receiving element are arranged opposite to each other outside a tapered tube having a built-in float. ,
A plurality of light-emitting elements that are individually turned on are arranged along the axial direction of the tapered tube, and a single light-receiving element is arranged to face these light-emitting elements. Then, for each light emitting element, the ratio between the light receiving element output signal at the time of flow rate measurement and the light receiving element output signal when the float is excluded from the detection range is detected, and the position of the float is detected based on the plurality of ratios. To measure the flow rate of the sample.

Here, if the light receiving elements are arranged so as to oppose the center position of a plurality of light emitting elements arranged at equal intervals, how much the float deviates from the reference position when this center position is used as the reference position. Can be easily recognized.

Further, the flow rate measuring method according to the present invention uses the area type flow meter, divides a plurality of light emitting elements into two substantially at their central positions, and arranges a light receiving element at a position facing the central position, and divides the light receiving elements into two. The individual light-emitting elements belonging to the set of light-emitting elements are individually turned on, and for each light-emitting element, the ratio of the output signal of the light-receiving element at the time of measuring the flow rate to the output signal of the light-receiving element when the float is removed from the detection range, respectively. Detect the sum of the light-receiving variables resulting from this ratio for each of the light-emitting element groups, compare the magnitude of the sum of the light-receiving variables, and detect the deviation of the float position with respect to the center position to detect the sample. It is characterized by measuring the flow rate of water.

The light receiving variable may be, for example, a value obtained by subtracting from 1 the ratio of the output voltage of the light receiving element when the flow rate is measured and the output voltage of the light receiving element when the float is removed from the detection range.

(Operation) According to the area type flow meter of the present invention, the plurality of light emitting elements are sequentially turned on individually, and the output light thereof is sequentially received by the single light receiving element. At this time, if all or part of the light from a certain light emitting element is blocked by the float with respect to the light receiving element, the light emitting element output signal at the time of the flow rate measurement and the light receiving when the float is removed are detected. The ratio with the element output signal is different from that of the other light emitting elements, and the above difference in the ratio has a certain causal relationship with the position of the float. Therefore, if attention is paid to these plurality of ratios, the degree of light blocking by the float at the position of each light emitting element can be known, and the position of the float can be detected.

Further, according to the flow rate measuring method of the present invention, the sum of the light receiving variables obtained for each of the bisected light emitting element groups is compared. Here, if the sums are equal to each other, the float is in front of the center position, and if the flow rate scale corresponding to the center position is a desired set flow rate, the current flow rate is equal to this set flow rate. Further, the degree of deviation of the float from the center position is detected based on the magnitude relation of the sum of the light receiving variables, that is, the deviation from the set flow rate is detected.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. First,
FIG. 1 shows a main part of one embodiment of an area type flow meter according to the present invention. In FIG. 1, reference numeral 1 denotes a sample gas passing from below to above by a suction pump (not shown). A tapered tube made of hollow conical glass or the like, 2 is a light-shielding float housed therein, 3 is a cylindrical outer envelope surrounding the tapered tube 1, and this outer envelope 3 is vertically oriented. Can be moved.

The inner surface of the outer enclosure 3, such as light-emitting element I ₁ of the light emitting diode of the plurality along the vertical direction (e.g., _{seven), I 2, ......, I} n
Are arranged at equal intervals, and these light emitting elements I ₁
The opposing surfaces of ~I _n, the light-emitting element I ₁ ~I _n single light receiving element R such as silicon photodiode to face the light-emitting element I ₄ at the center position of the is attached. The amplifier A is connected to the output side of the light receiving element R. A microcomputer system (not shown) is connected to the output side of the amplifier A.

Here, the light-emitting element I ₁ is the ~I _n being adapted pulsed current is applied periodically from the top at a constant time interval, and the light output waveform, the float 2 is not present in the detection range relationship between the output voltage V ₁ ~V _n light-receiving elements R according to the light output from each light-emitting element I ₁ ~I _n in the state is as shown in Figure 2. In the figure, the output voltage V ₁ ~V _n of the light-receiving element R is not constant, the light-emitting element I ₁ ~
Due to the difference in distance to the variations and the light-receiving element R of the characteristics of I _n.

Next, this operation will be described with reference to FIGS.

First, the light-receiving element R suction pump of the sample gas together with the float 2 has stopped to turn on the light-emitting element I ₁ ~I _n in the order in a state that is outside the lower i.e. the detection range of the tapered tube 1, shown in Figure 2 the output voltage V ₁ ~V _n were measured and stored in the memory of the microcomputer system them as reference values Vr ₁ through Vr _n.

Next, when the suction pump is operated to introduce the sample gas into the tapered tube 1, the float 2 rises in the tapered tube 1 to the height of the outer enclosure 3. In this case, the same way to turn on the light-emitting element I ₁ ~I _n sequentially, the corresponding light-receiving element R of the output voltage V ₁ ~V _n measurements of these values were measured Vm ₁ ~V
_mn and store it in memory.

Then, the reference value Vr ₁ through Vr _n corresponding to each light-emitting element I ₁ ~I _n
And the measurement value Vm ₁ ~Vm _n, consider the ratio Vm _n / Vr _n of both and a light receiving variable due to the amount of light received by the light receiving elements R, X (n) = 1 -Vm n / Vr n ...... ( In this embodiment, when n = 1 to 7) is defined, and this light receiving variable X (n) is calculated, X (n) is determined according to the position of the float 2, that is, the flow rate of the sample gas, as shown in FIG. 3 to FIG. The value of n) will change. Thus, focusing on the light receiving variable X (n), it is possible to know the degree of light shielding by the float 2 at the position of each light-emitting element I ₁ ~I _n, in other words, present at any height float 2 Therefore, the flow rate of the sample gas can be obtained.

Incidentally, the measurement principle of the present invention, since the arrangement interval of the light-emitting element I ₁ ~I _n MAY slightly longer than the outer diameter of the float 2, the number of light emitting elements when the length of the outer surrounding body 3 the same And cost can be reduced. The height between the float 2 is two light emitting elements even when present in (position), because as long as there in a position blocking the optical axis by the light emitting element I ₁ ~I _n appears a change in the light receiving variable, The position of the float 2 can be detected.

Furthermore, (in this example I ₄₎ light-emitting element in the center position among the plurality of light emitting elements I ₁ ~I _n consider the upper and lower two sets of light emitting element groups around the light receiving variable X for each light emitting element group XH = X (1) + X (2) + X (3)... XL = X (5) + X (6) + X (7)...

Now, when the float 2 is in front of the center position as shown in FIG. 4, XH = XL, and when the float 2 is above this position as shown in FIG. 3, XH = XL.
> XL, and XH <XL when the float 2 is below as shown in FIG.

That is, the microcomputer system uses XH
And by determining the magnitude relationship to calculate the XL, it can float 2 detects whether the one up and down relative to the front of the center position of the light-emitting element I ₁ ~I _n.

Therefore, for example, by attaching a flow rate scale to the outer peripheral surface of the tapered pipe 1 and performing the above-described arithmetic processing while adjusting the index attached to the center of the outer enclosure 3 to the flow rate scale, it is possible to measure the current flow rate, This makes it possible to control the flow rate to match a desired value.

In this type of area type flowmeter, the operation of the sample gas suction pump is stopped at regular intervals, and the float 2 is automatically removed from the detection range. by updating and re-measuring the reference value Vr _n of the light-receiving element output voltage, the light-emitting element I
The sensitivity of the brightness and the light-receiving element R of ₁ ~I _n can also always maintain a high measurement accuracy when ages.

In the above embodiment, lighting order of the light-emitting element I ₁ ~I _n at all may be random. Further, instead of detecting the position of the float 2 to calculate each the sum of light receiving variable X (n) light emitting element group which is bisected, simply receiving the variable X for each light-emitting element I ₁ ~I _{n (n)} From the patterns (FIGS. 3 to 5), it is also possible to estimate how much the position of the float 2 is above or below the reference position (for example, the center position). In this case, position of the light receiving element R is not limited to the front of the center of the light-emitting element I ₁ ~I _n.

Next, FIG. 6 shows another embodiment of the area type flow meter according to the present invention. In this embodiment, the light receiving element is provided with a plurality of like _{R 1, R 2, R 3} , a large number of light-emitting elements I ₁ ~I _n corresponding thereto are opposed to each other. The light receiving elements R ₁ , R ₂ ,
R ₃ is is provided with a plurality in order to expand the flow measurement range, in the measurement range by each light receiving element is shared, the relationship of a single light-receiving element as in the previous embodiment for the plurality of light emitting elements is established I have.

In this embodiment, the output voltage of the light-receiving element R ₁ or R ₂ or R ₃ at the time of sequentially lighting the light-emitting element I ₁ ~I _n corresponds to Vm _n and Vr _n in the above formula, identical to the previous embodiment According to the principle, the position of the float 2 can be accurately detected. In particular, by providing a plurality of light receiving elements, the detectable range of the float 2 and thus the flow rate measurement range can be greatly expanded. Also, even if the number of light receiving elements increases,
Since standard products such as silicon photodiodes can be used,
There is no major obstacle to economics.

In each of the above embodiments are described for the case in which a plurality of light emitting elements I ₁ ~I _n at regular intervals, but this arrangement is not necessarily equally spaced, closer to the example center portion Symmetrical arrangement with the center position as the center, such that the distance is made smaller and the distance becomes smaller as the distance from the part increases. That is, as when the flow rate measurement when the float 2 is removed from the detection range, as long as the difference of the light-receiving element output voltage corresponding to the position of the float 2 is clearly recognized for each light-emitting element, the light-emitting element I ₁ ~I _n Can be arranged in various modes.

Further, in the present invention, the types of the light emitting element and the light receiving element and the number of the light emitting elements are not limited to the above-described embodiment. Further, the sample whose flow rate is to be measured may be a liquid as well as a gas. In addition, the light receiving variables described above include the ratio of the output voltage of the light receiving element, Vm _n / Vr _n
Can also be used.

(Effect of the Invention) As described above, according to the present invention, the flow rate can be measured with at least a single light receiving element, and the cost can be greatly reduced by using a standard light receiving element. On the other hand, a larger number of light emitting elements are required than in the past. However, since many relatively inexpensive products such as photodiodes are provided for such light emitting elements, the economic effect as a whole is extremely large.

Furthermore, even if the light emitting device has a variation in characteristics, the measurement method is based on the ratio of the output signal of the light receiving device between the actual measurement and when the float is removed. Even if there is, accurate measurement can always be performed.

Further, since a plurality of light emitting elements are arranged to face at least one light receiving element, there is no possibility that a dead zone in which the position of the float cannot be detected is generated.

Furthermore, regardless of the light receiving area of the light receiving element, a plurality of light emitting elements can be provided in a range where light can reach, or the number of light receiving elements can be increased as necessary to greatly expand the detection range. There is an advantage that the position of the float can be accurately specified in multiple stages by referring to the pattern of the light receiving variable value of the light emitting element.

In addition, there is no need for artificial balance adjustment as in the past, and it is possible to automatically cope with various secular changes by a microcomputer program, thereby reducing labor. Having.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 5 show an embodiment of an area flow meter according to the present invention. FIG. 1 is a structural view of a main part, and FIG. 2 is a light emitting element and a light receiving element. Output Waveforms of Elements, FIGS. 3 to 5
FIG. 6 is an explanatory view of the operation, FIG. 6 is a main part configuration diagram showing another embodiment of the area flow meter according to the present invention, and FIG. 7 is a main part configuration diagram of a conventional area flow meter. 1 ...... tapered tube, 2 ...... float 3 ...... enclosure, I ₁ ~I _n ...... emitting element R, R ₁ to R ₃ ...... light receiving element, A ...... amplifier

Claims (3)

(57) [Claims] 1. A light-transmitting tapered tube through which a sample whose flow rate is to be measured passes in an axial direction, a light-shielding float housed inside the tapered tube, and the tapered tube outside the tapered tube. A light-emitting element and a light-receiving element disposed so as to be opposed to each other via the light-receiving element. The position of the float that moves in accordance with the flow rate of the sample is detected by the amount of light received by the light-receiving element to measure the flow rate of the sample. In the area type flow meter, a plurality of light emitting elements individually turned on are arranged along the axial direction of the tapered tube, and a single light receiving element is arranged opposite to these light emitting elements. ,
Detecting a ratio between the light-receiving element output signal during flow measurement and the light-receiving element output signal when the float is excluded from the detection range, and detecting the position of the float based on the plurality of ratios. Area flow meter. 2. The area type flow meter according to claim 1, wherein the light receiving elements are arranged so as to face a substantially central position of a plurality of light emitting elements arranged at substantially equal intervals. Flow meter. 3. A light-receiving element in which a sample is passed through a light-transmitting tapered tube in which a light-shielding float is housed, and which is disposed outside the tapered tube so as to face a light-emitting element via the tapered tube. The amount of light received by the element detects the position of the float that moves according to the flow rate of the sample to measure the flow rate of the sample. In the flow rate measurement method using an area type flow meter, along the axial direction of the tapered tube, The plurality of arranged light emitting elements are bisected at substantially the central position thereof, and the light receiving elements are arranged at positions opposing the central position, and the individual light emitting elements belonging to each of the bisected light emitting element groups are individually separated. Along with lighting, for each light emitting element, the ratio between the light receiving element output signal at the time of flow rate measurement and the light receiving element output signal when the float is excluded from the detection range is detected, and the ratio is caused by this ratio. The sum of the light receiving variables is obtained for each of the light emitting element groups, and the magnitude of the sum of the light receiving variables is compared to detect the deviation of the position of the float with respect to the center position. Flow measurement method.