JPS5965215A - Device for measuring air flow rate - Google Patents

Abstract

PURPOSE:To detect the flow rate of air accurately in various duct pipes, by providing a bypass air path in a duct, yielding a bypass flow by the pressure difference between a total pressure pipe and a static pressure pipe, and detecting the bypass rate by a hot wire type flowmeter. CONSTITUTION:A static pressure pipe 21 is communicated to one end of a bypass air path 20, wherein a hot wire type resistor 23 is provided. The other end thereof is communicated to a total pressure pipe 22, which is opened in the air blowing direction in a duct through opening parts 25. A bypass controlling means 28, which controls and regulates the amount of bypass air, is provided. A bridge circuit output signal controlling means 30 is connected to a hot wire type resistor 23 and can adjust the output signal of a bridge circuit built in a box 29. The initial adjustment at the time of starting operation is performed by the bypass flow rate controlling means 28 or the output signal controlling means 30. Thus the measured value of the flow rate can be corrected, and the flow rate can be measured accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention is suitable for use in relatively low wind pressures such as those for pill air conditioning systems.
The present invention relates to an air flow measuring device used to measure the total air flow rate in a duct when the air is blown by a blower of 0 to 80 rrmAg and is attached to various duct pipes.

[Prior art]

FIG. 1 shows a known example of a simple fluid flow rate measuring device that is mainly used for measuring the amount of water.

In the figure, the entire orifice 7 is provided in the middle of the pipe 1, and a float 3 is provided in the tapered pipe 2 so as to be able to move up and down.
5, the bypass flow generated by the pressure difference before and after the orifice passes from the bottom to the top of the tapered tube 2, and the flow rate in the tube 1 is detected by detecting the vertical movement of the float 3 in accordance with the increase/decrease in the flow rate. measure.

In the known example shown in FIG. 2, below the tapered pipe 2,
Total pressure pipes 5. Connect one end of static pressure/ba 4,
The other ends of the total pressure pipe 5 and the static pressure pipe 4 are communicated so as to open in the flow direction of the pipe 1 and in the direction perpendicular to the flow, respectively, and a bypass flow generated by the dynamic pressure of the opening 8 opened toward the flow of the total pressure pipe 5 is created. , from the bottom to the top of the tapered tube 2, and the flow rate inside the tube 1 is measured by detecting the vertical movement of the float 3 in accordance with the increase/decrease in the flow rate.

FIG. 3 shows a known example that has come to be used for measuring the intake air amount of an automobile internal combustion engine.

In the figure, the venturi part 12 runs through the entire wall of the air supply unit 11.
A hot wire resistor 14 is installed in the bypass air passage 13 that opens on the intake side on the upstream side of the venturi section, and the amount of intake air flowing into the intake passage 10 is determined by detecting the air flow rate (flow velocity) flowing through the bypass air passage. demand.

However, when measuring the airflow in the ducts of a building air conditioning system, similar problems arise.

(1) The static pressure of the blower is small (approximately 30 to 80 rmIAg), and the method of providing an orifice as shown in FIG. 1 is unusable due to the large resistance loss (approximately 20 to 40 mmAg).

(2) The wind speed inside the duct for building air conditioning is small;
(about 3 to 6 m/s), and since the air hydrometer is small, in the method shown in Figure 2, the float (1/1000 of water) does not move up and down due to dynamic pressure.

Although it is possible to use a light material as a float,
The movement of the float lacks stability, making it practically unusable.

(3) Furthermore, the air flow in the duct of a building air conditioning system is wide ranging from small air volume to large air volume (in practical use, 10 to 5000 ml).
/+n'++) Therefore, the duct is not a small one such as a water pipe, but a very large one. If the duct is large, the fluid flowing inside it is air with low specific gravity and the wind speed is slow (3 to 6 m/s), so the flow is unstable and the internal wind speed distribution tends to change ratios. The bypass valve is also easily affected, resulting in a large error in the measured flow rate.

(4) In the case of trench or pill air conditioning, the shape of the duct is not fixed and there are various shapes, so even if the cross-sectional area and air volume are the same, the wind speed distribution will naturally differ, and this will greatly affect the bypass volume. This results in a large error in the measured flow rate.

(5) In addition, in the case of building air conditioning, bend and branch the duct piping,
There are many sections that change in cross section, and even if the duct part to be measured is a straight pipe, it is susceptible to changes in the shape of the duct before and after it, which will cause the wind speed distribution to differ.
The amount of bypass is also affected, resulting in a large error in the measured value of flow h;

(6) In the case of ducts for air conditioning, as mentioned above, ducts range from small to very large, and in all cases, usable ducts are required, and for practical purposes, design drawings must be prepared at a design office etc. Since it is folded in advance, it is required to be standardized in advance, and there is a particularly strong demand for it to be supplied at low cost and in a short delivery time.

Because of the problems (1) to (6) mentioned above, the devices shown in FIGS. 1 to 3, which are often used for measuring the amount of water, are rarely used for air conditioning. In other words, the current situation is that there is no upstream measuring device that can easily measure the air flow rate in building air conditioning ducts.

For this reason, to measure the air flow rate in the duct for pill air conditioning, we had no choice but to measure the current value of the mode of the blower installed on site, and based on this measurement value, we used the blower's performance curve. Estimate the total air flow rate in the duct from the determined air flow rate, or use a hot-wire anemometer to measure the wind speed at each position of the wind pipe, and use this measurement value to integrate and calculate the air flow rate in the duct. The current situation is that

However, such methods require a great deal of effort and time, and it is necessary to constantly detect the air flow inside the duct and manage the operation, or use that information to control the operation side of the air conditioning system■1
It is impossible to do this.

Therefore, in the current air conditioning system, operation management based on constant flow rate measurement and operation opening side 1 based on monthly measurement are generally not performed at all.

[Purpose of the invention]

The purpose of the present invention is to be able to easily and accurately detect the air flow rate of a building air conditioning system for any type of duct piping at any time, and to be able to detect a wide range of ducts from small to large. Easy to standardize, cheap,
Moreover, our objective is to provide an airflow @4 measurement device that can be designed and manufactured in a short lead time.

[Summary of the invention]

In the present invention, a bypass air passage is provided in the duct, and in order to reduce resistance loss, a bypass flow is created by the pressure difference between the total pressure pipe and the static pressure pipe.As a result, the bypass flow rate becomes very small, but even the slightest flow can be detected. To deal with this problem, a flow rate measuring device was constructed using a hot wire type resistor.

In order to be able to put this kind of flow rate measuring device into practical use no matter what type of pipe it is installed in, a standard air flow is applied at the start of operation, and the initial adjustment is made so that the output signal of the flow rate measuring device displays a predetermined value. The measured values were corrected and made usable. For this reason, the bypass flow Mlf is regulated in either the bypass air path or the total pressure pipe and the bypass flow rate'
f: A bypass flow rate control means that can be adjusted is provided, and an output signal opening/opening means that allows the output signal to be adjusted is connected to a bridge circuit compressed into the hot wire resistor.

In addition, the present invention allows it to be installed and used in various duct pipes of different sizes and shapes, and can be standardized and manufactured as a flow rate measuring device.
An expansion means is incorporated into the total pressure pipe so that its length can be easily extended. Furthermore, since the hot-wire resistor and bridge circuit, which are both expensive and require high precision, can be made into one type of length, the hot-wire resistor and the bridge circuit are configured as one body and can be removed from the bypass air path. The structure is as follows.

[Embodiments of the invention]

FIG. 4 shows a principle diagram of the present invention. In FIG. 4, 20 is a bypass air passage, and a hot wire type resistor 33 is housed inside the bypass air passage. Reference numeral 21 denotes a static pressure pipe whose one end communicates with the binox air passage 20, and the other end 24 passes through a bracket 26 and is opened in a direction perpendicular to the air blowing direction of the duct 1 (non-air blowing direction).

22 is a total IF whose one end is connected to the bypass air passage 20;
#, the other end is opened through the shell through the bracket and through the opening 25 in the air blowing direction of the duct. In this case, one or more openings 25 are provided in the interior of the duct, facing the flow, depending on the size of the duct.

Further, an enlargement means 27 is provided in the total pressure pipe 22 so that its dimension can be extended.

Furthermore, a bypass air passage 20. Static pressure tube 21. A bypass passage control means 2 is installed in either of the total pressure pipes 22, the ventilation area of which is much smaller than the area of other ventilation passages, and capable of regulating the bypass wind and moon and controlling the bypass flow rate by fully adjusting it.
8 will be provided. Furthermore, a bridge circuit output signal sterilization means 30 is connected to the hot wire type resistor 23 and is connected to the bridge circuit built in the box 29 and whose output signal can be adjusted.

In addition, the hot wire resistor 23 is connected to a bridge circuit,
Each of the circuits is provided integrally with a box 29 containing the circuit so as to be removable from the bypass air passage 20.

Further, the bridge circuit output signal control means described above is provided separately from the bridge circuit due to the need to easily adjust the output signal. As described above, the present invention provides an enlarged configuration means 2 in which a total pressure pipe 22 is installed in various duct pipes having different shapes and sizes, as shown in FIG.
7, it is characterized by a structure that can be easily attached.

Furthermore, the present invention allows the measured value of the flow rate to be sent to both means 2 on the bypass flow path side.
8 or with the bridge circuit output signal auxiliary means 30, the structure is such that initial adjustment can be made at the start of operation to correct the measured value, and even if it is installed and used in various piping, there will be no error. It is characterized by the fact that it can be used with high precision because of the small number of errors.

Furthermore, the present invention has a structure in which the hot wire type resistor 23 and the bridge circuit are integrated and can be removed from the bypass air path 20, and a high temperature of 48 degrees is required, and an expensive hot wire type resistor is used. It is possible to construct a flow f4+i l measurement device that can be installed in ducts of various sizes, with one type of bridge circuit available, and can be standardized for various colored duct piping, and is an inexpensive flow rate measurement device. It is characterized by being able to provide a speech measurement device.

FIG. 5 shows a specific embodiment of the present invention.

In the figure, a total pressure drop 22 is provided inside the static pressure tube, and the ventilation path of the static pressure tube is configured between the static pressure tube and the total pressure tube. One end of the total pressure pipe 22 is fitted with a flange 36 as shown in FIG.
It is attached with bolts using No. 7 so as to communicate with the bypass air path.

The other end of the static pressure pipe 21 is opened in a direction perpendicular to the air blowing direction of the duct 1 . This static pressure pipe 21 is attached to a metal fitting 32 attached to the duct 1 via a nut 33. At this time, a ring-shaped backing 35 made of rubber or the like is provided between the static pressure pipe 21 and the metal fitting, and the metal fitting 32 attached to the duct 1 and the static pressure pipe 21 are integrated so as to form a bypass air path. has been done. In this case, the opening 25 of the total pressure pipe 22 can be easily aligned to face the flow of the duct 1 and is configured to be fixed.

Further, one end of the total pressure pipe 22 is attached to the bypass perforation passage forming main body 50 by an enlarged configuration means 27, the details of which are shown in FIG. A ring-shaped backing 38 is provided between the flange 36 provided on the total pressure pipe 22 and the bypass air passage forming body 50, and seals the total pressure section and the static pressure section.

Further, as shown in detail in FIG. 7, the other end of the total pressure pipe 22 is slightly inserted into the hole of the duct 1 and is attached to the duct 1 by a metal fitting 41 and a plug 42 attached to the duct 1. .

Further, in the portion of the total pressure pipe 22 located inside the duct, one or more numerous openings 25 are provided in the inner portion of the duct in a direction facing the flow, with the center axis 40 of the duct as a reference.

In the case of the present invention, when the duct diameter is expanded from Dl to , it is easy to extend the length of the necessary branch pressure pipes in the outer parts of the original general pressure pipe located on both sides thereof, and to provide necessary length openings (shaded area in Figure 13B). .

In general, in the case of ducts for pill air conditioning systems, the average wind speed does not change even if the duct diameter increases (3 to 6 m /
Therefore, the maximum wind speed at the center of the duct and the wind speed distribution at the position of the pot inside the duct will not change much.If the duct is expanded, if the total pressure pipe is expanded with the above configuration, the flow speed measurement accuracy will be improved. can be kept almost the same. The same applies when reducing the size of the duct.

FIG. 8 shows another embodiment in which the other end of the total pressure pipe 22 is inserted into the hole of the duct 1 for an extra length and is attached to the duct. In this case, a metal fitting 4 is attached to a metal fitting 41 attached to a duct 1.
4 with bolts 43, and connect the other end of the static pressure pipe 22 to duct 1.
It is configured to be installed on. In this case, the hollow part of the static pressure tube is
It is desirable to close it with a round bar 45 fixed to the metal fitting 44.

As a special case, this type has openings provided at equal intervals, and is suitable for use when the duct diameter is reduced. In the case of the present invention, as shown in detail in FIGS. 14A and 14B, when the duct diameter is reduced from Dl to
Adjust the tip of the total pressure pipe to the required length (shaded area in Figure 14A)
It is easy to take it out of the duct and configure the total pressure pipe into a substantially contracted shape. In this case as well, it is possible to maintain almost the same flow rate measurement accuracy.

Next, in the case of the present invention, the bypass flow passage 20 is provided with a bypass flow passage whose area is smaller than that of other ventilation passages, and which can regulate the bypass air flow and adjust the bypass diversion. Means 28 are provided. FIG. 9 shows an example of one means for controlling the bypass flow rate.

In FIG. 9, by turning the handle 57, the threaded portion 5 is
6 allows the lot 55 to move in and out, and the bypass flow rate bacteriostatic area 53 can be adjusted by moving a conical bacteriostatic body 54 provided at the tip thereof.

In FIG. 9, the rod 55 is fixed to the metal fitting 58 with a threaded portion 56, and the metal fitting 58 is fixed to the bypass air passage forming lid 5 with a threaded portion 59.
The lid 52 is attached to the bypass air passage forming main body 50 with bolts 52 and serves as a cap.

Further, in the present invention, a bridge circuit connected to a hot wire type resistor 23 built in the bypass air flow path is built in the box 29. FIG. 10 shows an embodiment of the typical bridge circuit. In Fig. 1O, a Wheatstone bridge is constructed by the hot wire resistor 13, that is, the flow rate measuring resistor 73a, the temperature compensating resistor 73b, and the resistor 71°72.73, and the potential difference at the midpoint is determined by using an operational amplifier 7o. It is detected by a differential amplifier circuit. A signal is input to the pace of the transistor 74, and closed loop control is performed so that the potential at the midpoint of the bridge is always equal.

According to the bridge equilibrium condition, the resistance Rw of the flow rate measuring resistor 73a is expressed by the following equation.

However, R1 is the resistance value of the resistor 71, R7 is the resistance value of the resistor 72, multiplied by the resistance value R of the resistor 73, and s is the resistance value of the temperature compensation resistor 73b. In reality, n w ) Rt, the flow rate measuring resistor 73a is in a heated state, and the temperature compensating resistor 73b is heated.
is heated slightly, but almost at atmospheric temperature. Therefore, when the air temperature rises, the resistance of Rt also increases accordingly, compensating for the influence of the rise in air temperature. Also, if the air temperature is constant, Rt is constant, and Rw is a constant value regardless of the air flow rate.
4 is activated to sterilize the current flowing through the bridge.

That is, bypass air path 20'f: The flow rate of air flowing through can be determined by the potential at the midpoint of this bridge or the potential at the emitter of transistor 74, and therefore the air flow rate in bypass air path 20 can be determined.

If the output signal of this bridge circuit is VI, then the following relationship exists between it and the air flow rate q passing through the bypass air passage 20.

V-=C, +c, v'r +++-...+(
2) Note that C, , C, is a constant related to the hot wire type resistor. FIG. 15 is a diagram showing the relationship between these output signals vI and air flows M and q.

- The average dynamic pressure of the air flow in the duct at the opening 25 of the force-boosting pressure pipe is Pv, the static pressure is PH, and the static pressure pipe opening 24
Letting the static pressure of Ps2 be PsI, PD, and the following relationship with the bypass airflow iq.

Here, S: Resistance coefficient of flow path side 1 means portion A: Flow path restrictor means Ventilation duct area: Ratio of air.

g: Acceleration of gravity Here, by selecting the number of openings 25 and their positions, the airflow jtQ and the average dynamic pressure Pvra in the duct 1 are determined.
can satisfy the following relationship.

Here, F: Ventilation duct area of the duct In the case of the present invention, where the following equation is established from equation (3) and equation (4), the air flow MIQ in the duct and the output signal V1
It has been experimentally confirmed that the relationship between .

With the bypass flow path side (goods) means shown in Figure 9,
By adjusting the area of one ventilation passage, it is possible to correct the output signal vIO value, that is, the measured value of the air flow rate in the duct, as shown in the diagram (11) in FIG.

Furthermore, the present invention includes providing a circuit that can adjust the output signal, an implementation of which is shown in FIG. 11, connected to the bridge circuit shown in FIG. 10.

In FIG. 11, the movable terminal voltage of the variable resistor 80 is -Vz, and the movable terminal voltage of the variable ill resistor 81 is -BV.
3, the inverting input terminal of the operational amplifier has a virtual zero potential, so the following equation holds true at point P.

Also, v3=扼(V, -Vz, ・・・・
...(7)B RIZ Here, the input signal voltage v2 is 4-v2. ~+V2b
When V, = +V, , Lz V3 = ・Vl m . . .
...(8) When rL+ is satisfied, the formula (7) ldV3=o, so if the variable resistor 80 is adjusted to satisfy the condition of formula (8), the output signal voltage can be reduced to zero. You can.

Also, if ■2 is +V, -, equation (7) is =K (Vx
b V□)・・・・・・・・・(9), so
By adjusting the variable resistor 81, 1((
That is, since B) can be set to any value, the change in input signal voltage (V2b V'2a ) k can be converted to any output signal voltage V.

FIG. 17 is a diagram showing the relationship between the output signal from the bridge circuit, that is, the input signal to the adjustment circuit of FIG. 11, and the output signal of the adjustment circuit after adjustment. Diagram (1) in the same figure shows the relationship between the output signal and the input signal without adjustment, and diagram (11) in the same figure shows the relationship after adjustment by the summer resistor 80 in FIG. The output signal V is expressed by the following relational expression with the input signal v1.

v, =v, +a...
(10) The value added by adjusting the aFi variable resistor 80 is shown here, and is normally adjusted so that when q=0, v=0. The diagram GiD in FIG. 17 shows the relationship after being eked by the variable resistor 81 in FIG. 11, and its output signal V3 is expressed by the following relational expression with the input signal V1.

v,=b−v,・・・・・・・・・
・(11) Here, b is adjusted by the variable resistor 81,
Indicates the multiplied value.

Variable resistor 80.8 of the output signal adjustment circuit shown in FIG.
1, the line diagrams (Ii) and (IiD
It is possible to correct the value of the output signal vI, ie the measured value of the flow rate in the duct, as shown in FIG.

Further, the bridge circuit output signal adjustment circuit described above is provided separately from the bridge circuit in accordance with the need to easily adjust the output signal.

As described above, the present invention makes it possible to correct the measured value of the flow in the duct by performing initial adjustment at the start of operation using both the bypass flow path control means and the output signal voltage 1 means of the bridge circuit. This is a possible configuration. In particular, both means allow extensive initial adjustment without impairing measurement accuracy, and are particularly practical for use in empty i'fl'j systems.

Furthermore, the present invention provides a bridge circuit to which the hot-wire resistor 23 is connected, a box 29 containing the bridge circuit.
and the bypass air passage 20.
It is provided so that it can be removed from the FIG. 12 shows an example of the configuration.

In FIG. 12, the box 29 is composed of a bottom plate 93 and a lid 94 screwed thereto, and a bridge circuit 91 shown in FIG. Further, it is included in the protective tube 92 of the hot wire type resistor 23 and fixed with an insulating material, and the protective tube 92 is fixed to the substrate. This integrated structure is removably attached to the main body 50 of the bypass air passage 20 with bolts 96.

In FIG. 12, the hot wire resistor 23, the bridge circuit board 9
1, integrated products require high precision, so it is important to configure them so that only one type is required, mass produce them, and manage production technology. Furthermore, it is necessary to use this product for other purposes, increase the number of production, and manufacture it at a low cost, and the present invention makes these possible.

Moreover, this part is particularly complex compared to other parts of the production process, and takes many days to produce. The present invention makes it possible to keep only this part in stock and manufacture the entire product in a short delivery time.

In addition, when used locally, it is important to keep in mind that this part requires high precision maintenance, and if it is not used for a long period of time, it is possible to remove and store this part. It is also possible to do so.

Figure εα18 shows another specific embodiment of the present invention.

In FIG. 18, the static pressure pipe 21 and the total pressure pipe 22 are formed by common blocks 103 and 104, and their ventilation passages are configured independently. Outside one end of the static pressure tube? M'e1
01, and use this and the attachment 102 to convert the total pressure pipe 22 into a total pressure pipe.

Several blocks 104 for forming static pressure pipes are provided so that they can be easily removed, and by easily replacing total pressure pipes of different lengths, an expansion configuration means is constituted that makes it possible to extend the length of the total pressure pipe. are doing.

FIG. 19 shows another example of an enlargement means built into the total pressure pipe 22 and capable of extending its length.

In FIG. 19, the tip of the total pressure pipe 22 is divided into total pressure pipe pieces 112 and 113, which are connected at angles of 114° and 115. Further, it is easy to replace the total pressure pipe piece 112 with another total pressure pipe piece having a different length, thereby showing the configuration of an enlarged configuration means that allows the length dimension of the total pressure pipe to be extended.

FIG. 20 shows another example of the total pressure pipe piece 112 in FIG. 18. FIG. 20 shows an example in which the total pressure pipe piece 122 has a donut shape, several branch pipes 121 are communicated with it, and one or more openings 25 are provided in the branch pipes.

FIG. 21 shows another embodiment of the expansion means provided in the total pressure pipe 22. In FIG. A piece 131 is provided at the tip of the general pressure pipe 22 so as to slide within its inner diameter, and a coil spring is inserted between it and a support plate 135 fixed within the inner diameter of the general pressure pipe 22, and the dimensions of the duct 1 are slightly changed. Total bone compression 22 yen
An example of a configuration in which the negative length dimension can be easily expanded will be shown.

FIG. 22 and FIG. 23 show another embodiment of one means for controlling the bypass flow f.

In the figure, by turning the handle 151, the screw 15
The rotor 152 connected by the rotor 9 is interlocked, and the disk integrated with the rotor is rotated.The control holes 153f of several diameters provided on the disk are used to rotate and move the disk. As a result, the bypass flow rate passing through the bypass air passage 20 is made to have an adjustable limit.

A ring-shaped backing 156 made of rubber or the like is provided between the rotor 152 and the bypass air passage forming lid, and the backing 156 is pressed by a metal fitting 160. Also, metal fittings 16
0 is pushing the coil spring 154 inserted into the rotor 152. The rotor 152 and the bypass air passage forming lid 51 are
It is integrated with a nozzle 151 and a screw 159. A ring-shaped backing 157 is provided between the pinox air passage forming device 51 and the bypass air passage forming body 50, and the bypass air passage forming lid 51, which is integrated with the rotor 152 and the handle 151, is secured with a screw 52. It is fixed to the bypass air passage forming main body 50.

As described above, the rotor 156, which has several types of side leg holes and is attached to the bypass air passage forming main body 50, has a coil spring 1.
54, it is fixed to the bypass air passage forming main body 151 by friction.

Furthermore, by matching the reference numeral 162 provided on the handle 151 with the reference numeral 161 on the bypass air path forming lid, the size of the control hole 153 of the rotor 152 with one hole in the split surface can be easily determined even from the outside of the device. It is structured in such a way that it can be understood.

According to this device, the reproducibility of the bypass flow control function 1 is improved, and even if the position of the dial is changed due to an erroneous operation, it can be easily and accurately returned to the original correct position.

FIG. 24 shows an example of the invention in which a piece 141 with a flow rate control hole 142 that can be easily taken out is provided in the middle of any one of the bypass air passage, the total pressure pipe, and the static pressure pipe.

In this case, a piece i4i with a different size of one hole in the flow direction
It becomes possible to adjust and control the bypass flow by replacing and replacing the bypass flow.

〔Effect of the invention〕

According to the present invention, the flow measuring device 9' can be attached to various ducts by means of an enlarged structure provided on the total pressure pipe, and the flow rate measuring device 9' can be attached to various ducts. It becomes possible to manufacture the set-up.

By using both the trench bypass bullet control means and the output signal control means, it is possible to perform initial adjustment at the start of operation and correct the measured value of flow f:, even when installed and used in various ducts. It becomes possible to measure with high precision.

Furthermore, the hot-wire type resistor and the bridge circuit connected to it are integrated, making it easy to remove from the bypass air path, requiring high precision and being expensive. It is possible to configure a flow rate measuring device that can be attached to a duct, and it is possible to design and manufacture it in a standardized and inexpensive manner.

As described above, the present invention makes it possible to practically measure the total air flow rate in a duct when air is blown at relatively low pressure and used in various duct piping, such as in a building air conditioning system.

[Brief explanation of drawings]

1, 2, and 3 are configuration diagrams of known examples, FIG. 4 is a principle diagram of the present invention, and FIG. 5 is a configuration diagram of an embodiment of the present invention,
Fig. 6 shows an embodiment of the means for enlarging the total pressure pipe, Fig. 7 shows how it is attached to the duct, Fig. 8 shows another embodiment of how it is attached to the duct, and Fig. 9 shows one implementation of the flow rate sterilization means. For example, FIG. 10 is an embodiment of the bridge circuit, FIG. 11 is an embodiment of the output signal control means, an explanatory diagram of the means, and FIGS. 15, 16, and 17 are diagrams showing the relationship with the output signal. , FIG. 18 is a block diagram showing another embodiment of the present invention, FIGS. 19, 20, and 21 are other embodiments of the enlarged configuration means, and FIGS. 22 1 to 24 are flow phase control diagrams. FIG. 7 is a diagram showing another embodiment of the microbial means. 20... Bypass air path, 21... Static pressure pipe, 22.
...Total pressure pipe, 23.. Hot wire type resistor, 24.. Static pressure pipe opening, 25.. Total pressure pipe opening, 27.. Expansion configuration means, 28.. Flow control M1 means, 29... Pridge No. 1 Figure Otsu 2 Mouth Otomo 3 Figure 3 'f, q Figure i/9 Mouth 11 Figure 12 Ward No. 14-A Figure % +5 Figure sf,, Otsu Ingukut) llq guy Quantity of air I (θ) Fig. 17 Input V1 No. 18 Mouth χ2θ゛゛ ward/22 % zI Fig. 2 Certain 22 Fig. 6 Ton 23 Kuni No. 24 Fig. 2 θ 11, l, 15 turtle 3,118. . 1982 Patent Application No. 174572 3. Person making the amendment 1st item 1"1" Patent Applicant (F Address: Marunouchi, Chiyo Il 1-ku, Tokyo 100-
'1' l-15th 1ぢ2, +1 I51sl
i Shikikai 1111 Tachitsu 2 work place u table i
Address: 3-3 Kanda Kajida-cho, Chiyoda-ku, IH Tokyo
-4 Name Representative of Japan Flowcell Co., Ltd.
Land 1) Foreign - 4th person

Claims (1)

[Claims] 1. A bypass air passage is provided in the duct, a hot wire resistor is installed in the bypass air passage, and the air flow rate flowing through the bypass air passage is detected to determine the air flow rate flowing through the duct tf. In this air flow measuring device, a static pressure pipe, a total pressure pipe, and the other end of the total pressure pipe are opened in the non-blowing direction and the blowing direction, respectively, at both ends of the bypass air flow path, and the bypass air flow rate is regulated within the above-mentioned range, and the bypass air flow rate is regulated within the above range. A bypass flow control means capable of adjusting the flow rate is provided, an expansion means capable of extending the length of the total pressure pipe is provided, and one or more openings are provided in a portion within the duct. An air flow measuring device that measures e%. 2. In addition to the bypass flow rate control means described in item (1), an output control means is provided which is connected to the bridge circuit incorporated in the hot wire resistor and whose output signal can be adjusted. An air flow rate measuring device according to claim 1. 3. The air flow measuring device according to claim 2, characterized in that the hot wire resistor and the bridge circuit are integrally constructed and can be removed from the bypass air path. 4. The air flow measuring device according to claim 2, wherein the output signal sterilization means connected to the bridge circuit is provided separately from the bridge circuit.