JPH0552908B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is capable of determining in which direction the airflow is flowing, how fast the airflow is, how the airflow is turbulent, or how eddies are generated. The present invention relates to an airflow measuring device that aims to measure airflow without contaminating the surrounding environment or making extensive preparations.

(Prior technology) Conventional techniques for visualizing airflow include injecting low-density substances into the air and using them as airflow tracers, and tufting, which involves attaching a filament of natural or scientific fiber to the end of a stick and placing it on the airflow to blow it away. The law is known. Of these, tracer methods include methods that use incense stick smoke or smoke from smoke tubes, methods that use white smoke from hydrolysis with chemicals such as titanium tetrachloride and ammonium chloride, and methods that use the use of white smoke produced by hydrolysis of chemicals such as titanium tetrachloride and ammonium chloride. There are methods such as releasing seed feathers, etc., or releasing balloons inflated with helium gas and adjusting the weight with weights. On the other hand, the tufting method includes a method using woolen strands, a method using silkworm cocoon thread, and a method using polymethylpentene filament.

All of these methods are useful in laboratories, but they are useful in places where you actually want to know the airflow conditions, such as in a VLSI production factory, near the surgical field, or in a building that is about to be completed. This is a very inappropriate method. In other words, the tracer substances will contaminate the surrounding environment,
Cocoon threads had the disadvantage that they could hardly be seen unless strong light was applied from a direction different from the line of sight and the background was made black (dark).

As a method of visualizing airflow in a space that requires cleanliness, there is a method of making pure water into a mist using an ultrasonic vibrator and blowing it out into the airflow, and a method of cooling pure water vapor with dry ice and condensing it into the airflow. Several methods have been proposed and put into practice, but in either case, the distance at which they can be visualized is short, and they cannot be seen unless a large amount is released, making it impossible to visualize fine details or the state of turbulence.

(Problems to be Solved by the Invention) The present invention has been made from this point of view, and uses a microcomputer to perform measurement, data recording, calculation, and display of calculation results by utilizing the super LSI technology that has developed rapidly in recent years. It is something to do. In other words, air movement is measured with a hot-wire anemometer, the measurement results are converted into signals, then stored magnetically or digitally calculated with a microcomputer, and the results are displayed on a small display device such as a liquid crystal. The displayed results include the calculated values and composite vector of the x, y, and z-direction components of the instantaneous airflow, and the average value and average composite vector of the x, y, and z-direction components of each instant measured multiple times during a certain time. This is an item in which all instantaneous resultant vectors measured during a certain period of time are superimposed and displayed so that the direction and degree of turbulence of the airflow can be understood. By doing this, it becomes possible to easily and cleanly measure airflow conditions in places where contamination is a problem, narrow places, or high places.

(Configuration of the Invention) In order to achieve the above object, the airflow measuring device of the present invention is configured as follows.

In other words, it uses a hot-wire sensor that can three-dimensionally measure airflow, controls the amount of power supplied to the hot-wire sensor, calculates the tributary velocity from the change in resistance due to the cooling phenomenon of the airflow, and calculates x of the wind speed. , y, and z-axis direction components, storing data, and displaying calculated values.

(Example) Next, an example of the present invention will be explained based on the drawings. Fig. 1 is an overall configuration diagram, Fig. 2 is a block diagram thereof, Fig. 3 is an example of display of measurement results, and Fig. 4 is a diagram showing the overall configuration. shows an example of the tip of a hot wire type wind speed sensor.

First, to explain from Fig. 1, the whole consists of two parts: the hot wire type wind speed sensor 1, the sensor control,
It consists of a measuring instrument main body 2 that performs signal transmission, reception, conversion, data recording and calculation, display of calculation results, etc., and both are connected by a wire 14 and a connector 15.

Six pins are set in pairs at the tip 11 of the hot-wire wind speed sensor 1, and a thin metal wire having a predetermined electrical resistance is stretched over the tip. This pin is placed, for example, as shown in FIG. In other words, the metal wires 41 and 42 have the same pin length and the same metal wire length, and are at right angles to each other. The third metal wire 43 has pins of varying lengths and is perpendicular to the metal wires 41, 42. A wire is connected to the bottom of each of the six pins, and a thin circular tube 12 is connected so as not to disturb the airflow.
The communication cord 1 is inserted into the sensor grip part 13 through the inside.
Connected to 4.

On the surface of the measuring instrument body 2, there is a display window 21 for displaying measurement results and a switch mounting section 22 for selecting the measuring instrument and measurement result display items. It contains electronic equipment mounted on the board and a portable power supply.

Figure 2 is a block diagram of this airflow measuring device. Information on electrical resistance changes from the sensor is converted into digital data by a signal converter installed inside the measuring device, enters the data recording device, and is sent to the CPU.
It is stored or sent to the CPU, calculated, and displayed on the display device under the control of the CPU. When a predetermined voltage is applied to the thin wire of the sensor section, a current flows in accordance with its electrical resistance, and at the same time, Joule heat is generated and the temperature rises. In still air, an upward air current is created around the heating element, creating a balance between the amount of heat carried by the air and the amount of heat generated by the electric current. The resistance value at this time is taken as the reference value. Placing this sensor in an air stream further increases the amount of heat carried away by the air stream. When the wire is cooled by the airflow, the temperature of the wire decreases and the electrical resistance value changes.
In other words, if a sensor is installed in the test wind duct and the relationship between the wind speed and the change in electrical resistance is measured in advance, then the wind speed can be determined by measuring the electrical resistance. This is the principle of the hot wire wind velocity type.

Hot wire anemometers are highly directional to airflow, so
Install three wires so that they are perpendicular to each other, find the airflow velocity perpendicular to each wire, and determine the sensor axis in advance (for example, indicate the reference axis by marking it on the sensor grip). ), the airflow velocities in x, y, and z can be determined by calculating the airflow velocities for

FIG. 3 shows an example of display of measurement results by the airflow measuring device of the present invention. FIG. 3a shows the measurement results in three dimensions (left diagram) or two dimensions (right diagram) continuously or at predetermined time intervals according to a program.
In this measurement mode, the display screen can also be stopped by operating a switch. b in Figure 3 captures a predetermined number of data (for example, 100 pieces) at a predetermined time interval (for example, 5 times per second), and later x.
The average wind speed, average wind speed, and average vector in the y and z directions are calculated and shown in three dimensions (left figure) or two dimensions (right figure). 3. c in FIG. 3 is expressed by performing the same measurements as b, synthesizing vectors from the airflow components in the x, y, and z directions at each moment, and superimposing all of them.

(Effects of the Invention) As described above, according to the present invention, if you bring the sensor to a place where you want to know the airflow state, you can easily check the direction and speed of the airflow in real time, or the average airflow within a certain period of time. You can see the state and airflow vectors superimposed on each other. In other words, it is possible to know the airflow conditions in areas that require high degree of cleaning and the airflow conditions in detailed areas. Data recorded in the measuring instrument can also be edited by importing it into another computer.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of the airflow measurement device of the present invention, Fig. 2
The figure is a block diagram, FIG. 3 is a display example of measurement results, and FIG. 4 is a structural diagram of the sensor tip.
In addition, 1 in the figure is a hot wire type wind sensor, and 2 is a measuring instrument main body.

Claims (1)

[Claims] 1. A pin is placed at the tip of the sensor, a thin electric wire is attached to the tip, and a current is passed through the wire to generate heat.
Place the sensor in the air stream you want to measure,
In a hot-wire anemometer, which determines the air flow velocity from changes in electrical resistance due to the cooling phenomenon of the air flow, three sets of thin electric wires are strung in a straight line at right angles to each other at the tip of the sensor, and the wind speed for each straight line is determined. Furthermore, the wind velocity components in the x, y, and z axis directions that are set in advance are determined, and a composite vector is determined from these x, y, and z direction components, and the x, y, and The calculated value of the wind speed component in the z-axis direction and the resultant vector can be displayed three-dimensionally or two-dimensionally, continuously or continuously, so that the screen can be stopped at any time, or it can be expressed at predetermined time intervals. airflow measuring device. 2 Measure the wind speed using three sets of hot wires a preset number of times, store each measurement value in the storage device, and after completing the measurement a predetermined number of times, measure the wind speed on the x, y, and z axes. The average wind speed component in the x, y, and z axis directions, the calculated value of the average composite vector, and the average composite vector are displayed three-dimensionally on the display screen provided on the surface of the measuring instrument. The airflow measuring device according to claim 1, characterized in that the airflow measuring device is expressed two-dimensionally. 3 Measure the wind speed using three sets of hot wires a preset number of times, store each measurement value in the storage device, and after completing the measurement a predetermined number of times, perform the measurement on the x, y, and z axes The resultant vector for each moment is determined from the wind speed component in each direction, and all resultant vectors are superimposed and expressed in three or two dimensions on the display screen provided on the surface of the measuring instrument, and x, y,
The airflow measuring device according to claim 1, characterized in that the calculation results of the average wind speed component in the z direction and the overall average wind speed are displayed. 4. The airflow measuring device according to claim 1, wherein the functions described in 1 to 3 can be selected by operating a switch provided on the surface of the measuring device.