JPS6239941B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for measuring gas flow velocity.
Conventionally, a thermal current meter, such as a hot wire current meter, has been mainly used to measure the flow velocity of gas. However, thermal anemometers require a temperature sensor. Furthermore, in order to measure rapid changes in flow velocity, the responsiveness of the temperature sensor to temperature must be increased, and this requires a special sensor with a small heat capacity and, therefore, a small size. These specialized sensors are generally difficult to obtain, difficult to manufacture, easily damaged, and expensive.

The first object of the present invention is to provide a gas flow rate measuring device that does not require a temperature sensor, and the second purpose is to provide a gas flow rate measuring device that is easy to manufacture, durable, and inexpensive. be.

Hereinafter, details of the present invention will be explained with reference to the drawings. The present invention is basically as shown in FIG.
It is composed of a microphone 1, an integrating circuit 2, and a processing circuit 3. The microphone 1 is a microphone with a windshield removed, which is used to detect normal voices. The integrating circuit 2 is an electronic circuit for integrating the output signal of the microphone, and a well-known circuit is used. The processing circuit 3 is a function generating circuit configured to detect the power of the output signal of the integrating circuit 2 and obtain an output signal corresponding to the gas flow velocity, and specifically, is usually configured as a square root circuit.

Next, the operation of the present invention will be explained.

According to experiments, when a manocrophon is placed so that the flowing gas to be measured hits the sound receiving surface of the microphone with the windshield removed, the output signal of the microphone is extremely high as the product of the flow velocity of the flowing gas and the acceleration of the flowing gas. It became clear that they are proportional by approximation. Therefore, when the output signal of this microphone is integrated by the integrating circuit 2, a signal that is proportional to the square of the flow velocity of the flowing gas with a very high approximation is obtained. By subjecting this signal to square root processing in the processing circuit 3, it is possible to obtain a signal that is proportional to a very high approximation to the flow velocity of the flowing gas to be measured.

Next, the present invention will be explained in more detail using FIGS. 2 and 3. FIG. 2 shows a specific example of the integrating circuit 2 and the processing circuit 3, and the integrating circuit 2 is composed of an operational amplifier 4, an input resistor 5, and a feedback capacitor 6.
The processing circuit 3 is a square root circuit using a known square circuit 8 as a feedback circuit of an operational amplifier 7 having an input resistor 9.

3A shows an example of a change in the flow velocity of the gas to be measured, B shows the output signal waveform of the microphone 1, C shows the output signal waveform of the integrating circuit 2, and D shows the output signal waveform of the processing circuit 3. As is clear from the comparison of waveform A indicating the gas flow velocity and output B of microphone 1, the output signal of microphone 1 is the product of the gas flow velocity υ and the gas acceleration, which can be considered as a waveform obtained by differentiating it, υ・α. represents. Also, as is clear from the comparison of waveforms A and C, the output signal of the integrating circuit 2 represents the square of the flow velocity, and as is clear from the comparison of waveforms A and D, the integral output C is processed by the processing circuit 3 to calculate its square root. The output obtained represents the flow velocity itself to be measured. Experiments have confirmed that this relationship also holds true for gases in different fluid states.

Although a square root circuit is generally used as the processing circuit 3, it may be better to shift the input/output characteristic slightly from the square root characteristic depending on the characteristics of the microphones used.

As described above, the gas flow rate measuring device according to the present invention can be configured from a microphone, an integrating circuit that integrates the microphone output, and a processing circuit that obtains approximately the square root of the integrated output, and does not require a temperature sensor. do not. Furthermore, according to the present invention, a microphone that is generally widely used as a gas flow sensor can be used, and the measurement circuit can be configured with only an integrating circuit and a simple processing circuit, so it is easy to manufacture, durable, and inexpensive. It is clear that it is possible to provide a gas flow rate measuring device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of a gas flow rate measuring device according to the present invention, FIG. 2 is a diagram showing a specific configuration example of the gas flow rate measuring device of FIG. 1, and FIG.
The figure is a diagram showing signal waveforms at various parts in FIG. 2. 1...Microphone, 2...Integrator circuit, 3...Processing circuit.

Claims (1)

[Claims] 1. A gas flow rate measuring device comprising a microphone, an integrating circuit that integrates the output signal of the microphone, and a processing circuit that processes the output signal of the integrating circuit.