JPH0217419A - Pressure difference type flowmeter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a differential pressure type flow meter that controls the flow rate of gas.

[Summary of the invention]

The present invention uses a crystal oscillator as a pressure detection sensor in a differential pressure flowmeter that controls the gas flow rate based on the pressure difference between the gases, thereby reducing the size of the flow rate detection chamber and the cost of the differential pressure flowmeter. It was an attempt.

[Conventional technology]

Conventionally, the technology for the sensor part of a flowmeter has been to provide a capillary bypass in a part of the main pipe that is the gas flow path, wrap a resistance wire around the outside of the capillary, and heat it by passing a current through the resistance wire. , a thermal type I flowmeter that adjusts the flow rate by detecting the temperature difference between the upstream and downstream sides caused by gas flowing in a capillary tube, and a diaphragm type pressure sensor using a diaphragm flat plate to measure the temperature between two chambers. There is a differential pressure type flow meter that adjusts the flow rate based on the pressure difference.

[Problem to be solved by the invention]

In the thermal mass flowmeter as described above, the capillary tube becomes clogged with dust and the like. Further, the differential pressure type flowmeter as described above has the drawback that the flow rate detection chamber becomes large and expensive.

[Means to solve the problem]

In order to solve the above problems, in the present invention, a crystal resonator is used as a pressure detection sensor of a differential pressure type flowmeter.

[Effect]

With the above configuration, clogging due to dust can be eliminated, and the flow rate detection chamber can be downsized and the price of the differential pressure type flowmeter can be reduced.

〔Example〕

Embodiments of the present invention will be described below based on the drawings. 1st
The figure shows a configuration diagram of a first embodiment of a differential pressure type flowmeter according to the present invention.

A first flow rate detection chamber 7 and a second flow rate detection chamber 8 are provided with a fixed throttle 9 sandwiching a crystal oscillator 6 as a pressure detection sensor.
By attaching the signal from the crystal oscillator 6 to the first
The pressure is detected by the pressure detection section 1 and the second pressure detection section 2, and the control means 3 converts the differential pressure signal into a flow rate signal. It controls the flow rate of gas.

FIG. 3 is a diagram showing a second embodiment of the present invention, and exemplifies a case where a PLI-circuit is applied to the pressure detection section described above. P L in the first pressure detection section 1 and the second pressure detection section 2
By providing the I-circuit 15, the phase difference between the drive voltage of the crystal oscillator 6 and the current flowing through the crystal oscillator 6 is always controlled to be zero, and the crystal oscillator 6 is always controlled at its own resonant frequency. The crystal oscillator 6 generates a pressure signal by converting the resonance frequency, which changes depending on the gas pressure in the first flow rate detection chamber 7 and the second flow rate detection chamber 8, from current to voltage and amplifying it. . The first question asked above?
Convert the pressure signals of the L quantity detection chamber 7 and the second flow rate detection chamber 8 from differential pressure signals to flow rate signals using the arithmetic circuit 16 of the control means 3.
The controller I roller 17 causes the display circuit 4 to display the flow rate. In addition, the flow rate is controlled by the flow rate control unit 5 in the certification adjustment unit 10 using the distribution signal.

FIG. 4 shows a third embodiment of the present invention, and illustrates a case where the signal processing in the second embodiment is digitally processed. An oscillation circuit 18 is provided in the first pressure detection section 1 and the second pressure detection section 2, and a constant frequency is applied to the crystal resonator 6, so that the crystal oscillator 6 generates a crystal by changing the gas pressure in the first flow rate detection chamber 7 and the second flow rate detection chamber 8. The vibration frequency of the vibrator 6 is divided through one frequency dividing circuit, and the period measuring circuit 20 of the control means 3 compares the period with a reference period generated by the reference signal generating circuit 21. The cycle difference is converted into a pressure value, the differential pressure is determined from each pressure value, the result is converted into a flow rate signal, and the controller 23 causes the display circuit 4 to display the flow rate. Further, the flow rate is controlled by the flow rate adjustment unit 10 via the flow rate control unit 5 using the flow rate signal. If the measuring circuit is digitally processed in this way, the measuring circuit can be made smaller and cheaper than the first embodiment.

〔Effect of the invention〕

According to the present invention, in a flow meter that controls the flow rate of gas, by using a differential pressure type flow meter that uses a crystal oscillator as a pressure detection sensor, clogging due to dust etc. can be prevented, and the flow rate detection chamber can be made smaller. I can do it. Further, by digitally processing the measuring circuit, there is an effect that the measuring circuit can be made smaller and lower in price.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a first embodiment of a differential pressure type flowmeter according to the present invention, Fig. 2 is a block diagram of a conventional thermal mass flowmeter, and Fig. 3 is a block diagram of a second embodiment of a differential pressure type flowmeter according to the present invention. Example configuration diagram, 4th
The figure is a configuration diagram of a third embodiment of a differential pressure type flowmeter according to the present invention. First pressure detection section Second pressure detection section Control means Display circuit Flow rate control section Crystal oscillator: First flow rate detection chamber/Second flow rate detection chamber Fixed throttle Flow rate adjustment section Flow rate detection section Control circuit Capillary laminar flow element PLI - circuit calculation Circuit Controller Oscillator Circuit Frequency Divider Circuit Period Measuring Circuit Reference Generation Circuit Arithmetic Circuit Controller Applicant Seiko Electronics Co., Ltd. Agent Patent Attorney Takayuki Hayashi Bridge Melon Diagram No. 3 of Seven Examples of the Second Practical Pressure Type Flow Control System Invented by Hibiki Figure 1 Diagram of the structure of Tokai's thermal energy flow meter Diagram 2 Diagram of the structure of the 3rd actual ratio of the 1st day l1lll2J otsu type 5 tile measurement Figure 4

Claims (1)

[Claims] First and second flow rate detection chambers provided on both sides of a fixed throttle, crystal oscillators provided in the first and second flow rate detection chambers, and a pressure signal connected to the crystal oscillator. first and second pressure detection sections for detecting; control means connected to the first and second pressure detection sections for controlling a flow rate signal from the pressure signal; and a display circuit that is maintained by the control means and displays the flow rate; A differential pressure type flowmeter comprising: a flow rate control section that controls the flow rate; and a flow rate adjustment section that adjusts the flow rate using the flow rate control section.