JP3053486B2 - Fluidic gas meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a fluid gas meter.

[0002]

2. Description of the Related Art Fluidics in which a small flow rate is measured by a thermal flow sensor (hereinafter abbreviated as flow sensor or FS) and a medium or large flow rate is measured by a fluidic oscillator (hereinafter abbreviated as fluidic or FD). The gas meter is provided with a flow rate range where both measurement areas overlap, and when the flow rate to be measured is in this flow rate range, the output change of the flow sensor due to temperature change and aging change is stable. (Japanese Patent Laid-Open No. 3-96817 or 3-264821)
No.).

[0003] Full I Dick (FD) is not oscillate in a small flow rate, since it is impossible measurement, measures the first predetermined flow rate Q ₁ or shown in FIG. 4, a flow sensor (FS) in the second predetermined to measure the flow rate Q ₂ below. Thus a flow rate range where the flow rate range of Q ₁ to Q ₂ is the overlap.

[0004] The prior art (in particular, Japanese Patent Laid-Open No.
264821), calibration is performed according to the procedure of the flowchart shown in FIG. In FIG. 5, FD and F
S is a flow rate measurement value by a fluidic and a flow sensor, respectively, k is a correction coefficient when calibrating the data of the flow sensor, and the integration of the small flow rate measurement values by the flow sensor is performed in steps 27 to 29 in steps 27 to 29. Thus, the integration of the measured values of the medium and large flow rates by the fluidic is obtained.

[0005] In an actual gas meter, the fluidic is stable with no change over time because the vibration constant (cc / p) is determined by the shape and size of the element. Since the flow sensor is a thermal sensor having a fine structure, the temperature drift and the change with time are slightly larger than those of the fluidic. Therefore, the data of the flow sensor is calibrated based on the fluidic measurement value. More specifically, since the analog signal of the flow sensor is A / D converted into a digital signal having a pulse number proportional to the flow rate, calibration is performed by changing the pulse number for this flow rate, that is, the pulse constant. .

FIG. 6 schematically shows a gas meter of this type. This gas meter is a fluidic oscillator (FD)
1, a sensor 2 that detects fluid vibration of the FD 1 and converts it into an electric signal, a thermal flow sensor (FS) 4 that detects a flow velocity of the nozzle unit 3 of the FD and converts it into an electric signal, It has an electronic circuit 5 for calculating the integrated flow rate by calculating signals of the detection sensor 2 and the flow rate detecting FS 4, and a display 6 for displaying the integrated flow rate obtained by the electronic circuit 5.

As the fluid vibration detecting sensor 2, a polymer piezoelectric sensor is used.
A flow sensor as described in JP-A-182315 is used.

The fluid vibration detecting sensor 2 generates an electric signal having a frequency corresponding to the fluid vibration, and the flow sensor generates an analog electric signal corresponding to the flow velocity of the nozzle portion 3. The flow sensor 4 has a fluid temperature detecting section disposed upstream and downstream of the heating section on the surface of the silicon chip where the flow is applied, and the electrical resistance of the fluid temperature detecting section on both sides of the heating section changes according to the flow rate. Therefore, this change is detected as an electric signal, amplified, A / D converted, and the flow rate is obtained by a microcomputer.

The electronic circuit 5 has a configuration shown in FIG. Reference numeral 4A denotes an A / D conversion circuit which converts a small flow analog electric signal detected by the flow sensor 4 into an electric pulse signal having a pulse number proportional to the flow rate.

Reference numeral 7 denotes a counter for temporarily storing a high-speed electric pulse (signal B) output from the A / D conversion circuit 4A for input to the microcomputer 8, reference numeral 9 denotes a power supply, and reference numeral 10 denotes a piezoelectric film circuit unit 11. This is a power supply control circuit for controlling a drive voltage supplied to the thermal flow sensor circuit unit 12.

Reference numeral 13 denotes an analog amplifier for amplifying the electric signal of the sensor 2, 14 denotes a waveform shaping circuit for shaping the output signal of the analog amplifier 13 into a rectangular wave, and 15 denotes a waveform shaping circuit 14.
Receives the output (signal A) of a signal determination circuit to be transmitted to the microcomputer 8 that when the frequency is above a certain value (that is, when the flow rate is above for Q ₁ in more) in signal A as signal J of the same frequency.

Reference numeral 16 denotes a clock control circuit which receives a command from the microcomputer 8 and converts the clock signal H into an A / D signal for A / D conversion.
It is sent to the conversion circuit 4A. Signal frequency of the sensor 2, i.e. the signal J when the predetermined value or more frequencies corresponding to a predetermined flow rate to Q ₁ signal A becomes the flow rate integrated value is calculated by the microcomputer 8. In a small flow rate region where the frequency of the signal A is equal to or less than a certain value, the microcomputer 8 calculates the signal B based on the FS4,
And the flow rate integrated value of the total number of pulses of the signal B is obtained and displayed on the display 6.

The analog voltage of the flow sensor 4 is synchronized with the clock signal, and the flow rate signal B having a pulse number proportional to the flow rate is obtained.
Are converted by the A / D conversion circuit 4A. This signal B is output at every interval (period) To (for example, To = 6 seconds).
The characteristics of the A / D conversion circuit 6 are determined so that 300 pulses are obtained at 0 [l / h] and the number of pulses is proportional to the flow rate.

Then, based on the measured value of FD, FS
When calibrating the measured value of, the analog signal of FS4
The calibration has been performed by changing the pulse constant when the digital conversion into an electric pulse is performed by the / D conversion circuit 4A.

The details of such a calibration operation are well known in the above-mentioned Japanese Patent Application Laid-Open No. 3-96817.

[0016]

Generally, the use of gas by gas consumers is determined by the heating power and the heating time depending on the object to be heated. This is detected by the gas meter as the gas flow rate and time.

The calibration of the flow sensor in the above-mentioned prior art is usually performed according to the procedure shown in the flow chart of FIG. 5, but the flow sensor is used for intermittent measurement at intervals of 6 seconds, and the fluidic is used for continuous measurement. Even if there is a measurement error due to the flow rate fluctuation in the measured value, the measured flow rate of the fluidic and the flow sensor is compared as it is and calibration is performed based on it, so that high-precision calibration cannot be performed as a result There was a problem.

That is, since the measurement method for comparing the measured flow rates of the fluidic and the flow sensor does not match the actual usage of the gas, the calibration calculation is not performed, or even if the calibration is performed, the conventional measurement is performed. In the logic, errors in flow rate fluctuations were included in the measurements of the fluidic and flow sensors, which prevented accurate calibration.

If the difference between the first and second predetermined flow rates Q ₁ and Q ₂ is reduced, the accuracy of calibration is improved. However, from the viewpoint of gas usage, the actual flow rate range between Q ₁ and Q ₂ is limited. Since the chance of entering the flow rate decreases, and the opportunity for calibration decreases as a result, the means for obtaining a good result is inconvenient.

Accordingly, an object of the present invention is to provide a gas meter which can solve the above-mentioned problems.

[0021]

In order to achieve the above object, a fluidic gas meter according to the present invention comprises a fluidic oscillation element (1) for medium and large flow rates and a thermal flow sensor (4) for small flow rates. And a flow rate range where both measurement areas overlap is provided. When the flow rate to be measured is in this flow rate range, the fluidic oscillation element (1)
In the gas meter for calibrating the measurement value of the thermal type flow sensor (4) based on the measurement value of (1), when the flow rate to be measured is in the flow rate range, the fluidic oscillation element (1) continuously performs the first time measurement. Flow measurement Q _n-1 and second flow measurement Q _n
, And the difference, that is, the flow rate fluctuation, is determined from the two measured values, and the calibration operation is performed when the difference is equal to or less than a certain value.

The above calibration operation may be completed within one minute.

[0023]

[Function] When the flow rate to be measured is in the overlapping flow rate range, the calibration operation is performed only when the difference between the flow rate values measured twice continuously by the fluidic is less than a certain value, for example, 5% or less. Is done.

If the difference between the two measured values is large, it is determined that the flow rate fluctuation is large and calibration is not performed.

[0025]

FIG. 1 is a flowchart of a calibration in an embodiment of the present invention. Hereinafter, the calibration procedure will be described with reference to FIGS.

Step 31: It is determined whether or not the measurement is being performed in the fluidic. Step 32: If measurement is being performed with fluidic, To
The measurement flow rate Q _n-1 of the fluidic during the measurement period of × n + t is obtained. Note that To is an interval of the intermittent measurement time of the flow sensor, n is an integer of 1, 2, 3,..., And t is To ×
Time until the first fluidic signal after n seconds (see FIG. 3).

Step 33: It is determined whether or not the measured flow rate of the fluid is within the calibration flow rate range (Q _{1 to} Q ₂ ). If it is within the same range, the process proceeds to step 34. Step 34: Toxn + t by fluidic again
Measure the flow rate per second → Qn. At the same time, measurement is performed n times by the flow sensor during To × n + t seconds to obtain a measured value Q _FS .

Step 35: Q ₁ ≦ F using Qn again
The determination of D ≦ Q _2. Step 36: Q _{n-1 of} step 32 and step 34
Is compared with Qn to determine whether the flow rate fluctuation is within a predetermined standard (for example, 5% or less). Step 3 if within the standard
Move to 7.

[0029] Step 37: calculates the pulse constant of the flow sensor by Q _n and Q _FS obtained in step 34. Step 38: Update the pulse constant of the flow sensor.

With the above procedure, the flow sensor gain calibration is performed.
Complete. Note that Q_n-1And Q_nThe longer the measurement time of
However, if the time is too long, the gas
Since it does not match the actual use situation and does not lead to gain calibration,
Q _n-1And Q_nThe total measurement time should be set within one minute
desirable.

[0031]

Since the fluidic gas meter of the present invention is calibrated as described above, even if the flow sensor is intermittently driven, the fluidic flow rate is stable at a certain level or less. After performing the gain calibration calculation of the flow sensor, the accuracy of the calibration is improved, and the measurement error of the small flow rate is reduced as a result. Since the simultaneous measurement time of the fluidic and flow sensor can be shortened,
(Especially, power consumption of the flow sensor with large current consumption can be saved.) It is useful for extending the battery life of the gas meter.

Furthermore, since the measurement time can be shortened, the chances of meeting the customer's gas use condition increase, and the opportunity of gain calibration increases.

[Brief description of the drawings]

FIG. 1 is a flowchart of calibration according to an embodiment of the present invention.

FIG. 2 is a diagram showing flow rate measurement during calibration according to the present invention.

FIG. 3 is a diagram showing a flow measurement time by a fluidic at the time of calibration according to the present invention.

FIG. 4 is a diagram of a sensor output according to a flow rate.

FIG. 5 is a flowchart of a conventional calibration.

FIG. 6 is a system diagram of a fluidic gas meter.

FIG. 7 is a block diagram of the electronic circuit shown in FIG. 6;

[Explanation of symbols]

 1 Fluidic oscillator 4 Thermal flow sensor

──────────────────────────────────────────────────続 き Continuing from the front page (73) Patent holder 000116633 Aichi Watch Electric Co., Ltd. 1-2-70, Millennial, Atsuta-ku, Nagoya-shi, Aichi (72) Inventor Katsuto Sakai 3-2-7 Takasago, Katsushika-ku, Tokyo −123 (72) Inventor Shigenori Okamura 4-1-2 Hirano-cho, Chuo-ku, Osaka City Inside Osaka Gas Co., Ltd. (72) Inventor Yukio Kimura 507-2 Shinhocho-cho, Tokai City, Aichi Prefecture Toho Gas Co., Ltd. 72) Inventor Masahito Naganuma 2-70, Millennial, Atsuta-ku, Nagoya City, Aichi Prefecture Inside Aichi Watch Electric Co., Ltd. (58) Field surveyed (Int.Cl. ⁷ , DB name) G01F 1/20 G01F 1/68 G01F 7/00

Claims (2)

(57) [Claims] 1. A medium-to-large flow rate is measured by a fluidic oscillator (1), and a small flow rate is measured by a thermal flow sensor (4), and a flow rate range in which both measurement ranges overlap is provided. When there is a target flow rate in the flow rate range,
In a gas meter for calibrating a measured value of a thermal type flow sensor (4) based on a measured value of a fluidic oscillation element (1), when the flow rate to be measured is in the flow rate range, the fluidic oscillation element (1) The first flow measurement Q _n-1 and the second flow measurement Q _n are performed continuously, and the difference, that is, the flow fluctuation is determined from the two measured values. A fluid gas meter configured to perform the calibration operation. 2. The gas meter according to claim 1, wherein the calibration operation is completed within one minute.