JPH02190735A - Electronic pressure gauge - Google Patents

Abstract

PURPOSE:To obtain the pressure gauge wherein a microcomputer makes a judgement based upon experiential knowledge by providing a semiconductor pressure sensor, an amplifying circuit, an A/D converting circuit, a control part, a display device, a printer, and an operation part. CONSTITUTION:The pressure in a conduit to be tested is transduced by a semiconductor pressure sensor 1 into an analog electric signal, which is amplified by the amplifying circuit 2 and converted by the A/D converting circuit 3 into a digital signal. This signal is processed by the microcomputer of the control part 4 at constant intervals of time. The display device 5 and printer 6 displays and prints the decision a pressure value, a measurement time, the decision result of a leak test, etc., with the control signal of the control part 4 respectively. The operation part 7 consists of plural switches and the microcomputer detects which switch is pressed to control the start of the leak test, printing, etc. Then the microcomputer is stored with a program including a leak test process and conducts the test.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electric pressure needle used for airtightness inspection of gas piping.

[Prior art]

To ensure safety, gas piping must be tested for airtightness to ensure there are no leaks.

For example, one way to test for gas leaks in the conduit installed from the gas meter cock to the gas valve is to ensure that all gas valves are closed, then attach a pressure gauge to one gas valve. Open the gas valve and gas meter cock, and after the pressure has stabilized, close the gas meter cock.
It is stipulated that pressure fluctuations be investigated over a specified period of time.

When conducting a specific test, instead of opening the gas meter cock, closing the gas meter cock after the pressure has stabilized, and checking for pressure fluctuations over a predetermined period of time, the gas meter cock should be kept closed and connected to the conduit under test. Connect two pressurizing balls to the other gas valve, open the gas valve, and operate the two fast balls to pump air into the pipe under test to a constant pressure, for example, 300 M of water column or more. The gas valve is pressurized, the gas valve is closed, and then pressure fluctuations are examined for a predetermined period of time. Two minutes or five minutes is used as this predetermined time.

A water column manometa with a minimum scale of 1fffffl was used as the pressure gauge.

[Problems to be solved by the present invention] Water column manometers are large in size and do not have time measurement or recording functions, so it is necessary to use a self-recording pressure gauge, which is not only inconvenient to transport, but also makes it difficult to judge whether or not there is a leak. The workers had a hunch that they were going to die.

When a second fastball is operated and pressurized, the temperature of the pressurized air rises above the outside temperature. After pressurization, during the process of examining pressure fluctuations, the temperature drops and approaches the outside temperature.During this period, the pressure drops as the temperature drops, and the operator's guess is whether the pressure drop is due to a leak or a temperature change. However, there was a problem that a reliable judgment could not be made.

An object of the present invention is to provide an electric pressure gauge that can automatically determine whether there is a leak by distinguishing the types of pressure fluctuations based on knowledge from many empirical facts.

As mentioned above, the change in temperature is not only due to the rise in temperature caused by the adiabatic change caused by pressurizing air into the conduit (but also due to the effect of temperature changes during measurement (test)). If the temperature rises during measurement, the temperature of the air inside the pipe will change, causing the pressure to tend to rise, etc.
It has been confirmed that increases and decreases in outside temperature affect measurements.

- As an example, when the total length of the conduit is 27 m, the gas meter is No. 5, and the total volume of the conduit is 9014 c + fl, the details of the pressure fluctuation including the pressurization with a 2-speed ball were recorded using a special measuring instrument. In FIG. 5, there is clearly a leak in this case.

As is clear from Figure 5, the pressure fluctuations are large during the initial period after pressurization with the second fastball, so in order to check for leaks, first wait for about 30 seconds and then check the pressure fluctuations. I can understand that it is better to judge whether there is a leak or not.

FIG. 2, like FIG. 5, shows how the pressure fluctuates when there is clearly a "leak", but in this case, the pressure is plotted at intervals of several seconds. The pressure at each point is decreasing and no increase has appeared.

In Figure 3, changes in pressure that appear to be due to changes in temperature, especially changes in temperature, appear along the way, and in this case, it has been empirically learned from experiments that it is better to judge that there is no leak.

An object of the present invention is to provide an electric pressure gauge that allows a microcomputer to make decisions based on these empirical findings.

[Means to solve the problem]

In order to achieve the above object, the electric pressure gauge of the present invention is an electric pressure gauge used for airtightness testing of piping, and includes a semiconductor pressure sensor (1) that converts pressure into an electric signal, and a semiconductor pressure sensor (1) that converts pressure into an electric signal. an amplifier circuit (2) that amplifies the output of the amplifier circuit (2), an A/D conversion circuit (3) that converts the output of the amplifier circuit (2) into a digital signal, and a microprocessor that processes the output of the A/D conversion circuit (3). a control unit (4) consisting of a computer;
It is equipped with a display device (5) that displays the calculation results, a printing device (6) that prints the calculation results, and an operation section (7) that outputs operation signals to the control section. It is characterized by having a microcomputer program.

[Effect]

The pressure within the conduit under test is converted into an analog electrical signal by a semiconductor pressure sensor (1), amplified by an amplifier circuit (2), and then converted into a digital signal by an A/D conversion circuit (3). This digital signal is subjected to arithmetic processing at fixed time intervals by a microcomputer in the control section (4).

A display device (5) and a printing device (6) display and print out pressure values, measurement times, leak test results, etc., respectively, based on control signals from the microcomputer of the control section (4).

The operation unit (7) consists of a plurality of switches, and a microcomputer detects which one of them has been pressed.
Controls the start of leakage test, start of printing, etc.

Further, the A/D conversion circuit (3) performs a conversion operation at regular intervals according to a control signal from a microcomputer.

The microcomputer stores and executes a program having a leakage test process derived from the microcomputer program.

That is, (1) Wait for about 30 seconds for the pressure to stabilize after the operator starts the airtight test by applying pressure to the pipe.

(2) After the pressure stabilization time has elapsed, the pressure value at that time is stored as an initial value.

(3) From then on, the elapsed time is measured, and the pressure value is stored at regular intervals, and the difference from the pressure value stored immediately before, that is, the pressure change during the current fixed time, is calculated, and the presence or absence of pressure change is determined. If there is a change, it is stored whether it is an upward or downward change.

(4) Repeat step (3) above until a predetermined time has elapsed, and monitor all pressure changes within the predetermined time.

(5) Store the pressure value after a predetermined period of time as the final value;
A difference from the initial value is calculated. Based on the results, the following judgments and processing are performed.

(5) When "-1r final value" - "initial value">"positive specified value", it is determined that there is no leakage, a message to that effect is displayed, and the measurement is ended.

(5L2 r Final value” - “Initial value” < “Negative specified value”)
In this case, it is determined that there is a leak, a message to that effect is displayed, and the measurement is ended.

(5L3 r Negative specified value” ≦ “Final value” - “Initial value”)
When ≦“positive specified value”, the following determination and processing are performed based on the state of pressure change stored in steps (3) and (4) above.

(5)-3-1 If the state of pressure change includes one or more drops and does not include any rises, it will be automatically treated as a "possible leak" and follow the steps in (2) above. Perform re-measurement using the following process.

(5)-3-2 The state of pressure change is (5)-3-1 above.
If the conditions are not met, it is determined that there is no leakage, a message to that effect is displayed, and the measurement is ended.

〔Example〕

In FIG. 1, 1 is a semiconductor pressure sensor, 2 is an amplifier circuit, 3 is an A/D conversion circuit, 4 is a control unit consisting of a microcomputer, 5 is a display, 6 is a printing device (printer),
Reference numeral 7 denotes an operation unit, which constitutes an electric pressure needle together with a power supply battery (not shown), and includes the above-mentioned (1) to (5)-3.
- It has a microcomputer program consisting of 1 step.

In addition, the fixed time of step (3) is 5 seconds, the "positive specified value" of step (5)-1 is water column + 2 mm,
The "negative specified value" in step (5)-2 is water column -2
In Peng, the predetermined time for step (4) is set at 2 minutes.

The criterion for step (5) above is based on the empirical fact that during the process of pressure reduction, a situation like the one described with reference to FIGS. 2 and 3 occurs due to temperature changes and leakage.

Pressure was applied to the conduit under test and pressure fluctuations every 5 seconds were measured for 2 minutes, and from a number of actual examples, the following (a),
This is based on the fact that the trend in (b) was observed.

(a) When there was a leak, the pressure change every 5 seconds always showed a decrease and no increase was observed.

(b) If there is no leakage, in most test examples, 5
When an increase appeared in the pressure change every second at least once and continued for an additional 2 minutes, an increase appeared in the pressure change every 5 seconds in all test examples.

Based on these empirical facts, we have made it possible for the microcomputer to automatically determine whether pressure fluctuations are due to leaks or temperature changes by examining pressure fluctuations during testing.

In the above example, the pressure change was checked every 5 seconds, but if the pressure change was taken 10 times at 0.5 second intervals and the average value was taken as the pressure change for 5 seconds,
- Minimize the influence of temporal disturbances and enable more accurate measurements. Flowcharts in this case are shown in FIGS. 4(A) to 4(D).

With conventional technology, the point at which measurement begins after pressurization is
In contrast, in the present invention, measurement starts from 30 seconds after pressurization, and the measurement conditions are standardized.

In addition, in the past, the determination of the presence or absence of a leak depended only on the difference in pressure values at the start and end, which sometimes resulted in inaccurate results.However, with the present invention, the operator can simply start the measurement once. Just by doing this, you can ensure that the pressure has stabilized for 30 seconds after pressurization, monitor the pressure change during measurement, and automatically re-measure if there is any uncertainty.

〔Effect of the invention〕

Measurement and judgment operations after pressurization are automated and results are obtained based on fixed judgment criteria, so there is no variation among operators and even inexperienced workers can perform them.

The presence or absence of a leak can be correctly identified by distinguishing a pressure drop caused by a temperature change from that caused by a leak.

Since the microcomputer makes the decision, the burden on the operator is lightened.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the electric pressure gauge of the present invention, Figures 2 and 3 are diagrams showing pressure fluctuations, and Figure 4 (A).
~(D) is a flowchart showing an example of a microcomputer program, and FIG. 5 is a diagram showing an example of pressure change. 1...Semiconductor pressure sensor, 2...Amplification circuit, 3...
・A/D conversion circuit, 4...control unit, 5...indicator,
6... Printing device, 7... Operating unit Figure 2 Pressure drop due to leak Figure 3 Pressure drop time due to temperature change '#, Figure 4 CB) 4r2 4121 (D)

Claims (1)

[Claims] 1. An electric pressure gauge used for airtightness testing of piping, comprising: a semiconductor pressure sensor (1) that converts pressure into an electrical signal; and an amplifier circuit (2) that amplifies the electrical signal; The amplifier circuit (
An A/D conversion circuit (3) that converts the output of 2) into a digital signal, a control section (4) consisting of a microcomputer that processes the output of the A/D conversion circuit (3), and a control unit (4) that processes the output of the A/D conversion circuit (3). It is equipped with a display (5) for displaying, a printing device (6) for printing the calculation results, and an operation section (7) for outputting operation signals to the control section, and running the following microcomputer program for measurement processing of the airtightness test. An electric pressure gauge characterized by having: (1) Wait for about 30 seconds for the pressure to stabilize after starting the airtight test by pressurizing the pipes by the operator. (2) After the pressure stabilization time has elapsed, the pressure value at that time is stored as an initial value. (3) From then on, the elapsed time is measured, and the pressure value is stored at regular intervals, and the difference from the pressure value stored immediately before, that is, the pressure change during the current fixed time, is calculated, and the presence or absence of pressure change is determined. If there is a change, it is stored whether it is an upward or downward change. (4) Repeat step (3) above until a predetermined time has elapsed, and monitor all pressure changes within the predetermined time. (5) Store the pressure value after a predetermined period of time as the final value;
A difference from the initial value is calculated. Based on the results, the following judgments and processing are performed. (5)-1 "Final value" - "Initial value">"Positive specified value"
In this case, it is determined that there is no leakage, a message to that effect is displayed, and the measurement is ended. (5)-2 "Final value" - "Initial value"<"Negative specified value"
In this case, it is determined that there is a leak, a message to that effect is displayed, and the measurement is ended. (5)-3 "Negative specified value" ≦ "Final value" - "Initial value"
When ≦“positive specified value”, the following determination and processing are performed based on the state of pressure change stored in steps (3) and (4) above. (5)-3-1 If the state of pressure change includes one or more drops, but does not include any rises, it will be automatically judged as "possible leak" and follow the steps in (2) above. Perform re-measurement using the following process. (5)-3-2 The state of pressure change is (5)-3-1 above.
If the conditions are not met, it is determined that there is no leakage, a message to that effect is displayed, and the measurement is ended.