JP3384457B2 - Differential pressure measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential pressure measuring device capable of self-diagnosing leakage of an enclosed liquid without removing the differential pressure measuring device from a measuring line. More specifically, the present invention relates to a differential pressure measuring device that detects leakage of enclosed liquid in the pressure receiving portion by utilizing the fact that the characteristic curve changes from the time of manufacturing due to leakage of the enclosed liquid in the seal diaphragm portion on one side of the pressure receiving portion. .

[0002]

2. Description of the Related Art FIG. 6 is an explanatory view of the configuration of a conventional example which has been generally used, for example, Japanese Patent Laid-Open No. 59-56137.
It is shown in FIG. In the figure, the housing 1
Flange 2 and flange 3 are fitted and assembled on both sides of and are fixed by welding or the like. Both flanges 2 and 3 are provided with a high-pressure fluid inlet 5 of pressure PH to be measured and pressure PL.
The low-pressure fluid inlet 4 is provided.

A pressure measuring chamber 6 is formed in the housing 1, and a center diaphragm 7 and a silicon diaphragm 8 are provided in the pressure measuring chamber 6. The silicon diaphragm 8 has a recess 82 in a single crystal silicon substrate 81.
Is formed.

The center diaphragm 7 and the silicon diaphragm 8 are separately fixed to the wall of the pressure measuring chamber 6, and the center diaphragm 7 and the silicon diaphragm 8 are separately fixed.
The pressure measuring chamber 6 is divided into two parts by both. Back plates 6A and 6B are formed on the wall of the pressure measuring chamber 6 facing the center diaphragm 7. The center diaphragm 7 has a peripheral edge portion welded to the housing 1.

Impurities such as boron are selectively diffused on one surface of the silicon substrate 81 to form four strain gauges 91. The four strain gages 91 are pulled when the silicon diaphragm 8 bends under the pressure difference ΔP,
Two are to be compressed and these are
Connected to Toston bridge circuit, resistance change is differential pressure Δ
It is detected as a change in P.

Reference numeral 92 is a lead whose one end is attached to the strain gauge 91. 93 is a hermetic terminal to which the other end of the lead 92 is connected. The support 9 is a
A metal terminal is provided, and a silicon diaphragm 8 is adhesively fixed to the end surface of the support 9 on the pressure measurement chamber 6 side by a method such as low-melting glass connection.

Pressure introducing chambers 10 and 11 are formed between the housing 1 and the flange 2 and the flange 3. Seal diaphragms 12 and 13 are provided in the pressure introducing chambers 10 and 11, respectively.
A back plate having a shape similar to that of the seal diaphragms 12 and 13 is formed on the walls 10A and 11A of the housing 1 which face each other.

The space formed by the seal diaphragms 12 and 13 and the back plates 10A and 11A and the pressure measuring chamber 6 are in communication with each other through communication holes 14 and 15. Filling liquids 101 and 102 such as silicon oil are filled between the seal diaphragms 12 and 13, and the filling liquids reach the upper and lower surfaces of the silicon diaphragm 8 through the communication holes 16 and 17. It is divided into two by the center diaphragm 7 and the silicon diaphragm 8, and it is taken into consideration that the amounts are almost equal.

In the above structure, when pressure is applied from the high pressure side, the pressure acting on the seal diaphragm 13 is transmitted to the silicon diaphragm 8 by the enclosed liquid 102. On the other hand, when pressure acts from the low pressure side, the pressure acting on the seal diaphragm 12 is transmitted to the silicon diaphragm 8 by the enclosed liquid 101.

As a result, the silicon diaphragm 8 is distorted according to the pressure difference between the high pressure side and the low pressure side, and the strain amount is electrically taken out by the strain gauge 91, and the differential pressure is measured. .

[0011]

However, in such a device, the filled liquids 101, 1 may be damaged for some reason.
When 02 started to leak, the leak leaked little by little and gradually, so the output became clearly abnormal and could not be detected until a failure occurred.

For example, if the seal diaphragms 12 and 13 are stuck to the housing 1 and the input does not change, the output does not change, or the enclosed liquids 101 and 102.
Is detected for the first time when the strain gauge 91 becomes abnormal due to insulation deterioration or wire breakage due to intrusion into the housing 1.

Alternatively, an input test is carried out, and an abnormal input is found only after checking for a faulty part. Furthermore, when the sealed liquids 12 and 13 leak into the sealed liquids 101 and 102, the characteristics of the differential pressure measuring device itself are directly affected, which hinders automatic control of the process.

The present invention solves this problem. The object of the present invention is to make a self-diagnosis of leakage of the enclosed liquid without removing the differential pressure measuring device from the measuring line. In addition, the function as a differential pressure measuring device is not affected at all,
It is to provide an extremely safe and reliable differential pressure measuring device.

[0015]

[Means for Solving the Problems] To achieve this object
In the present invention, (1) Differential pressure measuring device having at least one filled liquid chamber
At the high pressure side and low pressure side of the differential pressure measuring device.
While keeping the pressure equalized at the constant temperature,
From the upper limit measurable pressure to the initial zero point pressure characteristic value
Memory means for reading and a predetermined value Z during self-diagnosis₀≤ |
{(Ε₁−ε₀₀) / (P₁-P₀)}-{(Ε_Ten−ε₀₀)
/ (P₁-P₀)} |
CPU that determines that₁: During self-diagnosis
The pressure on the high pressure side and the pressure on the low pressure side of the differential pressure measuring device is set to the predetermined temperature.
The predetermined measurement pressure p₁Zero point obtained by equalizing pressure to
ε_Ten: The predetermined measurement stored in the memory means
Pressure p₁Initial zero point at, ε₀₀: Stored in the memory means
The predetermined calibration pressure p₀Initial zero point at
And a differential pressure measuring device. (2) First and first provided on both sides of the housing
In a differential pressure measuring device equipped with a second seal diaphragm
And covering the first seal diaphragm.
The first seal diaphragm and the third seal diaphragm chamber
Third seal diaphragm constituting the second die
And a second seal diaphragm provided to cover the aflam
Fourth seal diaphragm that constitutes the fourth seal diaphragm chamber
Separate the diaphragm and the third and fourth seal diaphragm chambers.
Fill the filled liquid with the high pressure side and low pressure side of the differential pressure measuring device.
While making the pressure side pressure equalized at a predetermined temperature
Initial zero point pressure from the specified calibration pressure to the upper limit measurable pressure
Memory means to store force characteristic values and self-diagnosis
Predetermined value Z ₀≤ | {(ε₁−ε₀₀) / (P₁-P₀)}-
{(Ε_Ten−ε₀₀) / (P₁-P₀)} | When it becomes
A CPU that determines that the enclosed liquid is leaking, but ε
₁: At the time of self-diagnosis,
The pressure is the predetermined temperature and the predetermined measurement pressure p₁Pressure equalized to
Zero point, ε_Ten: Stored in the memory means
The predetermined measurement pressure p₁Initial zero point at, ε₀₀: The memory
-The predetermined calibration pressure p stored in the means₀Early in
Differential pressure measurement characterized by having a zero point
The device is configured.

[0016]

In the above structure, during normal measurement, when pressure is applied from the high pressure side, the pressure acting on the seal diaphragm is transmitted to the silicon diaphragm by the enclosed liquid.

On the other hand, when pressure is applied from the low pressure side, the pressure acting on the seal diaphragm is transmitted to the silicon diaphragm by the enclosed liquid. Therefore, the silicon diaphragm is distorted according to the pressure difference between the high pressure side and the low pressure side, and the strain amount is electrically taken out by the strain gauge, and the differential pressure is measured.

At the time of self-diagnosis, a predetermined value Z ₀ ≤ | {(ε ₁ -ε ₀₀ )
_{/ (T 1 -t 0)}} - {(ε 10 -ε 00) / (t 1 -t 0)}
When it becomes |, it is judged that the enclosed liquid is leaking from the seal diaphragm. Where ε _{1 is} a zero point obtained by equalizing the pressures on the high-pressure side and the low-pressure side of the differential pressure measuring device to the predetermined measurement pressure p ₁ at the predetermined temperature during self-diagnosis, ε ₁₀ : stored in the memory means The initial zero point at the predetermined measured pressure p ₁ is set as follows: ε ₀₀ : The initial zero point at the predetermined calibration pressure p ₀ stored in the memory means. Hereinafter, detailed description will be given based on examples.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of the essential structure of an embodiment of the present invention. In the figure, the same symbols as those in FIG. 6 represent the same functions. Only parts different from FIG. 6 will be described below.

Reference numeral 31 stores a pressure characteristic value at an initial zero point from a predetermined calibration pressure to an upper limit measurable pressure while keeping the pressures of the high pressure side and the low pressure side of the differential pressure measuring device at a predetermined temperature. It is a memory means. 32 is a predetermined value Z ₀ ≦ | {(ε ₁ −ε ₀₀ ) / (p ₁ −) at the time of self-diagnosis.
_{p 0)} - {(ε} 10 -ε 00) / (p 1 -p 0)} | is sealed liquid 101 when it becomes that the CPU to determine that leaked. Where ε _{1 is} a zero point obtained by equalizing the pressures on the high pressure side and the low pressure side of the differential pressure measuring device to a predetermined measurement pressure p ₁ at a predetermined temperature during self-diagnosis, ε ₁₀ : stored in the memory means 31 , The initial zero point at the predetermined measured pressure p ₁ , and ε ₀₀ : the initial zero point at the predetermined calibration pressure p ₀ stored in the memory means 31.

The memory means 31 and the CPU 32 are
In this case, it is stored in the amplifier in the converter case. (Not shown)

[0022]

In the above structure, during normal measurement, when pressure is applied from the high pressure side, the pressure acting on the seal diaphragm 13 is transmitted to the silicon diaphragm 8 by the enclosed liquid 102.

On the other hand, when pressure is applied from the low pressure side, the pressure acting on the seal diaphragm 12 is transmitted to the silicon diaphragm 8 by the enclosed liquid 101. Therefore,
The silicon diaphragm 8 is distorted according to the pressure difference between the high pressure side and the low pressure side, and the strain amount is electrically taken out by the strain gauge 91, and the differential pressure is measured.

Next, at the time of self-diagnosis, the CPU 32
Therefore, at the time of self-diagnosis, a predetermined value Z ₀ ≦ | {(ε ₁ −
ε ₀₀ ) / (t ₁ −t ₀ )}-{(ε ₁₀ −ε ₀₀ ) / (t ₁ −
When t ₀ )} |, it is determined that the sealed liquids 101 and 102 have leaked from the seal diaphragm. Where ε _{1 is} a zero point obtained by equalizing the pressures on the high-pressure side and the low-pressure side of the differential pressure measuring device to the predetermined measurement pressure p ₁ at the predetermined temperature during self-diagnosis, ε ₁₀ : stored in the memory means An initial zero point at the predetermined measured pressure p ₁ that has been set, ε ₀₀ : an initial zero point at the predetermined calibration pressure p ₀ stored in the memory means,

Therefore, it is possible to obtain a differential pressure measuring device capable of self-diagnosing leakage of the filled liquids 101 and 102 without removing the differential pressure measuring device from the measuring line.

The specific self-diagnosis operation will be described below. FIG. 2 shows a static pressure characteristic diagram of a zero point error, and FIG. 3 shows an operation explanatory diagram when a static pressure characteristic curve is used. In FIG. 3, D shows an initial pressure characteristic curve, and Q shows a pressure characteristic curve in a liquid leakage state. (1) As shown in the flow 1 of FIG. 2 and FIG. 3, the pressure equalizer valve is opened to the pressure P ₁ at the temperature t ₁ and the pressure P ₁ currently used.
Measuring the zero point epsilon ₁ at a pressure P _1. ，

(2) As shown in the flow 2 of FIG. 3, the zero point ε ₀₀ at the temperature t ₁ and the atmospheric pressure p ₀ is calculated and obtained from the initial pressure characteristic curve stored in the memory means 31. (3) As shown in the flow 3 of FIG. 3, (ε ₁ −ε ₀₀ ) /
Calculate (p ₁ −p ₀ ). (4) As shown in the flow 4 of FIG. 3, the zero point ε ₁₀ at temperature t ₁ and atmospheric pressure p ₀ is calculated and obtained from the initial pressure characteristic curve stored in the memory means 31.

(5) As shown in the flow 5 of FIG. 3, the zero point ε ₀₀ at the temperature t ₁ and the atmospheric pressure p ₀ is calculated and obtained from the initial pressure characteristic curve stored in the memory means 31. (6) As shown in the flow 6 of FIG. 3, (ε ₁₀ −ε ₀₀ ) /
Calculate (p ₁ −p ₀ ). (7) As shown in the flow 7 of FIG. 3, Z = {(ε ₁ −
ε ₀₀ ) / (p ₁ −p ₀ )}-{(ε ₁₀ −ε ₀₀ ) / (p ₁ −
p ₀ )} is calculated.

(8) As shown in the flow 8 of FIG. 3, | Z |
If ≧ Z ₀ (Z ₀ is an error considering a certain margin), it is determined that the sealed liquids 102 and 101 are leaking from the seal diaphragms 13 and 12 on either the high pressure side or the low pressure side. .

(9) As shown in the flow chart 9 of FIG. 3, if Z <0 from the sign of Z, it is judged that the sealed liquid 101 is leaking from the low pressure side seal diaphragm 12 portion. If Z> 0, the high pressure side seal diaphragm 13
The enclosed liquid 102 leaks from the portion.

As a result, the differential pressure measuring device of the present invention operates even if there is a slight leakage of the filled liquids 101 and 102.
Only when the device is completely down does the filled liquid 101, 102
There is no danger of noticing the leakage of the filled liquid 101, 102
Can be easily and early detected. In addition, predictive diagnosis of down can be performed before the device goes down.

Furthermore, without stopping the flow of the measuring fluid,
Since it is easy to equalize the high pressure side and the low pressure side of the differential pressure measuring device as described above, a differential pressure measuring device that does not disturb the process flow can be obtained. Further, since it is possible to make a judgment excluding the influence of the pressure characteristic, the filled liquid 101, 1 can be more accurately determined.
A differential pressure measuring device capable of self-diagnosing 02 leakage is obtained.

Furthermore, since the measurement at the time of self-diagnosis is not necessary at two points but only at one point, it is sufficient to check only one point, and self-diagnosis can be performed extremely quickly and easily. That is, the zero point ε ₀ at the calibration pressure P ₀ in the pressure characteristic curve Q in the liquid leakage state is actually extremely small, and therefore this is ignored and the quick simplicity is adopted.

FIG. 4 is an explanatory view of the essential parts of another embodiment of the present invention, and FIG. 5 is an explanatory view of the essential parts of FIG. In the figure,
The same symbols as those in FIG. 6 represent the same functions. Below, FIG.
Only the differences will be explained.

Reference numeral 41 stores the pressure characteristic value of the initial zero point from the predetermined calibration pressure to the upper limit measurable pressure while keeping the pressures on the high pressure side and the low pressure side of the differential pressure measuring device at a predetermined temperature. It is a memory means. 42 is a predetermined value Z ₀ ≦ | {(ε ₁ −ε ₀₀ ) / (p ₁ − at the time of self-diagnosis.
p ₀ )}-{(ε ₁₀ −ε ₀₀ ) / (p ₁ −p ₀ )} |, the CPU determines that the enclosed liquids 103 and 104 are leaking. Where ε _{1 is} a zero point obtained by equalizing the pressures on the high pressure side and the low pressure side of the differential pressure measuring device to a predetermined measurement pressure p ₁ at a predetermined temperature during self-diagnosis, ε ₁₀ : stored in the memory means 41 The initial zero point at the predetermined measured pressure p ₁ is: ε ₀₀ : The initial zero point at the predetermined calibration pressure p ₀ stored in the memory means 41.

The memory means 41 and the CPU 42 are
In this case, it is stored in the amplifier in the converter case. (Not shown)

Reference numeral 51 is a third seal diaphragm which is provided so as to cover the first seal diaphragm 13 and constitutes the first seal diaphragm 13 and the third seal diaphragm chamber 52. Reference numeral 53 is a fourth seal diaphragm which is provided so as to cover the second seal diaphragm 12 and constitutes the second seal diaphragm 12 and the fourth seal diaphragm chamber 54.

Reference numeral 55 is a body provided between the first seal diaphragm 13 and the third seal diaphragm 51. 56 is a body provided between the second seal diaphragm 12 and the fourth seal diaphragm 53.
103 is an enclosed liquid filled in the third seal diaphragm chamber 52. 104 is the fourth seal diaphragm chamber 5
Filled liquid filled with 4.

In the above structure, when pressure is applied from the high pressure side, the pressure acting on the seal diaphragm 51 is changed by the enclosed liquids 103 and 102 to the silicon diaphragm 8.
Be transmitted to. On the other hand, when pressure acts from the low pressure side,
The pressure acting on the seal diaphragm 53 causes the filled liquid 10
4, 101 is transmitted to the silicon diaphragm 8.

Therefore, the silicon diaphragm 8 is distorted according to the pressure difference between the high pressure side and the low pressure side, and the strain amount is electrically taken out by the strain gauge 91, and the differential pressure is measured.

Next, at the time of self-diagnosis, the CPU 42
Therefore, at the time of self-diagnosis, a predetermined value Z ₀ ≦ | {(ε ₁ −
ε ₀₀ ) / (p ₁ −p ₀ )}-{(ε ₁₀ −ε ₀₀ ) / (p ₁ −
When p ₀ )} |, it is determined that the sealed liquids 103 and 104 have leaked from the seal diaphragm. Where ε _{1 is} a zero point obtained by equalizing the pressures on the high pressure side and the low pressure side of the differential pressure measuring device to a predetermined measurement pressure p ₁ at a predetermined temperature during self-diagnosis, ε ₁₀ : stored in the memory means 41 The initial zero point at the predetermined measured pressure p ₁ is: ε ₀₀ : The initial zero point at the predetermined calibration pressure p ₀ stored in the memory means 41.

Therefore, it is possible to obtain a differential pressure measuring device capable of self-diagnosing leakage of the filled liquids 103 and 104 without removing the differential pressure measuring device from the measuring line.

As a result, the differential pressure measuring device of the present invention operates even if there is a slight leakage of the filled liquids 103 and 104.
Only when the device is completely down, fill liquid 103, 104
There is no danger of noticing the leakage of the sealed liquid 103, 104
Can be easily and early detected. In addition, predictive diagnosis of down can be performed before the device goes down.

Furthermore, without stopping the flow of the measuring fluid,
Since it is easy to equalize the high pressure side and the low pressure side of the differential pressure measuring device as described above, a differential pressure measuring device that does not disturb the process flow can be obtained. Furthermore, since the judgment can be made excluding the influence of the pressure characteristic, the filled liquid 103, 1 can be more accurately determined.
A differential pressure measuring device capable of self-diagnosing the leakage of 04 is obtained.

In addition, the first seal diaphragm 13 is provided so as to cover the third seal diaphragm 51 and the second seal diaphragm 12, which constitute the third seal diaphragm chamber 52, and the second seal diaphragm 12. The 2 seal diaphragm 12 and the 4th seal diaphragm 53 which comprises the 4th seal diaphragm chamber 54 are provided, and the 3rd seal diaphragm chamber 52 and the 4th seal diaphragm chamber 54 are filled with the enclosed liquids 103 and 104. .

Therefore, the filled liquid 1 should be filled with the corrosive measuring liquid or the like.
Even if 03 and 104 leak, the filled liquid 101 and 102
Since there is no leakage, the function as a differential pressure measuring device is not impaired at all, and an extremely safe device can be obtained.

In the pressure equalizing state, the pipes through which the fluid to be measured flows are stopped from the conduits respectively communicating with the high pressure side and the low pressure side of the differential pressure measuring device, and the high pressure side and the low pressure side of the differential pressure measuring device are at atmospheric pressure. Release to P ₀ .

Alternatively, a three-way valve is used to stop the communication of the measurement fluid on the high pressure side and the low pressure side of the differential pressure measuring device to the piping,
In addition, various methods such as operating the high pressure side and the low pressure side so that the high pressure side and the low pressure side are equalized to the measurement pressure P ₁ can be adopted. It is easy to equalize the high pressure side and the low pressure side of the differential pressure measuring device without stopping the flow in the pressure difference measuring device.

Although the differential pressure measuring device has been described in the above embodiment, the present invention is not limited to this, and a pressure measuring device may be used. This is because the pressure measuring device is one in which the pressure of the differential pressure measuring device is set to atmospheric pressure or vacuum, and is essentially a differential pressure measuring device. In this case, the measurement pressure side is set to atmospheric pressure or vacuum to check the zero point.

[0050]

As described above, the present invention is (1) Differential pressure measuring device having at least one filled liquid chamber
At the high pressure side and low pressure side of the differential pressure measuring device.
While keeping the pressure equalized at the constant temperature,
From the upper limit measurable pressure to the initial zero point pressure characteristic value
Memory means for reading and a predetermined value Z during self-diagnosis₀≤ |
{(Ε₁−ε₀₀) / (P₁-P₀)}-{(Ε_Ten−ε₀₀)
/ (P₁-P₀)} |
CPU that determines that₁: During self-diagnosis
The pressure on the high pressure side and the pressure on the low pressure side of the differential pressure measuring device is set to the predetermined temperature.
The predetermined measurement pressure p₁Zero point obtained by equalizing pressure to
ε_Ten: The predetermined measurement stored in the memory means
Pressure p₁Initial zero point at, ε₀₀: Stored in the memory means
The predetermined calibration pressure p₀Initial zero point at
And a differential pressure measuring device. (2) First and first provided on both sides of the housing
In a differential pressure measuring device equipped with a second seal diaphragm
And covering the first seal diaphragm.
The first seal diaphragm and the third seal diaphragm chamber
Third seal diaphragm constituting the second die
And a second seal diaphragm provided to cover the aflam
Fourth seal diaphragm that constitutes the fourth seal diaphragm chamber
Separate the diaphragm and the third and fourth seal diaphragm chambers.
Fill the filled liquid with the high pressure side and low pressure side of the differential pressure measuring device.
While making the pressure side pressure equalized at a predetermined temperature
Initial zero point pressure from the specified calibration pressure to the upper limit measurable pressure
Memory means to store force characteristic values and self-diagnosis
Predetermined value Z ₀≤ | {(ε₁−ε₀₀) / (P₁-P₀)}-
{(Ε_Ten−ε₀₀) / (P₁-P₀)} | When it becomes
A CPU that determines that the enclosed liquid is leaking, but ε
₁: At the time of self-diagnosis,
The pressure is the predetermined temperature and the predetermined measurement pressure p₁Pressure equalized to
Zero point, ε_Ten: Stored in the memory means
The predetermined measurement pressure p₁Initial zero point at, ε₀₀: The memory
-The predetermined calibration pressure p stored in the means₀Early in
Differential pressure measurement characterized by having a zero point
Configured the device.

As a result, according to the structure of the first aspect, the differential pressure measuring device of the present invention operates even if there is a slight leakage of the enclosed liquid, so that the leakage of the enclosed liquid occurs only when the device is completely down. It is possible to easily and early detect the leakage of the enclosed liquid without the risk of being noticed. In addition, predictive diagnosis of down can be performed before the device goes down.

Furthermore, without stopping the flow of the measuring fluid,
It is easy to equalize the high pressure side and the low pressure side of the differential pressure measuring device, and a differential pressure measuring device that does not disturb the process flow can be obtained. Further, since it is possible to make a determination by removing the influence of the pressure characteristic, it is possible to obtain a differential pressure measuring device that can more accurately self-diagnose leakage of the enclosed liquid.

Furthermore, since the measurement at the time of self-diagnosis need not be at two points but only at one point, it is sufficient to check only one point, and self-diagnosis can be performed extremely quickly and easily. That is, since the zero point at the calibration temperature in the temperature characteristic curve in the liquid leakage state is actually extremely small, this is disregarded and quick simplicity is adopted.

In addition, according to the configuration of the second aspect, even if the filled liquids 103 and 104 leak due to the corrosive measuring liquid or the like, the filled liquids 101 and 102 do not leak, so that the differential pressure measuring device. As a result, a device with extremely high safety and reliability can be obtained without any loss of its function.

Therefore, according to the present invention, the leakage of the enclosed liquid can be self-diagnosed without removing the differential pressure measuring device from the measuring line. In addition, the function as the differential pressure measuring device is not affected at all, and it is possible to realize the differential pressure measuring device having extremely high safety and reliability.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a main part configuration of an embodiment of the present invention.

FIG. 2 is a temperature characteristic diagram of the zero point error of FIG.

FIG. 3 is an operation explanatory diagram when the temperature characteristic curve of FIG. 1 is used.

FIG. 4 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

5 is an explanatory diagram of a main part configuration of FIG.

FIG. 6 is an explanatory diagram of a configuration of a conventional example that is generally used from the past.

[Explanation of symbols]

1 ... Housing 2 ... Flange 3 ... Flange 4 ... Inlet 5 ... Inlet 6 ... Pressure measurement chamber 6A ... Back plate 6B ... Back plate 7 ... Center diaphragm 8 ... Silicon diaphragm 9 ... Support 10 ... Pressure introducing chamber 10A ... Back plate 11 ... Pressure introducing chamber 11A ... Back plate 12 ... Seal diaphragm 13 ... Seal diaphragm 14 ... Communication hole 15 ... Communication hole 16 ... Communication hole 17 ... Communication hole 31 ... Memory means 32 ... CPU 41 ... Memory means 42 ... CPU 51 ... Third seal diaphragm 52 ... Third seal diaphragm chamber 53 ... Fourth seal diaphragm 54 ... Fourth seal diaphragm chamber 55 ... Body 56 ... Body 81 ... Silicon substrate 82 ... recess 91 ... Strain gauge 92 ... Lead 93 ... Hermetic terminal 101 ... Filled liquid 102 ... Filled liquid 103 ... Filled liquid 104 ... Filled liquid

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01L 27/00 G01L 13/02

Claims (2)

(57) [Claims] 1. A differential pressure measuring device having at least one filled liquid chamber, wherein the pressures on the high pressure side and the low pressure side of the differential pressure measuring device are equalized at a predetermined temperature while the upper limit is exceeded from a predetermined calibration pressure. Memory means for storing the pressure characteristic value at the initial zero point up to the measurable pressure, and a predetermined value Z ₀ ≤ | {(ε ₁ −ε ₀₀ ) / (p ₁ −
_{p 0)} - {(ε} 10 -ε 00) / (p 1 -p 0)} | a CPU to the sealed liquid is determined to be leaking when it becomes
Where ε _{1 is} a zero point obtained by equalizing the pressures on the high pressure side and the low pressure side of the differential pressure measuring device to a predetermined measurement pressure p ₁ at the predetermined temperature during self-diagnosis, ε ₁₀ : the memory means And an initial zero point at the predetermined measured pressure p ₁ stored in the memory means, ε ₀₀ : an initial zero point at the predetermined calibration pressure p ₀ stored in the memory means. Differential pressure measuring device. 2. A differential pressure measuring device comprising first and second seal diaphragms respectively provided on both side surfaces of a housing, wherein the first seal diaphragm and the third seal are provided so as to cover the first seal diaphragm. A third seal diaphragm forming a diaphragm chamber, a fourth seal diaphragm covering the second diaphragm and forming a second seal diaphragm and a fourth seal diaphragm chamber, and the third and fourth seal diaphragm chambers. And the pressure characteristic value of the initial zero point from the predetermined calibration pressure to the upper limit measurable pressure while keeping the pressures on the high pressure side and the low pressure side of the differential pressure measuring device at a predetermined temperature. Memory means for storing and a predetermined value Z ₀ ≦ | {(ε ₁ −ε ₀₀ ) / (p ₁ −
_{p 0)} - {(ε} 10 -ε 00) / (p 1 -p 0)} | a CPU to the sealed liquid is determined to be leaking when it becomes
Where ε _{1 is} a zero point obtained by equalizing the pressures on the high pressure side and the low pressure side of the differential pressure measuring device to a predetermined measurement pressure p ₁ at the predetermined temperature during self-diagnosis, ε ₁₀ : the memory means And an initial zero point at the predetermined measured pressure p ₁ stored in the memory means, ε ₀₀ : an initial zero point at the predetermined calibration pressure p ₀ stored in the memory means. Differential pressure measuring device.