JP3180512B2 - 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-diagnosis of leakage of a sealed liquid without removing the differential pressure measuring device from a measuring line. More specifically, a differential pressure measuring device that detects leakage of the sealed liquid in the pressure receiving unit by utilizing the fact that the zero point output at the time of pressure equalization changes from the time of manufacture due to leakage of the sealed liquid in the seal diaphragm on one side of the pressure receiving unit. It is about.

[0002]

2. Description of the Related Art FIG. 6 is an explanatory view of the structure of a conventional example generally used in the prior art.
This is shown in FIG. In the figure, housing 1
Flanges 2 on both sides, flanges 3 are fixed by the mating assembled welding, inlet 5 of the high-pressure fluid in the pressure P _H to be measured cents on both flanges 2 and 3, the pressure P _L
Of the low-pressure fluid is provided.

[0003] 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 formed 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, respectively.
The pressure measuring chamber 6 is divided into two parts by the two. Back plates 6A and 6B are formed on the wall of the pressure measurement chamber 6 facing the center diaphragm 7. The center diaphragm 7 has its peripheral edge welded to the housing 1.

An impurity such as boron is selectively diffused on one surface of the silicon substrate 81 to form four strain gauges 91. The four strain gauges 91 pull when the silicon diaphragm 8 bends by receiving the differential pressure ΔP,
Two are subject to compression and these are
Connected to the Toston bridge circuit, the resistance change is differential pressure Δ
It is detected as a change in P.

A lead 92 has one end attached to the strain gauge 91. Reference numeral 93 denotes a hermetic terminal to which the other end of the lead 92 is connected. The support 9 is provided with
A silicon diaphragm 8 is adhered and fixed to an 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 flanges 2 and 3. Sealing diaphragms 12 and 13 are provided in the pressure introducing chambers 10 and 11, and the sealing diaphragms 12 and 13 are provided.
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 opposed to the above.

The space formed by the seal diaphragms 12 and 13 and the back plates 10A and 11A and the pressure measurement chamber 6 are in communication with each other through communication holes 14 and 15. Filled liquids 101 and 102 such as silicon oil are filled between the seal diaphragms 12 and 13, and the filled liquids reach the upper and lower surfaces of the silicon diaphragm 8 through the communication holes 16 and 17. Is divided into two parts by the center diaphragm 7 and the silicon diaphragm 8, but care is taken so that the amounts are substantially equal.

In the above configuration, when a pressure acts from the high pressure side, the pressure acting on the seal diaphragm 13 is transmitted to the silicon diaphragm 8 by the sealing 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 sealing liquid 101.

As a result, the silicon diaphragm 8 is distorted in accordance with the pressure difference between the high pressure side and the low pressure side, and the amount of this distortion is electrically taken out by the strain gauge 91 to measure the differential pressure. .

[0011]

However, in such an apparatus, for some reason, the sealed liquid 101, 1
When 02 began to leak, the leak was leaking little by little and gradually, so that the output became clearly abnormal and could not be found until a failure occurred.

For example, when the seal diaphragms 12 and 13 are attached to the housing 1 and an input is applied, the output does not change, or the sealed liquids 101 and 102 do not change.
Enters the housing 1 and is found for the first time when the strain gauge 91 becomes abnormal due to insulation deterioration or disconnection and the output becomes abnormal. Alternatively, an input test is performed, and a fault location is detected from an input error only when the fault is detected.

In addition, seal diaphragms 12 and 13
In the case where the sealing liquids 101 and 102 leak, 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. An object of the present invention is to provide a differential pressure measuring device capable of performing self-diagnosis of leakage of a sealed liquid without stopping the flow of a process.

The present invention solves this problem. An object of the present invention is to perform a self-diagnosis of leakage of a sealed liquid without removing a differential pressure measuring device from a measurement line. In addition, the function as a differential pressure measuring device is to provide a differential pressure measuring device which is not affected at all.

[0016]

In order to achieve this object, the present invention provides: (1) a differential pressure measuring apparatus having two filled liquid chambers on a high pressure side and a low pressure side, A memory means for storing a pressure characteristic value of an initial zero point from a predetermined calibration pressure to an upper limit measurable pressure while keeping the high pressure side and the low pressure side pressure equalized at a predetermined temperature; Predetermined value Z
₀ ≦ | ε _{s -ε} | and said sealed liquid is determined to be leaking when it becomes CPU, however, epsilon: the pressure of the high pressure side and low pressure side of the differential pressure measuring device at the time of self-diagnosis given At temperature
Zero point obtained by equalizing to a predetermined measurement pressure and the predetermined calibration
The difference from the zero point obtained by equalizing the pressure , ε _s : the initial zero at the predetermined measured pressure stored in the memory means
B and the difference between the initial zero point at the predetermined calibration pressure,
(2) First and second pressure measurement devices provided on both side surfaces of the housing, respectively.
In a differential pressure measuring device having a second seal diaphragm, a third seal diaphragm provided over the first seal diaphragm and forming the first seal diaphragm and the third seal diaphragm chamber, and covering the second seal diaphragm. The second seal diaphragm and the fourth seal diaphragm forming a fourth seal diaphragm chamber and the third and fourth seal diaphragm chambers are provided.
A sealed liquid satisfying Re respectively, pressure of the initial zero while the pressure in the high pressure side and low pressure side of the differential pressure measuring device such that a pressure equalization at a predetermined temperature from a predetermined calibration pressure until the upper limit measurable pressure
A memory means for storing a force characteristic value ; and a CPU for judging that the sealed liquid is leaking when a predetermined value Z ₀ ≤ | ε _s -ε | at the time of self-diagnosis, where ε: at the time of self-diagnosis the plant the pressure of the high pressure side and low pressure side of the differential pressure measuring device
The zero points obtained by the pressure equalization to a predetermined measuring pressure at a constant temperature
Difference from the zero point obtained by equalizing to a predetermined calibration pressure ,
ε _s : the predetermined measurement stored in the memory means
Initial zero point at pressure and initial zero point at the predetermined calibration pressure
A differential pressure measurement device. It is what constituted.

[0017]

In the above configuration, in a normal measurement state, when a pressure acts from the high pressure side, the pressure acting on the seal diaphragm is transmitted to the silicon diaphragm by the sealing liquid. On the other hand, when pressure acts from the low pressure side, the pressure acting on the seal diaphragm is transmitted to the silicon diaphragm by the sealing liquid. Therefore, the silicon diaphragm is distorted in accordance with the pressure difference between the high pressure side and the low pressure side, and the amount of this distortion is electrically extracted due to the strain gauge, and the differential pressure is measured.

Next, at the time of self-diagnosis, the CPU, the predetermined value Z ₀ ≦ during self | ε _s -ε | sealed when <br/> became liquid is determined to be leaking. Where ε: Predetermined pressure on high pressure side and low pressure side of differential pressure measuring device at self-diagnosis
Zero point obtained by equalizing to a predetermined measurement pressure at
Difference from zero point obtained by equalizing to positive pressure , ε _s : Initial zero point at a predetermined measurement pressure stored in the memory means
The difference from the initial zero point at a predetermined calibration pressure will be described in detail below with reference to examples.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of a main part configuration of an embodiment of the present invention. In the figure, the configuration of the same symbol as FIG. 6 represents the same function. Hereinafter, only differences from FIG. 6 will be described.

The reference numeral 21 denotes a predetermined calibration pressure P ₀ , in this case atmospheric pressure, while maintaining the temperature T ₀ at the time of calibration constant and keeping the pressures on the high pressure side and the low pressure side of the differential pressure measuring device equal. until the upper limit measurable pressure -P _n to P _n from a memory means for memory characteristics of the initial zero point.

Reference numeral 22 denotes a predetermined value Z ₀ ≤ | ε _s at the time of self-diagnosis.
When −ε | is satisfied, the CPU determines that the sealed liquid 101 or 102 is leaking. However, epsilon: the pressure of the high pressure side and low pressure side of the differential pressure measuring device at the time of self-diagnosis at a predetermined temperature
The zero point εm obtained by equalizing the pressure to the predetermined measurement pressure Pm and the predetermined point
Positive pressure, in this case, difference from zero point ε ₀ obtained by equalizing pressure to atmospheric pressure P ₀ , ε _s : stored in memory means 21
And that the initial zero epsilon ₁₁ and a predetermined calibration at predetermined measurement pressure Pm
Pressure, in this case the initial zero point ε ₀₁ at atmospheric pressure P ₀ and
The difference between

Note that the memory means 21 and the CPU 22
In this case, it is housed in the amplifier in the conversion unit case. (Not shown)

In the above configuration, in a normal measurement state, when a pressure acts from the high pressure side, the pressure acting on the seal diaphragm 13 is transmitted to the silicon diaphragm 8 by the sealing 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 filling liquid 101. Therefore,
The silicon diaphragm 8 is distorted in accordance with the pressure difference between the high pressure side and the low pressure side, and the amount of this distortion is electrically extracted by the strain gauge 91 to measure the differential pressure.

Next, at the time of self-diagnosis, the CPU 22
In the predetermined value Z ₀ ≦ | if became, | epsilon _s-epsilon
It is determined that the filling liquid 101 or 102 is leaking. However
Ε: Zero point εm obtained by equalizing the pressure on the high pressure side and the low pressure side of the differential pressure measuring device to a predetermined measurement pressure Pm at a predetermined temperature at the time of self-diagnosis and a predetermined calibration pressure, in this case, the atmospheric pressure P Difference from zero point ε ₀ obtained by equalizing pressure to ₀ , ε _s : initial zero point at predetermined measurement pressure Pm stored in memory means 21
ε ₁₁ and a predetermined calibration pressure, in this case , the initial pressure at atmospheric pressure P ₀
The difference from the period zero point ε ₀₁ .

Therefore, a differential pressure measuring device capable of self-diagnosis of leakage of the sealed liquid without stopping the process flow can be obtained.

In the equalized pressure state, the communication between the high pressure side and the low pressure side of the differential pressure measuring device from the pipe through which the measurement fluid flows is stopped, and the high pressure side and the low pressure side of the differential pressure measuring device are connected to the atmosphere P. Release to ₀ .

Alternatively, by using a three-way valve, the communication of the measurement fluid on the high pressure side and the low pressure side of the differential pressure measuring device to the pipe is stopped.
And operates so as to communicate between the high pressure side and the low pressure side, etc. of the high pressure side and low pressure side and the pressure equalization measurement pressure P _m to a variety of methods can be employed, the pipe of the flow of the measurement fluid 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 apparatus.

That is, a specific self-diagnosis operation will be described below. FIG. 2 shows a pressure characteristic diagram at the zero point, and FIG. 3 shows an operation explanatory diagram. In FIG. 2, A is an initial pressure characteristic curve, and X is a pressure characteristic curve in a liquid leakage state.

(1) As shown in the flow 1 of FIGS. 2 and 3,
In advance, at the time of manufacturing the differential pressure measuring device, while maintaining the temperature constant at the calibration temperature T ₀ and maintaining the high pressure side and the low pressure side in an equalized state, the pressure is equalized from the atmospheric pressure P ₀ to the required pressure P _n . The initial pressure characteristic at the zero point at this time is input to the memory means 21 by changing the pressure.

(2) As shown in the flow 2 of FIGS. 2 and 3,
A zero point ε ₀ obtained by equalizing the pressures on the high pressure side and the low pressure side of the differential pressure measuring device to the atmospheric pressure P ₀ is obtained. (3) As shown in the flow 3 in FIG. 3, the zero point ε ₀ is converted into the calibration temperature T ₀ state, and the zero point ε ₀ ′ is obtained by calculation.

(4) As shown in FIG. 2 and FIG.
Determining a zero epsilon ₁ obtained in the pressure P ₁ measures the pressure in the high pressure side and low pressure side of the differential pressure measuring device for pressure equalization. (5) As shown in the flow 5 of FIG. 3, the zero point ε ₁ is converted into the calibration temperature T ₀ state, and the zero point ε ₁ ′ is obtained by calculation. (6) As shown in the flow 6 of FIG. 3, ε = ε ₁ ′ −ε ₀ ′ is obtained.

(7) As shown in the flow 7 of FIGS. 2 and 3,
From the zero point characteristic stored in the memory means 21, the zero point ε _s = ε ₁₁ −ε ₀₁ of the measured pressure P ₁ is obtained from the atmospheric pressure P ₀ .

(8) As shown in the flow 8 of FIG.
Find _s− ε. (9) As shown in the flow 9 in FIG. 3, if | Z | ≧ Z ₀ (Z ₀ is an error taking a certain margin into consideration), either the high-pressure side or the low-pressure side seal diaphragm 13, 12 is used.
It is determined that the sealed liquids 102 and 101 are leaking from the portion.

(10) As shown in the flow 10 of FIG.
If Z <0, the sealed liquid 101 is leaking from the seal diaphragm 12 on the low pressure side. Z>
If it is 0, it is determined that the sealed liquid 102 is leaking from the high pressure side seal diaphragm 13.

Next, a specific operation of the differential pressure measuring device when the sealed liquids 101 and 102 leak will be described. Now, assuming that the low pressure side sealed liquid 102 leaks by ΔVcc, the volume change constant of the seal diaphragm 12 is Vcc / kgf / cm.
^If it is set to ² , the internal pressure of the silicon oil in the low pressure chamber changes by ΔP.

ΔP = ΔV / Vkgf / cm ^{2 When the} low-pressure side and the high-pressure side are equalized, it is detected that the zero point shifts by ΔP. Zero point error E ₁ = (ΔP / P) · 100%

As a result, the differential pressure measuring device of the present invention operates even if the sealed liquids 101 and 102 are slightly leaked.
Only when the device is completely down does the filled liquid 101, 102
Of the sealed liquids 101 and 102
Leakage can be easily and early detected. In addition, a down prediction diagnosis can be made before the apparatus goes down.

Further, without stopping the flow of the measurement fluid,
As described above, it is easy to equalize the high-pressure side and the low-pressure side of the differential pressure measuring device, so that a differential pressure measuring device that does not disturb the process flow can be obtained. Further, since the determination can be made without the influence of the pressure characteristic, a differential pressure measuring device capable of more accurately performing self-diagnosis of leakage of the sealed liquid can be obtained.

FIG. 4 is an explanatory diagram of a main portion of an embodiment of the present invention, and FIG. 5 is an explanatory diagram of a main portion of FIG. In the figure,
6 have the same functions. Hereinafter, FIG.
Only the differences will be described.

The reference numeral 31 designates a predetermined calibration pressure P ₀ , in this case atmospheric pressure, while keeping the pressure on the high pressure side and the low pressure side of the differential pressure measuring device at a constant _value at the temperature T ₀ at the time of calibration. until the upper limit measurable pressure -P _n to P _n from a memory means for memory pressure characteristics of the initial zero point.

Reference numeral 32 denotes a predetermined value Z ₀ ≦ | ε _s at the time of self-diagnosis.
When −ε | is satisfied, the CPU determines that the sealed liquid 103 or 104 is leaking. However, epsilon: the pressure of the high pressure side and low pressure side of the differential pressure measuring device at the time of self-diagnosis at a predetermined temperature
The zero point εm obtained by equalizing the pressure to the predetermined measurement pressure Pm and the predetermined point
Positive pressure, in this case, the difference from the zero point ε ₀ obtained by equalizing the pressure to the atmospheric pressure P ₀ , ε _s : stored in the memory means 31
And that the initial zero epsilon ₁₁ and a predetermined calibration at predetermined measurement pressure Pm
Pressure, in this case the initial zero point ε ₀₁ at atmospheric pressure P ₀ and
And the difference.

Note that the memory means 31 and the CPU 32
In this case, it is housed in the amplifier in the conversion unit case. (Not shown)

Reference numeral 41 denotes a third seal diaphragm provided so as to cover the first seal diaphragm 13 and constituting the first seal diaphragm 13 and the third seal diaphragm chamber 42. Reference numeral 43 denotes a fourth seal diaphragm provided so as to cover the second seal diaphragm 12 and constituting the second seal diaphragm 12 and the fourth seal diaphragm chamber 44.

Reference numeral 45 denotes a body provided between the first seal diaphragm 13 and the third seal diaphragm 41. Reference numeral 46 denotes a body provided between the second seal diaphragm 12 and the fourth seal diaphragm 43.
103 is a filling liquid filled in the third seal diaphragm chamber 42. 104 is the fourth seal diaphragm chamber 4
4 is the filling liquid filled in 4.

In the above configuration, in a normal measurement state, when a pressure acts from the high pressure side, the pressure acting on the seal diaphragm 41 is transmitted to the silicon diaphragm 8 by the sealing liquid 102.

On the other hand, when pressure acts from the low pressure side, the pressure acting on the seal diaphragm 43 is transmitted to the silicon diaphragm 8 by the filling liquid 101.

Accordingly, the silicon diaphragm 8 is distorted in accordance with the pressure difference between the high pressure side and the low pressure side, and the amount of this distortion 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
In the predetermined value Z ₀ ≦ | if became, | epsilon _s-epsilon
It is determined that the filling liquid 103 or 104 is leaking. However
Ε: Zero point εm obtained by equalizing the pressure on the high pressure side and the low pressure side of the differential pressure measuring device to a predetermined measurement pressure Pm at a predetermined temperature at the time of self-diagnosis and a predetermined calibration pressure, in this case, the atmospheric pressure P Difference from zero point ε ₀ obtained by equalizing pressure to ₀ , ε _s : initial zero point at predetermined measurement pressure Pm stored in memory means 31
ε ₁₁ and a predetermined calibration pressure, in this case , the initial pressure at atmospheric pressure P ₀
The difference from the period zero point ε ₀₁ .

Therefore, a differential pressure measuring device capable of self-diagnosis of leakage of the sealed liquid without stopping the flow of the process can be obtained.

In the equalized pressure state, the communication of conduits communicating with the high pressure side and the low pressure side of the differential pressure measuring device from the pipe through which the measurement fluid flows is stopped, and the high pressure side and the low pressure side of the differential pressure measuring device are connected to the atmospheric pressure. Release P ₀ .

Alternatively, by using a three-way valve, the communication of the measurement fluid on the high pressure side and the low pressure side of the differential pressure measuring device to the pipe is stopped.
And operates so as to communicate between the high pressure side and the low pressure side, etc. to pressure equalization pressure P ₁ measured with the high pressure side and low pressure side, a variety of methods can be employed, the pipe of the flow of the measurement fluid 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 apparatus.

As a result, the differential pressure measuring device of the present invention operates even if the sealed liquids 103 and 104 are slightly leaked.
Only when the device is completely down does the filled liquid 103, 104
Of the sealed liquids 103 and 104
Leakage can be easily and early detected. In addition, a down prediction diagnosis can be made before the apparatus goes down.

Further, without stopping the flow of the measurement fluid,
As described above, it is easy to equalize the high-pressure side and the low-pressure side of the differential pressure measuring device, so that a differential pressure measuring device that does not disturb the process flow can be obtained.

In addition, the first seal diaphragm 13 is provided to cover the first seal diaphragm 13, the third seal diaphragm 41 constituting the third seal diaphragm chamber 432, and the second seal diaphragm 12 is provided to cover the second seal diaphragm 12. The second seal diaphragm 12 and the fourth seal diaphragm 43 constituting the fourth seal diaphragm chamber 44 are provided, and the third seal diaphragm chamber 42 and the fourth seal diaphragm chamber 44 are filled with the filling liquids 103 and 104. .

Therefore, the sealed liquid 1 is not affected by the corrosive measuring liquid or the like.
03, 104 even if the sealed liquids 101, 102
Since there is no leakage, a device is obtained in which the function as a differential pressure measuring device is not impaired at all.

In the above-described embodiment, the zero point ε
₀, Ε₁Is the temperature of the standard state, that is, the calibration temperature T₀When converted to
Although explained, it is not limited to this, and the atmospheric pressure P₀Measured from
Constant pressure P ₁Zero point ε_sIs converted to the temperature at the time of self-diagnosis.
Of course, comparisons may be made.

In the above-described embodiment, the description has been given of the differential pressure measuring device. However, 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 one of the pressures of the differential pressure measuring device is set to atmospheric pressure or vacuum, and is substantially a differential pressure measuring device. In this case, the measurement pressure side is set to atmospheric pressure or vacuum, and the zero point is checked.

[0059]

As described above, the present invention provides: (1) a differential pressure measuring device having two filled liquid chambers, one on the high pressure side and the other on the low pressure side; A memory means for storing a pressure characteristic value at an initial zero point from a predetermined calibration pressure to an upper limit measurable pressure while keeping the pressure at a predetermined temperature in a pressure equalized state, and a predetermined value Z at the time of self-diagnosis.
₀ ≦ | ε _{s -ε} | and said sealed liquid is determined to be leaking when it becomes CPU, however, epsilon: the pressure of the high pressure side and low pressure side of the differential pressure measuring device at the time of self-diagnosis given At temperature
Zero point obtained by equalizing to a predetermined measurement pressure and the predetermined calibration
The difference from the zero point obtained by equalizing the pressure , ε _s : the initial zero at the predetermined measured pressure stored in the memory means
B and the difference between the initial zero point at the predetermined calibration pressure,
(2) First and second pressure measurement devices provided on both side surfaces of the housing, respectively.
In a differential pressure measuring device having a second seal diaphragm, a third seal diaphragm provided over the first seal diaphragm and forming the first seal diaphragm and the third seal diaphragm chamber, and covering the second seal diaphragm. The second seal diaphragm and the fourth seal diaphragm forming a fourth seal diaphragm chamber and the third and fourth seal diaphragm chambers are provided.
A sealed liquid satisfying Re respectively, pressure of the initial zero while the pressure in the high pressure side and low pressure side of the differential pressure measuring device such that a pressure equalization at a predetermined temperature from a predetermined calibration pressure until the upper limit measurable pressure
A memory means for storing a force characteristic value ; and a CPU for judging that the sealed liquid is leaking when a predetermined value Z ₀ ≤ | ε _s -ε | at the time of self-diagnosis, where ε: at the time of self-diagnosis the plant the pressure of the high pressure side and low pressure side of the differential pressure measuring device
The zero points obtained by the pressure equalization to a predetermined measuring pressure at a constant temperature
Difference from the zero point obtained by equalizing to a predetermined calibration pressure ,
ε _s : the predetermined measurement stored in the memory means
Initial zero point at pressure and initial zero point at the predetermined calibration pressure
A differential pressure measurement device. Was configured.

As a result, according to the first aspect of the present invention, even if there is a slight leakage of the sealed liquid, the differential pressure measuring device of the present invention operates, and the leakage of the sealed liquid is not performed until the device is completely down. The leakage of the sealed liquid can be easily detected at an early stage without any fear of noticing. In addition, a down prediction diagnosis can be made before the apparatus goes down.

Further, without stopping the flow of the measurement fluid,
As described above, it is easy to equalize the high-pressure side and the low-pressure side of the differential pressure measuring device, so that a differential pressure measuring device that does not disturb the process flow can be obtained. Further, since the determination can be made without the influence of the pressure characteristic, a differential pressure measuring device capable of more accurately performing self-diagnosis of leakage of the sealed liquid can be obtained.

In addition, according to the configuration of the second aspect, even if the sealing liquid leaks due to a corrosive measuring liquid or the like, the sealing liquid in the main body does not leak, so that the function as a differential pressure measuring device is achieved. A device is obtained which is completely intact.

Therefore, according to the present invention, it is possible to perform a self-diagnosis of leakage of the sealed liquid without removing the differential pressure measuring device from the measurement line. In addition, it is possible to realize a differential pressure measuring device whose function as a differential pressure measuring device is not affected at all.

[Brief description of the drawings]

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

FIG. 2 is a pressure characteristic diagram at a zero point in FIG.

FIG. 3 is a diagram illustrating the operation of FIG. 1;

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

FIG. 5 is an explanatory diagram of a main part configuration of FIG. 4;

FIG. 6 is an explanatory diagram of a configuration of a conventional example generally used in the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Housing 2 ... Flange 3 ... Flange 4 ... Inlet 5 ... Inlet 6 ... Pressure measuring chamber 6A ... Back plate 6B ... Back plate 7 ... Center diaphragm 8 ... Silicon diaphragm 9 ... Support 10 ... Pressure introduction Chamber 10A: Back plate 11: Pressure introduction chamber 11A: Back plate 12: Seal diaphragm 13: Seal diaphragm 14: Communication hole 15: Communication hole 16: Communication hole 17: Communication hole 21: Memory means 22: CPU 31 ... memory means 32 ... CPU 41 ... third seal diaphragm 42 ... third seal diaphragm chamber 43 ... fourth seal diaphragm 44 ... fourth seal diaphragm chamber 45 ... body 46 ... body 81 ... silicon substrate 82 ... concave part 91 ... strain gauge Di 92 ... lead 93 ... hermetic terminal 101 ... filling liquid 1 02 ... filled liquid 103 ... filled liquid 104 ... filled liquid

Claims (2)

(57) [Claims] 1. A differential pressure measuring device having two filled liquid chambers, a high pressure side and a low pressure side, 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. and memory means for memory pressure characteristic value of the initial zero point up upper limit measurable pressure from a predetermined calibration pressure, the predetermined value Z ₀ ≦ during self | ε _s -ε | the sealed fluid leaks when a Where: ε: the zero point obtained by equalizing the high pressure side and the low pressure side pressure of the differential pressure measuring device to the predetermined measurement pressure at the predetermined temperature at the time of self-diagnosis, and the predetermined calibration pressure The difference from the zero point obtained by equalizing the pressure , ε _s : stored in the memory means.
The initial zero point at the predetermined measurement pressure and the predetermined calibration pressure
A differential pressure difference from the initial zero point . 2. A differential pressure measuring device comprising first and second seal diaphragms provided on both side surfaces of a housing, respectively, wherein said first seal diaphragm and said third seal are provided so as to cover said first seal diaphragm. A third seal diaphragm forming a diaphragm chamber, a fourth seal diaphragm provided to cover the second diaphragm, and forming a second seal diaphragm and a fourth seal diaphragm chamber; and the third and fourth seal diaphragm chambers. Satisfy each
And be sealed liquid, the pressure characteristics of the initial zero point up the difference upper limit measurable pressure from a predetermined calibration pressure while the pressure in the high pressure side and the low pressure side so that the <br/> pressure equalization at a predetermined temperature of the pressure measuring device and memory means for memory values, when the self-diagnostic predetermined value Z ₀ ≦ | ε _s -ε | a CPU to determine that the sealed liquid when a is leaking, however, epsilon: the difference in time of self-diagnosis The difference between a zero point obtained by equalizing the pressure on the high pressure side and the low pressure side of the pressure measuring device to a predetermined measurement pressure at the predetermined temperature and a zero point obtained by equalizing the pressure to the predetermined calibration pressure , ε _s : is stored in said memory means
In the said predetermined calibration pressure and the initial zero point at a predetermined measurement pressure that
A differential pressure difference from the initial zero point .