JPH10197316A - Density correction-type liquid level detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To implement a density correction-type liquid level detecting device which is compact and lightweight and enables the reduction of the number of necessary instruments and also enables the simplification of an instrumentation system. SOLUTION: This device comprises a high-pressure side process connecting flange 4 arranged to a pressure deriving opening on a high pressure side and low pressure side, a low-pressure side process connecting flange 5, pressure propagating bodies 43, 44, and 52, which propagate the pressure of the connecting flanges 4 and 5 to a pressure receiving part '2, and a signal processing part '3 which processes the signals of a sensor body '1. Fluid pressure on a high-pressure side is propagated to the pressure receiving part 2 via seal diaphragms 41 and 42, a liquid 45, the pressure propagating bodies 43 and 44. The diaphragms 41 and 42 with a distance h0 between their centers are connected to the flange 4 and receive pressures P1 and P3 at a liquid level head and head ho. As the pressure P3 of density correction and the head pressure P1 of a liquid level can be obtained with the one flange 4, it is possible to reduce the number of component members and to simplify its configuration. The low-pressure side flange 5 propagates a low-pressure side fluid pressure P2 to the pressure receiving part '2 via a seal diaphragm 51, liquid 53, and the pressure propagating body 52.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention measures the pressure, differential pressure, temperature, fluid level, density, etc. of a fluid in a chemical plant or the like in order to control fluids such as liquids and gases in a chemical plant. The present invention relates to a process detection device used for controlling operation of a plant, and more particularly to a small and light liquid level detection device for measuring a fluid level in a tank.

[0002]

2. Description of the Related Art Measuring the pressure, temperature, level, and flow rate of a chemical plant is essential for safe and efficient operation of the plant. For this purpose, differential pressure / pressure detectors, level detectors, and temperature detectors have conventionally been used as process detection devices.

[0003] The differential pressure detector mainly measures the flow rate,
The tank density and liquid level can also be measured. FIG. 21 shows an example of installation of a detector when measuring the level of the fluid to be measured in the tank, and FIG. 22 shows a general structure of the detector.

In conventional measurement of the liquid level in a tank, as shown in FIG. 21, two pressure outlets are provided in a tank, and a differential pressure detector is installed in these two pressure outlets. Thus, the head change (hx) inside the tank is detected as a differential pressure.

In order to more accurately measure the liquid level, it is necessary to correct the influence of the density and temperature of the fluid to be measured. Therefore, as shown in FIG. Detect the density with a detector (head is constant at h0)
The temperature is detected by a temperature detector (not shown), the head change (hx) in the tank is corrected by the density signal and the temperature signal, and the liquid level measurement is realized.

FIG. 22 is a schematic diagram showing a configuration of a differential pressure detector for detecting a head change and a density change in a tank. The pressure or differential pressure sensor body '1 is incorporated in the pressure receiving section main body' 2 (shown in FIG. 21). Then, flanges 4 and 5 having pressure transmitting portions 43 and 52 for transmitting pressure from a process connection flange attached to the tank are fixed to the pressure / differential pressure sensor body '1 to the pressure receiving portion main body' 2. I have.

The head change (hx) is determined by the seal diaphragms 41 and 51 of the flanges 4 and 5 and the pressure transmitting parts 43 and 52.
The pressure / differential pressure sensor body ′ 1 in the pressure receiving section converts the electric signal into an electric signal through the sealed liquids 45 and 53 in the inside.

In order to supply this signal to the signal converter '3, a connector or the like 34 connected to the pressure / differential pressure sensor' 1 by a lead wire is attached to the signal converter '3. Then, the amplifier board 31 in the case 35 of the signal converter '3
The signal is normalized.

The signal converter '3 generally has a terminal board 32 internally provided with an amplifier board 31 for performing signal processing of a detecting section and a terminal board 32 for receiving power supply from the outside and sending it to the amplifier board 31. It consists of a box.

Further, the output signal of the differential pressure detector can be indicated by incorporating an analog or digital display 33 in the amplifier board 31. In FIG. 22, reference numerals 21 and 22 denote a pressure-receiving-side seal diaphragm, 23 denotes an overload protection diaphragm (center diaphragm), and 201 denotes a sealed liquid.

[0011]

However, in the above-mentioned conventional liquid level detecting device in a tank, the liquid level (head) and the density of the fluid to be measured are measured by separate detectors. However, since a plurality of detectors are required and cannot be measured by one detector, the measurement system is complicated.

Further, since the number of detection devices is large,
The maintenance man-hours had also increased.

In recent years, the number of measurement points has tended to increase in order to realize more advanced measurement. However, in order to secure the installation space for the detection equipment, a more miniaturized equipment has been desired. Has become. Also in this point, the necessity of a plurality of detectors is an obstacle to securing the installation space.

Further, in order to reduce the construction cost of piping and wiring other than the detection equipment at the time of plant planning, even if an attempt is made to reduce the number of detectors to be installed, a plurality of detection equipments are required. The construction costs for wiring, etc. could not be further reduced.

An object of the present invention is to realize a density-corrected liquid level detecting device which is small and lightweight, can reduce the number of necessary measuring instruments, and can simplify a measuring system.

[0016]

[Means for Solving the Problems]

(1) In order to achieve the above object, the present invention is configured as follows. That is, a plurality of pressures of the fluid to be measured are taken out by a connection flange provided at a pressure outlet of a tank containing the fluid to be measured, the plurality of pressures are transmitted, and a difference between the plurality of pressures and the pressure is detected. A pressure receiving section having a sensor; and a signal processing section having a signal processing circuit for processing a signal from the sensor by being joined to the pressure receiving section, and externally providing information such as a liquid level and a density of the fluid to be measured in the tank. In the density correction type liquid level detection device that transmits the pressure, the pressure correction device has two pressure transmitting bodies and constantly contacts the fluid to be measured, and detects the pressure on the high pressure side of the fluid to be measured and the correction pressure in the tank. A high-pressure side connection flange portion, having one pressure transmitter, and constantly in contact with the fluid to be measured, and a low-pressure side connection flange portion for detecting a low-pressure side pressure of the fluid to be measured in the tank; A pressure receiving section having a differential pressure sensor for simultaneously detecting a first pressure difference between the high pressure side pressure and the low pressure side pressure, and a second pressure difference between the high pressure side pressure and the correction pressure; A signal processing unit having a signal processing circuit for processing a signal indicating the first and second pressure differences from the pressure receiving unit.

(2) Preferably, in the above (1),
The signal processing unit has an information display unit for displaying information from the pressure receiving unit. The information display unit displays a numerical value calculated by the signal processing unit, and the value is determined by a signal processing circuit. When displaying the value after conversion by the function of, a mark indicating that the converted value is displayed is displayed, and when the displayed value is another variable, the other variable is displayed. Is a level meter comprising a set of predetermined marks, and the display of the level meter is changed according to the numerical value to be displayed.

(3) Preferably, in the above (1), the two pressure transmitting members of the high-pressure side connection flange are two low-rigidity metal diaphragms, and these two metal diaphragms are mutually fixed. A first pressure transmitting body and a third pressure transmitting body which are arranged at positions separated from each other and which are separable and transmit the high pressure side pressure and the correction pressure to the pressure receiving portion. A pressure transmitting body of the low-pressure side connection flange portion is a low-rigidity metallic diaphragm, and a second pressure transmitting portion for transmitting the low-pressure side pressure from the pressure transmitting body of the low-pressure side pressure flange to the pressure receiving portion. It has a pressure transmitter.

(4) Preferably, in the above (1), the pressure receiving section is a first pressure receiving section to which the high pressure side pressure is applied.
A first pressure receiving chamber in which a first detection fluid is sealed, and a second diaphragm to which the low pressure side pressure is applied, wherein a second detection fluid is sealed. A first pressure receiving chamber to which pressure from the first pressure receiving chamber is transmitted;
, A second isolation chamber to which the pressure from the second pressure receiving chamber is transmitted, and the first and second diaphragms are disposed between the first and second diaphragms. A third diaphragm for isolating the isolation chamber from each other;
A third communication path for transmitting the pressure from the isolation chamber to the differential pressure sensor, a fourth communication path for transmitting the pressure from the second isolation chamber to the differential pressure sensor, and the high pressure side flange. And a fifth communication path for transmitting the auxiliary pressure to the differential pressure sensor.

(5) Preferably, in the above (1), the differential pressure sensor includes a first pressure sensitive diaphragm for detecting a pressure difference between the high pressure side pressure and the low pressure side pressure; A semiconductor-type first resistor group formed on a first pressure-sensitive diaphragm and responsive to a pressure difference between the high-pressure side pressure and the low-pressure side pressure; and a high-pressure side pressure and the correction pressure. A second pressure-sensitive diaphragm for detecting a pressure difference between the first and second pressure-sensitive diaphragms, and a semiconductor-type second resistor formed on the second pressure-sensitive diaphragm and responsive to a pressure difference between the high-pressure side pressure and the correction pressure. A group, a semiconductor-type temperature-sensitive resistor responsive to temperature, an inlet for transmitting the high-pressure side pressure to one surface of the first pressure-sensitive diaphragm, and a low-pressure side pressure applied to the first pressure-sensitive diaphragm. And the inlet that transmits to the other side of the pressure diaphragm. A first fixed base having a port, and an inlet that is hermetically fixed to the first fixed base and that communicates with the inlets at positions corresponding to each of the two pressure inlets of the first fixed base. A second fixed base, a first pressure guide path communicating with the pressure inlet of the second fixed base, and introducing the pressure on the high pressure side to the pressure inlet of the second fixed base; A second communicating with the pressure inlet of the second fixed base to introduce the correction pressure into the pressure inlet of the second fixed base;
And a metal fitting having an airtight terminal for extracting an electric signal from the first and second resistor groups.

(6) A plurality of pressures of the fluid to be measured are taken out by a connection flange provided at a pressure outlet of a tank containing the fluid to be measured, and the plurality of pressures are transmitted, and the plurality of pressures and the pressures are transmitted. And a signal processing unit having a signal processing circuit for processing a signal from the sensor, which is joined to the pressure receiving unit, and the liquid of the fluid to be measured in the tank is externally provided. In a density correction type liquid level detection device for transmitting information such as position, density, etc., a pressure transmitter which constantly contacts the fluid to be measured and transmits pressure on the high pressure side of the fluid to be measured, and a correction of the fluid to be measured. A pressure transmitting body for transmitting pressure for use, a high pressure side connection flange portion having a pressure difference between the high pressure side pressure of the fluid to be measured in the tank and the correction pressure and a temperature of the fluid to be measured,
A low pressure side connection flange that has one pressure transmitting body, constantly contacts the fluid to be measured, and detects a low pressure side pressure of the fluid to be measured in the tank, and a pressure on the high pressure side and a pressure on the low pressure side. A pressure receiving portion having a differential pressure sensor for detecting a first pressure difference between the pressure receiving portion and a first pressure difference from the pressure receiving portion;
A signal processing unit having a signal processing circuit for processing a signal indicating a pressure difference between the high-pressure side pressure and the correction pressure detected by the flange-side sensor and a temperature of the fluid to be measured.

(7) Preferably, in the above (6),
The signal processing unit has an information display unit that displays information from the differential pressure sensor and the flange side sensor.

(8) Preferably, in the above (6), the two pressure transmitting members of the high-pressure side connection flange have low rigid metal diaphragms, and the two metal diaphragms are separated from each other by a predetermined distance. The flange-side sensor is disposed on a side opposite to the fluid to be measured in one of the two metal diaphragms, and is connected to the low-pressure side connection. The pressure transmitting body of the flange portion has a low-rigidity metallic diaphragm.

(9) Preferably, in the above (6), the differential pressure sensor includes a first pressure sensitive diaphragm for detecting a pressure difference between the high pressure side pressure and the low pressure side pressure; A semiconductor-type first resistor group formed on a first pressure-sensitive diaphragm and responsive to a pressure difference between the high-pressure side pressure and the low-pressure side pressure; and a semiconductor-type temperature-sensitive resistor responsive to temperature. An inlet for transmitting the pressure on the high pressure side to one surface of the first pressure-sensitive diaphragm, and an inlet for transmitting the pressure on the low pressure side to the other surface of the first pressure-sensitive diaphragm. A first fixed base having two pressure inlets, and hermetically fixed to the first fixed base, and communicating with the inlets at positions corresponding to each of the two pressure inlets of the first fixed base. A second fixed base having an inlet to be inserted, and the second fixed base A first pressure passage for communicating the pressure on the high pressure side to the pressure introduction port of the second fixed base, and a pressure introduction port of the second fixed base for communicating with the pressure introduction port; A second pressure guiding path for introducing pressure on the side to the pressure inlet of the second fixed base; and a metal fitting having an airtight terminal for extracting an electric signal from the first resistor group.

(10) Preferably, in (6) above, the flange-side sensor of the high-pressure-side connection flange contacts the fluid to be measured via a protective film.

(11) A plurality of pressures of the fluid to be measured are taken out by a connection flange provided at a pressure outlet of a tank containing the fluid to be measured, and the plurality of pressures are transmitted. And a signal processing unit having a signal processing circuit for processing a signal from the sensor, which is joined to the pressure receiving unit, and the liquid of the fluid to be measured in the tank is externally provided. In the density correction type liquid level detection device that transmits information such as position, density, etc.,
A high pressure side connection flange portion which has two pressure transmitting bodies, constantly contacts the fluid to be measured, and detects the high pressure side pressure and the correction pressure of the fluid to be measured in the tank, and one pressure transmitting body And a low-pressure side connection flange portion which is always in contact with the fluid to be measured and detects a low-pressure side pressure of the fluid to be measured in the tank, and a first of a high-pressure side pressure and a low-pressure side pressure. A pressure receiving unit having a differential pressure sensor for simultaneously detecting a pressure difference and a second pressure difference between the high-pressure side pressure and the correction pressure; A signal processing unit having a signal processing circuit for determining that a change has occurred from the steady state due to a factor and displaying the situation.

The pressure on the high pressure side of the fluid to be measured in the tank and the correction pressure are detected by the high pressure side connection flange,
The low pressure side connection flange detects the low pressure side pressure. Then, the pressure difference between the high pressure side and the low pressure side pressure and the pressure difference between the high pressure side pressure and the correction pressure are simultaneously detected by the differential pressure sensor in the pressure receiving unit. Thereby, the liquid level of the fluid to be measured in the tank can be measured with a simple configuration. Further, the density of the fluid to be measured in the tank can be measured.

Further, the high-pressure side connection flange portion has a flange-side sensor for detecting a pressure difference between a high-pressure side pressure of the fluid to be measured in the tank and a correction pressure and a temperature of the fluid to be measured. In this case, the pressure receiving section may simply detect the pressure difference between the high-pressure side pressure and the low-pressure side pressure, simplify the configuration, and reduce the size and weight.
In addition, density correction based on temperature becomes possible.

Further, if the flange side sensor of the high pressure side connection flange portion is configured to be in contact with the fluid to be measured via the protective film, the pressure and temperature of the fluid to be measured can be measured with higher accuracy. be able to.

[0030]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic sectional view of a density correction type liquid level detecting apparatus according to a first embodiment of the present invention.
FIG. 2 is a sectional view of a high-pressure side process connection flange of the example shown in FIG. 1. FIG. 3 is a sectional view of the pressure receiving section shown in FIG. 1, and FIG. 4 is a sectional view of the sensor section shown in FIG. FIG. 5 is a plan view of the sensor unit shown in FIG.
7 is a circuit configuration diagram of the sensor unit shown in FIG. 5, and FIG. 7 is a block diagram of the entire signal processing of FIG.

First, the principle of detection of this density correction type liquid level detecting device will be described with reference to FIGS. In FIG. 21, the relationship between the liquid level (hx) of the fluid to be measured in the tank, the density change of the fluid to be measured, and the temperature is represented by the following equations (1) to (4).
Can be represented by

First, the relationship between the liquid level head pressure and the detected pressure can be expressed by the following equation (1). Liquid level head pressure = γx (t) * hx = P1−P3 (1), and the liquid level head pressure changes depending on the specific weight γ of the fluid to be measured and the liquid level head hx. Here, γx (t) indicates the density and is a function that changes depending on the temperature t. P1 is a high pressure side pressure, and P3 is a correction pressure.

The relationship between the density head pressure and the detected pressure is expressed by the following equation (2). Density head pressure = γx (t) * h0 = P1−P2 (2) where h0 is a correction head and is a constant value. P2 is a low pressure side pressure. From the above equation (2), the density head pressure changes depending on the specific weight γ of the fluid to be measured and the liquid level head h0. However, since the liquid level head h0 is a fixed value determined at the time of installing or manufacturing the detector, it can detect only a change in the density of the fluid to be measured.

Therefore, the differential pressure signal (P1-
According to P2), the head of the liquid surface whose density change has been corrected is calculated from equation (1).

That is, the liquid level head hx can be expressed by the equation (3) from the equations (1) and (2). Liquid level head (hx) = (P1−P3) * h0 / (P1−P2)... (3) Also, since the density changes depending on the temperature, the value of the value is separately output by the temperature sensor. Correct correction is performed according to the following equation (4). γx (t) = {(P1 -P2) / h0} * f (t) = π0 * γ0 * (1 + αΔt + βΔt 2 + ...) ............ (4) where, in π0 = (P1-P2) / h0 Yes, a unique constant. Γ0 is a constant at a reference temperature,
α and β are their temperature coefficients. Δt is the difference between the reference temperature and the temperature of the fluid to be measured detected by the temperature sensor. F (t) is a correction term. Formula (1) to
According to (4), the liquid level in the tank can be obtained. Further, the value of the density of the fluid to be measured can also be obtained.

In FIG. 1, a density correction type liquid level detecting apparatus according to a first embodiment of the present invention is mainly composed of a high pressure side process connection flange 4 installed at a high pressure side and a low pressure side pressure outlet of a tank or the like. A low pressure side process connection flange 5, pressure transmitting members 43, 44, 52 for transmitting the pressure of the process connection flanges 4 and 5 to a pressure receiving section 2 having a pressure sensor body 1, and a pressure sensor body 2. 1 comprises a signal processing unit '3 having a signal processing circuit for processing a signal from the signal processor 1.

FIG. 2 shows in detail the structure of the process connection flange 4 (high pressure side) as described above.
In FIG. 2, the fluid pressure of the high-pressure side fluid is transmitted to the high-pressure side process connection flange 4 via high-pressure side seal diaphragms (low-rigidity metallic diaphragms) 41 and 42. Then, the transmitted pressure is applied to the pressure guiding paths 431, 441.
The liquid is transmitted to an incompressible liquid (silicon oil) 45 in the inside, and is transmitted to the pressure receiving unit 2 via the pressure transmitting bodies 43 and 44.

Each of the seal diaphragms 41 and 42 is provided between the center of each of the seal diaphragms 41 and 42 by h.
It is fixedly joined to the body of the process connection flange 4 with a distance of 0. Therefore, the head hx of the liquid surface of the fluid to be measured
And the respective pressures P1 and P3 at the head h0 can be received from the process.

Therefore, it is possible to simultaneously obtain the pressure P3 for density correction and the head pressure P1 at the liquid level with one process connection flange 4, thereby reducing the number of components and simplifying the configuration.

On the other hand, in FIG. 1, the low-pressure side process connection flange 5 is provided with a low-pressure-side sealing diaphragm (low-rigidity metallic diaphragm) on the low-pressure side fluid pressure P2.
51. Then, the transmitted pressure is transmitted to an incompressible liquid (silicon oil) 53 via the seal diaphragm 51, and transmitted to the pressure receiving unit 2 as the pressure P <b> 2 via the pressure transmitting body 52. This pressure P2 is a reference pressure, which is the internal pressure in the case of a closed tank and the atmospheric pressure in the case of an open tank. Accordingly, since the pressures P1, P2, and P3 shown in the above equations (1) and (2) are obtained, it is possible to measure the liquid surface with the density change of the fluid to be measured corrected.

FIG. 3 shows in detail the structure of the pressure receiving section '2 which detects each of the pressures P1, P2, P3 as a differential pressure. In FIG. 3, the pressure receiving portion '2 has a high pressure side pressure P1,
An incompressible liquid (silicone oil) stored in the member through the pressure guide path formed in the metal fitting 25 via the high-pressure side seal diaphragm 21 and the low-pressure side seal diaphragm 22, respectively, is applied to the low-pressure side pressure P2. ).

Then, these pressures P1 and P2 are transmitted to the surface side of the sensor body '1 through an isolation chamber formed by an overload protection diaphragm (center diaphragm) 23, and the other pressure P2 is The light is transmitted to the back surface of the sensor body '1 via a communication path 151 provided in the metal fitting of the sensor body' 1. As a result, the semiconductor pressure sensor '1 detects a pressure difference (P1-P2) between the high pressure and the low pressure.

On the other hand, another pressure P3 is applied to the pressure receiving section '2
And the diaphragm to which the pressure P2 is transmitted on the back surface of the semiconductor pressure sensor 1 via the communication path 241 provided in the main body of the semiconductor pressure sensor 1 and another communication path 152 provided in the metal fitting of the sensor body '1. It is transmitted to different diaphragms. As a result, the semiconductor pressure sensor '1 detects the pressure difference (P1-P3) between the high pressure and the correction pressure. Therefore, each of the pressures P1, P2, and P3 is equal to the differential pressure (P1-P
2), are simultaneously detected as differential pressure (P1-P3).

Further, the pressure receiving portion '2 is provided with a fixing member 27 in addition to the main body member 24, and the fixing member 27 and the center diaphragm 23 form one of the isolation chambers.
On the other surface side of the center diaphragm 23, the center bracket 2 is provided.
8 are provided and the other of the isolation chambers is formed.

The communication path 15 in the metal fitting of the sensor body '1
2 and the communication passage 241 of the pressure receiving portion main body member 24,
Further, a plate 26 is provided for sealing from outside air. With this plate 26, the overload protection mechanism and the pressure transmission path, which are the basics of the differential pressure detector, can be configured compactly, and the configuration of the pressure receiving section '2 can be simplified.

As shown in FIG. 1, a signal from the semiconductor pressure sensor body '1 is supplied to a flexible printed circuit (FPC) 34.
And the signal transmitted to the circuit board 31 and the final signal information is transmitted from the cable connected to the wiring connection port 36 to, for example, 4 to 2
0 mA analog constant current signal or 4-20 mA
As a signal obtained by superimposing a rectangular wave digital signal on the analog constant current signal, and further converted into a digital constant current signal and output to a host device or the like. The final signal information is displayed on the display or indicator 33 in various forms.

FIG. 4 shows in detail the structure of the sensor element '1 for detecting each of the pressures P1, P2, P3 as a differential pressure, and FIG. 5 is a plan view of the semiconductor pressure sensor element' 1.
4 and 5, the semiconductor pressure sensor body '1 is (1
(00) plane n-type single crystal silicon, and has circular thin portions 101 and 102 on one surface thereof.

The first process pressure, that is, the pressure P1 on the high pressure side is applied to one surface side of these thin portions 101 and 102, and the second process pressure, that is, the low pressure side, is applied to the other surface side. Pressure P2 and correction pressure P3 are applied. As a result, the thin portions 101 and 102 become a strain-generating body responsive to the differential pressure, and operate as a pressure-sensitive diaphragm for detecting the differential pressure.

On the upper surfaces of the differential pressure sensing diaphragms 101 and 102, a P-type resistor (gauge resistor) serving as a first differential pressure sensor is provided in the <110> axis direction where the piezoresistance coefficient on the (100) plane is maximized. P-type resistors (gauge resistors) 120 to 123 serving as second differential pressure sensors
Are formed by a thermal diffusion method or an ion implantation method in a direction parallel or perpendicular to the crystal axis, respectively.

Each of the resistors 111 to 114 and 120 to 12
3 is a differential pressure sensitive diaphragm 101 and 10 when a differential pressure is applied.
2 is disposed in the vicinity of the fixed portion where the radial distortion generated on the second portion becomes maximum. The directions in which the resistors are arranged are radial directions for the resistors 111, 120, 113, and 122, and tangential directions for the resistors 112, 121, 114, and 123.

One end of each of the resistors facing the same arrangement direction is connected, and the other end of each of the resistors is connected to the detection terminal, thereby forming a bridge circuit as shown in FIG.

Further, the differential pressure sensing diaphragms 101, 10
In the thick portions other than 2, static pressure detecting resistors 115 to 118 are formed on the static pressure sensing diaphragms 104 and 103 which are sensitive to static pressure, like the differential pressure resistors, and these are connected to a bridge circuit. Thus, a static pressure signal can be obtained.

Further, a temperature sensing resistor (semiconductor type temperature sensitive resistor) 119 which is sensitive to temperature is formed on the thick portion.
By taking out the change in the resistance value from the output terminal, the temperature of the process fluid can also be measured indirectly.

Then, the differential pressure sensing diaphragms 101, 1
The thicknesses of the shapes 02, 103, and 104 are set to desired shapes and thicknesses according to the differential pressure to be sensed, and are formed by anisotropic wet etching or dry etching. Further, it is possible to reduce the number of manufacturing steps by making the thicknesses the same and adjusting the sensitivity by the diameter.

As a result, the differential pressure sensing diaphragm 101
Upper resistors 111 to 114 and differential pressure-sensitive diaphragm 1
The resistances of the resistors 120 to 123 on 02 change due to the piezoresistive effect due to the distortion generated in the diaphragm, so that the change can be extracted as a signal.

The semiconductor pressure sensor body ′ 1 is connected to the housing 1 via a hollow first fixed base 11 and a second fixed base 13.
5 is attached. The first fixing base 11 is made of a ceramic (which has an approximate linear expansion coefficient with silicon) in consideration of electrical insulation between the semiconductor pressure sensor body '1 and the housing 15 and reduction of thermal strain due to a difference in linear expansion coefficient from the housing 15. For example, SiC) or Pyrex glass is desirable. However, when ceramics and the like are not available, the difference from the coefficient of linear expansion with silicon may be ignored when selecting the material.

The first fixed base 11 and the sensor chip 1 are
Anodic bonding method or oxide solder, metal solder, Au-
An Si alloy layer or a thin film of Au can be joined by forming a joining film by a sputtering method or an evaporation method. further,
A bonding layer 12 is formed on a bonding surface between the first fixed base 11 and the second fixed base 13.

The bonding layer 12 is formed by glazing the bonding surface of the fixing base 11 with an oxide solder such as a low melting point glass, or by using a metal solder, an Au—Si alloy layer, or Au.
Can be formed by sputtering or vapor deposition.

Alternatively, an organic or inorganic binder can be formed. The bonding layer 12 is attached to the second fixed base 1
By providing the third fixed base 11 on the bonding surface side of the first fixed base 11, the fixed base 12 can be easily bonded at a low temperature. Further, since the bonding layer is thin, the influence of the bonding strain can be reduced as much as possible.

The second fixed base 13 has holes 1034 and 1032 for transmitting respective pressures on the back side of the pressure-sensitive diaphragms 101 and 102 of the semiconductor sensor 1. And 1022.
Further, the hole 1034 of the second fixing base 13 is
5, and communicates the pressure P2 to the back surface of the pressure-sensitive diaphragm 101 of the semiconductor pressure sensor body '1.

On the other hand, the hole 1031 of the second fixing base 13 is
The pressure P3 is transmitted to the back surface of the pressure-sensitive diaphragm 102 of the semiconductor pressure sensor body '1 by communicating with another communication passage 152 provided in the metal fitting. The cylindrical portion 1032 is formed by processing a part of the member into a cylindrical shape, and the hole 1031 of the fixing base 13 can be easily formed in the cylindrical portion 1032.
Further, one end of the cylindrical portion 1032 is hermetically joined to the housing 15 and is isolated from the pressure P2. Further, a plate 14 is hermetically connected to the housing 15 at an extension of the cylindrical portion 1032 in order to isolate the pressure P3 from the outside air.

The first differential pressure (P1−
P2), the second differential pressure (P1−P3), the static pressure, and the temperature signal are transmitted via the lead wire 105 and the wiring board 19 to the hermetic terminal of the hermetic seal portion provided in the housing 15. It is taken out to the outside by 16 and 17, respectively.

According to the semiconductor pressure sensor body '1 having the above-described structure, the first differential pressure (P1-P2) and the second differential pressure (P1
-P3), the static pressure, and the temperature can be detected simultaneously, so that the configuration can be simplified and the size can be reduced.

By the way, the differential pressure sensing diaphragm 101,
The resistors on 102, 103 and 104 are subjected to distortion generated by the differential pressure or pressure on the diaphragm, and the resistance changes due to the piezoresistance effect, so that the signal can be taken out.

However, these resistors change their output even when the pressure on both sides of each differential pressure sensitive diaphragm is equal or in response to changes in temperature. The former output change is called a zero point change due to static pressure, and the latter output change is called a zero point change due to a temperature change.

The change in the zero point at the time of temperature change is mainly due to the variation of each resistance value of the resistor and the resistance value of the resistor as a function of the temperature. Therefore, the temperature sensor 119
The relationship between the output of the differential pressure sensor (shown in FIGS. 5 and 6) and the output of the differential pressure sensor is clearly related, so that compensation is easy.

That is, the relationship between the zero point change when the temperature changes or the zero point change of the differential pressure sensor when the static pressure is applied and the output of the static pressure sensor is collected in advance as information and stored in the sensor characteristic memory 315 shown in FIG. If stored, the microcomputer 314 can calculate the temperature change based on this information and compensate for the temperature change.

FIG. 7 is a diagram for explaining an example of a signal processing section for processing an electric signal from the semiconductor pressure sensor body '1. In FIG. 7, the semiconductor pressure sensor chip 1 includes:
The first differential pressure, the second differential pressure, the static pressure, and the change in the gauge resistance due to the temperature are output as electric signals, and selectively taken into the multiplexer (MPX) 311.

The signal of the sensor 1 taken into the multiplexer 311 is supplied to a programmable gain amplifier (PGA).
The signal is amplified at 312, then converted to a digital signal at an A / D converter 313, and converted to a microprocessor (MPU) 31.
4 is sent. Sensor characteristic memory 315 (EEPRO
M) previously stores the characteristics of the differential pressure, the static pressure, and the temperature sensor, and corrects and calculates the differential pressure signal values and the high-precision differential pressure values by using these data to perform a correction operation in the microprocessor 314. , The static pressure and the temperature signal value are calculated.

The result of this operation is obtained by the D / A converter 317 and V
The signal is converted to a normal analog signal via the / I converter 316, and the differential pressure, static pressure, and temperature signals can be sent to a computer or a signal converter as a higher-level control device as a DC current signal of 4 to 20 mA DC. It has become.

Then, in the device of this embodiment, information on the process state obtained from the semiconductor pressure sensor chip 1 is displayed on the display unit 33 in the signal processing unit '3. It is also possible to superimpose information as a digital signal on a direct current of 4 to 20 mA DC and send it. Further, although not shown in the drawing, it is possible to output process information by sending a digital signal based on a direct current from a signal processing circuit.

In a communication method in which a digital signal is superimposed on a DC current signal, or in a communication method in which a digital signal is used to communicate with a monitoring and control device provided externally, the digital I / O stored in the V / I converter 316 is used. The O-circuit displays information about the process status on, for example, an operator's console or a handheld terminal. From these devices, setting, change, output adjustment, input / output monitoring, and self-diagnosis of parameters such as a measurement range can be performed.

The signal processing section '3 is inserted into the recess (recess) 29 of the pressure receiving section' 2 via a connector holder. The joint of the signal processing unit '3 is a concave portion 2 provided in the pressure receiving unit' 2.
Since the explosion-proof joint surface can be formed in 9 and there is no need to prepare an excessive member, compactness and material saving can be achieved.

Further, in the fixing method, since the fixing member is fixed with bolts in the converter, it is convenient for explosion proof that the fastening member is exposed, environmental resistance is improved, and maintenance is improved.

FIG. 8 is an example showing the display divisions of the display unit 33. The divisions have three display divisions. The output of the detector is indicated by its value in display section 804,
For example, a differential pressure value and a head value are displayed.
A level mark 806 composed of a dot matrix mark of the LCD is displayed in an analog graph corresponding to the display value of 4.

Further, when the detector is out of the measurement range, the mark 812 is displayed at the time of overscale, and the mark 814 is displayed at the time of underscale. Then, a mark indicating the attribute is displayed in the display section 818 for the signal output state of the detection device and the zero point adjustment state of the device.

When the density value is displayed, a mark indicating the attribute is displayed in the display section 819. Further, even when a self-diagnosis result of the device or an abnormality occurs in the device itself, the information can be notified to a third party by blinking and lighting of the above-described section.

As described above, the detection device according to the first embodiment of the present invention uses only the display 33 at the time of maintenance.
The output value, the output mode, and the like can be checked collectively, so that an excellent detection device with easy maintainability management can be realized.

On the other hand, in the conventional apparatus, when a system is configured, generally, a signal comparator must convert this differential pressure information, and one signal comparator is used to convert signals from a plurality of detectors. , The response to the host device was delayed due to signal conversion.

On the other hand, since the detection device according to the first embodiment of the present invention has a function of converting a sensor signal internally, even when a large-scale system is configured, the signal collection response of the signal comparator can be improved. There is no delay.

Further, a display function for clearly indicating whether the output signal and the display signal are converted values is provided.
The operator can accurately grasp the display information.

Further, a hand-held terminal is connected to a two-wire transmission line from the detection device to be inspected at the time of maintenance so that the display contents of the display and the display contents of the hand-held terminal are equal before and after the conversion. Can be easily notified to the inspector.

As described above, according to the first embodiment of the present invention, one high-pressure side process connection flange 4
Since the pressure P1 on the high pressure side and the correction pressure P3 can be detected, the density correction type liquid level detection device which is small and lightweight, can reduce the number of necessary measuring instruments, and can simplify the measurement system. Can be realized.

FIG. 9 is a schematic sectional view of a second embodiment of the present invention, in which parts equivalent to those in the example of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In the example of FIG. 1, the high-pressure side process pressure flange 4 and the pressure receiving portion '2 are connected by a flexible metal pipe or the like. However, in the second embodiment, the pressure flange 4 and the pressure receiving portion' 2 are connected to each other. Is
They are arranged close to each other and are formed substantially integrally. 5
Reference numeral 31 denotes a process pressure introduction port, which introduces the pressure P2 into the pressure receiving section '2.

The low-pressure side pressure introducing flange 5 is not shown in FIG.
Is equivalent to the example. Other configurations are the same as those in the example of FIG. 9 and the example of FIG. 1, and thus illustration and description are omitted. Also in the above-described second embodiment of the present invention, the same effects as in the first embodiment can be obtained.

FIG. 10 is a sectional view of a high-pressure side process connection flange of a density correction type liquid level detecting device according to a third embodiment of the present invention. FIG. 11 is a sectional view of the pressure receiving portion of the device shown in FIG. FIG. 3 is a configuration diagram with a signal processing unit. FIG. 12 is a sectional view of the sensor unit shown in FIG. 11, and FIG.
FIG. 3 is a plan view of the sensor unit shown in FIG.

FIG. 14 is a detailed sectional view of the high-pressure side process connection flange 4 shown in FIG. 11, and FIG.
FIG. 12 is a plan view of the semiconductor pressure sensor shown in FIG. 11. FIG. 16 is a circuit diagram of the semiconductor pressure sensor shown in FIG. 15, and FIG. 17 is a diagram systematically showing signal processing. The detection principle of the detection device according to the third embodiment is similar to that of the above-described embodiment, but differs in the configuration.

That is, in the high-pressure side process connection flange 4, the fluid pressure of the high-pressure side fluid is transmitted to the incompressible liquid (silicon oil) 45 via the respective high-pressure side seal diaphragms 41, 4
One pressure P1 is transmitted to the pressure receiving portion '2 via the communication passage 431 and the pressure transmitting body 43 provided therein.

The other pressure P3 is converted into an electric signal by the semiconductor pressure sensor unit '100 via the seal diaphragm 41 and the seal diaphragm 42 fixed to the main body of the process connection flange 4 at a distance of h0 at the center thereof. This is the configuration.

The pressure P3 is transmitted to one surface of the semiconductor pressure sensor unit '100 via the seal diaphragm 42, and the pressure P3 of the seal diaphragm 41 is transmitted to the other surface.
1 is a communication passage 4 provided in the high-pressure side process connection flange 4
51.

Therefore, the head hx of the liquid surface of the fluid to be measured
Pressure P1 from the process and the head h0
Pressure difference P1-P3 in the semiconductor pressure sensor body '10
0 can be received as an electric signal. Therefore, it is possible to simultaneously obtain the electric signal for density correction and the head pressure of the liquid level with one process connection flange, and the number of assembling steps and the configuration are further simplified. On the other hand, the low-pressure side process connection flange 5 is the same as in the above-described first embodiment.

FIG. 11 shows the pressures P1, P2 and the differential pressure signal P1.
FIG. 4 is a diagram schematically illustrating a configuration of a pressure receiving unit 2 and a signal processing unit 3 that detect −P3. The pressure receiving section '2 is the first pressure receiving section described above.
Although there is not much difference between the embodiment and its configuration, the third embodiment
In the embodiment, since it is not necessary to provide a communication path for transmitting the differential pressure between the pressures P3 and P1, the configuration of a general differential pressure detector can be applied, and the configuration can be further simplified.

As shown in FIG. 11, the signal from the semiconductor pressure sensor body '1 in the pressure receiving section' 2 is transmitted to the flexible printed circuit (FPC) 34 and the circuit on the circuit board 31. Further, the electric signal of the differential pressure (P1-P3) of the semiconductor pressure sensor body '100 in the high-pressure side process connection flange 4 is sent to the signal processing unit 3 via the sensor signal cable 46.
It is configured to be connected to the circuit board 31 in the inside, and is configured to perform arithmetic and processing in the circuit board 31.

The final signal information is obtained by superimposing a rectangular wave digital signal on the analog constant current signal of, for example, 4 to 20 mA or the analog constant current signal of 4 to 20 mA from the cable connected to the wiring connection port 36. As a signal,
Further, it is converted and output to a digital constant current signal. The signal contents are displayed on the display or indicator 33 in various forms.

FIG. 12 is a diagram showing in detail the structure of the semiconductor pressure center member '1 for detecting each pressure P1, P2 as a differential pressure, and FIG. 13 is a plan view of the semiconductor pressure sensor member' 1. The semiconductor pressure sensor body '1 of the third embodiment
Although there is no great difference between the above-described embodiment and the configuration thereof, in the third embodiment, it is not necessary to provide the housing 15 with the communication passage 152 for transmitting the differential pressure between the pressures P1 and P3.

Further, since the fixing base 11 can be further simplified, the configuration of a general semiconductor sensor for detecting a differential pressure can be applied, and the configuration and the number of assembling steps can be further simplified.

FIG. 14 is a diagram showing in detail the structure of the center member '100 for detecting the difference between the pressures P1 and P3, and FIG. 15 is a plan view of the semiconductor pressure sensor member' 1. 14 and 15, when the head pressure of the fluid to be measured is applied to the high pressure side process connection flange 4 to the respective high pressure side first seal diaphragm 41 and second seal diaphragm 42, the incompressible Liquid (silicone oil) 45 is transmitted to the
One pressure P1 is transmitted to the pressure receiving portion '2 via one pressure transmitting body 43.

The other pressure P 3 is transmitted to the semiconductor pressure sensor 100 via the seal diaphragm 42. The seal diaphragm 41 includes a seal diaphragm 42 fixed to the main body of the process connection flange 4,
The distance between the centers is h0.

On one surface of the semiconductor pressure sensor body '100, a pressure P 1 is applied via a seal diaphragm 41 to a communication passage 451 provided in the high-pressure side process connection flange 4.
Is transmitted through a communication passage 151 provided in the housing 15.

Therefore, the differential pressure (P1-P3) signal from the sensor chip body '100 is transmitted to the outside by the terminals 16 and 17 of the hermetic seal portion provided on the housing 15 via the lead wire 105 and the wiring board 19. Each is taken out.

The semiconductor pressure sensor chip 1 has (100)
N-type single-crystal silicon having a circular thin portion 102 on one surface. By applying the process pressure P3 to the thin portion 102 and applying the process pressure P1 to the other surface, the thin portion 102 becomes a strain-sensitive body sensitive to a differential pressure, and operates as a sensitive diaphragm for detecting a differential pressure. .

On the upper surface of the differential pressure-sensitive diaphragm 102, the piezoresistance coefficient at the (100) plane becomes the maximum <1.
10> In the axial direction, a P-type resistor (gauge resistor) 120 that is a P-type resistor (gauge resistor) as the first differential pressure sensor
To 123 are formed in a direction parallel or perpendicular to the crystal axis by a thermal diffusion method or an ion implantation method. The resistors 120 to 123 are arranged in the vicinity of the fixed portion where the radial strain generated on the differential pressure sensitive diaphragm 102 at the time of applying the differential pressure is maximized.

The direction in which these resistors are arranged is as follows.
The resistors 120 and 122 are set in the radial direction,
, 123 are tangential directions, one end of each resistor facing the same arrangement direction is connected, and the other end of each resistor is connected to a detection terminal to form a bridge circuit.

A temperature-sensitive resistor 124 is formed in a thick portion other than the differential pressure-sensitive diaphragm 102, and a change in the resistance value is taken out from an output terminal so that the temperature of the process fluid can be measured. Has become.

The shape and thickness of the differential pressure-sensitive diaphragm 102 are set to desired shapes and thicknesses according to the differential pressure to be sensed, and are formed by anisotropic wet etching or dry etching. Thereby, the resistors 120 to 123 on the differential pressure sensitive diaphragm 102 are
Upon receiving the strain generated in the diaphragm 102, the resistance changes due to the piezoresistance effect. Thereby, the change can be extracted as a signal. FIG. 16 shows a connection diagram (bridge circuit) of these resistors.

The semiconductor pressure sensor chip 1 has a hollow first
The fixed base 11 and the second fixed base are mounted on the housing 15 via one or the other fixed base.
In the third embodiment, a case is described in which only the first fixed base 11 is used.

The first fixed base 11 is provided with the semiconductor pressure sensor 1
In consideration of electrical insulation from the housing 15 and reduction in thermal strain due to the difference in the coefficient of linear expansion from the housing 15, ceramics (for example, Si
C) or Pyrex glass is desirable, but if it is not available, the difference in the coefficient of linear expansion from silicon may be ignored when selecting the material.

The first fixed base 11 and the sensor chip 1 are
An oxide solder, a metal solder, an Au—Si alloy layer, or a thin film of Au can be joined by forming the joining layer 12 by a sputtering method or an evaporation method. Alternatively, the bonding layer 12 can be formed using an organic or inorganic binder.

By providing the bonding layer 12 on the bonding surface side of the first fixed base 11, the fixed base 11 and the semiconductor pressure sensor 1 can be easily bonded at a low temperature. Further, since the bonding layer 12 is thin, the influence of the bonding strain can be reduced as much as possible.

In the first fixed base 11, a hole 1022 for transmitting pressure is formed on the back side (the side to which the pressure P1 is applied) of the pressure-sensitive diaphragm 102 of the semiconductor sensor 1. The hole 1022 is provided in the communication passage 15 provided in the housing 15.
2, the pressure-sensitive diaphragm 1 of the semiconductor pressure sensor 1
The pressure P1 is transmitted to the back surface of the pressure sensor 02.

The signals of the differential pressure (P1-P3) and the temperature from the sensor body '100 in the pressure receiving portion are transmitted to the terminals 16 of the hermetic seal portion provided on the housing 15 via the lead wire 105 and the wiring board 19, respectively. 17 and signal cable 4
6 to the signal processing unit 3 respectively.

Semiconductor pressure sensor body '100 having such a configuration
According to this, the pressure difference (P1−P3) between the pressures P1 and P3 and the temperature can be detected simultaneously. Since this temperature is the fluid temperature of the process, it operates as a temperature detector.

Therefore, the structure can be simplified and the size can be reduced. Further, since the device also serves as a temperature detector, the number of necessary devices can be reduced.

FIG. 17 is a view for explaining an example of a signal processing section for processing electric signals from the semiconductor pressure sensor body 1 in the pressure receiving section '2 and the semiconductor pressure sensor body' 100 in the high-pressure side process connection flange 4. is there.

The semiconductor pressure sensor 1 in the pressure receiving section '2 is
The change of the gauge resistance due to the differential pressure, the static pressure and the temperature is output as an electric signal, and the semiconductor pressure sensor body '100 in the high-pressure side process connection flange 4 changes the gauge resistance due to the second differential pressure and the process temperature. Are output as electric signals. The semiconductor pressure sensor 1 and the body '100
Are selectively taken into a multiplexer (MPX) 311.

The signal of the sensor taken into the multiplexer 311 is supplied to a programmable gain amplifier (PGA) 3.
12, and then converted into a digital signal by an A / D converter 313, and a microprocessor (MPU) 314
Sent to. Sensor characteristic memory 315 (EEPRO
In M), the differential pressure and static pressure of the semiconductor pressure sensor 1 and the characteristics of each temperature sensor, the differential pressure of the semiconductor pressure sensor body '100, and the characteristics of the temperature sensor are stored in advance, and micro data is stored using these data. When the processor 314 performs the correction operation, the highly accurate differential pressure signal values, the static pressure, and the temperature signal values are calculated.

The result of this operation is obtained by the D / A converter 317 and V
The signal is converted into a normal analog signal via the / I converter 316, and a differential pressure, static pressure, and temperature signal can be transmitted as a direct current signal of 4 to 20 mA DC to a computer or a signal converter as a higher-level control device. ing.

In the device according to the third embodiment, the semiconductor pressure sensor 1 is provided in the same manner as in the above-described embodiment.
It is possible to display information on the process state obtained by the sensor unit 100 and the display unit 33 in the signal processing unit 3. Further, it is possible to output process information by superimposing information as a digital signal on a DC current of 4 to 20 mA DC and transmitting the digital signal by a DC current from a signal processing circuit (not shown). .

According to the third embodiment of the present invention described above, the same effects as those of the first embodiment can be obtained, and the following effects can be obtained. That is, since the differential pressure between the pressures P3 and P1 is detected at the connection flange 4 and converted into an electric signal and transmitted to the signal processing unit '3, a communication passage for the pressure transmission medium is provided inside. Since there is no need, the configuration of a general differential pressure detector can be applied, and the configuration can be further simplified.

FIG. 18 is a sectional view of the high-pressure side process connection flange 4 of the density correction type liquid level detecting device according to the fourth embodiment of the present invention, and FIG. 19 is a semiconductor pressure sensor body shown in FIG. It is an enlarged view of '101. In the fourth embodiment, other components are the same as those in the above-described embodiment, and thus illustration and description thereof are omitted. The detection principle of the detection device according to the fourth embodiment is the same as that of the above-described embodiment, but differs in the configuration.

That is, in the high-pressure side process connection flange 4, the fluid pressure P 1 of the high-pressure side fluid is transmitted to the incompressible liquid (silicon oil) 45 via the high-pressure side seal diaphragm 41, and the communication passage in the flange is formed. The pressure is transmitted to the pressure receiving section '2 via the pressure transmitting body 43 in the 431.

The other pressure P3 is detected on the surface of the semiconductor pressure sensor body '101, which is separated from the seal diaphragm 41 by a distance h0 at the center thereof, where there is no gauge resistance, and
It is configured to be converted into an electric signal.

The pressure P3 is transmitted by the process fluid being in direct contact with the surface of the semiconductor pressure sensor body '101 having no gauge resistance. Then, of the semiconductor pressure sensor body '101,
On the other surface, the pressure P1 applied to the seal diaphragm 41 is applied to the communication path 452 provided in the high-pressure side process connection flange 4 and the communication path 1501 in the fixed base 13 of the semiconductor pressure sensor body '101. Is transmitted via

For this reason, the head hx of the liquid surface of the fluid to be measured is
Can be received from the process fluid, and the pressure difference (P1-P3) at the head h0 can be received as an electrical signal from the semiconductor pressure sensor body '101.

Therefore, it is possible to simultaneously obtain the electric signal for density correction and the head pressure of the liquid level with one process connection flange 4, and the number of assembling steps and the configuration are further simplified. The low-pressure side process connection flange 5 is the same as in the above-described embodiment.

FIG. 19 is a diagram showing in detail the structure of the sensor body '101 which detects the difference between the pressures P1 and P3.

The head pressure P1 of the fluid to be measured is applied to the high pressure side process connection flange 4 to the first seal diaphragm 41 on the high pressure side, and transmitted to the incompressible liquid (silicone oil). Then, the head pressure P1 of the fluid to be measured transmitted to the incompressible liquid is transmitted to the pressure receiving unit '2 via the pressure transmitter 43.

As the other pressure P3, the differential pressure P1-P3 at the head h0 can be received as an electric signal from the semiconductor pressure sensor body 101.

On one surface of the semiconductor pressure sensor body 101, the pressure P 1 of the seal diaphragm 41 is applied via the seal diaphragm 41 to the communication passage 452 provided in the high-pressure side process connection flange 4 and to the fixed base. 11
It is transmitted through a communication path 1501 provided in the inside.

Therefore, a differential pressure (P1-P3) signal from the sensor chip body '101 and a process temperature signal to be described later are externally connected to the hermetic terminals 16 and 17 provided on the fixed base 11 via the lead wire 1200. And sent out to the signal processing unit by the signal cable 46.

The semiconductor sensor 1 of the semiconductor pressure sensor body '101 is a (100) plane n-type single crystal silicon, and has a circular thin portion 102 on one surface. When the pressure P3 is applied to the thin portion 102 on the substrate and the pressure P1 is applied to the other surface side, the thin portion 102 becomes a strain generating body sensitive to the differential pressure, and the pressure-sensitive diaphragm for detecting the differential pressure. Works as

On the upper surface of the differential pressure-sensitive diaphragm 102, that is, the surface opposite to the surface to which the process fluid pressure P3 is applied, the <110> axis direction at which the piezoresistance coefficient in the (100) plane is maximum is: P-type resistors (gauge resistors) 120 to 123, which are first differential pressure sensors, are formed by a thermal diffusion method or an ion implantation method in a direction parallel or perpendicular to the crystal axis, respectively. Each of the resistors 120 to 123 is arranged in the vicinity of the fixed portion where the radial distortion generated on the differential pressure sensitive diaphragm 102 at the time of applying the differential pressure is maximized.

The direction in which these resistors are arranged is as follows.
The resistors 120 and 122 are radial, and the resistors 121 and 123 are tangential. Then, one end of each of the resistors facing the same arrangement direction is connected, and the other end of each of the resistors is connected to the detection terminal, thereby forming a bridge circuit.

A resistor 119 sensitive to temperature is formed on the upper surface of the thick portion other than the differential pressure sensing diaphragm 102, and a change in the resistance value is taken out from an output terminal to reduce the temperature of the process fluid. As described later, the measurement can be performed with high accuracy.

The thickness of the shape of the differential pressure-sensitive diaphragm 102 is set to a desired shape and thickness according to the differential pressure to be sensed, and is formed by anisotropic wet etching or dry etching.

Thus, the differential pressure sensing diaphragm 102
The upper resistors 120 to 123 receive distortion generated in the diaphragm, and the resistance changes due to the piezoresistance effect, so that the change can be extracted as a signal. The connection diagram (bridge circuit) of these resistors is the same as the circuit shown in FIG.

Further, the differential pressure sensing diaphragm 102 is
Since the material is a highly elastic material due to the mechanical properties of the material, by forming a protective film 1011 of gold, platinum, or the like on this surface,
Since its corrosion resistance is improved and has the same function as another seal diaphragm 42 (shown in FIG. 10) of the high-pressure side process connection flange 4, it is possible to directly guide the process fluid to this surface. Therefore, the temperature-sensitive resistor 119 can measure the temperature of the process fluid with high accuracy.

The detection resistors 120 to of the semiconductor pressure sensor 1
The surface side having 123 is attached to the housing 1510 via the hollow fixed base 11. In consideration of the electrical insulation of the semiconductor pressure sensor 1 and the reduction of thermal strain due to the difference in the coefficient of linear expansion from the housing 1510, the fixing table 11 is made of ceramics (for example, Si
C) or Pyrex glass is desirable, but if it is not available, the difference in linear expansion coefficient from silicon may be ignored when selecting the material.

The fixed base 11 and the sensor chip 1 are formed by an oxide solder, a metal solder, an Au—Si alloy layer or Au.
Can be hermetically bonded via a bonding layer 12 in which a bonding film is formed by a sputtering method or a vapor deposition method. Alternatively, an organic or inorganic binder can be formed. By providing the bonding layer 12 on the bonding surface side of the fixed base 11, the fixed base 11 and the semiconductor pressure sensor 1 can be easily bonded at a low temperature. Further, since the bonding layer 12 is thin, the influence of the bonding strain can be reduced as much as possible.

Further, the fixed base 11 has the semiconductor sensor 1
And a communication path 1501 for transmitting pressure to the detection resistance surface side of the pressure-sensitive diaphragm 102.
Then, the head pressure P1 of the fluid to be measured applied to the seal diaphragm 41 of the high-pressure side process connection flange 4 is:
The pressure is transmitted to the detection resistance surface side of the pressure-sensitive diaphragm 102 via the communication passage 452 of the high-pressure side process connection flange 4, the passage 1501 of the fixed base 11, and the recess 131.

Further, the fixing base 11 is provided with a spacer 152
0 and the housing 1510 ensure the holding and airtightness, and are attached to the high-pressure side process connection flange 4.
On the surface of the housing (holding bracket) 1510, like the pressure-sensitive diaphragm 102 of the semiconductor sensor body '101,
A protective film 1011 of gold, platinum or the like is formed, and the corrosion resistance is improved.

The lead pad 1200 of each resistor provided on the fixed base 11 is electrically connected to the hermetic terminals 16 and 17 provided on the fixed base 15 at the time of joining. Therefore, the signals of the differential pressure (P1-P3) and the temperature from the sensor body '101 are transmitted to the lead pad 1200, the airtight terminal 16,
17 and can be taken out. further,
This signal is transmitted to the signal processing unit '3 via the signal cable 46.

According to the semiconductor pressure sensor body '101 having the above structure, the pressure difference (P1-P3) between the pressures P1 and P3 and the temperature can be simultaneously detected. Since this temperature is the fluid temperature of the process, it operates as a temperature detector.
Further, the process fluid can be directly sensed.

Therefore, the structure can be simplified and the device can be made more compact. Further, since the device also serves as a temperature detector, the number of devices can be reduced.

In the apparatus according to the fourth embodiment, as in the first to third embodiments, information on the process state obtained from the semiconductor pressure sensor 1 and the semiconductor pressure sensor body '101 is used. It can be displayed on the display unit 33 in the signal processing unit '3.

Further, information is superimposed and transmitted as a digital signal on a DC current of 4 to 20 mA DC, and process information is output by transmitting a digital signal based on the DC current from a signal processing circuit (not shown). Is possible.

According to the fourth embodiment of the present invention described above, the same effects as those of the third embodiment can be obtained, and the fluid temperature of the process can be simultaneously detected with high accuracy. No temperature detector is required.

Therefore, the measurement system can be simplified, the number of devices can be reduced, and maintenance costs and costs can be reduced.
Maintenance costs can be reduced.

Next, a description will be given of a process in the case where the above-described density correction type liquid level detecting device malfunctions for some reason. In the above-described detection device, generally, the most frequent causes of malfunctions are corrosion of the metal diaphragm in the flange portion which is always in contact with the process fluid and bruising during installation and removal during the periodic inspection. As a result, the function may not be performed. Next, as a factor that causes an operation failure, there is a conduction failure of each component due to corrosion of a contact portion of the signal processing unit, insulation failure, or the like. Should such a situation occur, the operation of the plant would be hindered and the production efficiency would decrease.

For this reason, in the above-described detection device,
When encountering a situation that causes operation failure, transmit the operation status to a higher-level device, and display it on the above-mentioned display,
We are promptly urging them to take countermeasures.

When a pinhole is always generated in the metal diaphragm of the flange portion in contact with the process fluid for some reason, when the pressure transmitting element is a metal diaphragm, the sealing pressure generated during manufacturing in the pressure transmitting is released. Also, if a pinhole is generated in the pressure-sensitive diaphragm of the sensor body for some reason, if the pressure transmitting element is a sensor body, the front and back of the pressure-sensitive diaphragm become equal in pressure, so that the diaphragm does not operate as a strain-causing element. Since the process fluid comes into contact with the semiconductor-type resistor on the pressure diaphragm, electrical characteristics such as insulation change, and the output value greatly fluctuates.

For this reason, when these output values fluctuate, a determination is made, and the signal processing unit '3 shifts to the task of abnormal processing and executes the processing.

On the other hand, in the conventional detecting device shown in FIG. 22, under the above-mentioned situation, the pressure of the pressure transmitting body is released, so that the output fluctuates and the change is captured. For example, an abnormal signal can be transmitted. However, since the sealed liquid in the pressure transmitting body is an incompressible fluid, the pressure of the process fluid is sent out to the pressure receiving portion,
It is difficult to distinguish whether the change is a change in the process state or a change due to an abnormality.

In the embodiment of the present invention, as described above, the pressure difference between the high-pressure side pressure P1 and the correction pressure P3, or the second pressure difference (P1-P3) is applied to the flange portion in contact with the process fluid. And the other differential pressure, that is, the first differential pressure (P1-P2), it is possible to simultaneously extract the fluctuation of the first differential pressure or the fluctuation of the second differential pressure. By using these two events and the specified value of the second differential pressure value preset in the sensor characteristic memory 315 in the processing unit '3, the situation can be determined, and the accuracy can be made extremely high. Can be.

Further, as described above, when the pressure transmitting element is a sensor body, when a pinhole is generated in the pressure-sensitive diaphragm, the front and back of the pressure-sensitive diaphragm become equal in pressure, and the semiconductor on the pressure-sensitive diaphragm becomes uniform. Since the process fluid comes into contact with the resistor body of the resistive semiconductor, the electrical characteristics such as insulation change and the output value greatly fluctuates.

On the other hand, it is conceivable to construct a capacitance type pressure sensor by utilizing the displacement of the pressure-sensitive diaphragm due to the applied pressure. That is, if the capacitance between the diaphragm and the fixed base 11 is measured, the measured capacitance can be converted into the applied pressure and the pressure can be measured.

When the fourth embodiment of the present invention is applied to this capacitance-type sensor, as described above, when a pinhole is generated in the pressure-sensitive diaphragm, the dielectric constant changes greatly. , Its capacity varies greatly. Therefore, it is easier to determine the situation, and the abnormality detection accuracy can be further increased.

FIG. 20 is a diagram showing a display example of the display unit of the processing unit in each of the embodiments described above. In FIG. 20 (1), normal measurement (differential pressure or liquid level) is performed, but the over display 812 indicates that the value exceeds the set value.

FIG. 20 (2) shows a section display 819.
Is lit, indicating that the numerical value displayed is the density γ, and that the value exceeds the set value from the over display 818.

FIG. 20 (3) shows that the self-diagnosis result of the signal processing unit in the detection device is abnormal. At this time, the output / conversion display mark lights up,
In the example, the display 804 indicates that there is an abnormality in the A / D converter.

FIG. 20 (4) shows that either the metal diaphragm of the flange portion in contact with the process fluid in the detection device or the pressure-sensitive diaphragm of the sensor body has an abnormality. At this time, the display mark 820 (SD) and the display mark 819 (γ) are turned on, and the other division displays 814, 812, and 804 blink at a fixed cycle, indicating that the detector is abnormal. ing.

At this time, when an abnormality occurs in the main body of the detection device (display states shown in (3) and (4) of FIG. 20), the detection device simultaneously transmits the signal to the two-wire transmission line. Burn out and burn down the constant current signal value of the output,
Notify third parties promptly.

If the display is configured as described above,
This makes it possible to promptly notify a third party of the non-operation state of the detection device itself, so that the damage can be reduced and the restoration period can be shortened.

[0164]

Since the present invention is configured as described above, it has the following effects. As mentioned above,
According to the present invention, the liquid level (head) and the density of the fluid to be measured can be measured by one detector, so that it is small and lightweight, the number of necessary measuring instruments can be reduced, and the measuring system is simplified. , It is possible to realize a density correction type liquid level detecting device capable of performing the above.

Also, since the number of detection devices can be reduced,
The maintenance man-hour can also be reduced. Furthermore, as a detection device, installation space and construction costs for one device can be sufficient.

Further, the wiring port and the display provided in the signal processing section make it possible to easily inform the operator of the signal output of the detector and the state of the signal display.

According to the detection device of the present invention,
Even if the equipment is out of service, the operating status of the equipment is displayed on the display of the operator of the higher-level equipment, which is a third party, or the display itself. It communicates information that it needs to be maintained by itself and encourages prompt action. For this reason, it is possible to reduce the degree of damage to the production due to the malfunction of the equipment, and it is possible to shorten the restoration period.

As described above, the detection device according to the present invention has excellent environmental resistance, is very easy to use at the time of maintenance and inspection, and can also reduce the plant operation cost. Furthermore, since the equipment itself can be configured to be stable and highly reliable, the operation efficiency of the plant can be improved, and more labor can be saved.

[Brief description of the drawings]

FIG. 1 is a schematic cross section of a density correction type liquid level detection device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a high-pressure side process connection flange of the example shown in FIG. 1;

FIG. 3 is a sectional view of a pressure receiving section shown in FIG. 1;

FIG. 4 is a cross-sectional view of the sensor section shown in FIG.

5 is a plan view of the sensor unit shown in FIG.

6 is a circuit configuration diagram of the sensor unit shown in FIG.

FIG. 7 is a block diagram of the entire signal processing of FIG. 1;

FIG. 8 is a diagram showing an example of a display configuration division of the display device 33.

FIG. 9 is a schematic sectional view of a density correction type liquid level detecting device according to a second embodiment of the present invention.

FIG. 10 is a sectional view of a high-pressure side process connection flange of a density correction type liquid level detection device according to a third embodiment of the present invention.

11 is a configuration diagram of a pressure receiving unit and a signal processing unit of the device shown in FIG.

FIG. 12 is a sectional view of the sensor section shown in FIG.

FIG. 13 is a plan view of the sensor unit shown in FIG.

FIG. 14 is a detailed sectional view of a high-pressure side process connection flange shown in FIG. 11;

FIG. 15 is a plan view of the semiconductor pressure sensor shown in FIG. 11;

FIG. 16 is a circuit diagram of the sensor unit shown in FIG.

FIG. 17 is a diagram systematically showing signal processing in the third embodiment.

FIG. 18 is a sectional view of a high-pressure side process connection flange 4 of a density correction type liquid level detection device according to a fourth embodiment of the present invention.

19 is an enlarged view of the semiconductor pressure sensor body shown in FIG.

FIG. 20 is a diagram illustrating a display example of a display unit of a processing unit in each embodiment.

FIG. 21 is an explanatory diagram illustrating a configuration of an instrumentation system for liquid level measurement.

FIG. 22 is a schematic configuration diagram of a conventional liquid level detection device.

[Explanation of symbols]

'1 Sensor body 1 Sensor chip' 2 Pressure receiving part '3 Signal processing part 4 High pressure side process connection flange 5 Low pressure side process connection flange 12 Joining material 11 First fixed base 13 Second fixed base 14 Plate 15 Housing 16, 17 Hermetic terminal 19 Wiring board 21, 22 Pressure receiving part side seal diaphragm 23 Overload protection diaphragm (center diaphragm) 24 Pressure receiving part main body member 25 Metal fitting 26 Plate 27 Fixing metal fitting 29 Depressed part 31 Signal processing circuit board 32 Terminal plate 33 Display or instruction Total 34 FPC 35 Case 36 Wiring connection port 41, 42, 51 Process connection side seal diaphragm 43, 44, 52 Pressure transmitter 45, 53, 201 Filled liquid 46 Signal line '100,' 101 Sensor body 101, 102 Differential pressure sensitive Diaphragm 103, 104 Static pressure sensitive diaphragm Ram 105 Lead wire 111-114, 120-123 Differential pressure detecting resistor 115-117 Static pressure detecting resistor 119, 124 Temperature detecting resistor 131 Recessed portion 151, 152 Impedance path of first fixed base 153 O-ring or sealing material for housing Reference numeral 241: a pressure guiding passage in the pressure receiving portion 311 MPX 312 PGA 313 A / D converter 314 microcomputer 315 sensor characteristic storage element 316 V / I converter 317 D / A converter 431, 451, 452 Pressure guiding passage or communication passage 531 in the flange Process pressure inlet 1011 Protective film 1021, 1022, 1031, 1034, 1501
Pressure inlet or pressure guide passage of fixed base 1032 Cylindrical part 1200 Lead wire 1510 Housing (holding fitting) 1520 Spacer

Claims (11)

[Claims] A plurality of pressures of the fluid to be measured are taken out by a connection flange provided at a pressure outlet of a tank containing the fluid to be measured, the plurality of pressures are transmitted, and a difference between the plurality of pressures and the pressure is obtained. And a signal processing unit having a signal processing circuit for processing a signal from the sensor, which is connected to the pressure receiving unit, and the liquid level and density of the fluid to be measured in the tank are externally provided. In the density correction type liquid level detection device that transmits information such as, the pressure measurement device has two pressure transmitters, constantly contacts the fluid to be measured, and has a And a low pressure side connection flange that has a single pressure transmitter and that constantly contacts the fluid to be measured and detects the pressure on the low pressure side of the fluid to be measured in the tank. A first pressure difference between the pressure of the pressure and the low pressure side of the high pressure side,
A pressure receiving section having a differential pressure sensor for simultaneously detecting a second pressure difference between the high pressure side and the correction pressure; and a signal for processing a signal indicating a first and second pressure difference from the pressure receiving section. And a signal processing unit having a processing circuit. 2. The density correction type liquid level detecting device according to claim 1, wherein the signal processing section has an information display section for displaying information from the pressure receiving section, and the information display section includes the signal processing section. The numerical value calculated by the unit is displayed, and when the value is displayed by the signal processing circuit after being converted by a predetermined function, a mark indicating that the converted value is displayed is displayed. And when the numerical value to be displayed is another variable,
A level meter comprising a set of predetermined marks displaying a mark indicating that another variable is displayed, wherein the display of the level meter is changed according to the numerical value to be displayed. Density corrected liquid level detector. 3. The density correction type liquid level detecting device according to claim 1, wherein the two pressure transmitting members of the high pressure side connection flange are two metal diaphragms of low rigidity, and the two metal diaphragms are: A first pressure transmitting member and a third pressure transmitting member which are spaced apart from each other by a predetermined distance and are arranged at separable positions and transmit the high pressure side pressure and the correction pressure to the pressure receiving portion; The pressure transmitting body of the low-pressure side connection flange portion is a low-rigidity metallic diaphragm, and transmits a low-pressure side pressure from the low-pressure side pressure flange pressure transmitting body to the pressure receiving portion. A density correction type liquid level detecting device having two pressure transmitting bodies. 4. A density correction type liquid level detecting device according to claim 1, wherein said pressure receiving portion has a first diaphragm to which said high pressure side pressure is applied, and said first pressure receiving portion is filled with a first detection fluid. A first pressure receiving chamber, a second diaphragm to which the low pressure side pressure is applied, a second pressure receiving chamber in which a second detection fluid is sealed, and pressure from the first pressure receiving chamber is transmitted. A first isolation chamber, a second isolation chamber to which pressure from the second pressure receiving chamber is transmitted, and a first isolation chamber disposed between the first diaphragm and the second diaphragm. A third diaphragm for isolating the first and second isolation chambers from each other; a third communication passage for transmitting pressure from the first isolation chamber to the differential pressure sensor; A fourth communication passage for transmitting the pressure difference to the differential pressure sensor; And a fifth communication path for transmitting a force to said differential pressure sensor, density correction form liquid level detecting device, characterized in that it comprises. 5. A density-corrected liquid level detecting device according to claim 1, wherein said differential pressure sensor includes a first pressure-sensitive diaphragm for detecting a pressure difference between said high pressure side pressure and said low pressure side pressure. A first resistor group of a semiconductor type formed on the first pressure-sensitive diaphragm and responsive to a pressure difference between the high-pressure side pressure and the low-pressure side pressure; A second pressure-sensitive diaphragm for detecting a pressure difference from the pressure; and a second semiconductor-type diaphragm formed on the second pressure-sensitive diaphragm and responsive to a pressure difference between the high-pressure side pressure and the correction pressure. A temperature-sensitive resistor which is sensitive to temperature; an inlet for transmitting the high pressure side pressure to one surface side of the first pressure sensitive diaphragm; and a low pressure side pressure which is transmitted to the first pressure sensitive diaphragm. With the inlet that transmits to the other side of the pressure-sensitive diaphragm A first fixed base having an introduction port, and an introduction that is airtightly fixed to the first fixed base and communicates with these introduction ports at positions corresponding to the two pressure introduction ports of the first fixed base. A second fixed base having a port, a first pressure guide path communicating with the pressure inlet of the second fixed base, and introducing the pressure on the high pressure side to the pressure inlet of the second fixed base. A second pressure passage communicating with the pressure inlet of the second fixed base and introducing the correction pressure into the pressure inlet of the second fixed base; and the first and second resistance groups. A metal fitting having an airtight terminal for extracting an electric signal from the liquid crystal device. 6. A plurality of pressures of the fluid to be measured are taken out by a connecting flange provided at a pressure outlet of a tank containing the fluid to be measured, the plurality of pressures are transmitted, and a difference between the plurality of pressures and the pressure is obtained. And a signal processing unit having a signal processing circuit for processing a signal from the sensor, which is connected to the pressure receiving unit, and the liquid level and density of the fluid to be measured in the tank are externally provided. In the density correction type liquid level detection device for transmitting information such as, a pressure transmitter which constantly contacts the fluid to be measured and transmits the pressure on the high pressure side of the fluid to be measured, And a high pressure side connection flange having a flange side sensor for detecting the pressure difference between the pressure on the high pressure side of the fluid to be measured in the tank and the correction pressure and the temperature of the fluid to be measured, One pressure A low pressure side connection flange portion which has a transmitting body, constantly contacts the fluid to be measured, and detects the pressure on the low pressure side of the fluid to be measured in the tank, and a second connection between the pressure on the high pressure side and the pressure on the low pressure side. A pressure receiving unit having a differential pressure sensor for detecting a pressure difference of 1; a first pressure difference from the pressure receiving unit; a differential pressure between the high-pressure side pressure detected by the flange-side sensor and a correction pressure; A signal processing unit having a signal processing circuit for processing a signal indicating the temperature of the fluid to be measured. 7. The density correction type liquid level detecting device according to claim 6, wherein the signal processing unit has an information display unit for displaying information from the differential pressure sensor and the flange side sensor. Density corrected liquid level detector. 8. The density correction type liquid level detecting device according to claim 6, wherein the two pressure transmitting members of the high pressure side connection flange have low rigid metal diaphragms, and the two metal diaphragms are mutually fixed. The flange-side sensor is disposed at a position that is separated from the metal-diaphragm, and the flange-side sensor is disposed on an opposite side of one of the two metal diaphragms to be measured. A density correction type liquid level detecting device, wherein the pressure transmitting body of the side connection flange portion has a low-rigidity metallic diaphragm. 9. A density correction type liquid level detecting device according to claim 6, wherein said differential pressure sensor includes a first pressure sensitive diaphragm for detecting a pressure difference between said high pressure side pressure and said low pressure side pressure. A first group of semiconductor-type resistors formed on the first pressure-sensitive diaphragm and responsive to a pressure difference between the high-pressure side pressure and the low-pressure side pressure; and a temperature-sensitive semiconductor type temperature group. A resistor, an inlet for transmitting the pressure on the high pressure side to one surface of the first pressure-sensitive diaphragm, and an inlet for transmitting the pressure on the low pressure side to the other surface of the first pressure-sensitive diaphragm. A first fixed base having two pressure inlets; and a first fixed base that is air-tightly fixed to the first fixed base, and these inlets are provided at positions corresponding to the two pressure inlets of the first fixed base. A second fixed base having an inlet communicating with the second fixed base; A first pressure guiding path communicating with the pressure inlet of the fixed base and introducing the pressure on the high pressure side to the pressure inlet of the second fixed base; and a pressure introducing port of the second fixed base. A second pressure guiding path for introducing the pressure on the low pressure side to the pressure inlet of the second fixed base, and a metal fitting having an airtight terminal for extracting an electric signal from the first resistor group. A density correction type liquid level detection device, characterized in that: 10. The density correction type liquid level detecting device according to claim 6, wherein the flange side sensor of the high pressure side connection flange portion contacts the fluid to be measured via a protective film. Liquid level detector. 11. A plurality of pressures of the fluid to be measured are taken out by a connection flange provided at a pressure outlet of a tank containing the fluid to be measured, the plurality of pressures are transmitted, and a difference between the plurality of pressures and the pressure is obtained. And a signal processing unit having a signal processing circuit for processing a signal from the sensor, which is connected to the pressure receiving unit, and the liquid level and density of the fluid to be measured in the tank are externally provided. In the density correction type liquid level detection device that transmits information such as, the pressure measurement device has two pressure transmitters, constantly contacts the fluid to be measured, and has a And a low pressure side connection flange that has a single pressure transmitting body and that constantly contacts the fluid to be measured and detects the pressure on the low pressure side of the fluid to be measured in the tank. When a first pressure difference between the pressure of the pressure and the low pressure side of the high pressure side,
A pressure receiving unit having a differential pressure sensor for simultaneously detecting a second pressure difference between the high-pressure side pressure and the correction pressure; and wherein the first pressure difference and the second pressure difference are in a steady state due to an external factor. And a signal processing unit having a signal processing circuit that determines that a change has occurred from the data and displays the situation.