JP2822816B2 - Semiconductor sensor, transmitter and process status display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential pressure / pressure transmitter for detecting a flow rate, a pressure, a liquid level, a density, etc. in various plants and the like, and a function for discriminating damage, abnormality or stability of the equipment itself. The present invention relates to a differential pressure and pressure transmitter provided with:

[0002]

2. Description of the Related Art Differential pressure and pressure transmitters are field sensors widely used in various plants to measure various process variables. Generally, a differential pressure and pressure transmitter receives a pressure of a fluid to be measured in a process by a seal diaphragm, and receives a pressure-electric conversion element as a pressure-electric conversion element through an incompressible sealing liquid sealed inside. The pressure is transmitted to a sensor or the like and converted into an electric signal. Various improvements have been made in these pressure transmitters, so that their static characteristics and quality are improved, and a configuration with excellent stability can be achieved. On the other hand, JP-A-55-95373
As disclosed in the issue, even if an abnormality occurs in the pressure sensor, by providing a means for detecting the abnormality,
Improvements have also been proposed that reliably and promptly notify the abnormality of the pressure sensor and further improve the reliability of the device.

The seal diaphragm, which is one of the components of the differential pressure and pressure transmitter and the interface with the process fluid, is the most important component in the construction of the equipment and is the component most susceptible to damage. It is.
For this reason, if any abnormality or deterioration occurs in the seal diaphragm, the static characteristics of the device change and the measurement accuracy cannot be maintained, and if the seal diaphragm is broken, the process fluid is As a result, the equipment malfunctions and the plant cannot be controlled. In addition, if the equipment is damaged or abnormal, maintenance work such as investigation of the cause or replacement is required, and the plant cannot be operated efficiently. Conventionally, the damage or abnormality of the equipment due to the damage or abnormality of the sealing diaphragm, or the aging of the equipment has been an important control item of the equipment. No attempt has been made to detect such damages, abnormalities or changes over time, and it has been difficult to detect them at an early stage.
For this reason, various troubles have occurred in the operation of the plant. Furthermore, based on the experience of plant operation, measures such as preparing equipment for maintenance separately in advance have been implemented so as not to hinder plant operation. For this reason, management of maintenance equipment and maintenance costs are also required, and an efficient and labor-saving plant could not be constructed.

[0004]

In the structure of the conventional pressure transmitter, there is no means for detecting damage or abnormality of the components of the device itself and no system for informing the higher-level control device of the signal. The long-term quality and stability of the equipment itself cannot be guaranteed.

2) Since it is not possible to notify a higher-level control device of the damage or abnormality of the equipment itself, labor saving of equipment maintenance cannot be achieved, and improvement, maintenance and labor saving of the quality of plant operation cannot be achieved.

There was a problem that

Further, in the conventional differential pressure / pressure transmitter configuration, there is no means for detecting a change with time of the equipment itself and a system for notifying the signal to a higher-level control device. 1) Quality of plant operation I can't measure the improvement.

2) It is not possible to save labor for maintenance of equipment in plant operation, nor to save labor for plant operation.

There was a problem that

A first object of the present invention is to provide a configuration method capable of guaranteeing long-term quality and stability of a device itself by providing means for detecting damage or abnormality of components of the device itself. Another object of the present invention is to provide a system that can improve and maintain the quality of plant operation and can save labor by constructing a system that informs a host controller of the signal and provides the signal.

Another object of the present invention is to provide a system for measuring the qualitative improvement of plant operation and providing a signal to a higher-level control device by providing means for detecting the change with time of the equipment itself. It is another object of the present invention to provide a system that can save labor of equipment maintenance and plant operation in plant operation.

[0012]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
The feature of the present invention is that it comes into contact with a fluid and reduces the influence of pressure from the fluid.
A semiconductor sensor that receives the fluid and detects the pressure of the fluid.
And physical property detection means for detecting a change in physical properties of the fluid.
That is.

Still further, a seal diaphragm for receiving a fluid pressure from the process fluid, a sealed fluid for transmitting the pressure received by the seal diaphragm to pressure detecting means, and the sealed fluid being filled in contact with the seal diaphragm the transmission equipped with a pressure-receiving chamber, said pressure detecting means, Ru der further comprising a physical sensor for detecting the physical properties of the encapsulating fluid.

[0014]

[Operation] Assume that the diaphragm in contact with the process fluid of the differential pressure and pressure transmitter is damaged by some factor, and a small crack or void is generated in the diaphragm. At this time, the process fluid penetrates or diffuses into the sealed liquid through the minute cracks or voids, so that the physical properties of the sealed liquid change. As the physical property change, for example, a change in the dielectric constant of the sealing liquid, an ion concentration, a pH of the sealing liquid, or a humidity rate or a moisture rate of the sealing liquid changes. By detecting at least one of these physical property changes by the sensing means, it is possible to quickly and accurately determine that the device is in an abnormal state.

Further, the seal diaphragm in contact with the process fluid of the pressure transmitter has its equilibrium position (zero point position of the equipment) constant during normal operation, and its operating position (span position) during pressure measurement. Position) is also constant. For this reason, the operation of the seal diaphragm is detected by the sensing means, the signals are periodically stored in a storage element provided in the signal processing means, and the difference from predetermined reference data is calculated in the signal processing means. Computation is performed by a device (microprocessor). As a result, if any cause, for example, an abnormality occurs in the flow path of the sealed liquid or the seal diaphragm is deteriorated, an abnormality occurs in the operation of the seal diaphragm, which causes a difference from the reference data. Therefore, even during a normal operation, it is possible to quickly and accurately determine that the pressure transmitter has changed with time.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

The pressure transmitter used for the process control includes a pressure transmitter for detecting the pressure of the process fluid, a pressure transmitter for detecting the absolute pressure, and a differential pressure transmitter for detecting the differential pressure between the process fluids. There are two types of differential pressure transmitters, but in the following description of the embodiment, the description will be made focusing on the differential pressure transmitter most used for process control.

FIG. 1 is a sectional view showing the structure of a differential pressure transmitter according to the present invention. Inside the differential pressure transmitter, a single-chip composite sensor 110 composed of a differential pressure sensor, a static pressure sensor and a temperature sensor is separated from the high pressure side and the low pressure side, and the composite sensor 110 is protected from excessive differential pressure. Diaphragm 112 and a high pressure side and a low pressure side liquid contacting diaphragms 114a and 114b which are in contact with the process fluid and receive pressure are accommodated in a main body member 118 of the differential pressure transmitter. The pressure applied to each of the liquid contacting diaphragms 114a and 114b is transmitted to the composite sensor 110 via a sealed liquid 120 such as silicon oil which is an incompressible fluid having a high insulating property inside, and the pressure is an electric signal. Is converted to In this differential pressure transmitter, the high-pressure side pressure receiving chamber 126a and the low-pressure side pressure receiving chamber 126b respectively have physical property change detection sensors 150a, 15a for detecting changes in the physical properties of the sealed liquid on the low pressure side and the high pressure side.
0b, and these physical property change detection sensors 1
The physical property values detected by 50a and 150b are also converted into electric signals.

Signals detected by the composite sensor 110, the high-pressure side physical property change detection sensor 150a, and the low-pressure side physical property change detection sensor 150b are transmitted to the signal processing circuit 122 via hermetic seal pins 130, 131, and 132. . In the signal processing circuit 122, an amplifier for amplifying the signal, a microprocessor 130 for performing a correction operation of the signal, a storage element for storing the operation result, and a detection set value of the differential pressure transmitter can be changed via a communication path. A communication signal processing circuit for performing bidirectional communication with a higher-level instrument is provided.

FIG. 2 is a main enlarged sectional view of FIG. 1 showing a portion characterizing the structure of the present invention. When a change in the physical properties of the sealing liquid 120 occurs, the change in the physical properties is enclosed. FIG. 9 shows an embodiment in which sensing is performed by a change in the dielectric constant of a liquid, and the physical property change detection sensor 15 is used for sensing.
Capacitors using a sealing liquid as a dielectric are formed as 0a and 150b to serve as sensing means.

A conductor electrode 330 is formed on the liquid contacting diaphragms 114a and 114b on the side in contact with the filling liquid 120 via an insulating film 320. On the other hand, the pressure receiving member 1
18 has another electrode 3 facing the electrode 330;
32 are formed. These electrodes are arranged in the high pressure side pressure receiving chamber 126a and the low pressure side pressure receiving chamber 126b of the pressure receiving part, respectively, and can sense the high pressure side and the low pressure side, respectively.

A parallel plate capacitor is formed by these electrodes, and its dielectric constant is equal to the relative dielectric constant of the filling liquid 120. Further, these electrodes are connected to the signal processing circuit 122 via insulating terminals 131 and 132 having airtightness provided on the pressure receiving member 118. In this embodiment, each of the parallel plate capacitors is provided close to a fixing portion of the liquid contact diaphragm.
The reason for this is that almost no shape displacement occurs near the fixed portion of the liquid-contacting diaphragm, so that the capacity change occurs only when the relative permittivity of the sealed liquid changes. If the liquid contacting diaphragms 114a and 114b that are in contact with the process fluid of the differential pressure transmitter are damaged by some factor (for example, due to corrosion or the like) and a minute crack or a gap is generated in the liquid contacting diaphragm, the minute crack or The process fluid penetrates or diffuses through the gap into the sealed liquid 120 in the pressure receiving chamber. For this reason,
Since the physical properties of the filling liquid change, the relative permittivity also starts to change. At this time, the capacitance between the parallel plate capacitors also starts to change at the same time.

This capacitance change is caused by the insulation terminals 131 and 13
2, the signal is sent to the signal processing circuit 122 and converted into an electric signal. Therefore, according to such a configuration, it is found that the liquid contact diaphragm, which is one of the components of the differential pressure transmitter, has been damaged or abnormal, and by transmitting the signal, the differential pressure transmitter itself has the same function. Damage or abnormality can be found accurately and quickly, and it is also possible to find it from a higher-level instrument that controls the differential pressure transmitter via communication means.

In the above embodiment, the example in which the physical property detection sensor is provided in the pressure receiving chamber of the differential pressure transmitter is shown. In the following embodiment, an example in which the physical property detection sensor is provided in a place other than the pressure receiving chamber is shown.

The differential pressure transmitter shown in FIG.
In this embodiment, a and 150b are provided in the high-pressure side measurement chamber 386a and the low-pressure side isolation chamber 376b, respectively, and the state of the seal diaphragm can be detected even in such places. Because the seal diaphragm 114a,
When the 114b is damaged, the process fluid enters from the damaged portion and mixes with the sealed liquids 320 and 321 to change the physical properties of those sealed liquids. However, the effect is not limited to the pressure receiving chamber and the sealed liquid is filled. This is because the effect propagates in a space. Therefore, the state of the seal diaphragm can be detected even if the physical property detection sensor is disposed in the isolation chamber and the measurement chamber which are separated from the pressure receiving chamber as in the embodiment of the present drawing. Even if a physical property detection sensor is mounted on 110, detection is possible.

In the arrangement example of the physical property detection sensors shown in FIGS. 3 and 4, an example is shown in which the capacitance detection sensor shown in FIG. 2 is provided.

FIG. 4 is an enlarged view of a main part of FIG. 3. In FIG. 4, a conductive electrode 43 is provided in the low-pressure side isolation chamber 376b.
A capacitance detection sensor is formed by 2b and 430b, and a capacitance detection sensor is formed in the high pressure side measurement chamber 386a by conductive electrodes 432a and 430a. As a result, even if the seal diaphragms 114a and 114b on the low pressure and high pressure sides are broken, the state can be detected. In this embodiment, the composite sensor 110 and the airtight terminal 33 are further provided.
Since 0,331 can be shared, there is an effect that the wiring structure can be simplified.

FIG. 5 shows an example in which the physical property detection sensor is mounted on a composite sensor.

In the figure, a physical property detection sensor 150 is mounted on a composite sensor 110 via an insulating film 520, and its output is transmitted from a bonding wire 580 through wiring on the composite sensor, and further to a bonding wire 581.
Through the airtight terminal 531 to the outside.
In this embodiment, when the composite sensor is incorporated into the pressure receiving member, by mounting the physical property detection sensor, the output can be taken out from the common airtight terminal with the composite sensor, so that the processing of the main body member of the differential pressure transmitter can be reduced. I have to. Further, in the present embodiment, the example in which the physical property detection sensor 150 is mounted on the composite sensor 110 has been described.
It is also possible to form the physical property detection sensor on the same substrate in the step of making 0, and to take out the output from the hermetic terminal 531 from which the output of the composite sensor is taken out. In this embodiment, the physical property detection sensor is arranged only in the high pressure side measurement chamber 386a.
By providing a physical property detection sensor in the portion of the composite sensor facing the low pressure side measurement chamber 386b, the state of the low pressure side seal diaphragm can also be detected.

In the above embodiment, when a change in physical properties of the sealed liquid occurs, the change is sensed by a change in capacitance between the plate capacitors.
Other than this method, there is a method of sensing the physical property change, such as a method of sensing an ion concentration, a concentration of a pH, or a humidity rate or a moisture rate of a sealed liquid. Here is an example.

FIG. 6 shows the structure of the sensors of the hygrometer and the moisture meter.

The humidity / moisture meter has lead wires 6 on a substrate 618.
80, 681 are formed, and a moisture-sensitive or water-sensitive film 6 is formed thereon.
10, and a protective film 620 is further formed thereon. When the seal diaphragm is broken, the process fluid mixes with the filling liquid, and the humidity and moisture content of the filling liquid change. This change is detected by the humidity or water sensitive film of the humidity / moisture sensor, and the electrical resistance changes. The change is detected from the lead wires 680 and 681. By using such a sensor of a hygrometer or a moisture meter instead of the flat plate capacitor shown in FIGS. 2 and 4, the output value when the seal diaphragm is not damaged at first as shown in the graph of FIG. By detecting the change from R ₁ , α ₁ ) to the output value (R ₂ , α ₂ ) at the time of the breakage, it is possible to detect the state of the seal diaphragm.

FIG. 8 shows the configuration of the ion concentration sensor and the pH sensor. An element in which impurities are diffused is formed over a semiconductor substrate 818, and SiO ₂ insulation is formed on the surface of the element. Further, specific ions such as K
(Monovalent cations), Na (monovalent cations), H (monovalent cations), Ca (divalent cations), a thin film 810 that reacts with Cl ^{−, and the} like. / A
An electrode of gCl or the like is formed to form a sensor. If such a sensor is provided at a place in contact with the sealed liquid of the differential pressure transmitter, if the seal diaphragm is damaged, ions in the measurement fluid enter, and the ion concentration of the sealed liquid changes. Therefore, by detecting this change, the state of the seal diaphragm can be detected.

As described above, one or more sensors capable of detecting the physical properties of the sealed liquid are provided in the portion of the differential pressure transmitter where the sealed liquid is stored, and the output of the sensor is monitored to prevent the seal diaphragm from being damaged or damaged. Abnormality can be detected.

FIG. 9 shows a sensor for detecting a temporal change of the differential pressure transmitter.

The electrode 33 is provided between the seal diaphragms 114a and 114b and the main body member 118 via an insulating film 320.
0, 332 are fixed to form a parallel capacitor, and a detection signal from this capacitor is taken out from the insulating terminals 131, 132 to the outside. Using the filling liquid 120 as a dielectric, the capacitance C _x of the parallel capacitor is expressed by the following equation.

[0037]

(Equation 1)

[0038] With this end sealing diaphragm to operate under pressure P, the change of the capacitance C _x of the parallel capacitor, as long as the wetted diaphragm is not damaged, since the change in the dielectric constant of the fill fluid can not occur, The change in the volume is changed only by the operation of the liquid contact diaphragm.

At this time, the seal diaphragm 1 with respect to the pressure
14a movements, since the primary relation, the change in capacitance C _x of the capacitor is a capacitance change which is inversely proportional to the pressure P.
Therefore, the change in the change and the capacitance C _x of the pressure P is related.

The other pressure receiving chamber is provided in the other
The capacitor changes in a similar manner, but in the case of a differential pressure transmitter it operates in reverse. Thus, the change in capacitance of each capacitor can be related to pressure and differential pressure individually or in the form of their sum or difference. Further, the relationship is similarly established even when the temperature changes.

FIG. 10 is a differential pressure transmitter to the pressure P _H in each of the high-pressure receiving chamber to the normal operation, the voltage ΔP when adding P _L, the high pressure side, the low-pressure side pressure receiving chamber It is a graph showing the relationship of the capacity of the provided parallel capacitor, from this graph the relationship between the pressure applied to each pressure receiving chamber and the output relationship of each capacitor, and the respective differential pressures of the pressure applied to each pressure receiving chamber. It can be seen that the linear relationship holds for the output relationship of the capacitors. From this, the equilibrium position (the zero point position of the differential pressure transmitter) of the liquid contacting diaphragm which is in contact with the process fluid of the differential pressure transmitter is constant during its normal operation, and is also measured at the time of measuring the differential pressure. It can be seen that the operating position (span position of the differential pressure transmitter) is also related by a predetermined value.

Therefore, these data are collected at the same time as the data is created to determine the characteristics of the differential pressure transmitter at the time of manufacture, and the data is collected by the differential pressure sensor, the static pressure sensor,
Using pressure and temperature as parameters in addition to temperature sensor, etc.
It is stored in the storage unit of the differential pressure transmitter as a characteristic equation of the capacitance change or contact data.

By providing these reference data in the differential pressure transmitter, the position of the seal diaphragm is detected by the parallel plate capacitors provided in each of the pressure receiving chambers, and these signals are processed by the signal processing means of the differential pressure transmitter. The signal is periodically stored in a storage unit provided therein, and from this signal value, a microprocessor provided in the signal processing means performs an operation to obtain the pressure applied to each differential pressure chamber and the differential pressure. At this time, if the position of the seal diaphragm when a predetermined pressure is applied changes for some reason, the above-mentioned position signal and the result of the comparison operation differ from the predetermined reference data and the operation result data. For this reason, even during normal operation, any factor of the differential pressure transmitter, for example, deterioration due to aging of the seal diaphragm, or drift such as when an abnormality occurs in the flow path of the sealed liquid, is caused by one component. It can be detected by a change in the capacitance of a capacitor of a seal diaphragm, and the signal can be transmitted. Therefore,
The change with time of the differential pressure transmitter itself can be determined quickly and with high accuracy.

As described above, the embodiments of the present invention have been described mainly with respect to the differential pressure transmitter, but it is apparent that these configurations can be applied to a pressure transmitter for detecting the absolute pressure.

That is, unlike the differential pressure transmitter, the pressure transmitter for detecting the absolute pressure has only one pressure receiving chamber, an isolation chamber, a measuring chamber, and a seal diaphragm in contact with the process fluid. This can be dealt with by providing a physical property detection sensor and an operation detection sensor for the seal diaphragm in the portion filled with the filled liquid and the seal diaphragm, respectively, and providing signal processing means for processing an output signal from this sensor.

FIG. 11 shows a signal processing circuit 122 of the differential pressure transmitter.
FIG. The composite sensor 110 outputs a change in gauge resistance due to the differential pressure, static pressure, and temperature as an electric signal,
A multiplexer (MPX) 231 selectively takes in the data. At the same time, the output of the electrical signal from at least one or more of the above-mentioned sensing means 150 provided in the pressure receiving chamber and other portions in contact with the sealed liquid is also supplied to the multiplexer 231.
It is taken in. In the embodiment of the aforementioned sensing means,
Since the method for detecting a change in the dielectric constant, the water content, and other physical properties of the sealed liquid is exemplified, a circuit for converting the output from the detecting means into a frequency may be provided to make a circuit configuration easy to perform digital processing. .

Various signals taken into the multiplexer 231 are supplied to a programmable gain amplifier (PGA) 23.
3 and then converted to a digital signal by an A / D converter 234, and then converted to a microprocessor (MPU) 130.
Sent to. The memory 239 (EPROM) has a differential pressure,
The characteristics of the static pressure and temperature sensors (the characteristics of the pressure and temperature sensors in the case of a pressure transmitter) are stored in advance, and the microprocessor 130 performs a correction operation using these data to achieve high precision. Differential pressure signal value and static pressure,
Calculate the temperature signal value. This operation result is converted into a normal analog signal via a D / A converter 237 and a V / I converter 238, and is sent to a computer 740 as a higher-level control device as a signal of 4 to 20 mA DC. It has become.

On the other hand, a signal from at least one or more sensing means provided in the pressure receiving chamber is stored in a memory (EEPROM) 239, which is another storage element, periodically or as needed according to a command from the microprocessor 130. And updated in some cases. The microprocessor 130 performs a comparison operation on a basis of the data stored in the memory (EEPROM) 239 periodically or as needed with reference data of these differential pressure transmitters. If these reference data and the comparison result do not differ from the previous result, the normal task as the differential pressure transmitter (the differential pressure signal value, the static pressure, and the temperature signal value are calculated, and the calculation result is D / D The signal is converted into a normal analog signal via the A converter 237 and the V / I converter 238, and the signal is converted into a signal of 4 to 20 mA DC and transmitted to the computer 740 as a higher-level control device.) .

FIG. 12 is an example of a flow rate and pressure measurement system using the differential pressure and pressure transmitter of the present invention. The differential pressure generated at both ends of the orifice 710 for determining the flow rate provided in the middle of the pipeline 700 such as a chemical plant is measured by the differential pressure transmitter 720, while the pressure of the pipeline is measured by the pressure transmitter 730, The flow rate and pressure in the pipeline are transmitted to the host computer 740 as a differential pressure (flow rate) and pressure signal. In accordance with the measured flow rate and pressure signals, the control computer 740 controls an actuator such as a pump for supplying a fluid into the pipeline to adjust the flow rate and the pressure so that the appropriate flow rate and pressure can be supplied. The communicator 750 is connected to the differential pressure and pressure transmitters 720 and 730.
Digital bidirectional communication is performed at an arbitrary position between the transmission lines between the two-wire transmission line that connects the control computer 740 and the upper control computer 740 to operate the differential pressure and pressure transmitters, It is a portable input / output device for instructing a change, setting, update, or the like for changing or setting the amount or for maintenance management.

In the present system, the differential pressure, which is in contact with the non-measuring fluid flowing in the pipeline of the pressure transmitter, and the damage or abnormality of the diaphragm which is a component of the pressure transmitter can be sensed. , It can be determined that the pressure transmitter itself is in an abnormal state. In normal operation where the diaphragm is not damaged, its equilibrium position (zero point position of the device) is constant, and its pressure measurement and its operation position (span position) are set to predetermined values. ing. Therefore, if the positions can be sensed, it is possible to determine that the differential pressure and pressure transmitter itself has changed with time by processing and calculating the data of those signals by a microprocessor.

In the conventional system, even if an error occurs in the measured value of the differential pressure, the pressure transmitter, or the like due to some factor, and it is possible to operate even if a part of the device is damaged. Nevertheless, these situations are based on preventive maintenance through regular inspections of the plant, and rely on the experience and intuition of daily maintenance and operation personnel to detect abnormal conditions and changes over time with extremely high precision. I couldn't do that. Therefore, even if an abnormal state or a change over time occurs in measuring equipment such as a differential pressure or a pressure transmitter, the malfunction can be identified only after a plant malfunction has occurred or after a predetermined response period has elapsed. It was not possible to achieve the expected improvement in the operation rate, quality improvement and maintenance, and labor saving.

FIG. 13 shows an example of the storage state of the data stored in the memory (EEPROM) 239. In FIG. 13, a broken line A shows a change state of a signal from a pressure / differential pressure transmitter provided with a parallel plate capacitor as a characteristic detection sensor. Since the value is almost constant until time t3, it can be determined that the transmitter is operating normally. However, at time t4, the value changes suddenly. This is because, due to the hardware configuration, the relative permittivity of the sealed liquid inside has changed, so that the liquid contacting diaphragm in contact with the process fluid of the differential pressure transmitter is damaged by some factor (for example, due to corrosion or the like), and It can be determined that minute cracks or voids have occurred in the liquid diaphragm.

At this time, the microprocessor 130
Executes an abnormal task, superimposes an abnormal signal on an analog signal via a D / A converter 237 and a V / I converter 278, and sends the result of the operation to a computer 740 as a higher-level control device. Notify the request for transmitter replacement and repair. FIG. 14 shows an example of the transmitted signal. Normal signal values are shown until time t3, but at time t4, the abnormal signal is superimposed on the analog signal. The abnormal signal has a predetermined recognition code, and has a code system capable of discriminating at least a device damage due to an external factor and a factor due to a temporal change of the device. The output signal is transmitted as a value obtained by holding the output signal accompanying the recognition code or a value obtained by swinging the output signal to the plus side or the minus side. This abnormality information is stored again in the memory (EEPROM) 239 and stored until the device is disposed.

As a result, the abnormal state of the differential pressure transmitter itself can be promptly and accurately notified to the plant maintenance and operation personnel as necessary. It is easy and labor-saving, and the quality can be maintained without impairing the operation rate of the plant.

The signal processing circuit 122 further includes a digital I / O having a bidirectional communication signal processing function for enabling bidirectional communication with the input / output device 750.
An O circuit 240 is provided. For this reason, the abnormal state can be checked at any time during the on-site patrol for daily inspection of the plant, as well as the computer 740 as a higher-level control device, so that the plant can be operated more efficiently.

Although a parallel plate capacitor has been described as an example of a sensor for detecting an abnormality, a pressure / differential pressure transmitter provided with a sensor for measuring ion concentration, pH, humidity and moisture content may be used as a sensor. The signal processing as described above can be applied.

As a sensor for detecting a change with time, a parallel plate capacitor is provided near the center of the seal diaphragm, and an equilibrium position (a zero point position of the differential pressure transmitter) and an operation position (a differential pressure transmitter) are determined based on the capacitance change. Is set as a predetermined value, and the data is stored in the memory (EEPROM).
The processing operation of the differential pressure and the abnormal signal of the pressure transmitter stored in the reference data 239 as the reference data will be described below.

These differential pressure and pressure transmitters detect the position of the seal diaphragm by the parallel plate capacitors provided in each of the pressure receiving chambers, and compare and calculate the signal data and the reference data by the microprocessor 130. . FIG. 15 shows an example of a storage state of data stored in the memory (EEPROM) 239. In FIG. 15, the broken line Ba
Shows the change state of the storage state of the zero point position of the differential pressure transmitter, and the broken line Bb shows the change state of the storage state of the span position of the differential pressure transmitter of the differential pressure transmitter. Since the value is almost constant until time t3, it can be determined that the transmitter is operating normally. However, at time t
The value has a slight gradient between 3 and time t4 (θz,
θs), and tends to increase or decrease after time t4. Due to the hardware configuration, it can be determined that drift has occurred in the device due to aging due to some factor in the differential pressure transmitter, and the amount thereof has exceeded an allowable value.

At this time, the microprocessor 130
Executes an abnormal task (this task is an example) as shown in FIG.
An abnormal signal is superimposed on an analog signal via the V / I converter 37 and the V / I converter 238 and sent to a computer 740 as a higher-level control device to notify the necessity of replacement or maintenance of the transmitter. FIG. 17 shows an example of the transmitted signal. Normal signal values are shown until time t3, but at time t4, an abnormal signal 762 is superimposed on the analog signal. This abnormal signal has a code capable of recognizing a change with time, and the signal to be transmitted is output as a value obtained by holding the output signal accompanying the recognition code or a value which is swung to the plus side or the minus side. Transmitting a signal. This abnormality information is stored again in the memory (EEPROM) 239 and stored until the device is disposed.

As a result, the time-dependent change of the differential pressure transmitter itself can be notified to the plant maintenance and operation personnel quickly and with high accuracy, if necessary. It is easy and labor-saving, and the quality can be maintained without impairing the operation rate of the plant. Further, as described above, the input / output device 750 can check at any time during the on-site patrol for daily inspection of the plant, so that the plant can be operated more efficiently.

As described above, in the detection method according to this embodiment, the parallel plate capacitor is installed near the center of the seal diaphragm, and the change in the capacitance causes the differential pressure, the zero point position of the pressure transmitter and the differential pressure, the span of the pressure transmitter. The position is set in a given species,
Although the master data and the measured data are compared or calculated to determine the change over time of the device, the method described below does not change the effect. That is, as master data, a signal from the differential pressure or static pressure sensor of the composite sensor and a signal from the parallel plate capacitor are compared with respect to a zero point position and a span position. In this method, the allowable value is set, the value is used as reference data, and comparison or calculation is performed. (In FIG. 11, this master data is mapped and stored in the EPROM 236.) In this case, since the data of the differential pressure or static pressure sensor has already been created, this is a more efficient method. I can say. Further, as a method other than detecting their positions by a change in capacitance, a minute rod is provided in the liquid-contacting diaphragm, and an insertion hole having an inductance is provided in the pressure-receiving chamber of the pressure-receiving portion in correspondence with the rod. . Since the inductance changes due to the operation of the seal diaphragm, it serves as a sensor for detecting the position.

In the above-described embodiment of the present invention, the microcomputer 130 which accommodates the signal from the physical property detection sensor in the storage device accommodated in the differential pressure / pressure transmitter and further accommodates the signal in the signal processing means. Although the abnormality determination is performed, the abnormality determination can be performed centrally by the control computer.

FIG. 18 shows a system in which the control computer 740 performs an abnormality judgment in a centralized manner. Output signals from the physical property detection sensors of the differential pressure transmitter 720 and the pressure transmitter 730 are transmitted to the control computer 740 via the transmission line 741 as needed or at a predetermined timing.
At this time, control computer 7 for detecting data from the sensor
As a transmission method to 40, the detection data is 4 to 20 mA.
A digital signal can be transmitted by superimposing a digital signal on a DC current of 4 to 20 mA or by converting it into a digital signal only. By collecting these sensor detection data, the control computer 740 can monitor the sensor output itself of each differential pressure and pressure transmitter. Thus, for example, even if the differential pressure / pressure transmitter does not generate an abnormal signal, the control computer can automatically issue a warning 771 to a plant supervisor.

Also, as described above, the control computer 740
The centralized management of the state of the sensor by the operator enables the plant monitor to control the control computer 7 as shown in FIG.
It becomes possible to directly read the sensor information of the differential pressure and pressure transmitters on the information display screen 40.

Although the embodiment of the present invention has been described centering on a differential pressure transmitter, it goes without saying that the present invention can also be applied to a pressure transmitter. That is, by providing a physical property change detection sensor at a portion in contact with the sealed liquid that transmits the process fluid pressure to the pressure sensor means, it is possible to detect breakage of the seal diaphragm, and the position and operation of the seal diaphragm of the pressure transmitter. It is possible to detect a change with the passage of time by providing a sensor for detecting the change over time.

[0066]

As described above in detail, according to the pressure transmitter of the present invention, it is possible to detect abnormalities and changes over time of the pressure transmitter itself. Therefore, 1) the long-term quality and stability of the equipment itself can be guaranteed.

2) It is possible to save labor for equipment maintenance, and to improve and maintain the quality of plant operation and to save labor.

3) The quality of plant operation can be improved.

4) Since a preventive maintenance system for plant equipment can be established, a highly reliable instrumentation system can be constructed.

The effect is as follows.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a differential pressure transmitter according to an embodiment of the present invention.

FIG. 2 is an example provided with a dielectric constant sensor in the embodiment of FIG.

FIG. 3 is an overall configuration diagram of another embodiment of the differential pressure transmitter according to the present invention.

FIG. 4 is an example in which a dielectric constant sensor is provided in the embodiment of FIG. 3;

FIG. 5 shows another embodiment of the differential pressure transmitter according to the present invention.

FIG. 6 shows another type of sensor used in the transmitter of the present invention.

FIG. 7 is an explanatory diagram of the operation of the sensor of FIG. 6;

FIG. 8 shows another type of sensor used in the transmitter of the present invention.

FIG. 9 shows another embodiment of the transmitter of the present invention.

FIG. 10 is an explanatory diagram of the operation of the transmitter of FIG. 9;

FIG. 11 shows an embodiment of the overall configuration of the signal processing of the transmitter according to the present invention.

FIG. 12 is an overall configuration diagram of a plant system using the transmitter of the present invention.

FIG. 13 is an explanatory diagram of the operation of the transmitter according to the present invention.

FIG. 14 is an explanatory diagram of an output signal of the transmitter according to the present invention.

FIG. 15 is another explanatory diagram of the operation of the transmitter according to the present invention.

FIG. 16 is a flowchart of processing means of FIG. 15;

FIG. 17 is an explanatory diagram of an output signal of the transmitter in FIG. 15;

FIG. 18 is an overall configuration diagram of a plant system using the transmitter of the present invention.

FIG. 19 is an example of information display of the plant system of FIG. 18;

[Explanation of symbols]

110: Composite sensor, 112: Center diaphragm, 1
14a, 114b: seal diaphragm, 118: body member, 120: filled liquid, 122: signal processing circuit, 126
a, 126b: pressure receiving chamber, 130: MPU, 131, 13
2: Terminal, 150: Physical property change detection sensor, 231: MP
X, 233 ... PGA, 234 ... A / D converter, 236 ...
EPROM, 237 D / A converter, 238 V / I converter, 239 EEPROM, 240 Digital I / O, 32
0: insulating film, 330, 332: electrode, 700: pipeline, 710: orifice, 720: differential pressure transmitter, 73
0: pressure transmitter, 740: control computer, 741 ...
Transmission line, 750: input / output device, 761, 762: signal waveform.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Teruo Kobayashi 882 Ma, Katsuta-shi, Ibaraki Hitachi, Ltd. Measuring Instruments Division (56) References JP-A-4-194718 (JP, A) -57040 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01L 27/00 G01L 13/00

Claims (7)

(57) [Claims] 1. A semiconductor sensor which is in contact with a fluid and detects the pressure of the fluid under the influence of the pressure from the fluid, comprising a physical property detecting means for detecting a change in the physical properties of the fluid. 2. A semiconductor sensor as in claim 1 wherein said physical property detecting sensor semiconductors sensor, characterized in that to detect the dielectric constant of the fluid. 3. The semiconductor sensor according to claim 1, wherein said physical property detection sensor detects a moisture content of said fluid. 4. The semiconductor sensor according to claim 1, wherein said physical property detection sensor detects the humidity of said fluid. 5. The semiconductor sensor according to claim 1, wherein said physical property detection sensor detects PH of said fluid. 6. The semiconductor sensor according to claim 1, wherein said physical property detecting sensor detects an ionic concentration of said fluid. 7. A sealing diaphragm for receiving a fluid pressure from a process fluid, a sealing fluid for transmitting the pressure received by the sealing diaphragm to pressure detecting means, and a pressure receiving chamber in contact with the sealing diaphragm and filled with the sealing fluid. The transmitter according to claim 1, wherein the pressure detecting means includes a physical property detection sensor for detecting physical properties of the sealed fluid .