JP2002013996A - Pressure detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure detecting device with the high range ability, high resolution and high accuracy. SOLUTION: A switch block unit 2 energiges any one of switches SW1-SW3 on the basis of the selecting signal 10, and selects one sensor signal from a multi diaphragm sensor unit 1. This sensor signal is amplified by an amplifier 11 and converted to the numerical conversion data by an AD converting unit 12. A microcomputer 13 reads out this conversion data, and inputs the selecting signal 101 to the switch block unit 12 so as to select a sensor having the optimal pressure range. The microcomputer 13 computes for correction, and inputs the input pressure signal corresponding to a value of the sensor signal to an output circuit 14. The output circuit 14 transmits the input pressure signal as the current signal I onto two-core cable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure detecting device, and more particularly, to a pressure detecting device having a higher pressure detecting function.

[0002]

2. Description of the Related Art A pressure detecting device is a pressure sensor which is most suitable for incorporation of industrial equipment and devices handling hydraulic pressure and pneumatic pressure, and a differential pressure transmission which converts a process variable into an electric signal by adopting a principle of a force balance method. There is a vessel. The pressure detector is
The pressure is converted into an electric signal by using a pressure sensor element including a diaphragm and a piezoresistive element (hereinafter, referred to as a strain gauge). For example, there has been known a pressure sensor element which is made of a semiconductor such as silicon, thereby enabling downsizing and cost reduction.

FIGS. 12A and 12B are a cross-sectional view and a circuit diagram illustrating the operation of a conventional pressure sensor element. The pressure sensor element is made of silicon 2 as shown in FIG.
The diaphragm 41 and the strain gauge 23 are formed on the substrate 9. Specifically, the pressure sensor element is silicon 29
The diaphragm 41 having a thin portion is formed by etching or the like in a part of the portion, a portion where stress is easily generated under pressure is provided, and the strain gauge 23 is disposed in the vicinity thereof. When an external force is applied to the semiconductor crystal to generate a stress in the crystal, the strain gauge 23 changes the electric conduction of the crystal. FIG.
As shown in (2), when a constant current flows through the strain gauge 23, a voltage Vt proportional to the pressure is generated in a direction perpendicular to the current.

[0004] The conventional pressure detecting device corresponds to a target pressure measurement range by setting a diaphragm shape determined by an inner diameter and a thickness to a predetermined value.

[0005]

However, the conventional pressure detecting device can cover the entire measuring range by setting the shape of the diaphragm to a predetermined value. For this reason, the measurement range is limited by the detection resolution of distortion and displacement, and the factors of the sub-burst pressure of the diaphragm.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide a pressure detecting device capable of obtaining high range ability, high resolution, and high accuracy. Aim.

[0007]

To achieve the above object, a pressure detecting device according to the present invention comprises a diaphragm for converting pressure into mechanical strain and a strain gauge for converting the mechanical strain into an electric signal. A pressure sensor having a pressure range different from each other, a set sensor comprising a plurality of diaphragms and strain gauges, a selection means for selecting one of the output signals of the set sensor, and an output signal selected by the selection means And a control means for controlling the selection by the selection means according to the measurement result.

According to the pressure detecting device of the present invention, the control means controls one of a plurality of output signals from the set sensor by controlling the control means in accordance with the measurement result. , High accuracy.

In the pressure detecting device according to the present invention, each of the plurality of sets of sensors has a pressure range corresponding to each set of sensors, and outputs electric signals of the same level in each pressure range. Preferably, the plurality of sets of sensors output different levels of electrical signals for one input pressure. In this case, the control performed by the control unit with respect to the selection performed by the selection unit is facilitated.

Further, in the pressure detecting device according to the present invention, the control means selects an output signal of a set sensor that outputs an electric signal having a maximum level from among output signals of the set sensors, Is selected, and when the output signal of the one set sensor is below a predetermined level, the output signal of the one set sensor is corrected by the output signal of the other set sensor. Compensating means, or comparing means for comparing the output signal of each set sensor and the electric signal level corresponding to the maximum pressure of each set sensor, wherein the current pressure falls within the pressure range by the comparing means It is also possible to select the output signal of the set sensor determined to be present.

It is also a preferred embodiment of the present invention that the plurality of sensors are integrated on one silicon substrate. In this case, miniaturization and cost reduction can be achieved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a pressure detecting device according to the present invention will be described based on an embodiment of the present invention with reference to the drawings. FIG. 1 is a block diagram of a pressure detecting device according to a first embodiment of the present invention. The pressure detecting device according to the present embodiment includes a multi-diaphragm sensor unit (set sensor) 1 including a high-pressure sensor S1, a medium-pressure sensor S2, and a low-pressure sensor S3, and a switch block unit (selection unit) including switches SW1 to SW3. 2 and a conversion unit (control means) 3 for controlling the switch block unit 2. High pressure sensor S1, medium pressure sensor S2, and low pressure sensor S3
Have a diaphragm having a shape corresponding to a predetermined measurement range. The conversion unit 3 includes an amplifier 11, an AD converter 12,
It comprises a microcomputer 13, an output circuit 14, and a regulator 15.

The outputs of the high-pressure sensor S1, the medium-pressure sensor S2, and the low-pressure sensor S3 are output from switches SW1 to SW
3 is connected to one of the contacts. Switches SW1 to S
The other contact of W3 is connected to the input of the amplifier 11.
The AD converter 12 has a signal input connected to a signal output of the amplifier 11 and a data output connected to a data input of the microcomputer 13. The signal output of the microcomputer 13 is connected to the signal input of the output circuit 14.

Between the converter 3 and an external DC power supply,
They are connected by a cable having a length of several meters corresponding to the distance between two points. The cable is a two-core cable including a positive core connected to the positive output of the DC power supply, and a negative core connected to the negative output of the DC power via the load resistor R.
The positive core of the cable is connected to the input of the regulator 15 and the current input of the output circuit 14, and the negative core of the cable is connected to the current output of the output circuit 14.

The multi-diaphragm sensor unit 1 inputs three sensor signals to the switch block unit 2. The switch block unit 2 selects one of the switches SW1 to SW3 based on the selection signal 101 and conducts. This sensor signal is amplified by the amplifier 11 and the AD converter 12
Is converted to numerical data. Microcomputer 1
3 reads the converted data and recognizes the value of the selected sensor signal. The microcomputer 13 inputs the selection signal 101 to the switch block unit 2 based on a predetermined selection condition, and selects one of the necessary sensor signals. The microcomputer 13 performs a calculation based on the sensor signal and inputs an input pressure signal to the output circuit 14.

The output circuit 14 transmits the input pressure signal as a current signal I on a cable. The current signal I is
The current value changes within a predetermined range according to the input pressure signal. From the voltage generated across the load resistor R,
Recognize the value of the measured input pressure. Regulator 15
Converts a supply voltage from a DC power supply into a constant voltage, and supplies the constant voltage to an amplifier 11, an AD converter 12, a microcomputer 13, an output circuit 14, a high-voltage sensor S1, an intermediate-voltage sensor S2, and a low-voltage sensor S3. .

FIG. 2 is a characteristic diagram showing each sensor signal from the multi-diaphragm sensor unit 1 with respect to the input pressure. The low pressure sensor S3 has an input pressure of 0 to 0.5 [Mp
a), the sensor S2 for medium pressure has an input pressure of 0 to
The measurement range of 5 [Mpa] and the high-pressure sensor S1 have a measurement range of the input pressure of 0 to 50 [Mpa]. All sensor signals change linearly within the range of 0 to K [mV]. The sensor signal upper limit K is an upper limit that defines a range in which measurement cannot be performed if the input pressure becomes higher than this.

FIGS. 3 (a), 3 (b) and 3 (c) are an upper sectional view, a lateral sectional view, and a vertical sectional view showing an example of the multi-diaphragm sensor unit 1 of FIG. FIG. In this example, a low-pressure diaphragm 30, a medium-pressure diaphragm 31, and a high-pressure diaphragm 32 in each of which a strain gauge 23 is arranged are provided in a silicon 29 on a glass 28, which is employed in a differential pressure transmitter. Low pressure diaphragm 3
0, the diaphragm 31 for medium pressure, and the diaphragm 32 for high pressure, all the spaces on one side are connected by the internal piping 26,
A low pressure is applied through the low pressure side glass hole 24, and all the spaces on the other side are connected by the surface piping 27, and a high pressure is applied through the high pressure side glass hole 25.

FIG. 4 is a sectional view showing another example of the multi-diaphragm sensor unit 1 of FIG. This example is adopted in a pressure sensor, and includes a low pressure diaphragm 30, a medium pressure diaphragm 31, and a high pressure diaphragm 32 in which a strain gauge 23 is disposed in a silicon 29. In the low-pressure diaphragm 30, the medium-pressure diaphragm 31, and the high-pressure diaphragm 32, pressure is applied to all the diaphragms from one direction.

FIG. 5 shows the microcomputer 13 of FIG.
5 is a flowchart illustrating a first example of the operation of FIG. In this example, the sensor signal is selected from a preset measurement range. The measurer has a measurement range A in which an input pressure of 0 to 50 [Mpa] can be measured, a measurement range B in which an input pressure of 0 to 5 [Mpa] can be measured, and 0 to 0.5 [Mpa].
Any one of the measurement ranges C in which the input pressure can be measured is set. When the power supply of the pressure detecting device is turned on, the microcomputer 13 executes the processing 1.

A preset measurement range is read (step S11), and a high-pressure sensor S1 and a medium-pressure sensor S
2, and one sensor that can correspond to the measurement range is selected from the low-pressure sensor S3 (step S12). It is determined whether the value of the sensor signal from the selected sensor is equal to or less than the sensor signal upper limit K (step S13). "N
If "O", an alarm output is generated as exceeding the range of the measurement range, and the measurer is notified that the measurement range needs to be changed (step S14), and it is determined whether the measurement is completed (step S17). ", Turn the power off.
The process 1 is ended with F, and if “NO”, the process is continued from the step S11.

If the determination in step S13 is "YES", correction is made based on the ambient temperature condition and the static pressure condition, and the input pressure value is obtained by range conversion based on the measurement range (step S15). Next, the input pressure value is output (step S16), and the process is continued from step S17.

FIG. 6 shows the microcomputer 13 of FIG.
9 is a flowchart illustrating a second example of the operation of FIG. This example is a first method in which selection is made after referring to all sensor signals. The microcomputer 13 executes the process 2 as in the process 1 in FIG. As in step S11 in FIG. 5, the measurement range is read (step S21), and the high-pressure sensor S1, the medium-pressure sensor S2, and the low-pressure sensor S are read.
3 is read out (step S2).
2).

It is determined whether the value of the sensor signal from the high-pressure sensor S1 is equal to or less than the sensor signal upper limit K (step S).
23). If "YES", a sensor signal that satisfies the condition that the value is the largest among the plurality of sensor signals and the value of the sensor signal is equal to or less than the sensor signal upper limit K is selected (step S25). Subsequent steps S26 to S28
Are the same as steps S15 to S17 in FIG. If the determination in step S23 is "NO", an alarm output is generated as in step S14 of FIG. 5 (step S2).
4), the process is continued from step S28.

FIG. 7 shows the microcomputer 13 of FIG.
9 is a flowchart illustrating a third example of the operation of FIG. This example is a second method in which all the sensor signals are referred to and then selected. The microcomputer 13 executes the process 3 as in the process 1 in FIG. First steps S31 to S3
Step 4 is the same as steps S21 to S24 in FIG.

If the determination in step S33 is "YES", it is determined whether the value of the sensor signal from the low pressure sensor S3 is equal to or less than the sensor signal upper limit K (step S35).
If "YES", the sensor signal from the low pressure sensor S3 is selected (step S39), and the subsequent step S40
Steps S42 to S42 are the same as steps S26 to S28 in FIG.

If the determination in step S35 is "NO", it is determined whether the value of the sensor signal from the medium pressure sensor S2 is equal to or less than the sensor signal upper limit K (step S36).
If "NO", the sensor signal from the high pressure sensor S1 is selected (step S37), and the process is continued from step S40. If "YES", the sensor signal from the intermediate pressure sensor S2 is selected. (Step S38), the process is continued from Step S40.

FIG. 8 shows the microcomputer 13 of FIG.
9 is a flowchart showing a fourth example of the operation of FIG. In this example, a sensor signal is mainly selected from the high pressure sensor S1, and a sensor signal from the middle pressure sensor S2 or the low pressure sensor S3 is auxiliary selected. The microcomputer 13 executes the processing 4 as in the processing 1 in FIG. As in step S11 in FIG. 5, the measurement range is read (step S51).

The value of the sensor signal from the high pressure sensor S1 is read out (step S52), and it is determined whether the value of the sensor signal from the high pressure sensor S1 is equal to or less than the sensor signal upper limit K (step S53). If “YES”, it is determined whether or not the value of the sensor signal from the high-pressure sensor S1 is larger than a value obtained by dividing the sensor signal upper limit K by 10 (step S55). If "YES", the value of the sensor signal from the high-pressure sensor S1 is selected as it is, and the subsequent steps S58 to S60 are the same as steps S15 to S17 in FIG.

If the determination in step S55 is "NO", the values of the sensor signals from the medium pressure sensor S2 and the low pressure sensor S3 are read out (step S56), and the values of the medium pressure A correction value for the area or the low-pressure area is calculated, and the correction value is added to the value of the sensor signal from the high-pressure sensor S1 (step S57), and the processing is continued from step S58.

FIG. 9 is a block diagram of a pressure detecting device according to a second embodiment of the present invention. It differs from the previous embodiment in that it has a comparator section. The pressure detecting device of the present embodiment has comparators CP1 and CP2. In the figure, the output circuit 14, the regulator 15, the power supply line, and the ground line are omitted.

The comparators CP1 and CP2 compare the sensor signal value with the sensor signal upper limit value K. If the sensor signal value is greater than 1.05 times the sensor signal upper limit value K, the comparison result value is changed to the H level. If the value of the sensor signal is equal to or less than the sensor signal upper limit K, the hysteresis characteristic is set so that the value of the comparison result is at the L level. Comparator CP
1 inputs the value of the comparison result to the value of the sensor signal from the medium pressure sensor S2 to the microcomputer 13 as the medium pressure comparison signal 102. The comparator CP2 is
The value of the comparison result with respect to the value of the sensor signal from the low voltage sensor S3 is input to the microcomputer 13 as the low voltage comparison signal 103.

FIG. 10 shows the microcomputer 1 of FIG.
FIG. 3 is a diagram showing the contents of a selection table stored in 3. If the intermediate voltage comparison signal 102 and the low voltage comparison signal 103 are “H level” and “H level”, “L level” and “H level”, or “L level” and “L level”,
The selection operation of the microcomputer 13 is described as “Switch SW
Only 1 is ON, only switch SW2 is ON, or only switch SW3 is ON.

FIG. 11 shows the microcomputer 1 of FIG.
9 is a flowchart illustrating an example of the operation of FIG. In this example, a selection is made based on a selection table in the microcomputer 13. The microcomputer 13 executes the processing 5 as in the processing 2 in FIG. Step S71-
S74 is the same as steps S21 to S24 in FIG.

If the determination in step S73 is "YES", the switch SW1 is selected based on the selection operation according to the selection table.
To SW3 only (step S7)
5), it is determined whether the number of times of switch switching per second in step S75 is equal to or less than a predetermined number α (step S75)
76). For example, 2 or 3 is set as the value of α. If “YES”, the next step S
Steps 78 to S80 are the same as steps S26 to S28 in FIG. If "NO", only the switch SW1 is turned ON (step S77), and the process is continued from step S78.

According to the above-described embodiment, since the selection condition can be obtained by mounting the comparator, the number of processes corresponding to the program is reduced.

As described above, the present invention has been described based on the preferred embodiment. However, the pressure detecting device of the present invention is not limited to the configuration of the above-described embodiment, but rather the configuration of the above-described embodiment. Various modifications and changes of the pressure detection device are included in the scope of the present invention.

[0038]

As described above, the pressure detecting device of the present invention has a plurality of sensors each having a different shape of the diaphragm corresponding to a predetermined measuring range. Since one sensor signal is selected, high range capability, high resolution, and high accuracy are obtained.

Further, since the selection condition can be obtained by mounting the comparator means, the number of processes corresponding to the program can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of a pressure detecting device according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing each sensor signal from a multi-diaphragm sensor unit 1 with respect to an input pressure.

FIGS. 3A, 3B, and 3C are top cross-sectional views showing an example of the multi-diaphragm sensor unit 1 of FIG.
It is a side sectional view of a horizontal direction, and a side sectional view of a vertical direction.

FIG. 4 is a sectional view showing another example of the multi-diaphragm sensor unit 1 of FIG.

FIG. 5 is a first operation example of the microcomputer 13 shown in FIG. 1;
It is a flowchart which shows an example.

FIG. 6 shows a second operation of the microcomputer 13 of FIG.
It is a flowchart which shows an example.

FIG. 7 shows a third operation of the microcomputer 13 of FIG.
It is a flowchart which shows an example.

FIG. 8 shows a fourth operation of the microcomputer 13 of FIG. 1;
It is a flowchart which shows an example.

FIG. 9 is a block diagram of a pressure detecting device according to a second embodiment of the present invention.

10 is a diagram showing the contents of a selection table stored in the microcomputer 13 of FIG.

11 is a flowchart showing an example of the operation of the microcomputer 13 in FIG.

FIGS. 12A and 12B are a cross-sectional view and a circuit diagram illustrating the operation of a conventional pressure sensor element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multi-diaphragm sensor part (group sensor) 2 Switch block part (selection means) 3 Conversion part (control means) 11 Amplifier 12 A / D converter 13 Microcomputer 14 Output circuit 15 Regulator 21 Electrode 22 Lead 23 Strain gauge 24 Low-pressure side glass hole 25 High-pressure side glass hole 26 Internal piping 27 Surface piping 28 Glass 29 Silicon 30 Low-pressure diaphragm 31 Medium-pressure diaphragm 32 High-pressure diaphragm 41 Diaphragm 101 Selection signal 102 Medium-pressure comparison signal 103 Low-voltage comparison signal S1 High-pressure sensor S2 Medium-pressure sensor S3 Low pressure sensor SW1 to SW3 Switch CP1, CP2 Comparator

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F055 AA40 BB20 CC02 DD05 EE13 FF07 FF11 GG11 GG34 4M112 AA01 BA01 CA06 CA12 EA02 GA03

Claims (7)

[Claims] 1. A pressure detecting device having a diaphragm for converting pressure into mechanical strain and a strain gauge for converting the mechanical strain into an electric signal, wherein a plurality of diaphragms and strains whose pressure ranges to be measured are different from each other. A set sensor composed of a gauge, a selection means for selecting one of the output signals of the set sensor, a control means for measuring the output signal selected by the selection means, and controlling the selection in the selection means according to the measurement result And a pressure detection device. 2. The pressure detecting apparatus according to claim 1, wherein each of the plurality of sensors has a corresponding pressure range, and outputs electric signals of the same level in each pressure range. 3. The pressure detecting device according to claim 1, wherein said plurality of sets of sensors output electric signals of mutually different levels with respect to one input pressure. 4. The pressure detecting device according to claim 1, wherein said control means selects an output signal of a set sensor that outputs an electric signal having a maximum level from among output signals of said set sensors. 5. The control means according to claim 1, wherein said pressure range is maximum.
Selecting an output signal of one of the paired sensors, and further comprising, when the output signal of the one of the paired sensors is below a predetermined level, an output signal of the one of the paired sensors based on an output signal of the other of the paired sensors. The pressure detection device according to claim 1, further comprising a correction unit that corrects the pressure. 6. The control means includes comparison means for comparing an output signal of each set sensor with an electric signal level corresponding to a maximum pressure of each set sensor, and the control means controls a current pressure to be within a pressure range. The pressure detection device according to claim 1, wherein an output signal of the set sensor determined to be within the range is selected. 7. The pressure detecting device according to claim 1, wherein said plurality of set sensors are integrated on one silicon substrate.