Diaphragm vacuum gauge

Abstract

To provide a diaphragm vacuum gauge with an extended lower limit of a pressure measurement range.SOLUTION: A diaphragm vacuum gauge provided herein comprises: a pressure adjustment chamber 1 provided to be in communication with a measured chamber via a pipe 2; a pressure measurement chamber 3 provided to be in communication with the pressure adjustment chamber 1; a pressure receiving unit 5 having capacitance that changes with displacement of a diagram by pressure of a measured medium in the pressure measurement chamber 3; a temperature sensor 8 configured to measure temperature of the measured medium in the pressure measurement chamber 3; and a circuitry unit 10 configured to convert the capacitance into a measured pressure value and correct the measured pressure value according to the temperature measured by the temperature sensor 8 and temperature of the measured medium in the measured chamber.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a diaphragm vacuum gauge.

Background Art

[0002] As pressure sensors such as vacuum gauges used in semiconductor manufacturing equipment and the like, products of various types using different measurement principles are utilized according to the required pressure range. For example, one of them, a capacitance-type diaphragm vacuum gauge, is a device in which a movable diaphragm (diaphragm) receives pressure and its deflection amount is detected as a capacitance value (see Patent Document 1 and Patent Document 2). Since the diaphragm vacuum gauge has little gas species dependence in the flow measurement value, it is often used in process equipment such as semiconductor film formation processes and etching processes.

[0003] The diaphragm vacuum gauge usually has a minimum pressure range full scale of about 1.3 Pa in many cases. The reason for this is that, due to the structure of the vacuum gauge, the measurable pressure range is determined by the thickness of the diaphragm. That is, in order to measure a lower pressure than usual, it is necessary to make the diaphragm thinner. On the contrary, for high pressures, the vacuum gauge is designed so that the diaphragm becomes thicker to meet the specifications.

[0004] When the diaphragm of the diaphragm vacuum gauge is made thinner to measure a lower pressure, it becomes more susceptible to the influence of disturbances, so there are more restrictions in terms of design or use. Specifically, the influence of residual stress due to the sensor mount (package) becomes more prominent, or the measurement accuracy deteriorates due to the influence of disturbances such as temperature and vibration during the use of the vacuum gauge. Thus, there is a structural lower limit to the practical pressure measurement range of the diaphragm vacuum gauge, but in some situations, measurements below the lower limit may be required, and improvement is demanded.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] The present invention has been made to solve the above problems, and an object thereof is to provide a diaphragm vacuum gauge capable of expanding the lower limit of the pressure measurement range. [Means for Solving the Problems]

[0007] The diaphragm vacuum gauge of the present invention includes a pressure adjustment chamber provided to communicate with a chamber to be measured via a pipe, communicates with the measurement chamber via the pipe, and a pressure measurement chamber provided to communicate with the pressure adjustment chamber, a pressure receiving portion configured to change the capacitance according to the displacement of a diaphragm due to the pressure of a medium to be measured in the pressure measurement chamber, a first temperature sensor configured to measure the temperature of the medium to be measured in the pressure measurement chamber, a pressure measurement portion configured to convert the capacitance into a pressure measurement value, and a pressure correction portion configured to correct the pressure measurement value based on the temperature measured by the first temperature sensor and the temperature of the medium to be measured in the chamber to be measured, from the measurement chamber wherein the medium to be measured flows into the pressure adjustment chamber and the pressure measurement chamber via the pipe, and the pressure measurement value is corrected by converting a temperature difference between the temperature of the medium to be measured in the pressure measurement chamber and the temperature of the medium to be measured in the chamber to be measured into a pressure difference.

[0008] In one configuration example of the diaphragm vacuum gauge of the present invention, the pressure adjustment chamber and the pressure measurement chamber communicate with each other via a throttle, and the throttle is a fixed throttle or a variable throttle. Also, one configuration example of the diaphragm vacuum gauge of the present invention further includes a second temperature sensor configured to measure the temperature of the medium to be measured in the pressure adjustment chamber, and a temperature estimation unit configured to estimate the temperature of the medium to be measured in the measurement chamber from the temperature measured by the second temperature sensor. Further, the diaphragm vacuum gauge of the present invention includes a pressure adjustment chamber provided to communicate with a measurement chamber to be measured via a pipe, a pressure measurement chamber provided to communicate with the pressure adjustment chamber, a pressure receiving portion configured such that the capacitance changes in accordance with displacement of a diaphragm due to the pressure of a medium to be measured in the pressure measurement chamber, a first temperature sensor configured to measure the temperature of the medium to be measured in the pressure measurement chamber, a second temperature sensor configured to measure the temperature of the medium to be measured in the pressure adjustment chamber, a temperature estimation unit configured to estimate the temperature of the medium to be measured in the measurement chamber to be measured from the temperature measured by the second temperature sensor, a pressure measurement unit configured to convert the capacitance into a pressure measurement value, and a pressure correction unit configured to correct the pressure measurement value based on the temperature measured by the first temperature sensor and the temperature of the medium to be measured in the measurement chamber to be measured, and is characterized in that the pressure measurement value is corrected by converting a temperature difference between the temperature of the medium to be measured in the pressure measurement chamber and the temperature of the medium to be measured in the measurement chamber to be measured into a pressure difference.

[0009] Further, the diaphragm vacuum gauge of the present invention includes a pressure measurement chamber provided to communicate with a measurement chamber to be measured via a pipe, a pressure receiving portion configured such that the capacitance changes in accordance with displacement of a diaphragm due to the pressure of a medium to be measured in the pressure measurement chamber, and a first temperature sensor configured to measure the temperature of the medium to be measured in the pressure measurement chamber. a heat flux sensor configured to measure the heat flux in the pipe, and a temperature estimation unit configured to estimate the temperature of the medium to be measured in the measurement chamber from the heat flux measured by the heat flux sensor, The diaphragm vacuum gauge includes a pressure measurement unit configured to convert the capacitance into a pressure measurement value, and a pressure correction unit configured to correct the pressure measurement value based on the temperature measured by the first temperature sensor and the temperature of the medium to be measured in the measurement chamber to be measured, and is characterized in that the pressure measurement value is corrected by converting a temperature difference between the temperature of the medium to be measured in the pressure measurement chamber and the temperature of the medium to be measured in the measurement chamber to be measured into a pressure difference. 。

[0010] Further, the diaphragm vacuum gauge of the present invention includes a pressure adjustment chamber provided to communicate with the measurement chamber via a pipe, a pressure measurement chamber provided to communicate with the pressure adjustment chamber, a pressure receiving portion configured such that the capacitance changes in accordance with the displacement of a diaphragm due to the pressure of the medium to be measured in the pressure measurement chamber, a first temperature sensor configured to measure the temperature of the medium to be measured in the pressure measurement chamber, a pressure measurement unit configured to convert the capacitance into a pressure measurement value, and a pressure correction unit configured to correct the pressure measurement value based on the temperature measured by the first temperature sensor and the temperature of the medium to be measured in the measurement chamber. A heater configured to heat the pressure measurement chamber, and a control unit configured to supply power to the heater to generate heat so that the temperature difference between the temperature of the measurement medium in the pressure measurement chamber and the temperature of the measurement medium in the measurement chamber becomes a predetermined value and corrects the pressure measurement value by converting the temperature difference between the temperature of the medium to be measured in the pressure measurement chamber and the temperature of the medium to be measured in the measurement chamber into a pressure difference It is characterized by this. In addition, the diaphragm vacuum gauge of the present invention includes a pressure measurement chamber provided to communicate with a chamber to be measured via a pipe, a pressure receiving portion configured such that the capacitance changes in accordance with the displacement of a diaphragm due to the pressure of the medium to be measured in the pressure measurement chamber, a first temperature sensor configured to measure the temperature of the medium to be measured in the pressure measurement chamber, a pressure measurement portion configured to convert the capacitance into a pressure measurement value, a pressure correction portion configured to correct the pressure measurement value based on the temperature measured by the first temperature sensor and the temperature of the medium to be measured in the chamber to be measured, a heater configured to heat the pressure measurement chamber, and a control portion configured to supply power to the heater to generate heat such that the temperature difference between the temperature of the medium to be measured in the pressure measurement chamber and the temperature of the medium to be measured in the chamber to be measured becomes a predetermined value. The pressure measurement value is corrected by converting the temperature difference between the temperature of the medium to be measured in the pressure measurement chamber and the temperature of the medium to be measured in the chamber to be measured into a pressure difference. Further, in one configuration example of the diaphragm vacuum gauge of the present invention, the pressure receiving portion includes a first electrode formed on a pedestal, the diaphragm disposed at a gap from the pedestal, and the diaphragm formed to face the first electrode. A second electrode, a third electrode formed on the pedestal outside the first electrode, and a fourth electrode formed on the diaphragm outside the second electrode so as to face the third electrode, and a first electrode between the first and second electrodes. A capacitance calculation unit configured to calculate the capacitance, a capacitance difference calculation unit configured to calculate a value obtained by subtracting the second capacitance between the third and fourth electrodes from the first capacitance, and the calculation result of the capacitance calculation unit and the capacitance difference calculation unit. And a capacitance correction unit configured to correct the first capacitance based on the second capacitance, wherein the pressure measurement unit is characterized by converting the corrected first capacitance into the pressure measurement value. Also, the diaphragm vacuum gauge of the present invention It includes a pressure adjustment chamber provided to communicate with a chamber to be measured via a pipe, a pressure measurement chamber provided to communicate with the pressure adjustment chamber, a pressure receiving portion configured such that the capacitance changes in accordance with the displacement of a diaphragm due to the pressure of the medium to be measured in the pressure measurement chamber, a first temperature sensor configured to measure the temperature of the medium to be measured in the pressure measurement chamber, a pressure measurement portion configured to convert the capacitance into a pressure measurement value, Only when the pressure measurement value falls below the lower limit of the specified pressure measurement range , and a pressure correction portion configured to correct the pressure measurement value based on the temperature measured by the first temperature sensor and the temperature of the medium to be measured in the chamber to be measured. The pressure measurement value is corrected by converting the temperature difference between the temperature of the medium to be measured in the pressure measurement chamber and the temperature of the medium to be measured in the chamber to be measured into a pressure difference. It is characterized by this. Further, the diaphragm vacuum gauge of the present invention includes a pressure measurement chamber provided to communicate with a measurement chamber to be measured via a pipe, a pressure receiving portion configured such that its capacitance changes according to the displacement of a diaphragm due to the pressure of a medium to be measured in the pressure measurement chamber, a first temperature sensor configured to measure the temperature of the medium to be measured in the pressure measurement chamber, a pressure measurement portion configured to convert the capacitance into a pressure measurement value, and a pressure correction portion configured to correct the pressure measurement value based on the temperature measured by the first temperature sensor and the temperature of the medium to be measured in the measurement chamber to be measured only when the pressure measurement value falls below the lower limit of a specified pressure measurement range, and is characterized in that the temperature difference between the temperature of the medium to be measured in the pressure measurement chamber and the temperature of the medium to be measured in the measurement chamber to be measured is converted into a pressure difference to correct the pressure measurement value.

Effect of the Invention

[0011] According to the present invention, by correcting the pressure measurement value by converting the temperature difference between the temperature of the measurement medium in the pressure measurement chamber and the temperature of the measurement medium in the measurement chamber into a pressure difference, the lower limit of the pressure measurement range of the diaphragm vacuum gauge can be extended (lowered).

Brief Description of the Drawings

[0012]

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Embodiments for Carrying Out the Invention

[0013] [Principle of the Invention] The inventor focused on the temperature difference between the gas to be measured and the gas in the diaphragm vacuum gauge as an element that can change the measurement conditions without improving the structure of the diaphragm vacuum gauge itself. By heating the gas supplied to the diaphragm vacuum gauge to a specified temperature near or inside the vacuum gauge, the pressure can be increased to a measurable range (within the lower limit) for measurement. The inventor conceived that if the pressure value is converted based on the temperature difference caused by heating, the lower limit of the pressure measurement range can be equivalently expanded. The conversion may be performed based on physical principles or by experimentally obtaining the relationship between the pressure difference caused by the temperature difference in advance.

[0014] [First Embodiment] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, a system is assumed in which a diaphragm vacuum gauge is connected to a chamber to be measured via a pipe. The diaphragm vacuum gauge is self-heating to prevent foreign matter deposition, and since the temperature is different from that of the chamber to be measured, it is known that a pressure difference due to heat transfer occurs between the two spaces.

[0015] Regarding the relationship between this pressure and temperature, when assuming a state where two chambers 200 and 201 are connected by a pipe 202 with a diameter d as shown in FIG. 1, approximate formulas have been proposed for each of the intermediate flow (Equation (1)) and the molecular flow (Equation (2)).

[0016] [Number]

[0017] [Number]

[0018] In Equation (1) and Equation (2), P 1 , P 2 are the pressures of the gas in chambers 200 and 201 respectively, T 1 , T 2 are the temperatures of the gas in chambers 200 and 201, and a, b, and c are coefficients depending on the gas type and temperature. From the relationship between Equation (1) and Equation (2), it has been reported that the pressure difference between the chamber under measurement and the pressure-receiving part of the diaphragm vacuum gauge is as shown in Figure 2 (Literature: Yasuhide Yoshikawa et al., "Development of Sapphire High-Temperature Diaphragm Vacuum Gauge", azbil Technical Review, Azbil Corporation, January 2011).

[0019] In the example of Figure 2, the gas species is N 2 , the temperature T 1 of the gas in the chamber under measurement is 25 °C, and the diameter d of the pipe connecting the chamber under measurement and the diaphragm vacuum gauge is 12.7 mm. The horizontal axis of Figure 2 is the pressure P 1 of the gas in the chamber under measurement, and the vertical axis is the pressure difference between the chamber under measurement and the pressure-receiving part of the diaphragm vacuum gauge. 203 in Figure 2 shows the characteristics when the self-heating temperature of the pressure-receiving part of the diaphragm vacuum gauge is 125 °C, and 204 shows the characteristics when the self-heating temperature is 200 °C.

[0020] Figure 3 is a diagram showing the result of analyzing the relationship between the pressure P 1 of the gas in the measurement target (chamber under measurement) and the pressure measurement value P 2 of the diaphragm vacuum gauge based on these approximate relationships. Here, the temperature difference between the temperature T 1 of the gas in the chamber under measurement and the self-heating temperature T 2 (T 1 < T 2 ) of the pressure-receiving part of the diaphragm vacuum gauge is 125 °C. In Figure 3, 300 shows the relationship between the pressure P 1 and P 2 , and 301 shows the relationship between the pressure P 1 and P 2 when there is no heat transfer between the chamber under measurement and the diaphragm vacuum gauge. A1 in Figure 3 is called the viscous flow region, A2 is called the intermediate flow region, and A3 is called the molecular flow region.

[0021] According to Figure 3, in the intermediate flow and molecular flow regions, which are the pressure ranges frequently used in semiconductor film formation and etching processes, it can be seen that the pressures P 1 and P 2 are different, and a pressure difference due to heat transfer is generated. Specifically, as shown in FIG. 4, when there is a heat transfer (when the temperature difference between the chamber to be measured and the diaphragm vacuum gauge is large), the pressure P of the gas in the chamber to be measured 1 is actually lower than the pressure measurement value P 2 of the diaphragm vacuum gauge.

[0022] Therefore, the pressure measurement value P 2 of the diaphragm vacuum gauge is usually corrected to be close to the actual pressure P 1 of the chamber to be measured. That is, in order to regard the phenomenon of heat transfer as an error factor, the pressure measurement value P 2 of the diaphragm vacuum gauge is corrected and changed by performing a correction calculation. Specifically, as shown in FIG. 3, the pressure measurement value P 2 = 0.023 Torr of the diaphragm vacuum gauge is corrected to 0.01 Torr.

[0023] In this embodiment, by actively using the relationship shown in FIG. 3, it is possible to perform measurement while maintaining the measurement accuracy up to a lower pressure range without exceeding the physical measurement limit of the diaphragm vacuum gauge. For example, if the measurement lower limit in the specification of the diaphragm vacuum gauge is assumed to be 0.01 Torr, the straight line L1 in FIG. 3 indicates the actual measurement value lower limit.

[0024] However, when the temperature of the diaphragm vacuum gauge is changed, it becomes possible to measure up to the level shown by the straight line L2 in FIG. 3. If the temperature difference between the chamber to be measured and the diaphragm vacuum gauge is made larger than 125 ° C, it becomes possible to further lower the lower limit of the pressure measurement range. Specifically, as shown in FIG. 4, if the diaphragm vacuum gauge side is heated to a high temperature and the temperature difference between the chamber to be measured and the diaphragm vacuum gauge is made 400 ° C, the measurement pressure difference also reaches around 75% of the pressure measurement value P 2 of the diaphragm vacuum gauge.

[0025] In this embodiment, the measured temperature data on the chamber to be measured side or the measured temperature data on the diaphragm vacuum gauge side that can predict the measured temperature data are used as parameters. A correlation table between this temperature parameter and the actual pressure value is created at the time of calibrating the diaphragm vacuum gauge, and the output of the diaphragm vacuum gauge is determined based on this correlation table.

[0026] As a result, even in a pressure range of 1.3 Pa or less where it becomes difficult to manufacture a diaphragm vacuum gauge due to, for example, a very low pressure, the pressure measurement range can be expanded to the lower limit side by approximately 58% (when the temperature difference between the chamber to be measured and the diaphragm vacuum gauge is 125 °C). As a specific measured value, it becomes possible to measure up to a chamber pressure of 0.56 Pa.

[0027] In this embodiment, it is necessary to accurately grasp the temperature of the chamber to be measured. However, in a semiconductor manufacturing apparatus or the like, since the chamber to be measured is usually temperature-controlled, the temperature measured in the chamber to be measured may be used. Alternatively, a temperature sensor or a heat flux sensor that can predict the temperature of the chamber to be measured may be installed on the diaphragm vacuum gauge side, and the calculated value (for example, the integrated value) may be used. In addition, in case the temperature cannot be accurately grasped, minimum calibration may be performed at the time of shipment. The diaphragm vacuum gauge has a self-heating function by a heater to prevent the deposition of by-products, and this heater is used with its capacity enhanced to a level higher (about 500 °C) than normal (about 200 °C).

[0028] Patent Document 1 describes that an error occurs due to heat transfer, and a method for performing pressure measurement in which the error is corrected and the heat transfer effect is reflected is disclosed. In Patent Document 1, there is no intention to utilize the error, and the problem to be solved is also different from that of the present invention. The purpose of the method disclosed in Patent Document 1 is to display a measurement value closer to the true value.

[0029] Patent Document 2 discloses correcting non-linear temperature dependence. Neither Patent Document 1 nor Patent Document 2 provides a means for correcting the error due to the temperature difference and calibrating the diaphragm vacuum gauge, and does not conceive a means for exceeding the measurement limit by actively using the pressure difference. The present invention provides an effective solution to a new problem of measuring a pressure range below the conventional lower limit using a current diaphragm vacuum gauge.

[0030] Hereinafter, the diaphragm vacuum gauge of this embodiment will be described in more detail. FIG. 5 is a block diagram showing the configuration of the diaphragm vacuum gauge according to this embodiment. The diaphragm vacuum gauge includes a pressure adjustment chamber 1 provided so as to communicate with a measurement chamber 12 via a pipe 2, a pressure measurement chamber 3 provided so as to communicate with the pressure adjustment chamber 1 via a throttle 4, a pressure receiving portion 5 whose capacitance changes according to the displacement of a diaphragm due to the pressure of the medium to be measured (for example, process gas) in the pressure measurement chamber 3, a heater 6 (heater) for heating the pressure measurement chamber 3, and the temperature T of the medium to be measured in the pressure adjustment chamber 1 3 is measured by a temperature sensor 7, and the temperature T of the medium to be measured in the pressure measurement chamber 3 2 is measured by a temperature sensor 8, and a circuit portion 10 that converts the capacitance of the pressure receiving portion 5 into a pressure measurement value.

[0031] FIG. 6 is a cross-sectional view showing the configuration of the main part of the pressure receiving portion 5 of the diaphragm vacuum gauge. A concave portion is formed in the center of the pedestal 50 of the pressure receiving portion 5. A diaphragm 51 configured to be deformable according to the pressure P of the medium to be measured is joined to the surface of the pedestal 50 where this concave portion is formed. The concave portion of the pedestal 50 forms a reference vacuum chamber 52 together with the diaphragm 51.

[0032] A fixed electrode 53 is formed on the surface of the pedestal 50 on the reference vacuum chamber 52 side, and a movable electrode 54 is formed on the surface of the diaphragm 51 on the reference vacuum chamber 52 side so as to face the fixed electrode 53. In this way, the fixed electrode 53 and the movable electrode 54 are arranged so as to face each other with a gap therebetween. When the diaphragm 51 receives the pressure P of the medium to be measured and bends, the distance between the movable electrode 54 and the fixed electrode 53 changes, and the capacitance between the movable electrode 54 and the fixed electrode 53 changes. The pressure P of the medium to be measured received by the diaphragm 51 can be detected from this change in capacitance.

[0033] Also, a fixed electrode 55 is formed on the surface of the pedestal 50 outside the fixed electrode 53 on the reference vacuum chamber 52 side. A movable electrode 56 is formed on the surface of the diaphragm 51 outside the movable electrode 54 on the reference vacuum chamber 52 side so as to face the fixed electrode 55. The fixed electrode 55 and the movable electrode 56 are formed at the edge of the diaphragm 51. Even if the diaphragm 51 is bent under the pressure P of the medium to be measured, the edge of the diaphragm 51 hardly deforms, so the capacitance between the movable electrode 56 and the fixed electrode 55 is hardly changed. This capacitance is provided to remove measurement errors based on temperature changes inside and outside the sensor and humidity changes inside the reference vacuum chamber 52. The diaphragm 51 and the pedestal 50 are made of an insulator such as sapphire.

[0034] The medium to be measured introduced from the pipe 2 flows into the pressure adjustment chamber 1 and then into the pressure measurement chamber 3 through the throttle 4. By providing the throttle 4, it becomes possible to change the diameter d of the pipe. By acquiring data (temperature, pressure) associated with a plurality of diameters d, it is possible to grasp mainly many parameters in the intermediate flow region. That is, the measurement accuracy can be improved by inserting the throttle 4. The throttle 4 may be a fixed throttle with a fixed aperture, or a variable throttle whose aperture can be changed from the outside. In the case of a variable throttle, the degree of the throttle can be adjusted.

[0035] FIG. 7 is a block diagram showing the configuration of the circuit unit 10 of the diaphragm vacuum gauge. The circuit unit 10 includes a signal detection unit 100 that outputs a signal with an amplitude proportional to the capacitance between the movable electrode 54 and the fixed electrode 53, and a signal with an amplitude proportional to the value obtained by subtracting the capacitance between the movable electrode 56 and the fixed electrode 55 from the capacitance between the movable electrode 54 and the fixed electrode 53, an AD conversion unit 101 that converts the outputs of the signal detection unit 100 and the temperature sensors 7 and 8 into digital signals, an arithmetic processing unit 102, a memory 103 that stores the program of the arithmetic processing unit 102, a power supply 104 that supplies a power supply voltage to each part of the circuit unit 10, and an interface unit 105.

[0036] FIG. 8 is a block diagram showing the configuration of the signal detection unit 100. The signal detection unit 100 includes a signal generator 1000, amplifiers 1001 and 1002 each consisting of a capacitance Cf and an operational amplifier A1, a subtractor 1003, low-pass filters 1004 and 1005 of differential input type, a switch 1006 provided between the amplifier 1001 and the low-pass filter 1004, and a switch 1007 provided between the amplifier 1002 and the low-pass filter 1005. In FIG. 8, the capacitance between the movable electrode 54 and the fixed electrode 53 is represented by Cx, and the capacitance (reference capacitance) between the movable electrode 56 and the fixed electrode 55 is represented by Cr.

[0037] The signal generator 1000 applies a sinusoidal sensor drive signal Esin(2πft) to the first electrode (e.g., the fixed electrode 53), the third electrode (e.g., the fixed electrode 55) of the pressure receiving unit 5, and the switches 1006 and 1007 during pressure measurement. E is the amplitude, f is the frequency, and t is the time.

[0038] The amplifier 1001 converts the current output from the second electrode (e.g., the movable electrode 54) of the pressure receiving unit 5 into a voltage and amplifies it, and outputs a signal with an amplitude proportional to the capacitance Cx. The amplifier 1002 converts the current output from the fourth electrode (e.g., the movable electrode 56) of the pressure receiving unit 5 into a voltage and amplifies it, and outputs a signal with an amplitude proportional to the capacitance Cr. The subtractor 1003 subtracts the output signal of the amplifier 1002 from the output signal of the amplifier 1001.

[0039] The switch 1006 and the low-pass filter 1004 constitute a synchronous detection unit 1008. The cut-off frequency of the low-pass filter 1004 is set to pass the sensor drive signal Esin(2πft). The synchronous detection unit 1008 demodulates a signal synchronized with the sensor drive signal Esin(2πft) from the output of the amplifier 1001.

[0040] Specifically, when the sensor drive signal Esin(2πft) output from the signal generator 1000 is positive, the switch 1006 connects the output terminal of the amplifier 1001 and the non-inverting input terminal of the low-pass filter 1004. Also, when the sensor drive signal Esin(2πft) is negative, the switch 1006 connects the output terminal of the amplifier 1001 and the inverting input terminal of the low-pass filter 1004. Thereby, a signal synchronized with the sensor drive signal Esin(2πft) can be demodulated from the output of the amplifier 1001.

[0041] On the other hand, the switch 1007 and the low-pass filter 1005 constitute the synchronous detection unit 1009. The cut-off frequency of the low-pass filter 1005 is set to pass the sensor drive signal Esin(2πft). The synchronous detection unit 1009 demodulates a signal synchronized with the sensor drive signal Esin(2πft) from the output of the subtractor 1003.

[0042] Specifically, when the sensor drive signal Esin(2πft) output from the signal generator 1000 is positive, the switch 1007 connects the output terminal of the subtractor 1003 and the non-inverting input terminal of the low-pass filter 1005. Also, when the sensor drive signal Esin(2πft) is negative, the switch 1007 connects the output terminal of the subtractor 1003 and the inverting input terminal of the low-pass filter 1005. Thereby, a signal synchronized with the sensor drive signal Esin(2πft) can be demodulated from the output of the subtractor 1003.

[0043] The AD conversion unit 101 converts the outputs of the signal detection unit 100 (the outputs of the synchronous detection unit 1008 and the synchronous detection unit 1009) and the outputs of the temperature sensors 7 and 8 into digital signals. As shown in FIG. 7, the arithmetic processing unit 102 includes a temperature estimation unit 1020, a control unit 1021, a capacitance calculation unit 1022, a capacitance difference calculation unit 1023, a capacitance correction unit 1024, a pressure measurement unit 1025, and a pressure correction unit 1026.

[0044] FIG. 9 is a flowchart for explaining the operation of the arithmetic processing unit 102. The temperature estimation unit 1020 estimates the temperature T of the medium to be measured in the chamber 12 to be measured from the temperature T measured by the temperature sensor 7 (step S100 in FIG. 9). The relationship between the temperature T of the medium to be measured in the pressure adjustment chamber 1 and the temperature T of the medium to be measured in the chamber 12 to be measured has been confirmed by a prior test. The temperature estimation unit 1020 may calculate the temperature T from the temperature T using a preset formula, or may obtain the value of the temperature T corresponding to the temperature T from a preset table. 3 from the temperature T of the medium to be measured in the chamber 12 to be measured 1 (step S100 in FIG. 9). The temperature T of the medium to be measured in the pressure adjustment chamber 1 3 and the temperature T of the medium to be measured in the chamber 12 to be measured 1 The relationship between them has been confirmed by prior tests. The temperature estimation unit 1020 may calculate the temperature T from the temperature T using a preset formula, or may obtain the value of the temperature T corresponding to the temperature T from a preset table. 3 from the temperature T 1 or calculate the temperature T from a preset table 3 corresponding to the temperature T 1 value.

[0045] The control unit 1021 supplies power to the heater 6 to generate heat so that the difference T between the temperature T estimated by the temperature estimation unit 1020 and the temperature T measured by the temperature sensor 8 becomes a predetermined value (for example, 500 ° C) (step S101 in FIG. 9). In this way, the pressure measurement chamber 3 is heated so that the temperature difference T between the temperature T of the medium to be measured in the pressure measurement chamber 3 and the temperature T of the medium to be measured in the chamber 12 to be measured becomes a predetermined value. The predetermined value for determining the temperature difference can be arbitrarily set within the range of 0 ° C to 500 ° C. 1 and the temperature T measured by the temperature sensor 8 2 The difference T 2 -T 1 becomes a predetermined value (for example, 500 ° C) (step S101 in FIG. 9). In this way, the pressure measurement chamber 3 is heated so that the temperature difference T between the temperature T of the medium to be measured in the pressure measurement chamber 3 and the temperature T of the medium to be measured in the chamber 12 to be measured becomes a predetermined value. The predetermined value for determining the temperature difference can be arbitrarily set within the range of 0 ° C to 500 ° C. 2 and the temperature T of the medium to be measured in the chamber 12 to be measured 1 The temperature difference T 2 -T 1 becomes a predetermined value. The predetermined value for determining the temperature difference can be arbitrarily set within the range of 0 ° C to 500 ° C.

[0046] The capacitance calculation unit 1022 calculates the value of the capacitance Cx from the amplitude of the output signal of the synchronous detection unit 1008 (step S102 in FIG. 9). The capacitance difference calculation unit 1023 calculates the value of the capacitance difference (Cx - Cr) from the amplitude of the output signal of the synchronous detection unit 1009 (step S103 in FIG. 9).

[0047] The capacitance correction unit 1024 calculates a value (Cx - Cr) / Cx obtained by correcting the capacitance Cx with the reference capacitance Cr based on the calculation results of the capacitance calculation unit 1022 and the capacitance difference calculation unit 1023 (step S104 in FIG. 9). The pressure measurement unit 1025 converts the capacitance (Cx - Cr) / Cx calculated by the capacitance correction unit 1024 into a pressure measurement value P 2 (step S105 in FIG. 9).

[0048] The pressure correction unit 1026 obtains a value obtained by correcting the pressure measurement value P based on the temperature T of the measurement medium in the pressure measurement chamber 3 measured by the temperature sensor 8 2 and the temperature T of the measurement medium in the measurement chamber 12 estimated by the temperature estimation unit 1020 1 (step S106 in FIG. 9). 2 Specifically, a correlation table associating the temperature T

[0049] , T 2 , T 1 with the pressure measurement value P 2 and the actual pressure value P of the measurement medium in the measurement chamber 12 1 is created during the calibration of the diaphragm vacuum gauge and set in the pressure correction unit 1026. The pressure correction unit 1026 obtains the pressure value P 2 , T 1 corresponding to the temperature T 2 and the pressure measurement value P 1 . In this way, the pressure measurement value P 2 can be corrected to be close to the actual pressure value P 1 of the measurement chamber 12.

[0050] Then, the pressure correction unit 1026 outputs the calculated pressure value P 1 to, for example, a host device via the interface unit 105 (step S107 in FIG. 9). The arithmetic processing unit 102 performs the processing of steps S100 to S107 at each measurement cycle until the pressure measurement operation ends, for example, according to a user's instruction (YES in step S108 in FIG. 9).

[0051] Thus, in this embodiment, the lower limit of the pressure measurement range of the diaphragm vacuum gauge can be extended.

[0052] [Second Embodiment] Next, a second embodiment of the present invention will be described. FIG. 10 is a block diagram showing the configuration of a diaphragm vacuum gauge according to the second embodiment of the present invention. The diaphragm vacuum gauge of this embodiment includes a pressure adjustment chamber 1a, a pressure measurement chamber 3a, a pressure receiving portion 5, a heater 6, temperature sensors 7 and 8, and a circuit portion 10.

[0053] In the first embodiment, the pressure adjustment chamber 1 and the pressure measurement chamber 3 are arranged in series, and the measurement medium flowing into the pressure adjustment chamber 1 flows into the pressure measurement chamber 3 through the throttle 4. In contrast, in this embodiment, the pressure adjustment chamber 1a and the pressure measurement chamber 3a are arranged in parallel. A baffle 9 is provided between the pressure adjustment chamber 1a, the pressure measurement chamber 3a, and the pipe 2a. The measurement medium introduced from the measurement chamber 12 through the pipe 2a hits the surface of the baffle 9 and the same amount is introduced into the pressure adjustment chamber 1a and the pressure measurement chamber 3a through the gap around the baffle 9. Further, the pressure adjustment chamber 1a and the pressure measurement chamber 3a communicate with each other through a throttle 4a.

[0054] The configurations of the pressure receiving portion 5, the heater 6, and the circuit portion 10 are the same as those in the first embodiment. Since the structure of the pressure adjustment chamber 1a is different from that of the first embodiment, the temperature T of the measurement medium in the pressure adjustment chamber 1a 3 and the temperature T of the measurement medium in the measurement chamber 12 1 Needless to say, the relationship is calibrated for this embodiment. Using this relationship, the temperature estimation unit 1020 of the circuit unit 10 can estimate the temperature T of the measurement medium in the measurement chamber 12 from the temperature T measured by the temperature sensor 7. 3 Similarly, it goes without saying that the correlation table used by the pressure correction unit 1026 of the circuit unit 10 is also calibrated for this embodiment. 1

[0055] Thus, in this embodiment, the same effects as those of the first embodiment can be obtained. In the first and second embodiments, the temperature T of the medium to be measured in the measurement chamber 12 is estimated by the temperature estimation unit 1020. 1 However, when a temperature sensor is provided in the measurement chamber, the value of the temperature T may be obtained from this temperature sensor. 1

[0056] [Third Embodiment] Next, a third embodiment of the present invention will be described. FIG. 11 is a block diagram showing the configuration of a diaphragm vacuum gauge according to the third embodiment of the present invention. The diaphragm vacuum gauge of this embodiment includes a pressure measurement chamber 3b provided to communicate with the measurement chamber 12 via a pipe 2b, a pressure receiving portion 5, a heater 6, a temperature sensor 8, a circuit portion 10b, and a heat flux sensor 11 that measures the heat flux in the pipe 2b.

[0057] In the first and second embodiments, the pressure adjustment chambers 1 and 1a were provided. However, in this embodiment, the medium to be measured is directly introduced from the measurement chamber 12 into the pressure measurement chamber 3b via the pipe 2b. In this case, the measurement chamber 12 serves as a pressure adjustment chamber, and the pipe 2b serves as a throttle.

[0058] The pressure receiving portion 5 and the heater 6 are the same as those in the first embodiment. FIG. 12 is a block diagram showing the configuration of the circuit portion 10b of this embodiment. The circuit portion 10b includes a signal detection unit 100, an AD conversion unit 101, an arithmetic processing unit 102b, a memory 103b, a power supply 104, and an interface unit 105. The signal detection unit 100 and the AD conversion unit 101 are as described in the first embodiment.

[0059] As shown in FIG. 12, the arithmetic processing unit 102b includes a temperature estimation unit 1020b, a control unit 1021, a capacitance calculation unit 1022, a capacitance difference calculation unit 1023, a capacitance correction unit 1024, a pressure measurement unit 1025, and a pressure correction unit 1026b.

[0060] FIG. 13 is a flowchart for explaining the operation of the arithmetic processing unit 102b. The temperature estimation unit 1020b estimates the temperature T of the measured medium in the measurement chamber 12 from the heat flow rate measured by the heat flow sensor 11 (step S200 in FIG. 13). The relationship between the heat flow in the pipe 2b and the temperature T of the measured medium in the measurement chamber 12 has been confirmed by a prior test. The temperature estimation unit 1020b may calculate the temperature T from the heat flow rate according to a preset formula, or may obtain the value of the temperature T corresponding to the heat flow rate from a preset table. 1 Let the heat flux obtained by area conversion of the heat flow rate measured by the heat flow sensor 11 be q (W / m 1 ), and assuming heat transfer by convective heat transfer, the relationship between the heat flux q, the temperature T measured by the temperature sensor 8, and the temperature T of the measured medium in the measurement chamber 12 is as follows. 1 q = k(T 1 - T

[0061] ) ···(3) 2 ) 2 In equation (3), k is the heat transfer coefficient. From equation (3), the temperature T can be calculated from the heat flux q and the temperature T. 1 2 1

[0062] 2 1

[0063] The operations of the control unit 1021, the capacity calculation unit 1022, the capacity difference calculation unit 1023, the capacity correction unit 1024, and the pressure measurement unit 1025 (steps S201 to S205 in FIG. 13) are the same as those in the first embodiment.

[0064] Similar to the first embodiment, the pressure correction unit 1026b is based on the temperature T of the measured medium in the pressure measurement chamber 3 measured by the temperature sensor 8 and the temperature T of the measured medium in the measurement chamber 12 estimated by the temperature estimation unit 1020b. And based on the pressure measurement value P 2 1 2Obtain the corrected value (step S206 in FIG. 13). Specifically, the pressure correction unit 1026b obtains the value of the pressure P 2 ,T 1 corresponding to the temperature T 2 and the pressure measurement value P 1 from a preset correlation table. Needless to say, the correlation table is calibrated for this embodiment.

[0065] Then, the pressure correction unit 1026b outputs the calculated pressure value P 1 to, for example, a host device via the interface unit 105 (step S207 in FIG. 13). The arithmetic processing unit 102b performs the processing of steps S200 to S207 at each measurement cycle until the pressure measurement operation ends, for example, according to a user's instruction (YES in step S208 in FIG. 13).

[0066] Thus, in this embodiment, the same effects as those of the first embodiment can be obtained. In this embodiment, the temperature T 1 of the measurement medium in the measurement chamber 12 is estimated by the temperature estimation unit 1020b. However, when a temperature sensor is provided in the measurement chamber 12, the value of the temperature T 1 may be obtained from this temperature sensor.

[0067] In the first to third embodiments, the pressure correction units 1026 and 1026b always correct the pressure measurement value P 2 , but it is not limited thereto. That is, the pressure correction units 1026 and 1026b usually output the pressure measurement value P 2 as the pressure value P 1 without correction, and correct the pressure measurement value P 2 only when the pressure measurement value P 2 falls below the lower limit of the specified pressure measurement range by the processing of steps S106 and S206.

[0068] Also, in the first to third embodiments, the value (Cx - Cr) / Cx obtained by correcting the capacitance Cx with the reference capacitance Cr is calculated, but it is not limited thereto, and the capacitance Cx is related to the pressure measurement value P2 It may be converted.

[0069] The arithmetic processing units 102 and 102b described in the first to third embodiments can be realized by a computer including a CPU (Central Processing Unit), a storage device, and an interface, and a program for controlling these hardware resources. A configuration example of this computer is shown in FIG. 14.

[0070] The computer includes a CPU 400, a storage device 401, and an interface device (I / F) 402. The heater 6, the AD conversion unit 101, etc. are connected to the I / F 402. In such a computer, a program for realizing the method of the present invention is stored in the storage device 401. The CPU 400 executes the processes described in the first to third embodiments according to the program stored in the storage device 401.

Industrial Applicability

[0071] The present invention can be applied to pressure measurement technology.

Explanation of Reference Numerals

[0072] 1, 1a... pressure adjustment chamber, 2, 2a... pipe, 3, 3a, 3b... pressure measurement chamber, 4, 4a... throttle, 5... pressure receiving part, 6... heater, 7, 8... temperature sensor, 10, 10b... circuit part, 11... heat flow sensor, 12... chamber to be measured, 100... signal detection part, 101... AD conversion part, 102, 102b... arithmetic processing part, 103, 103b... memory, 104... power supply, 105... interface part, 1020, 1020b... temperature estimation part, 1021... control part, 1022... capacity calculation part, 1023... capacity difference calculation part, 1024... capacity correction part, 1025... pressure measurement part, 1026, 1026b... pressure correction part.

Claims

1. A pressure adjustment chamber provided to communicate with the measurement chamber via a pipe, A pressure measurement chamber provided to communicate with the measurement chamber via the pipe and to communicate with the pressure adjustment chamber, A pressure receiving part configured such that the capacitance changes according to the displacement of a diaphragm due to the pressure of the medium to be measured in the pressure measurement chamber, A first temperature sensor configured to measure the temperature of the medium to be measured in the pressure measurement chamber, A pressure measurement part configured to convert the capacitance into a pressure measurement value, A pressure correction part configured to correct the pressure measurement value based on the temperature measured by the first temperature sensor and the temperature of the medium to be measured in the measurement chamber, The medium to be measured flows into the pressure adjustment chamber and the pressure measurement chamber from the measurement chamber via the pipe, A diaphragm vacuum gauge characterized in that the temperature difference between the temperature of the medium to be measured in the pressure measurement chamber and the temperature of the medium to be measured in the measurement chamber is converted into a pressure difference to correct the pressure measurement value.

2. In the diaphragm vacuum gauge according to Claim 1, The pressure adjustment chamber and the pressure measurement chamber communicate with each other via a throttle, The throttle is a fixed throttle or a variable throttle, characterized in that it is a diaphragm vacuum gauge.

3. In the diaphragm vacuum gauge according to Claim 1 or 2, A second temperature sensor configured to measure the temperature of the medium to be measured in the pressure adjustment chamber, A diaphragm vacuum gauge further comprising a temperature estimation part configured to estimate the temperature of the medium to be measured in the measurement chamber from the temperature measured by the second temperature sensor.

4. A pressure adjustment chamber provided to communicate with the measurement chamber via a pipe, A pressure measurement chamber provided to communicate with the pressure adjustment chamber, A pressure receiving part configured such that the capacitance changes according to the displacement of a diaphragm due to the pressure of the medium to be measured in the pressure measurement chamber, A first temperature sensor configured to measure the temperature of the medium to be measured in the pressure measurement chamber, A second temperature sensor configured to measure the temperature of the medium to be measured in the pressure adjustment chamber, A temperature estimation part configured to estimate the temperature of the medium to be measured in the measurement chamber from the temperature measured by the second temperature sensor, A pressure measurement part configured to convert the capacitance into a pressure measurement value, A pressure correction unit configured to correct the pressure measurement value based on the temperature measured by the first temperature sensor and the temperature of the medium to be measured in the chamber to be measured. A diaphragm vacuum gauge characterized in that a temperature difference between the temperature of the medium to be measured in the pressure measurement chamber and the temperature of the medium to be measured in the chamber to be measured is converted into a pressure difference to correct the pressure measurement value.

5. A pressure measurement chamber provided to communicate with the chamber to be measured via a pipe. A pressure receiving unit configured such that the capacitance changes according to the displacement of the diaphragm due to the pressure of the medium to be measured in the pressure measurement chamber. A first temperature sensor configured to measure the temperature of the medium to be measured in the pressure measurement chamber. A heat flux sensor configured to measure the heat flux in the pipe. A temperature estimation unit configured to estimate the temperature of the medium to be measured in the chamber to be measured from the heat flux measured by the heat flux sensor. A pressure measurement unit configured to convert the capacitance into a pressure measurement value. A pressure correction unit configured to correct the pressure measurement value based on the temperature measured by the first temperature sensor and the temperature of the medium to be measured in the chamber to be measured. A diaphragm vacuum gauge characterized in that a temperature difference between the temperature of the medium to be measured in the pressure measurement chamber and the temperature of the medium to be measured in the chamber to be measured is converted into a pressure difference to correct the pressure measurement value.

6. A pressure adjustment chamber provided to communicate with the chamber to be measured via a pipe. A pressure measurement chamber provided to communicate with the pressure adjustment chamber. A pressure receiving unit configured such that the capacitance changes according to the displacement of the diaphragm due to the pressure of the medium to be measured in the pressure measurement chamber. A first temperature sensor configured to measure the temperature of the medium to be measured in the pressure measurement chamber. A pressure measurement unit configured to convert the capacitance into a pressure measurement value. A pressure correction unit configured to correct the pressure measurement value based on the temperature measured by the first temperature sensor and the temperature of the medium to be measured in the chamber to be measured. A heater configured to heat the pressure measurement chamber. A control unit configured to supply power to the heater to generate heat so that the temperature difference between the temperature of the medium to be measured in the pressure measurement chamber and the temperature of the medium to be measured in the chamber to be measured becomes a predetermined value. A diaphragm vacuum gauge characterized by converting the temperature difference between the temperature of the medium to be measured in the pressure measurement chamber and the temperature of the medium to be measured in the chamber to be measured into a pressure difference to correct the pressure measurement value.

7. A pressure measurement chamber provided to communicate with the chamber to be measured via a pipe, A pressure receiving part configured such that the capacitance changes according to the displacement of the diaphragm due to the pressure of the medium to be measured in the pressure measurement chamber, A first temperature sensor configured to measure the temperature of the medium to be measured in the pressure measurement chamber, A pressure measurement part configured to convert the capacitance into a pressure measurement value, A pressure correction part configured to correct the pressure measurement value based on the temperature measured by the first temperature sensor and the temperature of the medium to be measured in the chamber to be measured, A heater configured to heat the pressure measurement chamber, A control part configured to supply power to the heater to generate heat so that the temperature difference between the temperature of the medium to be measured in the pressure measurement chamber and the temperature of the medium to be measured in the chamber to be measured becomes a predetermined value, and comprising A diaphragm vacuum gauge characterized by converting the temperature difference between the temperature of the medium to be measured in the pressure measurement chamber and the temperature of the medium to be measured in the chamber to be measured into a pressure difference to correct the pressure measurement value.

8. In the diaphragm vacuum gauge according to any one of claims 1 to 7, The pressure receiving part is A first electrode formed on a pedestal, The diaphragm disposed with a gap from the pedestal, A second electrode formed on the diaphragm so as to face the first electrode, A third electrode formed on the pedestal outside the first electrode, Composed of a fourth electrode formed on the diaphragm outside the second electrode so as to face the third electrode, A capacitance calculation part configured to calculate a first capacitance between the first and second electrodes, A capacitance difference calculation part configured to calculate a value obtained by subtracting a second capacitance between the third and fourth electrodes from the first capacitance, Further comprising a capacitance correction part configured to correct the first capacitance by the second capacitance based on the calculation result of the capacitance calculation part and the calculation result of the capacitance difference calculation part, The pressure measurement part is a diaphragm vacuum gauge characterized by converting the corrected first capacitance into the pressure measurement value.

9. A pressure adjustment chamber provided to communicate with the chamber to be measured via a pipe, A pressure measurement chamber provided to communicate with the pressure adjustment chamber, A pressure-receiving part configured such that the capacitance changes in accordance with the displacement of a diaphragm due to the pressure of a medium to be measured in the pressure measurement chamber; A first temperature sensor configured to measure the temperature of the medium to be measured in the pressure measurement chamber; A pressure measurement part configured to convert the capacitance into a pressure measurement value; A pressure correction part configured to correct the pressure measurement value based on the temperature measured by the first temperature sensor and the temperature of the medium to be measured in the measurement chamber only when the pressure measurement value falls below the lower limit of a specified pressure measurement range; and A diaphragm vacuum gauge characterized in that a temperature difference between the temperature of the medium to be measured in the pressure measurement chamber and the temperature of the medium to be measured in the measurement chamber is converted into a pressure difference to correct the pressure measurement value.

10. A pressure measurement chamber provided to communicate with a measurement chamber via a pipe; A pressure-receiving part configured such that the capacitance changes in accordance with the displacement of a diaphragm due to the pressure of a medium to be measured in the pressure measurement chamber; A first temperature sensor configured to measure the temperature of the medium to be measured in the pressure measurement chamber; A pressure measurement part configured to convert the capacitance into a pressure measurement value; A pressure correction part configured to correct the pressure measurement value based on the temperature measured by the first temperature sensor and the temperature of the medium to be measured in the measurement chamber only when the pressure measurement value falls below the lower limit of a specified pressure measurement range; and A diaphragm vacuum gauge characterized in that a temperature difference between the temperature of the medium to be measured in the pressure measurement chamber and the temperature of the medium to be measured in the measurement chamber is converted into a pressure difference to correct the pressure measurement value.

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