JP5151934B2 - Vacuum gauge - Google Patents

Description

  The present invention relates to a vacuum gauge using a vibrating body, and more particularly to a vacuum gauge configured to vibrate the vibrating body in two directions having different measurable pressure ranges.

  Conventionally, a vacuum sensor that measures the pressure of an atmosphere using a tuning fork type vibrating body is known (see Patent Document 1). The principle of measuring the atmospheric pressure using a tuning fork type vibrator is to vibrate the vibrator and specify the vacuum pressure of the atmosphere from its vibration characteristics.

Conventionally, a pressure sensor that measures a gas pressure from vibration characteristics of a vibrating body by vibrating the vibrating body in two directions is also known (see Patent Document 2).
Japanese Patent Laid-Open No. 62-137533 Japanese Patent Laid-Open No. 08-338776 (paragraph in FIG. 5, 0059)

  When a vibrating body is used in a vacuum gauge, generally, the Q value of a plate-like vibrator is inversely proportional to the gas pressure P. Accordingly, the Q value of the plate-like vibrator can be expressed as the following formula (1), where C is a coefficient depending on the shape of the vibrator in relation to the gas pressure P.

The practical measurement range of the Q value of the vibrator of a vacuum gauge (also referred to as a vacuum sensor) is about 100 to 100,000. Therefore, there has been a problem that the measurable pressure range is limited to about 3 digits.

  Moreover, the pressure sensor in the above-mentioned patent document 2 employs a configuration in which two separate electrodes for vibrating the vibrating body in two directions with electrostatic force are provided and the vibration direction is switched depending on the pressure of the gas to be measured. Therefore, there is a problem that the gas pressure cannot be continuously measured and the circuit configuration becomes complicated.

  In order to solve the above-described problems, the present invention can vibrate a vibrating body in two directions having different measurable pressure ranges with an electrostatic force generated by a pair of excitation electrodes. An object of the present invention is to provide a vacuum gauge that does not require a circuit for switching the vibration direction according to pressure.

  In order to solve the above-described problem, a vacuum gauge according to the present invention includes a vibrating body formed so as to vibrate in a first vibration direction and a second vibration direction orthogonal to the first vibration direction. A vibrating electrode unit for driving the vibrating body by electrostatic force, a vibration detecting unit for detecting the vibration of the vibrating body, and amplifying the detection signal by changing the phase based on the detection signal of the vibration detecting unit. A drive signal generating unit that generates a drive signal for exciting the vibrating body by applying the drive signal to the excitation electrode unit to hold the vibrating body in a resonance state, A vacuum gauge for measuring atmospheric pressure from vibration characteristics, comprising: first and second excitation electrodes installed along the first vibration direction on both sides of the vibrating body as the excitation electrode portion A set of excitation electrodes, and the vibrating body is connected to a second vibration method The first and second vibration detectors are arranged above or below the one set of excitation electrodes and detect vibrations in the first and second vibration directions of the vibrating body as the vibration detectors, respectively. And applying a reverse-phase drive signal based on the detection signal of the first vibration detection unit to the one set of excitation electrodes to vibrate the vibrating body in the first vibration direction to measure the pressure. A second measuring unit configured to apply a driving signal having the same phase based on the detection signal of the pressure measurement unit and the second vibration detection unit to the one set of excitation electrodes to vibrate the vibrating body in the second vibration direction and measure the pressure; The pressure measurement unit is provided (invention of claim 1).

  According to the first aspect of the present invention, the pressure can be measured by vibrating in both the first and second vibration directions in which the pressure range in which the vibrating body can be measured by the electrostatic force generated by one set of excitation electrodes is different. As a result, the pressure range that can be measured with a simple configuration can be expanded.

  2. The vacuum gauge according to claim 1, wherein the drive signal generation unit amplifies the phase shift circuit that changes the phase of the detection signal of the first or second vibration detection unit, and the output signal of the phase shift circuit And an inverting circuit that inverts the phase of the output signal of the amplifier, and outputs each of the output signals of the inverting circuit and the amplifier as a reverse-phase drive signal based on the detection signal of the first vibration detection unit. By applying to each of the first and second excitation electrodes, the resonance state in the first vibration direction of the vibrating body is maintained, and as a drive signal having the same phase based on the detection signal of the second vibration detection unit The resonance state of the vibrating body in the second vibration direction may be maintained by applying the output signal of the amplifier to both the first and second excitation electrodes. ).

  In the vacuum gauge according to claim 1, any one of a reverse-phase drive signal based on the detection signal of the first vibration detection unit and an in-phase drive signal based on the detection signal of the second vibration detection unit It is preferable to have means for switching the vibration direction of the vibrating body by selecting whether to apply a drive signal to the set of excitation electrodes (invention of claim 3).

  In addition, the vacuum gauge of the present invention includes a vibrator configured to vibrate in a first vibration direction and a second vibration direction orthogonal to the first vibration direction, and the vibration body. A vibrating electrode unit driven by electric power, a vibration detecting unit for detecting the vibration of the vibrating member, and based on the detection signal of the vibration detecting unit, the phase of the detection signal is changed and amplified to add the vibrating member. A drive signal generation unit that generates a drive signal to vibrate, and applies the drive signal to the excitation electrode unit to hold the vibrating body in a resonance state, and the atmospheric pressure is determined from the vibration characteristics of the vibrating body. A set of excitation electrodes comprising first and second excitation electrodes installed along the first vibration direction on both sides of the vibrator as the excitation electrode portion And the set of the vibrating bodies in the second vibration direction. First and second vibration detectors that are arranged above or below the vibrating electrode and detect vibrations in the first and second vibration directions of the vibrator as the vibration detectors, respectively, and the drive signal The generation unit outputs a first addition signal obtained by adding the inversion side signal of the drive signals based on the detection signal of the first vibration detection unit and the drive signal based on the detection signal of the second vibration detection unit. Applying to the first excitation electrode and adding the non-inversion side signal of the drive signal based on the detection signal of the first vibration detection unit and the drive signal based on the detection signal of the second vibration detection unit A pressure measuring unit that applies a second addition signal to the second excitation electrode and measures the pressure by simultaneously vibrating the vibrating body in the first and second vibration directions. (Invention of Claim 4).

  According to the invention of claim 4 as well, it is possible to measure the pressure by vibrating in both the first and second vibration directions in which the pressure range in which the vibrating body can be measured by the electrostatic force generated by one set of excitation electrodes is different. Therefore, the measurable pressure range can be expanded with a simple configuration.

  According to the invention of claim 4, unlike the case where the vibration direction is switched by the gas pressure by simultaneously vibrating the vibrating body in the first and second vibration directions and simultaneously measuring each pressure, A wide range of pressures can be continuously measured.

Further, according to the fourth aspect of the present invention, since a circuit for switching the vibration direction of the vibrating body is not required, the circuit can be simplified.
5. The vacuum gauge according to claim 4, wherein the drive signal generator includes first and second phase shift circuits that change phases of detection signals of the first and second vibration detectors, respectively. First and second amplifiers for amplifying output signals of the first and second phase shift circuits, an inverting circuit for inverting the phase of the output signal of the first amplifier, and an output signal of the first amplifier; A first addition circuit for adding the output signal of the second amplifier, and a second addition circuit for adding the output signal of the inverting circuit and the output signal of the second amplifier, By applying the first and second addition signals output from the first and second addition circuits to the first and second excitation electrodes, respectively, in the first and second vibration directions of the vibrating body, If you keep each resonance state There (invention of claim 5).

  The vacuum gauge according to any one of claims 1 to 5, wherein the drive signal generation unit is a signal obtained by changing the phase of the detection signal of the vibration detection unit so that the voltage of the drive signal is constant. The pressure measurement unit may measure the pressure based on the magnitude of the detection signal of the vibration detection unit (invention of claim 6).

  The vacuum gauge according to any one of claims 1 to 5, wherein the drive signal generation unit detects the detection signal of the vibration detection unit so that the magnitude of the detection signal of the vibration detection unit is constant. The gain of the amplification with respect to the signal whose phase is changed may be adjusted, and the pressure measurement unit may measure the pressure based on the voltage of the drive signal (invention of claim 7).

  The vacuum gauge according to any one of claims 1 to 7, further comprising an initial excitation signal source that outputs an initial excitation signal having a frequency corresponding to a natural frequency of the vibrating body, and at the time of initial driving of the vibrating body, Instead of the drive signal based on the detection signal of the vibration detection unit, an initial drive signal based on the initial excitation signal may be applied to the excitation electrode unit (invention of claim 8).

  9. The vacuum gauge according to claim 1, wherein the vibration detection unit detects vibration of the vibrating body by detecting a capacitance between the vibrating body and a detection electrode. 10. It is good to make it (thing of invention of Claim 9).

  According to the present invention, evaluation is possible by measuring the pressure by vibrating a vibrating body from one set of excitation electrodes in both the first vibration direction and the second vibration direction, which have different measurable pressure ranges. It is possible to widen the pressure range. In addition, by simultaneously oscillating the vibrating body in the first vibration direction and the second vibration direction and simultaneously measuring the pressure in each vibration direction, it is possible to continuously measure the pressure with an expandable pressure range. Is possible. In addition, since a circuit for switching the vibration direction is not necessary, the circuit can be simplified.

The best mode for carrying out the invention will be described below with reference to the drawings.
[Embodiment 1]
FIG. 1 is a plan view of a structure constituting a mechanical part of a vacuum gauge according to an embodiment of the present invention, and FIG. 2 is a side view of the structure shown in FIG. In FIG. 1 and FIG. 2, the structure constituting the mechanism of the vacuum gauge includes a vibrating body 4 including a weight 1, a beam 2 and a vibrating body fixing portion 3, excitation electrodes 5 and 6 for exciting the vibrating body 4, It comprises vibration detection electrodes 7 and 8 for detecting vibrations in the first vibration direction of the vibrating body 4, and a vibration detection electrode 9 for detecting vibrations in the second vibration direction orthogonal to the first vibration direction. The

  FIG. 3 is a cross-sectional view taken along the line A-A ′ of FIG. 1, and the beam 2 is disposed above the surface B-B ′ of the excitation electrodes 5 and 6. It should be noted that the arrangement at the top is merely an example, and the beam 2 may be positioned below the surface B-B ′ of the excitation electrodes 5 and 6.

Next, the relationship between the shape of the vibrating body 4, the Q value of the vibrating body 4, and the gas pressure P will be described. The vibrating body 4 receives a resistance force due to collision of gas molecules. In the molecular flow region, the resistance force by the gas molecules is directly proportional to the gas pressure P. As the gas pressure decreases, the resistance force that the vibrating body 4 receives from the gas molecules decreases, so the Q value (resonance sharpness) of the vibrating body increases. However, the vibrating body 4 has a specific Q value Q _E and never exceeds the specific Q value Q _E. That is, the lower limit of the pressure of the gas that can vibrator 4 is measured, meant to be limited by the specific Q value Q _E.

The Q value of the vibrating body 4 and the gas pressure P are _expressed as follows: fr is the natural frequency of the vibrating body 4, m is the mass of the weight, S is the area that receives the gas resistance, R is the gas constant, T is the temperature, and M is Assuming mass per 1 mol of gas molecule,

It is known that
FIG. 4 is a diagram illustrating an example of the design value of the vibrating body according to the embodiment of the present invention. FIG. 5 illustrates the relationship between the Q value and the gas pressure P in the design value of the vibrating body illustrated in FIG. FIG. As shown in FIG. 5, the gas pressure that can be measured when vibrating in the first vibration direction is about 10 Pa to about 10,000 Pa, and the gas that can be measured when vibrating in the second vibration direction. The pressure is about 0.1 Pa to about 100 Pa. That is, the gas pressure that can be measured according to the vibration direction can be changed. Note that the natural frequencies in the first and second vibration directions of the vibrating body shown in FIG. 4 are about 1680 Hz and about 560 Hz, respectively, when the vibrating body is made of silicon, for example.

  Next, the circuit configuration of the vacuum gauge according to the embodiment of the present invention will be described. FIG. 6 is a block diagram showing a circuit configuration of the vacuum gauge according to the first embodiment of the present invention, in which a voltage corresponding to a change in electrostatic capacitance between the vibrating body 4 and the vibration detecting electrodes 7, 8 and 9 is shown. Capacitance voltage conversion circuits 10, 11 and 12 to output, difference circuit 13 to output the difference between the output of capacitance voltage conversion circuit 10 and the output of capacitance voltage conversion circuit 11, output of capacitance voltage conversion circuit 12 and output of difference circuit 13 A control circuit 14 that outputs a corresponding output signal and a control signal (not shown), a phase shift circuit 15 that changes the phase of the signal output from the control circuit 14, an amplifier 16 that amplifies the output of the phase shift circuit 15, and a control circuit 14 Switch circuits 17 and 18 for switching the connection according to the control signal from, an inverting circuit 19 for inverting the phase of the signal output from the amplifier 16, and an initial excitation signal source 21 for the vibrating body 4.

  Next, the operation of the circuit configuration of the vacuum gauge according to the first embodiment of the present invention will be described. In FIG. 6, when the gas pressure is high (about 10 Pa or more), the gas pressure P is evaluated by vibrating the vibrating body 4 in the first vibration direction. When the vibrating body 4 is vibrated in the first vibration direction, the switch circuit 18 is connected to D and E, and the signal output from the initial vibration signal source 21 is opposite to the vibration electrodes 5 and 6. Applied as a phase signal. The output of the control circuit 14 is in a state where the output signal of the difference circuit 13 is output. A signal having a frequency corresponding to the natural frequency in the first vibration direction of the vibrating body 4 is output from the signal source 21 for initial excitation, and a signal having a reverse phase is applied to the excitation electrodes 5 and 6 to thereby generate the vibrating body. 4 is vibrated in the first vibration direction. The initial excitation signal source 21 is used only during initial driving. After the vibrating body 4 starts to vibrate, the switch circuit 17 is switched and A and C are connected. Note that the switching control of the switch circuit 17 is performed, for example, when the amplitude of the vibrating body 4, that is, the magnitude of the output signal of the control circuit 14 (the output signal of the difference circuit 13) output in accordance with the displacement of the vibrating body 4 is set in advance. The switch circuit control unit (not shown) detects that the set value has been reached, and the switch circuit control unit gives a switch signal from the B side to the C side at the detection timing. it can.

  Then, in a state where A and C are connected by the switch circuit 17, the phase of the output signal of the difference circuit 13 output from the control circuit 14 is shifted by the phase shift circuit 15, amplified by the amplifier 16, and further amplified by the amplifier 16 Is inverted by an inverting circuit 19. The output of the inverting circuit 19 and the output of the amplifier 16 are respectively applied to the excitation electrode 5 and the excitation electrode 6 so that the resonance state of the vibrating body 4 in the first vibration direction is maintained.

  On the other hand, when the gas pressure is low (less than about 10 Pa), the gas pressure P is evaluated by vibrating the vibrating body 4 in the second vibration direction. When the vibrating body 4 is vibrated in the second vibration direction, the switch circuit 18 is connected to D and F, and the signal output from the initial vibration signal source 21 is in phase with the vibrating electrodes 5 and 6. It is a state applied as a signal. Since the vibrating body 4 is disposed above the excitation electrodes 5 and 6, electrostatic attraction acts in the second vibration direction, and the vibration body 4 is excited in the second vibration direction. Further, the output of the control circuit 14 is a state in which the output signal of the capacitance voltage conversion circuit 12 is output. A signal having a frequency corresponding to the natural frequency of the vibration body 4 in the second vibration direction is output from the initial vibration signal source 21 and the in-phase signal is applied to the vibration electrodes 5 and 6 so that the vibration body 4 Is vibrated in the second vibration direction. The initial excitation signal source 21 is used only during initial driving. After the vibrating body 4 starts to vibrate, the switch circuit 17 is switched and A and C are connected. The switching control of the switch circuit 17 can be performed in the same manner as described in the case where the vibrating body 4 is vibrated in the first vibration direction.

  Then, in a state where A and C are connected in the switch circuit 17, the phase of the output signal of the capacitance voltage conversion circuit 12 output from the control circuit 14 is shifted by the phase shift circuit 15, and the output signal of the phase shift circuit 15 is changed. The output of the amplifier 16 to be amplified is applied to both the excitation electrode 5 and the excitation electrode 6 so that the resonance state of the vibrating body 4 in the second vibration direction is maintained.

  When the gain of the amplifier 16 is adjusted so that the voltage of the drive signal applied to the excitation electrodes 5 and 6 is constant, the amplitude of the vibrating body 4 corresponding to the Q value of the vibrating body 4, that is, The magnitude of the output signal of the control circuit 14 (the output signal of the difference circuit 13 or the capacity voltage conversion circuit 12) that is output according to the displacement of the vibrating body 4 changes. Therefore, it is possible to measure the gas pressure by converting the output signal of the control circuit 14 into a Q value and further converting it into a gas pressure P. In addition, by switching the vibration direction of the vibrating body 4 by the switch circuit 18 according to the gas pressure, it is possible to measure a wide range of gas pressures. Further, the conversion from the output signal (amplitude of the vibrating body) of the control circuit 14 output according to the displacement of the vibrating body 4 to the pressure P value may be performed directly without passing through the Q value. .

  Here, in the case of the vibrator having the design values shown in FIG. 4 and made of silicon, the voltage of the drive signal applied to the excitation electrodes 5 and 6 is constant in the first vibration direction, for example. The relationship between the magnitude of the output signal of the control circuit 14 (the amplitude of the vibrating body) and the pressure P value when adjusting the gain of the amplifier 16 is as shown in FIG. 7 (about 10 Pa or more). In the high pressure region, the amplitude is almost inversely proportional to the pressure, and on the low pressure side, the amplitude is saturated toward its maximum limit value.

  Then, for example, the characteristic data of the relationship between the magnitude of the output signal of the control circuit 14 (amplitude of the vibrating body) and the pressure P value is acquired, and the conversion means provided with the storage unit storing the data table of the characteristic data The output signal (amplitude of the vibrating body) during actual measurement may be converted into a pressure P value, and a storage unit storing a relational expression approximately obtained from the characteristic data curve is provided. Alternatively, the conversion means may convert the output signal (the amplitude of the vibrating body) during actual measurement into a pressure P value.

  Further, the amplitude of the vibrating body 4, that is, the magnitude of the output signal of the control circuit 14 (the output signal of the difference circuit 13 or the capacity voltage converting circuit 12) output according to the displacement of the vibrating body 4 (the amplitude of the vibrating body) The gain of the amplifier 16 can be adjusted so that is constant. In this case, since the voltage of the drive signal applied to the excitation electrodes 5 and 6 changes corresponding to the Q value of the vibrating body 4, the drive signal is converted into the Q value and further converted into the gas pressure P. Thus, the pressure of the gas can be measured. Further, the conversion from the drive signal to the Q value may be performed directly without using the Q value.

  Here, in the case of the vibrator having the design values shown in FIG. 4 and the material being silicon, for example, in the first vibration direction, the magnitude of the output signal of the control circuit 14 (the amplitude of the vibrator) is constant. The relationship between the magnitude of the drive signal (drive voltage) and the pressure P value when the gain of the amplifier 16 is adjusted is as shown in FIG. 8 in the high-pressure region (about 10 Pa or more). The voltage is approximately proportional to the pressure, and on the low pressure side, the drive voltage decreases so as to saturate toward the minimum limit value.

Then, for example, the characteristic data of the relationship between the magnitude of the drive signal and the pressure P value is acquired, and the drive signal at the time of actual measurement is converted from the drive signal to the pressure P value by the conversion unit including the data table of the characteristic data. The conversion from the drive signal at the actual measurement to the pressure P value may be performed by a conversion means having a storage unit storing a relational expression approximately obtained from the curve of the characteristic data. It is good also as a structure to perform.
[Embodiment 2]
FIG. 9 is a block diagram showing a circuit configuration of a vacuum gauge according to the second embodiment of the present invention, where the same reference numerals as those in FIG. 6 denote the same names. 9, the circuit of the vacuum gauge according to the second embodiment of the present invention includes phase shift circuits 25 and 26, amplifiers 27 and 28, switch circuits 29 and 30, adder circuits 32 and 33, and an initial drive signal source 34. And 35 are newly provided. Further, since the structure of the vibrating body 4 is the same as that of the first embodiment of the present invention, the description thereof is omitted here.

  Next, the operation of the circuit configuration of the vacuum gauge according to the second embodiment of the present invention will be described. In FIG. 9, the initial drive signal source 34 has a frequency corresponding to the natural frequency in the first vibration direction of the vibrating body 4, and the initial drive signal source 35 has a characteristic in the second vibration direction of the vibration body 4. A signal with a frequency corresponding to the frequency is output. In the adder circuit 33, the output of the initial drive signal source 34 and the output of the initial drive signal source 35 are added, and in the adder circuit 32, the output of the initial drive signal source 34 and the initial drive signal source 35 that have passed through the inverting circuit 19 are added. The outputs are added. The outputs of the adding circuits 32 and 33 are applied to the excitation electrodes 5 and 6, and the vibrating body 4 is vibrated in the first vibration direction and the second vibration direction.

  The initial excitation signal sources 34 and 35 are used only during initial driving. After the vibrating body 4 starts to vibrate, the switch circuits 29 and 30 are switched to connect J and K, and G and H, respectively. Each switching control of the switch circuits 29 and 30 can be performed in the same manner as the switching control of the switch circuit 17 described in the first embodiment.

  Then, in a state where J and K and G and H are connected in the switch circuits 29 and 30, respectively, the phase of the output signal of the difference circuit 13 is shifted by the phase shift circuit 25 and amplified by the amplifier 27. Further, the phase of the output signal of the capacitor voltage conversion circuit 12 is shifted by the phase shift circuit 26 and amplified by the amplifier 28. In the adding circuit 33, the output of the amplifier 27 and the output of the amplifier 28 are added, and in the adding circuit 32, the output of the amplifier 27 and the output of the amplifier 28 that have passed through the inverting circuit 19 are added. The outputs of the adder circuits 32 and 33 are applied to the excitation electrodes 5 and 6 so that the respective resonance states in the first and second vibration directions of the vibrating body 4 are maintained.

  When the gains of the amplifiers 27 and 28 are respectively adjusted so that the voltage of the drive signal applied to the excitation electrodes 5 and 6 is constant, each of the vibrator 4 in the first and second vibration directions Corresponding to the Q value, the amplitudes of the vibrating body 4 in the first and second vibration directions, that is, the magnitudes of the output signals of the difference circuit 13 and the capacitance-voltage conversion circuit 12 output according to the displacement of the vibrating body 4 Changes. Therefore, it is possible to measure the gas pressure by converting these output signals into respective Q values in the first and second vibration directions and further converting them into the gas pressure P, respectively. As described in the first embodiment, the conversion from each output signal (amplitude of the vibrating body) of each of the difference circuit 13 and the capacity voltage conversion circuit 12 to each pressure P value is directly performed without passing through the Q value. You may make it convert into.

  Further, the amplifier 27 is set so that the amplitude of the vibrating body 4, that is, the magnitudes of the output signals of the difference circuit 13 and the capacity-voltage conversion circuit 12 (the amplitude of the vibrating body) output according to the displacement of the vibrating body 4 are constant. It is also possible to adjust the gains of 28 and 28 respectively. In this case, the voltage of each output signal that is output from the amplifiers 27 and 28 to the excitation electrodes 5 and 6 changes corresponding to each Q value in the first and second vibration directions of the vibrating body 4. It is possible to measure the gas pressure by converting the output signals 27 and 28 into Q values in the first and second vibration directions and further converting them into the gas pressure P, respectively. As described in the first embodiment, the conversion from the output signals of the amplifiers 27 and 28 to the pressure P values may be performed directly without passing through the Q value.

  In the second embodiment, two pressure P values are obtained corresponding to each Q value in the first and second vibration directions, and the pressure level of the gas at the time of measurement is in a high pressure region (for example, about 10 Pa or more). ) Or a low-pressure region (for example, less than about 10 Pa), an output signal (not shown) that selects and outputs a pressure P value corresponding to any Q value in the first or second vibration direction By providing the selection circuit, an appropriate pressure measurement signal can always be output from the vacuum gauge.

It is a top view of the structure which comprises the mechanism part of the vacuum gauge which concerns on embodiment of this invention. It is a side view of the structure shown in FIG. It is sectional drawing along the A-A 'line of the structure shown in FIG. It is a figure which shows an example of the design value of the vibrating body which concerns on the 1st Embodiment of this invention. FIG. 5 is a diagram illustrating a relationship between a Q value and a gas pressure P in the design value of the vibrating body illustrated in FIG. 4. It is a block diagram which shows the circuit structure of the vacuum gauge which concerns on the 1st Embodiment of this invention. FIG. 5 is a diagram showing the relationship between the amplitude of the vibrating body and the gas pressure P when the amplifier gain is adjusted so that the drive voltage is constant in the first vibration direction of the vibrating body having the design value shown in FIG. 4. FIG. 5 is a diagram illustrating a relationship between a driving voltage and a gas pressure P when the amplifier gain is adjusted so that the amplitude of the vibrating body is constant in the first vibration direction of the vibrating body having the design value illustrated in FIG. 4. It is a block diagram which shows the circuit structure of the vacuum gauge which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Weight 2 Beam 3 Vibrating body fixing | fixed part 4 Vibrating body 5,6 Excitation electrode 7-9 Vibration detection electrode
10-12 capacity voltage conversion circuit
13 Difference circuit
14 Control circuit
15, 25, 26 Phase shift circuit
16, 27, 28 amplifier
17, 18, 29, 30 Switch circuit
19 Inversion circuit
21, 34, 35 Initial drive signal source
32, 33 Adder circuit

Claims (9)

A vibrator configured to vibrate in a first vibration direction and a second vibration direction orthogonal to the first vibration direction, and an excitation electrode unit that drives the vibration body by electrostatic force; A vibration detection unit that detects the vibration of the vibration body, and a drive signal that generates a drive signal for exciting the vibration body by changing the phase of the detection signal based on the detection signal of the vibration detection unit A vacuum gauge that measures the pressure of the atmosphere from the vibration characteristics of the vibrating body by holding the vibrating body in a resonance state by applying the drive signal to the excitation electrode unit,
As the excitation electrode portion, a set of excitation electrodes including first and second excitation electrodes installed along the first vibration direction on both sides of the vibration body, and the vibration body, In the second vibration direction, disposed above or below the set of excitation electrodes,
The vibration detection unit includes first and second vibration detection units that detect vibrations in the first and second vibration directions of the vibrating body, respectively.
A first pressure measurement unit that measures a pressure by applying a drive signal having a reverse phase based on a detection signal of the first vibration detection unit to the set of excitation electrodes to vibrate the vibrating body in a first vibration direction When,
A second pressure measuring unit configured to apply a driving signal having the same phase based on the detection signal of the second vibration detecting unit to the one set of excitation electrodes to vibrate the vibrating body in the second vibration direction and measure the pressure; Comprising
A vacuum gauge characterized by that. The vacuum gauge according to claim 1,
The drive signal generation unit includes a phase shift circuit that changes a phase of a detection signal of the first or second vibration detection unit, an amplifier that amplifies an output signal of the phase shift circuit, and a phase of the output signal of the amplifier And an inverting circuit for inverting
By applying the output signals of the inverting circuit and the amplifier to the first and second excitation electrodes, respectively, as driving signals having opposite phases based on the detection signal of the first vibration detection unit, While maintaining the resonance state in the first vibration direction,
By applying the output signal of the amplifier to both the first and second excitation electrodes as an in-phase drive signal based on the detection signal of the second vibration detection unit, the second vibration direction of the vibrating body A vacuum gauge characterized by maintaining a resonance state in The vacuum gauge according to claim 1,
Any one of the driving signal of the opposite phase based on the detection signal of the first vibration detection unit and the driving signal of the same phase based on the detection signal of the second vibration detection unit is applied to the set of excitation electrodes. A vacuum gauge comprising means for switching the vibration direction of the vibrating body by selecting whether to apply. A vibrator configured to vibrate in a first vibration direction and a second vibration direction orthogonal to the first vibration direction, and an excitation electrode unit that drives the vibration body by electrostatic force; A vibration detection unit that detects the vibration of the vibration body, and a drive signal that generates a drive signal for exciting the vibration body by changing the phase of the detection signal and amplifying the detection signal based on the detection signal of the vibration detection unit A vacuum gauge that measures the pressure of the atmosphere from the vibration characteristics of the vibrating body by holding the vibrating body in a resonance state by applying the drive signal to the excitation electrode unit,
As the excitation electrode portion, a set of excitation electrodes including first and second excitation electrodes installed along the first vibration direction on both sides of the vibration body, and the vibration body, In the second vibration direction, disposed above or below the set of excitation electrodes,
The vibration detection unit includes first and second vibration detection units that detect vibrations in the first and second vibration directions of the vibrating body, respectively.
The drive signal generation unit adds a reverse signal in the drive signal based on the detection signal of the first vibration detection unit and a drive signal based on the detection signal of the second vibration detection unit. A signal is applied to the first excitation electrode, and a non-inversion side signal among drive signals based on the detection signal of the first vibration detection unit and a drive signal based on the detection signal of the second vibration detection unit are Applying a second addition signal obtained by addition to the second excitation electrode;
A pressure measuring unit that measures the pressure by simultaneously vibrating the vibrating body in the first and second vibration directions;
A vacuum gauge characterized by that. The vacuum gauge according to claim 4,
The drive signal generation unit includes first and second phase shift circuits that change phases of detection signals of the first and second vibration detection units, and outputs of the first and second phase shift circuits, respectively. First and second amplifiers for amplifying a signal, an inverting circuit for inverting the phase of the output signal of the first amplifier, and adding the output signal of the first amplifier and the output signal of the second amplifier And a second addition circuit for adding the output signal of the inverting circuit and the output signal of the second amplifier,
By applying the first and second addition signals output from the first and second addition circuits to the first and second excitation electrodes, respectively, in the first and second vibration directions of the vibrating body A vacuum gauge characterized by holding each resonance state. The vacuum gauge according to any one of claims 1 to 5,
The drive signal generation unit adjusts an amplification gain for a signal obtained by changing the phase of the detection signal of the vibration detection unit so that the voltage of the drive signal is constant,
The vacuum gauge according to claim 1, wherein the pressure measuring unit measures pressure based on a magnitude of a detection signal of the vibration detecting unit. The vacuum gauge according to any one of claims 1 to 5,
The drive signal generation unit adjusts an amplification gain for a signal obtained by changing the phase of the detection signal of the vibration detection unit so that the magnitude of the detection signal of the vibration detection unit is constant.
The vacuum gauge, wherein the pressure measuring unit measures pressure based on a voltage of the drive signal. The vacuum gauge according to any one of claims 1 to 7,
An initial excitation signal source for outputting an initial excitation signal having a frequency corresponding to the natural frequency of the vibrator;
A vacuum gauge, wherein an initial drive signal based on the initial excitation signal is applied to the excitation electrode unit instead of a drive signal based on a detection signal of a vibration detection unit when the vibrating body is initially driven. The vacuum gauge according to any one of claims 1 to 8,
The said vibration detection part detects the vibration of the said vibrating body by detecting the electrostatic capacitance between the said vibrating body and a detection electrode, The vacuum gauge characterized by the above-mentioned.