JP5353358B2 - Vacuum gauge - Google Patents
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- JP5353358B2 JP5353358B2 JP2009076112A JP2009076112A JP5353358B2 JP 5353358 B2 JP5353358 B2 JP 5353358B2 JP 2009076112 A JP2009076112 A JP 2009076112A JP 2009076112 A JP2009076112 A JP 2009076112A JP 5353358 B2 JP5353358 B2 JP 5353358B2
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Abstract
Description
本発明は、振動体を利用した真空計に関し、特に、広い範囲の気体の圧力を測定することができるようにした真空計に関する。 The present invention relates to a vacuum gauge using a vibrating body, and more particularly to a vacuum gauge capable of measuring a wide range of gas pressures.
従来、下記特許文献１に示されるように、被測定真空空間と導通する開口部を備えた密閉筐体の内壁面に振動自在となるように保持させた弾性体の振動特性から真空を測定する真空計が知られている。弾性体に接着固定した２つの圧電素子のうち、１つの圧電素子に高周波電圧を連続的に、もしくは、パルス的に印加することで弾性体を加振し、振動体の振動振幅をもう１つの圧電素子を介して検出する。加振電圧を一定とする場合は、気体の圧力が低下するに従い、弾性体の振幅は大きくなる。この振幅を検出することで間接的に気体の圧力を測定する。また、弾性体の振幅を一定に保持するようにし、一定振幅で振動させるために真空度の変化に伴って変化する加振電圧の変化量を検出することで、間接的に気体の圧力を測定することもできる。 Conventionally, as shown in the following Patent Document 1, a vacuum is measured from the vibration characteristics of an elastic body that is held so as to be able to vibrate on an inner wall surface of a sealed casing having an opening that is electrically connected to a vacuum space to be measured. A vacuum gauge is known. Of the two piezoelectric elements bonded and fixed to the elastic body, the elastic body is vibrated by applying a high-frequency voltage to one piezoelectric element continuously or in pulses, and the vibration amplitude of the vibrating body is set to another It detects through a piezoelectric element. When the excitation voltage is constant, the amplitude of the elastic body increases as the gas pressure decreases. The pressure of the gas is indirectly measured by detecting this amplitude. In addition, the pressure of the gas is indirectly measured by detecting the amount of change in the excitation voltage that changes with the change in the degree of vacuum in order to keep the amplitude of the elastic body constant and vibrate at a constant amplitude. You can also
一般に振動体の振幅aNは、振動体に加えた外力F0に比例して大きくなる。これを式で表すと、以下の式１となる。ただし、式１において、aNは振幅[m]、F0は外力[N]、QはQ値、mは振動体の質量[kg]、およびwRは固有角周波数[rad/s]である。 In general, the amplitude a N of the vibrating body increases in proportion to the external force F 0 applied to the vibrating body. When this is expressed by an equation, the following equation 1 is obtained. In Equation 1, a N is the amplitude [m], F 0 is the external force [N], Q is the Q value, m is the mass of the vibrating body [kg], and w R is the natural angular frequency [rad / s]. is there.
また、振動体のQ値を表すQは、気体の圧力Pに反比例して低下する。これを式で表すと、以下の式２となる。ただし、式２において、Sは並進方向の面積[m2]、Mは気体の質量[mol/kg]、Rは気体定数[J/mol・K]、およびTは温度[K]である。 Further, Q representing the Q value of the vibrating body decreases in inverse proportion to the gas pressure P. This is expressed by the following formula 2. In Equation 2, S is an area [m 2 ] in the translation direction, M is a gas mass [mol / kg], R is a gas constant [J / mol · K], and T is a temperature [K].
上記式１および式２から以下の式３を導出すると、振動体の振幅aNは、気体の圧力Pに反比例して低下することがわかる。 When the following formula 3 is derived from the above formulas 1 and 2, it can be seen that the amplitude a N of the vibrating body decreases in inverse proportion to the gas pressure P.
また振動体の左右の駆動電極に逆相の駆動信号を印加して振動体を加振した場合、振動体に加わる力は駆動信号の電圧に比例する。これを式で表すと、以下の式４となる。ただし、式４において、VDは駆動信号の電圧[V]、およびLは比例定数[N/V]である。 Further, when a vibration signal is applied to the left and right drive electrodes of the vibration member to vibrate the vibration member, the force applied to the vibration member is proportional to the voltage of the drive signal. This is expressed by the following expression 4. In Equation 4, V D is the voltage [V] of the drive signal, and L is a proportionality constant [N / V].
上記した式３および式４から、以下の式５を導出すると、 From Equation 3 and Equation 4 described above, the following Equation 5 is derived:
という関係を得る。ただし、Kは、以下の式６のように、 The relationship is obtained. However, K is as shown in Equation 6 below.
と表すことができる。図８に振動体の振幅aNを一定に保持した場合の測定可能な圧力Pａと駆動信号の電圧VDとの関係の一例を示す。上記式５で示したように、振動体の振幅aNが一定に保持されているため、気体の圧力Pに比例して駆動信号の電圧VDは大きくなる。そのため、気体の圧力が高い領域では駆動信号の電圧VDが非常に高くなる。一方、気体の圧力が低い領域では、駆動信号の電圧VDが低くなるので検出が困難になる。 It can be expressed as. FIG. 8 shows an example of the relationship between the measurable pressure Pa and the drive signal voltage V D when the amplitude a N of the vibrating body is kept constant. As shown in the above equation 5, since the amplitude a N of the vibrating body is kept constant, the voltage V D of the drive signal increases in proportion to the gas pressure P. Therefore, in the region where the gas pressure is high, the drive signal voltage V D is very high. On the other hand, in a region where the gas pressure is low, detection becomes difficult because the voltage V D of the drive signal is low.
本発明は、上記の点に鑑みてなされたものであり、１つの真空計でより広い範囲の気体の圧力を測定することができるようにした真空計を提供することを目的とする。 This invention is made | formed in view of said point, and it aims at providing the vacuum gauge which enabled it to measure the pressure of the gas of a wider range with one vacuum gauge.
上記課題を解決するために、本発明の真空計は、錘，梁および振動体固定部からなる振動体と、該振動体を静電力により駆動する加振電極部と、前記振動体の振動を検出する振動検出部と、前記振動体を加振する駆動信号を生成する駆動信号生成部とを有し、前記駆動信号を前記加振電極部に印加して前記振動体を共振状態に保持して、振動体の振動特性から気体の圧力を測定する圧力測定部を備えた真空計であって、前記駆動信号生成部は、前記振動検出部の検出信号の大きさが振幅指令値として予め設定された第一の一定の電圧値となるように前記駆動信号の電圧を調整し、前記圧力測定部は、前記駆動信号の電圧に基づいて気体の圧力を測定するとともに、測定した前記気体の圧力領域に応じて前記駆動信号生成部に対する前記振幅指令値を予め設定された第二の一定の電圧値に切り替えることで、気体の圧力がより高い領域に対応する振幅指令値が、気体の圧力がより低い領域に対応する振幅指令値よりも小さい振幅に設定されるように制御することを特徴とする（請求項１の発明）。 In order to solve the above-described problems, a vacuum gauge according to the present invention includes a vibrating body including a weight, a beam, and a vibrating body fixing portion , an excitation electrode unit that drives the vibrating body with an electrostatic force, and vibrations of the vibrating body. A vibration detection unit for detecting, and a drive signal generation unit for generating a drive signal for exciting the vibrator, and applying the drive signal to the excitation electrode unit to hold the vibrator in a resonance state. A vacuum gauge having a pressure measuring unit that measures the gas pressure from the vibration characteristics of the vibrating body, wherein the drive signal generating unit sets the magnitude of the detection signal of the vibration detecting unit as an amplitude command value in advance. voltage to adjust the first predetermined voltage value so as to the drive signal, the pressure measuring unit is configured to measure the pressure of the gas on the basis of the voltage of the drive signal, the pressure of the measured the gas The amplitude finger for the drive signal generation unit according to a region By switching to a second constant voltage value that is set the value in advance, the amplitude command value pressure of gas corresponding to higher areas is smaller than the amplitude command value the pressure of the gas corresponding to the lower domain amplitude and wherein the benzalkonium be controlled so as to be set to (the invention of claim 1).
上記請求項１の発明によれば、気体の圧力領域に応じて振幅指令値を予め設定された第一の一定の電圧値から第二の一定の電圧値に切り替えることで、気体の圧力がより高い領域に対応する振幅指令値が、気体の圧力がより低い領域に対応する振幅指令値よりも小さい振幅に設定されるように制御する圧力測定部を備えているので、駆動信号の電圧の調整により一定に制御される振動体の振幅を、圧力が高い領域では小さい振幅に保持し、圧力が低い領域では大きい振幅に保持するようにすることができる。これにより、圧力が高い領域では、振動体の振幅が小さく保持されることによって駆動信号の電圧を低く抑えることができるとともに、圧力が低い領域では振動体の振幅が大きく保持されることによって駆動信号の電圧が高くなり検出が容易になる。 According to the first aspect of the invention, the pressure of the gas is further increased by switching the amplitude command value from the preset first constant voltage value to the second constant voltage value according to the gas pressure region. Adjusting the voltage of the drive signal because it has a pressure measurement unit that controls the amplitude command value corresponding to the high region to be smaller than the amplitude command value corresponding to the region where the gas pressure is lower Thus, the amplitude of the vibrating body controlled to be constant can be maintained at a small amplitude in a region where the pressure is high, and can be maintained at a large amplitude in a region where the pressure is low. As a result, in the region where the pressure is high, the amplitude of the vibrating body is kept small by holding the vibration body low, and in the region where the pressure is low, the amplitude of the vibrating body is kept large, thereby driving the drive signal. The voltage becomes higher and detection becomes easier.
上記請求項１に記載の真空計において、前記駆動信号生成部は、前記振動検出部の検出信号に基づき、この検出信号の位相を変えて増幅又は減衰することにより前記振動体を加振する駆動信号を生成するようにするとよい(請求項２の発明)。 2. The vacuum gauge according to claim 1, wherein the drive signal generation unit is configured to vibrate the vibrating body by amplifying or attenuating by changing the phase of the detection signal based on the detection signal of the vibration detection unit. A signal may be generated (invention of claim 2).
上記請求項２に記載の真空計において、前記駆動信号生成部は、前記振動検出部の検出信号の位相を変化させる位相シフト回路と、該位相シフト回路の出力信号を増幅又は減衰して駆動信号を出力する駆動電圧調整回路とからなり、前記駆動電圧調整回路は、前記振動検出部の検出信号の大きさが振幅指令値として予め設定された第一および第二の一定の電圧値となるように前記増幅の利得を制御するようにするとよい(請求項３の発明)。 3. The vacuum gauge according to claim 2, wherein the drive signal generation unit includes a phase shift circuit that changes a phase of a detection signal of the vibration detection unit, and an output signal of the phase shift circuit by amplifying or attenuating the drive signal. The drive voltage adjustment circuit is configured so that the magnitude of the detection signal of the vibration detection unit becomes the first and second constant voltage values preset as amplitude command values. It is preferable to control the gain of the amplification.
上記請求項２または３に記載の真空計において、前記振動体の固有周波数に対応した周波数の初期励振信号を出力する初期励振用信号源を備え、前記振動体の初期駆動時には、前記振動検出部の検出信号に基づく駆動信号に代えて、前記初期励振信号に基づく初期駆動信号を前記加振電極部に印加するようにするとよい(請求項４の発明)。 4. The vacuum gauge according to claim 2, 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, wherein the vibration detection unit Instead of the drive signal based on this detection signal, an initial drive signal based on the initial excitation signal may be applied to the excitation electrode section (invention of claim 4).
上記請求項１ないし４のいずれか１項に記載の真空計において、前記振動検出部は、前記振動体と検出電極との間の静電容量の変化を検知して電圧に変換することにより前記振動体の振動を検出するようにするとよい（請求項５の発明）。
5. The vacuum gauge according to claim 1, wherein the vibration detector detects a change in capacitance between the vibrating body and a detection electrode and converts the change into a voltage. It is preferable to detect the vibration of the vibrating body (the invention of claim 5).
本発明によれば、気体の圧力が高い領域では、振動体の振幅を小さく保持することにより駆動信号の電圧VDを小さくすることができる。一方、気体の圧力が低い領域では振動体の振幅を大きく保持することにより駆動信号の電圧VDが大きくなり検出が容易になる。 According to the present invention, in the region where the gas pressure is high, the voltage V D of the drive signal can be reduced by keeping the amplitude of the vibrating body small. On the other hand, in the region where the gas pressure is low, the amplitude of the vibrating body is kept large, whereby the voltage V D of the drive signal is increased and the detection becomes easy.
以下、本発明の実施の形態について、詳細に説明する。
図１は本発明の実施形態に係る真空計の機構部分を成す構造体の平面図である。また図２は、図１に示す構造体の側面図である。図１および図２において真空計の機構部分を成す構造体は、錘1、梁2および振動体固定部3からなる振動体4、振動体を加振する加振電極5および6、振動体の振動を検出するための振動検出電極7および8から構成される。
［実施形態１］
図３は、本発明の実施形態に係る真空計の第１の回路構成を示すブロック図であり、振動体4の固有周波数に対応した駆動信号を生成する駆動用信号源10、駆動信号の電圧を調節する駆動電圧調整回路11、駆動電圧調整回路11の出力電圧の位相を180度反転させる反転回路12、振動体4と振動検出電極7および8との間の静電容量の変化に応じた電圧を出力する容量電圧変換回路13および14、容量電圧変換回路13および14の出力電圧の差分をとる差分回路15、駆動電圧調整回路11の出力電圧および差分回路15の出力電圧を検出し気体の圧力に応じた電圧を出力する電圧圧力変換回路16から構成される。
Hereinafter, embodiments of the present invention will be described in detail.
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. FIG. 2 is a side view of the structure shown in FIG. 1 and 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, It is composed of vibration detection electrodes 7 and 8 for detecting vibration.
[Embodiment 1]
FIG. 3 is a block diagram showing a first circuit configuration of the vacuum gauge according to the embodiment of the present invention. The driving signal source 10 generates a driving signal corresponding to the natural frequency of the vibrating body 4, and the voltage of the driving signal. Drive voltage adjustment circuit 11 that adjusts the output voltage, inverter circuit 12 that inverts the phase of the output voltage of drive voltage adjustment circuit 11 by 180 degrees, and changes in capacitance between vibration body 4 and vibration detection electrodes 7 and 8 Capacitance voltage conversion circuits 13 and 14 that output voltage, difference circuit 15 that takes the difference between the output voltages of capacitance voltage conversion circuits 13 and 14, the output voltage of drive voltage adjustment circuit 11 and the output voltage of difference circuit 15 are detected to detect the gas The voltage / pressure conversion circuit 16 outputs a voltage corresponding to the pressure.
次に、本発明の実施形態に係る真空計の第１の回路構成の動作について説明する。図６は、図３に示した第１の回路構成における出力信号の波形例を示すものであり、図６（a）は容量電圧変換回路13および14における出力信号波形、図６（b）は差分回路15における出力信号波形、図６（c）は駆動用信号源10における出力信号波形、図６（d）は駆動電圧調整回路11における出力信号波形、図６（e）は電圧圧力変換部16における出力信号波形を示すものである。駆動用信号源10から出力された信号（図６（c）参照）は駆動電圧調整回路11によって増幅もしくは減衰され、さらに、駆動電圧調整回路11の出力の位相は反転回路12で反転される。反転回路12の出力および駆動電圧調整回路11の出力がそれぞれ加振電極5および6に印加されることで、振動体4が加振される。振動体4が振動することで振動体4と振動検出電極7および8との間の静電容量が変化するので、この静電容量の変化を容量電圧変換回路13および14で静電容量の変化、すなわち、振動体4の振幅に応じた電圧に変換する。容量電圧変換回路13および14の出力電圧（図６（ａ）参照）は逆位相であるので、差分回路15で出力電圧の差分をとることで振動体の振幅に応じた最終的な出力電圧（図６（ｂ）参照）を得る。差分回路15の出力は駆動電圧調整回路11にフィードバックされ、差分回路15の出力電圧が，設定された一定の電圧値となるように、すなわち、振動体の振幅が，振幅の指令値として設定された一定の振幅値となるように駆動電圧調整回路11のゲイン（利得）を制御する。電圧圧力変換回路16では、差分回路15の出力電圧（振動体の振幅）と駆動電圧調整回路11の出力信号（駆動信号）から気体の圧力Pを演算し、気体の圧力Pに応じた電圧（図６（ｅ）参照）を出力する。 Next, the operation of the first circuit configuration of the vacuum gauge according to the embodiment of the present invention will be described. FIG. 6 shows an example of the waveform of the output signal in the first circuit configuration shown in FIG. 3, FIG. 6 (a) shows the output signal waveform in the capacitor voltage conversion circuits 13 and 14, and FIG. 6 (b) shows the output signal waveform. The output signal waveform in the difference circuit 15, FIG. 6 (c) is the output signal waveform in the drive signal source 10, FIG. 6 (d) is the output signal waveform in the drive voltage adjustment circuit 11, and FIG. 6 (e) is the voltage-pressure converter. 16 shows an output signal waveform in FIG. A signal (see FIG. 6C) output from the drive signal source 10 is amplified or attenuated by the drive voltage adjustment circuit 11, and the phase of the output of the drive voltage adjustment circuit 11 is inverted by the inversion circuit 12. By applying the output of the inverting circuit 12 and the output of the drive voltage adjusting circuit 11 to the excitation electrodes 5 and 6, respectively, the vibrating body 4 is vibrated. Since the capacitance between the vibrating body 4 and the vibration detection electrodes 7 and 8 changes when the vibrating body 4 vibrates, this capacitance change is changed by the capacitance-voltage conversion circuits 13 and 14. That is, the voltage is converted into a voltage corresponding to the amplitude of the vibrating body 4. Since the output voltages of the capacitive voltage conversion circuits 13 and 14 (see FIG. 6A) are in opposite phases, the difference between the output voltages is obtained by the difference circuit 15 to obtain the final output voltage (corresponding to the amplitude of the vibrator). FIG. 6B is obtained. The output of the difference circuit 15 is fed back to the drive voltage adjustment circuit 11 so that the output voltage of the difference circuit 15 becomes a set constant voltage value, that is, the amplitude of the vibrating body is set as an amplitude command value. The gain of the drive voltage adjustment circuit 11 is controlled so as to have a constant amplitude value. In the voltage-pressure conversion circuit 16, the gas pressure P is calculated from the output voltage (amplitude of the vibrating body) of the difference circuit 15 and the output signal (drive signal) of the drive voltage adjustment circuit 11, and a voltage corresponding to the gas pressure P ( (See FIG. 6E).
図４は、本発明の実施形態に係る真空計における気体の圧力Pと振動体の振幅aNの関係を示す図である。また図５は、本発明の実施形態に係る真空計における気体の圧力Pと駆動電圧VDの関係を示す図である。図４において気体の圧力PがP1以下である場合、振動体を振幅a0で振動させる。このときの気体の圧力Pと駆動電圧VDの関係は図５（a）で表される。駆動電圧調整回路11において、上記した式５に示したように、振動体の振幅a0を一定に保持するように駆動電圧を制御した場合、気体の圧力Pに比例して駆動信号の電圧は高くなる。気体の圧力が高くなりP=P1となった場合、電圧圧力変換回路16の出力電圧に従い駆動電圧調整回路11における振幅aNの指令値をa0から、例えば、a0/10に切り替える。このとき、気体の圧力が同じである場合は振幅が1/10となるので駆動信号の電圧も1/10となる。気体の圧力PがP1以上である場合、気体の圧力Pと駆動電圧VDの関係は図５（b）で表される。図５より分かるように、気体の圧力Pが低い領域では振動体の振幅を大きくすることで駆動電圧が高くなりSN比が大きくなる。一方、気体の圧力Pが高い領域では振幅を小さくすることで、低い駆動電圧で気体の圧力Pを検出することが可能となる。なお、駆動電圧調整回路11を使用せず、駆動用信号源10の出力信号の電圧を制御し、駆動用信号源10の出力信号の電圧から圧力を評価することも可能である。
［実施形態２］
図７は、本発明の実施形態に係る真空計の第２の回路構成を示すブロック図であり、図１と同一符号は同一名称部分を示しており、スイッチ回路17および位相シフト回路18が新たに追加されている。スイッチ回路17は始めAとCが接続されており、駆動用信号源10の駆動信号によって初期加振される。駆動信号は、振動体の固有周波数に対応した正弦波もしくは矩形波である。また、パルス状の信号でもよい。駆動用信号源10は初期加振にのみ使用され、振動体4が振動し始めた後はスイッチ回路17が切り替えられAとBが接続される。なお、スイッチ回路17の切替制御は、例えば、振動体4の振幅、すなわち、振動体4の変位に応じて出力される差分回路15の出力信号の大きさが予め設定した値に到達したことを図示されないスイッチ回路用制御部で検出し、その検出タイミングで前記スイッチ回路用制御部からスイッチ回路17にC側からB側への切替信号を与えることにより行うことができる。
FIG. 4 is a diagram illustrating the relationship between the gas pressure P and the amplitude a N of the vibrating body in the vacuum gauge according to the embodiment of the present invention. FIG. 5 is a diagram showing the relationship between the gas pressure P and the drive voltage V D in the vacuum gauge according to the embodiment of the present invention. In FIG. 4, when the gas pressure P is P 1 or less, the vibrating body is vibrated with the amplitude a 0 . The relationship between the gas pressure P and the drive voltage V D at this time is represented by FIG. In the drive voltage adjustment circuit 11, as shown in Equation 5 described above, when controlling the drive voltage to hold the amplitude a 0 of the vibrator constant, the voltage of the drive signal in proportion to the pressure P of the gas Get higher. If the pressure of the gas becomes becomes P = P 1 higher, a command value of the amplitude a N from a 0 in the driving voltage adjustment circuit 11 in accordance with the output voltage of the voltage pressure transducer circuit 16, for example, switched to a 0/10. At this time, when the gas pressure is the same, the amplitude is 1/10, so the voltage of the drive signal is also 1/10. When the gas pressure P is equal to or higher than P1, the relationship between the gas pressure P and the drive voltage V D is represented in FIG. As can be seen from FIG. 5, in the region where the gas pressure P is low, the drive voltage increases and the SN ratio increases by increasing the amplitude of the vibrating body. On the other hand, by reducing the amplitude in the region where the gas pressure P is high, the gas pressure P can be detected with a low driving voltage. Note that it is also possible to control the voltage of the output signal of the drive signal source 10 without using the drive voltage adjustment circuit 11, and to evaluate the pressure from the voltage of the output signal of the drive signal source 10.
[Embodiment 2]
FIG. 7 is a block diagram showing a second circuit configuration of the vacuum gauge according to the embodiment of the present invention. The same reference numerals as those in FIG. 1 denote the same names, and the switch circuit 17 and the phase shift circuit 18 are newly added. Has been added to. The switch circuit 17 is initially connected to A and C, and is initially excited by the drive signal of the drive signal source 10. The drive signal is a sine wave or a rectangular wave corresponding to the natural frequency of the vibrating body. Further, it may be a pulse signal. The driving signal source 10 is used only for initial excitation. After the vibrating body 4 starts to vibrate, the switch circuit 17 is switched and A and B are connected. The switching control of the switch circuit 17 is performed, for example, by confirming that the amplitude of the vibrating body 4, that is, the magnitude of the output signal of the difference circuit 15 output according to the displacement of the vibrating body 4 has reached a preset value. Detection can be performed by a switch circuit control unit (not shown), and a switching signal from the C side to the B side is given from the switch circuit control unit to the switch circuit 17 at the detection timing.
スイッチ回路17でAとBとが接続された状態において、上記した実施形態1の場合と同様に、振動体4が振動することで振動体4と振動検出電極7および8との間の静電容量が変化するので、この静電容量の変化を容量電圧変換回路13および14で静電容量の変化、すなわち、振動体4の振幅に応じた電圧に変換する。容量電圧変換回路13および14の出力電圧（図６（ａ）参照）は逆位相であるので、差分回路15で出力電圧の差分をとることで振動体の振幅に応じた最終的な出力信号（図６（ｂ）参照）を得る。この出力信号の位相を位相シフト回路18でシフトし、駆動電圧調整回路11によって雰囲気の圧力に応じたゲイン（利得）で増幅もしくは減衰し、さらに、駆動電圧調整回路11の出力の位相を反転回路12で反転させる。反転回路12の出力および駆動電圧調整回路11の出力をそれぞれ加振電極5および6に印加させることで振動体4の共振状態が保持される。 In the state where A and B are connected by the switch circuit 17, as in the case of the first embodiment described above, the vibration between the vibrating body 4 and the vibration detection electrodes 7 and 8 is caused by the vibration of the vibrating body 4. Since the capacitance changes, the capacitance change is converted into a voltage according to the capacitance change, that is, the amplitude of the vibrating body 4 by the capacitance-voltage conversion circuits 13 and 14. Since the output voltages of the capacitive voltage conversion circuits 13 and 14 (see FIG. 6A) are in opposite phases, the difference between the output voltages is obtained by the difference circuit 15 to obtain a final output signal (corresponding to the amplitude of the vibrator). FIG. 6B is obtained. The phase of this output signal is shifted by the phase shift circuit 18 and amplified or attenuated by the drive voltage adjustment circuit 11 with a gain (gain) corresponding to the atmospheric pressure, and the output voltage of the drive voltage adjustment circuit 11 is inverted by an inversion circuit. Invert at 12. By applying the output of the inverting circuit 12 and the output of the drive voltage adjusting circuit 11 to the excitation electrodes 5 and 6, respectively, the resonance state of the vibrating body 4 is maintained.
上記した実施形態１の場合と同様に、雰囲気の圧力に応じて一定に保持する振幅を切り替えること、すなわち、電圧圧力変換回路16の出力電圧に従い駆動電圧調整回路11における振幅の指令値を切り替えることで、図５に示した雰囲気の圧力Pと駆動電圧Vの関係を得る。 As in the case of the first embodiment described above, the amplitude to be held constant is switched according to the atmospheric pressure, that is, the amplitude command value in the drive voltage adjustment circuit 11 is switched according to the output voltage of the voltage-pressure conversion circuit 16. Thus, the relationship between the atmospheric pressure P and the drive voltage V shown in FIG.
なお、上記した実施形態１および実施形態２では、ある１箇所の気体の圧力Pで振幅を切り替えているが、複数箇所で振幅を切り替えること、もしくは、連続的に切り替えることも可能である。また、一定に保持する振幅を切り替える圧力P1の付近では、例えば、ノイズの影響によって駆動電圧がV0からV0/10もしくはV0/10からV0と何回も切り替わり出力が安定しなくなることもあり得るので、ヒステリシスを持たせることによって出力を安定させることが可能である。また、差分回路15の出力ではなく容量電圧変換回路13、14の出力で駆動電圧調整回路11を制御することも可能である。 In the first embodiment and the second embodiment described above, the amplitude is switched by the pressure P of one gas at a certain location, but the amplitude can be switched at a plurality of locations or can be switched continuously. Further, in the vicinity of the pressure P1 to switch the amplitude is kept constant, for example, also switches the output V 0 many times the driving voltage by the influence of noise from the V 0/10 or V 0/10 from V 0 is no longer stable Therefore, it is possible to stabilize the output by providing hysteresis. It is also possible to control the drive voltage adjustment circuit 11 not by the output of the difference circuit 15 but by the output of the capacity voltage conversion circuits 13 and 14.
１ 錘
２ 梁
３ 振動体固定部
４ 振動体
５、６ 加振電極
７、８ 振動検出電極
10 駆動用信号源
11 駆動電圧調整回路
12 反転回路
13、14 容量電圧変換回路
15 減算回路
16 電圧圧力変換回路
17 スイッチ回路
18 位相シフト回路
DESCRIPTION OF SYMBOLS 1 Weight 2 Beam 3 Vibrating body fixing | fixed part 4 Vibrating body 5, 6 Excitation electrode 7, 8 Vibration detection electrode
10 Driving signal source
11 Driving voltage adjustment circuit
12 Inversion circuit
13, 14 Capacitance voltage conversion circuit
15 Subtraction circuit
16 Voltage pressure conversion circuit
17 Switch circuit
18 Phase shift circuit
Claims (5)
前記駆動信号生成部は、前記振動検出部の検出信号の大きさが振幅指令値として予め設定された第一の一定の電圧値となるように前記駆動信号の電圧を調整し、
前記圧力測定部は、前記駆動信号の電圧に基づいて気体の圧力を測定するとともに、測定した前記気体の圧力領域に応じて前記駆動信号生成部に対する前記振幅指令値を予め設定された第二の一定の電圧値に切り替えることで、気体の圧力がより高い領域に対応する振幅指令値が、気体の圧力がより低い領域に対応する振幅指令値よりも小さい振幅に設定されるように制御することを特徴とする真空計。 A vibrating body including a weight, a beam, and a vibrating body fixing portion, a vibrating electrode unit that drives the vibrating body by electrostatic force, a vibration detecting unit that detects vibration of the vibrating body, and a drive that vibrates the vibrating body A driving signal generating unit that generates a signal, applying the driving signal to the excitation electrode unit to hold the vibrating body in a resonance state, and measuring the gas pressure from the vibration characteristics of the vibrating body A vacuum gauge equipped with a measuring unit,
The drive signal generation unit adjusts the voltage of the drive signal so that the magnitude of the detection signal of the vibration detection unit becomes a first constant voltage value preset as an amplitude command value,
The pressure measuring unit measures the gas pressure based on the voltage of the drive signal, and the amplitude command value for the drive signal generating unit is set in advance according to the measured gas pressure region. By switching to a constant voltage value, the amplitude command value corresponding to the region where the gas pressure is higher is controlled to be set to an amplitude smaller than the amplitude command value corresponding to the region where the gas pressure is lower. Vacuum gauge characterized by.
前記駆動信号生成部は、前記振動検出部の検出信号に基づき、この検出信号の位相を変えて増幅又は減衰することにより前記振動体を加振する駆動信号を生成することを特徴とする真空計。 The vacuum gauge according to claim 1,
The drive signal generation unit generates a drive signal for exciting the vibrating body by amplifying or attenuating by changing the phase of the detection signal based on the detection signal of the vibration detection unit. .
前記駆動信号生成部は、前記振動検出部の検出信号の位相を変化させる位相シフト回路と、該位相シフト回路の出力信号を増幅又は減衰して駆動信号を出力する駆動電圧調整回路とからなり、
前記駆動電圧調整回路は、前記振動検出部の検出信号の大きさが振幅指令値として予め設定された第一および第二の一定の電圧値となるように前記増幅の利得を制御することを特徴とする真空計。 The vacuum gauge according to claim 2,
The drive signal generation unit includes a phase shift circuit that changes the phase of the detection signal of the vibration detection unit, and a drive voltage adjustment circuit that amplifies or attenuates the output signal of the phase shift circuit and outputs the drive signal.
The drive voltage adjustment circuit controls the gain of the amplification so that the magnitude of the detection signal of the vibration detection unit becomes a first and second constant voltage value preset as an amplitude command value. Vacuum gauge.
前記振動体の固有周波数に対応した周波数の初期励振信号を出力する初期励振用信号源を備え、
前記振動体の初期駆動時には、前記振動検出部の検出信号に基づく駆動信号に代えて、前記初期励振信号に基づく初期駆動信号を前記加振電極部に印加することを特徴とする真空計。 The vacuum gauge according to claim 2 or 3,
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 the vibration detection unit during the initial drive of the vibrating body.
前記振動検出部は、前記振動体と検出電極との間の静電容量の変化を検知して電圧に変換することにより前記振動体の振動を検出することを特徴とする真空計。
The vacuum gauge according to any one of claims 1 to 4,
The said vibration detection part detects the vibration of the said vibrating body by detecting the change of the electrostatic capacitance between the said vibrating body and a detection electrode, and converting into a voltage, The vacuum gauge characterized by the above-mentioned.
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