JP2010210371A - Vibration sensor measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vibration sensor measuring apparatus, improving accuracy in the measurements of physical quantities by the stable vibrations of a vibrator and noise removal, and also improving the yield of vibrators. <P>SOLUTION: In the vibration sensor measuring apparatus, vibrators 102 (102a and 102b) in which physical quantities to be measured act between first fixed electrodes 100 (100a, 100b), with a bias voltage applied thereto, and second fixed electrodes 101 (101a, 101b), opposedly arranged at a predetermined interval, and which vibrate according to electrostatic attraction force acting between the first fixed electrodes and them, are provided. The first fixed electrodes are driven by a first drive signal generated on the basis of output signals of vibrators, and the second fixed electrodes are provided with a plurality of measuring systems driven by a second drive signal having a reversed phase with respect to that of the first drive signal. The vibrator in each measuring system is formed in such a way as to have a different natural frequency. Physical quantities are measured on the basis of output signals of the vibrators. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a vibration type sensor measurement device, and more particularly to stabilization of operation, noise removal, and improvement in the yield of vibrators.

  As shown in FIG. 6, a vibration sensor is used as one type of measuring device for measuring a physical quantity such as pressure, and the vibration sensor is vibrated according to a change in electrostatic attraction force acting between the vibration sensor and the electrode. There is something to make.

  In FIG. 6, the vibrator 11 and the reference vibrator 12 arranged on the left and right are installed to face the fixed electrode 10 with a predetermined distance DISB.

  The vibrator 11 has a natural frequency determined by its shape (for example, a beam), and a self-excited circuit that vibrates at this natural frequency is formed. That is, the electrostatic attraction force Fc acting between the fixed electrode 10 to which the bias voltage Vb is applied and the vibrator 11 → the vibrator 11 → the current / voltage conversion unit 20 → the differential amplification unit 22 → the drive unit 30 → the drive signal. A positive feedback loop is formed by feedback of the KB to the fixed electrode 10 to form a self-excited circuit.

The self-exciting operation of the vibrator 11 will be described.
A bias voltage Vb is applied between the fixed electrode 10 and the vibrator 11 and between the fixed electrode 10 and the reference vibrator 12 via a resistor.

  The fixed electrode 10 is driven by a drive signal KB. Note that the frequency of the drive signal KB matches the natural frequency of the vibrator 11. Since the voltage applied to the fixed electrode 10 changes according to the drive signal KB, the vibrator 11 has a natural frequency according to the change in the electrostatic attractive force Fc acting between the fixed electrode 10 and the vibrator 11. Vibrate.

  At this time, the electrostatic current SB in which the noise current NA is superimposed on the current in phase with the drive signal KB from the fixed electrode 10 to the vibrator 11 through the capacitance formed between the fixed electrode 10 and the vibrator 11. Flows. The electrostatic current SB is output from the vibrator 11 and converted into a voltage by the current / voltage conversion unit 20.

  However, the natural frequencies of the vibrator 11 and the reference vibrator 12 are different. Therefore, even if the voltage applied to the fixed electrode 10 changes at the natural frequency of the vibrator 11, the reference vibrator 12 hardly vibrates, and the noise current having the same amplitude and the same phase as the noise current NA from the reference vibrator 12. NB is output and converted into a voltage by the current / voltage converter 21.

  The differential amplifier 22 differentially amplifies the output voltages of the current / voltage converters 20 and 21 to cancel the components of the noise currents NA and NB, and outputs the natural frequency component of the vibrator 11. For this reason, the frequency of the physical quantity output signal Po that is the output of the differential amplifier 22 matches the natural frequency of the vibrator 11.

  The physical quantity output signal Po is input to an auto gain control unit (hereinafter referred to as AGC unit) 31 and also input to an AC / DC conversion unit 32. The AC / DC converter 32 converts the DC voltage to the amplitude of the physical quantity output signal Po, and outputs the DC voltage to the error amplifier 33. The error amplifier 33 amplifies the error between the DC voltage of the AC / DC converter 32 and the set voltage Vs (DC) and outputs the amplified error to the AGC unit 31. The AGC unit 31 outputs to the fixed electrode 10 an alternating drive signal KB in which the amplitude of the physical quantity output signal Po is matched with the set voltage Vs.

  On the other hand, when the pressure of the fluid to be measured acts on the vibrator 11, the distortion of the vibrator 11 changes and the natural frequency changes. That is, the natural frequency of the vibrator 11 changes according to the pressure applied to the vibrator 11. Here, since the frequency of the physical quantity output signal Po matches the natural frequency of the vibrator 11, the pressure can be known from the frequency of the physical quantity output signal Po (pressure measurement signal).

  Patent Document 1 describes that a vibrating gate vibrates according to a change in electrostatic attraction force.

Japanese Patent No. 3292286

  By the way, when an external vibration having a frequency close to the natural frequency of the reference vibrator 12 is transmitted to the reference vibrator 12, the reference vibrator 12 is vibrated by the external vibration, and this vibration signal is transmitted via the current / voltage conversion unit 21. Therefore, the measurement accuracy of the physical quantity may deteriorate due to being superimposed on the physical quantity output signal Po.

  Further, in order to maintain insulation between the vibrator 11 and the reference vibrator 12, the vibrator 11 needs to be manufactured while keeping an accurate distance DISA from the reference vibrator 12. In addition to this, since it is necessary to separate the natural frequencies of the vibrator 11 so that the reference vibrator 12 does not vibrate at the natural frequency of the vibrator 11, the shapes of the vibrator 11 and the reference vibrator 12 that determine the natural frequency are determined. Must be manufactured accurately. As described above, since the vibrator 11 and the reference vibrator 12 need to be accurately manufactured in the distance DISA and the shape of both, there is a problem that the manufacturing yield is reduced and the manufacturing cost is increased.

  Further, when the natural frequency of the vibrator 11 and the reference vibrator 12 becomes close to each other due to manufacturing errors, the vibrator 11 vibrates at the natural frequency, and the reference vibrator 12 may also vibrate. is there. As a result, the vibration energy of the vibrator 11 is absorbed by the reference vibrator 12, the vibration of the vibrator 11 becomes unstable, the frequency of the physical quantity output signal Po becomes unstable, and the measurement accuracy of the physical quantity deteriorates. is there.

  The present invention solves these problems, and an object of the present invention is to provide a vibration type sensor measuring apparatus that realizes stable vibration of a vibrator, improvement of measurement accuracy of physical quantities by noise removal, and improvement of yield of the vibrator. There is to do.

In order to achieve such a problem, the invention according to claim 1 of the present invention is:
Electrostatic attraction acting between the first fixed electrode due to the physical quantity to be measured acting between the second fixed electrode arranged at a predetermined interval so as to face the first fixed electrode to which the bias voltage is applied. A vibrator that vibrates according to force is provided, the first fixed electrode is driven by a first drive signal generated based on an output signal of the vibrator, and the second fixed electrode is opposite to the first drive signal. A plurality of measurement systems driven by the phase second drive signal;
The vibrators in the respective measurement systems are formed so as to have different natural frequencies, and the physical quantity is measured based on output signals of the vibrators.

The invention according to claim 2 is the vibration sensor measuring device according to claim 1,
The second fixed electrode is formed separately according to the vibrator.

The invention according to claim 3 is the vibration sensor measuring device according to claim 1,
The second fixed electrode is integrally formed so as to be common to the vibrators, and the vibrators are driven by a common drive signal obtained by adding the output signals of the vibrators.

According to a fourth aspect of the present invention, in the vibration type sensor measuring device according to any one of the first to third aspects,
The first fixed electrode, the second fixed electrode, and the vibrator are provided on the same silicon wafer.

  According to the present invention, stable vibration of the vibrator can be obtained, and the measurement accuracy of the physical quantity can be improved and the yield of the vibrator can be improved.

It is a block diagram which shows an example of embodiment of this invention. It is a block diagram which shows an example of the structure of a 1st fixed electrode, a 2nd fixed electrode, and a vibrator | oscillator. FIG. 2 is a signal waveform example diagram in each part of FIG. 1. It is a block diagram which shows the other example of embodiment of this invention. It is a block diagram which shows the other example of embodiment of this invention. It is a block diagram which shows an example of the conventional vibration type sensor measuring apparatus.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an example of an embodiment of the present invention. Components identical with those in FIG.

  In FIG. 1, second fixed electrodes 101 are arranged at a predetermined interval DIST so as to face the first fixed electrode 100 to which the bias voltage Vb is applied, and between the first fixed electrode 100 and the second fixed electrode 101. Is provided with a vibrator 102. The vibrator 102 maintains a distance DIS1 (first interval) from the first fixed electrode 100, and maintains a distance DIS2 (second interval) from the second fixed electrode 101. For signals having frequencies other than the natural frequency of the vibrator 102, a capacitor C1 (not shown) is equivalently formed between the vibrator 102 and the first fixed electrode 100, and the vibrator 102 and the second A capacitor C <b> 2 (not shown) is equivalently formed between the fixed electrode 101. Note that the capacitance C1 is inversely proportional to the first interval DIS1, and the capacitance C2 is inversely proportional to the second interval DIS2.

  For the signal of the natural frequency of the vibrator 102, a resistor RS1 (not shown) is equivalently formed between the vibrator 102 and the first fixed electrode 100, and the vibrator 102 and the second fixed electrode. A resistor RS2 (not shown) is equivalently formed between the resistor 101 and the resistor 101.

  The output signal SENS of the vibrator 102 is input to the current / voltage conversion unit 110 and converted into a voltage, and is output as a physical quantity output signal Po (alternating current) and also input to the drive unit 120.

  In the drive unit 120, the AC / DC conversion unit 32 converts the physical quantity output signal Po (AC) into DC, and inputs the converted DC voltage to one input terminal of the error amplification unit 33. A set voltage Vs (direct current) is input to the other input terminal of the error amplifying unit 33, and these errors are amplified and output to one input terminal of the AGC unit 31.

  The physical quantity output signal Po is input to the other input terminal of the AGC unit 31, and the auto gain control output signal SAGC in which the amplitude of the physical quantity output signal Po coincides with the set voltage Vs is supplied to the first amplification unit 121 and the second amplification unit. To the unit 122.

  The first amplifying unit 121 drives the first fixed electrode 100 with a first driving signal KD1 obtained by amplifying the AGC output signal SAGC according to the amplification factor determined by the first feedback resistor R1. The second amplifying unit 122 drives the second fixed electrode 101 with the second drive signal KD2 obtained by amplifying the AGC output signal SAGC according to the amplification factor determined by the second feedback resistor R2.

  FIG. 2 is a configuration diagram illustrating an example of the structure of the first fixed electrode 100, the second fixed electrode 101, and the vibrator 102.

  In FIG. 2, a diaphragm 201 having a thin intermediate portion is formed on a silicon wafer 200, and a first fixed electrode 100, a second fixed electrode 101, and a vibrator 102 are formed in the diaphragm 201. As described above, the first fixed electrode 100, the second fixed electrode 101, and the vibrator 102 are provided on the same silicon wafer 200.

  The first fixed electrode 100 (shaded portion) and the second fixed electrode 101 (shaded portion) maintain a predetermined distance DIST. A vibrator 102 is formed between the first fixed electrode 100 and the second fixed electrode 101. The vibrator 102 faces the first fixed electrode 100 with a first distance DIS1, and the second fixed electrode 101 and the second fixed electrode 101 are opposed to each other. Opposite the two distances DIS2.

  When the pressure PRS of the fluid to be measured is applied to the diaphragm 201, the diaphragm 201 is deformed, and the vibrator 102 is distorted.

  Returning to FIG. 1, the vibrator 102 has a natural frequency determined by, for example, the shape of the beam, and a self-excited circuit that vibrates the vibrator 102 at the natural frequency is formed. That is, the first fixed electrode 100 to which the bias voltage Vb is applied → the electrostatic attractive force Fc acting between the first fixed electrode 100 and the vibrator 102 → the vibrator 102 → the current / voltage conversion unit 110 → the drive unit 120 → A positive feedback loop is formed by feedback of the first drive signal KD1 to the first fixed electrode 100, and a self-excited circuit is configured.

  First, the self-exciting operation of the vibrator 102 will be described in the case where the first interval DIS1 and the second interval DIS2 are equal and the capacitance C1 and the capacitance C2 are equal.

  The bias voltage Vb is connected between the first fixed electrode 100 and the circuit common voltage Vcom via a resistor. The vibrator 102 is (virtually) grounded to the circuit common voltage Vcom by the operational amplifier of the current / voltage conversion unit 110. As a result, the bias voltage Vb is applied between the first fixed electrode 100 and the vibrator 102. On the other hand, no bias voltage is applied between the second fixed electrode 101 and the vibrator 102.

  The first fixed electrode 100 is driven by the first drive signal KD1. The frequency of the first drive signal KD1 matches the natural frequency of the vibrator 102. Since the voltage applied to the first fixed electrode 100 is changed by the first drive signal KD1, the vibrator 102 responds to the change in the electrostatic attractive force Fc acting between the first fixed electrode 100 and the vibrator 102. Vibrates at the natural frequency.

  At this time, the first electrostatic current SD1 flows from the first fixed electrode 100 to the vibrator 102. The first electrostatic current SD1 is a current in which a noise current N1 is superimposed on a current in phase with the first drive signal KD1. The current in phase with the first drive signal KD1 flows from the first fixed electrode 100 to the vibrator 102 via the resistor RS1, and the noise current N1 flows from the first fixed electrode 100 to the vibrator 102 via the capacitor C1.

  On the other hand, the second fixed electrode 101 is driven by the second drive signal KD2 having a phase opposite to that of the first drive signal KD1, but since no bias voltage is applied, the second fixed electrode 101 is not connected between the second fixed electrode 101 and the vibrator 102. The electrostatic attraction force Fc corresponding to the frequency of the second drive signal KD2 does not work. Therefore, a noise current N2 having the same amplitude and opposite phase as the noise current N1 flows from the second fixed electrode 101 to the vibrator 102 as the second electrostatic current SD2 via the capacitor C2.

  Among the currents flowing into the vibrator 102, the noise current N1 and the noise current N2 have the same amplitude and opposite phase, and therefore cancel each other. For this reason, a current in phase with the first drive signal KD1 flows from the vibrator 102 to the current / voltage conversion unit 110 as the vibrator output signal SENS.

  The current / voltage conversion unit 110 converts the current of the transducer output signal SENS into a voltage and outputs the voltage as a physical quantity output signal Po. Note that the frequency of the physical quantity output signal Po matches the natural frequency of the vibrator 102.

  The physical quantity output signal Po is input to the AGC unit 31 and also input to the AC / DC conversion unit 32. The AGC unit 31, the AC / DC converting unit 32, and the error amplifying unit 33 are the same as those shown in FIG. 6, and the AGC unit 31 has an AGC output signal SAGC in which the amplitude of the physical quantity output signal Po is matched with the set voltage Vs. (AC) is output to the first amplifying unit 121 and the second amplifying unit 122.

  The first amplifier 121 outputs a first drive signal KD1 obtained by amplifying the AGC output signal SAGC to drive the first fixed electrode 100, and the second amplifier 122 receives a second drive signal KD2 obtained by amplifying the AGC output signal SAGC. The second fixed electrode 101 is driven by outputting. Since the sign of the amplification factor G1 of the first amplification unit 121 is different from the sign of the amplification factor G2 of the second amplification unit 122, the first drive signal KD1 and the second drive signal KD2 are in opposite phases.

  As shown in FIG. 2, when the pressure PRS of the fluid to be measured that acts (applies) to the vibrator 102 changes, the strain of the vibrator 102 changes and the natural frequency changes. That is, the natural frequency of the vibrator 102 changes according to the pressure applied to the vibrator 102. Since the natural frequency of the vibrator 102 in FIG. 1 matches the frequency of the physical quantity output signal Po, the pressure PRS can be known from the frequency of the physical quantity output signal Po (pressure measurement signal).

  FIG. 3 is a signal waveform diagram in each part of FIG. 1, (a) is an AGC output signal SAGC (voltage), (b) is a first drive signal KD1 (voltage), and (c) is a second drive signal KD2 (voltage). ), (D) is the first electrostatic current SD1, (e) is the second electrostatic current SD2, (f) is the transducer output signal SENS (current), and (g) is the physical quantity output signal Po (voltage). . The waveform of the first electrostatic current SD1 in (d) is a waveform in which (d2) is superimposed on (d1).

  When the amplification factor G1 of the first amplification unit 121 is positive, the AGC output signal SAGC of (a) is in phase with the first drive signal KD1 of (b), and the amplification factor G2 of the second amplification unit 122 is negative. , (C) second drive signal KD2 is out of phase with (A) AGC output signal SAGC and (b) first drive signal KD1. In addition, the voltage amplitude of the 1st drive signal KD1 of (b) is set to 1st amplitude A1, and the voltage amplitude of the 2nd drive signal KD2 of (c) is set to 2nd amplitude A2.

  In the first electrostatic current SD1 in (d), SD1a in (d1) is a current in phase with the first drive signal KD1 in (b), and SD1b in (d2) is a noise current N1.

  The second electrostatic current SD2 in (e) is a noise current N2 of the same amplitude and opposite phase as SD1b in (d2).

  The transducer output signal SENS in (f) is the same as SD1a in (d1) because SD1b in (d2) cancels out SD2 in (e).

  The physical quantity output signal Po in (g) is obtained by converting the transducer output signal SENS current in (f) into a voltage, and the frequency thereof corresponds to the pressure PRS of the fluid to be measured.

  As described above, since the first interval DIS1 is equal to the second interval DIS2 and the capacitor C1 is equal to the capacitor C2, the impedance Z1 of the capacitor C1 is equal to the impedance Z2 of the capacitor C2. If the first amplitude A1 is equal to the second amplitude A2, the noise current N1 in (d2) has the same amplitude as the noise current N2 in (e) and is in an opposite phase relationship from Ohm's law. Cancel each other.

  In order to make the first amplitude A1 equal to the second amplitude A2, the absolute value of the amplification factor G1 may be made equal to the absolute value of the amplification factor G2. That is, when the ratio between the first interval DIS1 and the second interval DIS2 is “1”, the ratio between the first amplitude A1 and the second amplitude A2, and the absolute value of the amplification factor G1 and the absolute value of the amplification factor G2 If both ratios are set to “1”, the noise current N1 and the noise current N2 can be canceled.

  Next, a description will be given of a case where the first interval DIS1 is smaller than the second interval DIS2 (DIS1 <DIS2) and the capacitance C1 is larger than the capacitance C2 (C1> C2) due to manufacturing errors, for example. To do.

  Since the capacitor C1 is larger than the capacitor C2, the impedance Z1 of the capacitor C1 is smaller than the impedance Z2 of the capacitor C2 (Z1 <Z2).

  Therefore, if the first amplitude A1 is made smaller than the second amplitude A2 (A1 <A2), the noise current N1 has the same amplitude as the noise current N2 according to Ohm's law, and the noise current N1 and the noise current N2 are Can be countered. In order to make the first amplitude A1 smaller than the second amplitude A2, the absolute value of the amplification factor G1 may be made smaller than the absolute value of the amplification factor G2 (| G1 | <| G2 |).

  Thus, the first amplitude A1 and the second amplitude A2 are based on the first interval DIS1 and the second interval DIS2. For example, the ratio between the first interval DIS1 and the second interval DIS2 (DIS1 / DIS2), the ratio between the first amplitude A1 and the second amplitude A2 (A1 / A2), the absolute value of the amplification factor G1, and the amplification factor G2 The ratio to the absolute value (| G1 | / | G2 |) may be proportional to each other.

  When the first interval DIS1 is larger than the second interval DIS2 (DIS1> DIS2), the magnitude relationship described above may be reversed.

  Further, in order to realize the above-described proportional relationship, at least one of the first amplification unit 121 and the second amplification unit 122 may be a variable amplification unit that can change the amplification factors G1 and G2.

  According to the circuit configuration of FIG. 1, the physical quantity (pressure) can be measured in a state where the noise current N1 and the noise current N2 are substantially canceled, and the physical quantity measurement accuracy can be improved.

Since the reference vibrator 12 as shown in FIG. 6 is not used, external vibration is not transmitted to the reference vibrator, and vibration energy of the vibrator 102 is not absorbed by the reference vibrator. Thereby, since the vibrator 102 vibrates stably, the measurement accuracy of the physical quantity can be improved.
In addition, since the vibrator 102 does not need to be accurately manufactured in relation to the reference vibrator (the distance and shape between the two), the yield of the vibrator 102 can be improved and the manufacturing cost can be reduced.

  Further, since the amplification factors G1 and G2 can be changed by selectively changing the first feedback resistor R1 and the second feedback resistor R2 in accordance with the first interval DIS1 and the second interval DIS2, the proportional relationship described above can be realized more easily. The measurement accuracy of the physical quantity can be improved by substantially canceling out the noise current N1 and the noise current N2.

  Further, since the amplification factors G1 and G2 can be changed by variable amplification of the first amplification unit 121 and the second amplification unit 122 according to the first interval DIS1 and the second interval DIS2, the proportional relationship described above is realized more easily and flexibly. The measurement accuracy of the physical quantity can be improved by substantially canceling out the noise current N1 and the noise current N2.

  Further, as shown in FIG. 2, by providing the first fixed electrode 100, the second fixed electrode 101, and the vibrator 102 on the same silicon wafer 200, the vibrator 102 can be manufactured more easily and the yield can be improved. In addition, manufacturing costs can be reduced.

  Further, the physical quantities are not limited to the pressures in the embodiments, and these physical quantities can also be measured by changing the strain of the vibrator 102 by applying physical quantities such as flow rate, temperature, density, and the like to the vibrator 102.

  FIG. 4 is a block diagram showing another embodiment of the present invention, in which the circuit configuration of FIG. 1 is provided with two systems as indicated by subscripts a and b. In FIG. 4, the shapes of the vibrators 102a and 102b used in the respective systems are adjusted so that the resonance frequencies are different.

  A bias voltage Vba is applied between the first fixed electrode 100a and the vibrator 102a so as to generate an electrostatic attraction force, and no electrostatic attraction force is generated between the second fixed electrode 101a and the vibrator 102a. At the same potential. Similarly, a bias voltage Vbb is applied between the first fixed electrode 100b and the vibrator 102b so that an electrostatic attraction force is generated, and the electrostatic attraction force is applied between the second fixed electrode 101b and the vibrator 102b. It is kept at the same potential so that it does not occur.

  The output signal SAGCa of the AGC unit 31a is input to the first amplification unit 121a and the second amplification unit 122a, and the output signal SAGCb of the AGC unit 31b is input to the first amplification unit 121b and the second amplification unit 122b.

  The output signal of the first amplifier 121a is applied to the first fixed electrode 100a, the output signal of the second amplifier 122a is applied to the second fixed electrode 101a, and the output signal of the first amplifier 121b is the first fixed electrode 100b. The output signal of the second amplifying unit 122b is applied to the second fixed electrode 101b. The first amplifying unit 121a and the first amplifying unit 121b are configured as inverting amplifiers, and the second amplifying unit 122a and the second amplifying unit 122b are configured as non-inverting amplifiers.

  The electrostatic attraction force between the first fixed electrode 100a and the vibrator 102a is changed according to the output of the first amplifying unit 121a, and the vibrator 102a vibrates, but the second fixed electrode 101a and the vibrator 102a are vibrated. Since no bias voltage is applied, the vibrator 102a does not vibrate by the output of the second amplifying unit 122a. Similarly, the electrostatic attraction force between the first fixed electrode 100b and the vibrator 102b changes according to the output of the first amplifying unit 121b to vibrate the vibrator 102b, but the second fixed electrode 101b and the vibrator 102b. Since no bias voltage is applied between them, the vibrator 102b does not vibrate by the output of the second amplifying unit 122b.

  By forming a positive feedback loop between the first fixed electrode 100a where the electrostatic attraction force is generated and the vibrator 102a, the vibrator 102a resonates at its own natural frequency, and its amplitude is the error amplifier 33a. It is kept constant by the function of the AGC unit 31a. Similarly, since a positive feedback loop is formed between the first fixed electrode 100b where the electrostatic attraction force is generated and the vibrator 102b, the vibrator 102b resonates at its own natural frequency, and its amplitude is The error amplifier 33b and the AGC unit 31b keep the constant.

  With the resonance of the vibrator 102a, the output signal SENSa and positive phase noise are output from the first fixed electrode 100a to which the bias voltage Vba is applied, but from the second fixed electrode 101a to which the bias voltage is not applied, Due to the action of the second amplifying unit 122a, only anti-phase noise is output. Similarly, with the resonance of the vibrator 102b, the output signal SENSb and positive phase noise are output from the first fixed electrode 100b to which the bias voltage Vbb is applied, but the second fixed electrode 101b to which the bias voltage is not applied. From, only the reverse phase noise is output by the action of the second amplifying unit 122b.

  These normal phase noise and reverse phase noise are canceled by being added together. Thereby, only the output signal SENSa is output from the vibrator 102a, and only the output signal SENSb is output from the vibrator 102b.

  The output signal SENSa is converted into a voltage signal by the current / voltage converter 110a and input to the AGC unit 31a, the AC / DC converter 32a, and the Schmitt trigger 130a, and the output signal SENSb is converted into a voltage signal by the current / voltage converter 110b. And input to the AGC unit 31b, the AC / DC conversion unit 32b, and the Schmitt trigger 130b.

  The Schmitt trigger 130a outputs a frequency signal a corresponding to the output signal SENSa to an arithmetic processing unit (not shown), and the Schmitt trigger 130b outputs a frequency signal b corresponding to the output signal SENSb to a common arithmetic processing unit (not shown).

  An arithmetic processing unit (not shown) performs various calculations using the frequency signal a and the frequency signal b, and calculates physical quantity measurement values such as pressure and temperature.

  According to the configuration of FIG. 4, the measurement signal of the same physical quantity to be measured can be obtained from each of the two measurement circuits composed of the vibrators 102a and 102b having different resonance frequencies. The sum and difference can be calculated based on these two measurement signals, and a high-precision calculation result that cannot be obtained with only one measurement signal can be obtained.

  Incidentally, in manufacturing the electrostatic drive type vibrator as shown in FIG. 4, it is extremely difficult to separate and form the two second fixed electrodes 101 a and the second fixed electrodes 101 b. Although it is practical to integrate the second fixed electrodes 101a and the second fixed electrodes 101b, the two second fixed electrodes 101a and the second fixed electrodes 101b are integrated with the circuit configuration of FIG. However, noise cannot be removed.

  FIG. 5 is a block diagram showing another embodiment of the present invention in which the same effect as the configuration of FIG. 4 can be obtained while integrating the two second fixed electrodes, and is a part common to FIG. Are given the same reference numerals.

  4 differs from FIG. 5 in that the second fixed electrode 101c is integrated in FIG. 5, the first amplifying unit 121c, the second amplifying unit 122c, and the bias voltage Vbc are unified, and the adding unit 140. It is to have established. The first amplification unit 121c is configured as an inverting amplifier, and the second amplification unit 122c is configured as a non-inverting amplifier.

  In FIG. 5, the output signal SAGCa of the AGC unit 31 a is input to one input terminal of the adding unit 140, and the output signal SAGCb of the AGC unit 31 b is input to the other input terminal of the adding unit 140.

  The output signal of the adding unit 140 is applied to the first fixed electrode 100a and the first fixed electrode 100b through the first amplifying unit 121c, and is applied to the second fixed electrode 101c through the second amplifying unit 122c. A common bias voltage Vbc is applied to the first fixed electrode 100a and the first fixed electrode 100b.

  In such a configuration, the two vibrators 102a and 102b are simultaneously driven by the output signal of the adder 140 obtained by adding the output signal SAGCa of the AGC unit 31a and the output signal SAGCb of the AGC unit 31b.

  Thereby, one system is formed by the two vibrators 102a and 102b, and the noises of the two vibrators 102a and 102b are canceled simultaneously.

  That is, since the natural frequencies of the two vibrators 102a and 102b are different, even if the vibrator 102b is driven at the natural frequency of the vibrator 102a, the vibrator 102b hardly vibrates. Therefore, when viewed from the vibrator 102b, the natural frequency component of the vibrator 102a becomes noise, and when viewed from the vibrator 102a, the natural frequency component of the vibrator 102b becomes noise. However, these noises are the same as in the conventional configuration. Canceled by

  According to the configuration of FIG. 5, while using an electrostatically driven vibrator having a structure that is relatively easy to manufacture, similarly to FIG. 4, a measurement signal of the same physical quantity to be measured is constituted by vibrators 102a and 102b having different resonance frequencies. Can be obtained from each of the two measurement circuits, so that the arithmetic processing unit can perform a sum or difference calculation based on these two measurement signals, which is not possible with only one measurement signal. An arithmetic processing result is obtained.

  Note that the amount of noise cancellation may be adjusted by adjusting the gain of a non-inverting amplifier used as the second amplification unit 122.

  In the above-described embodiment, an example in which the two vibrators 102a and 102b are driven simultaneously has been described. However, three or more vibrators may be driven at the same time.

  As described above, according to the present invention, it is possible to realize a vibration type sensor measurement device that can achieve stable vibration of a vibrator, improvement of measurement accuracy of a physical quantity, and improvement of yield of the vibrator.

DESCRIPTION OF SYMBOLS 100 1st fixed electrode 101 2nd fixed electrode 102 Vibrator 110 Current / voltage conversion part 120 Drive part 121 1st amplification part 122 2nd amplification part 130 Schmitt trigger 140 Addition part 200 Silicon wafer DIS1 1st space | interval DIS2 2nd space | interval DIST Predetermined interval Fc Electrostatic attractive force KD1 First drive signal KD2 Second drive signal Po Physical quantity output signal PRS Pressure SENS Vibrator output signal

Claims (4)

Electrostatic attraction acting between the first fixed electrode due to the physical quantity to be measured acting between the second fixed electrode arranged at a predetermined interval so as to face the first fixed electrode to which the bias voltage is applied. A vibrator that vibrates according to force is provided, the first fixed electrode is driven by a first drive signal generated based on an output signal of the vibrator, and the second fixed electrode is opposite to the first drive signal. A plurality of measurement systems driven by the phase second drive signal;
The vibrator in each of these measurement systems is formed so as to have different natural frequencies, and the physical quantity is measured based on an output signal of these vibrators.   The vibration type sensor measurement device according to claim 1, wherein the second fixed electrode is formed separately according to the vibrator.   The said 2nd fixed electrode is integrally formed so that it may be common to each said vibrator | oscillator, and each said vibrator | oscillator is driven by the common drive signal which added the output signal of these vibrator | oscillators. The vibration type sensor measuring device as described.   4. The vibration type sensor measurement device according to claim 1, wherein the first fixed electrode, the second fixed electrode, and the vibrator are provided on the same silicon wafer. 5.

Images