JPS60612B2 - vibrating transducer - Google Patents

Description

Detailed Description of the Invention The present invention utilizes the fact that the natural frequency of a cylindrical vibrator changes depending on the density of the fluid surrounding the vibrator, the tension applied to the vibrator, etc. This relates to a vibrating transducer that measures force, pressure, etc.

More specifically, the present invention is effective when applied to a transducer of a type in which a vibrator is vibrated in a plurality of vibration modes at the same time, as shown in Japanese Patent No. 54-208, which was previously proposed by the applicant. Regarding vibration transducers. SUMMARY OF THE INVENTION An object of the present invention is to realize a vibrating transducer that has a simple configuration, vibrates stably, and can therefore measure various physical quantities with high precision. FIG. 1 is a block diagram showing an embodiment of the present invention.

In the figure, MR collectively represents mechanical oscillators, to which pressure, force, torque, temperature, density, etc. to be measured are given. PD,,PD2,...P
Dn is a phase comparison circuit whose one input signal is the vibration signal from the mechanical vibrator MR, LF, LF2...
- LFn is a loop filter, V○,, VQ to V0n are voltage controlled oscillators, MO is a modulator, and the output signal is applied to the mechanical resonator M eye to drive the mechanical resonator MR. The output signal of each voltage controlled oscillator V○, ~V0h is applied to a modulator MO, and each phase comparator FD, ~V0h is applied to a modulator MO, respectively.
It is applied to the other input terminal of PDn. It is also applied to the arithmetic circuit CKI. Phase comparator circuit PD,,PD
2......, loop filter LF,, LF2
......, voltage controlled oscillator V○,,V02・
・・・・・・・・・is a phased lock loop PLL,
PLL2... constitutes PLLn. The number of these PLLs is provided corresponding to the number of vibration modes of the mechanical vibrator MR, and each PLL outputs a different frequency signal f, f2, . . . m. Second
The figure is a configuration diagram showing an example of the mechanical vibrator in FIG. 1, in which a is a vertical cross-sectional view and b is a cross-sectional view taken along line bb in figure a.

Here, a thin-walled cylindrical type 1 is used as a mechanical vibrator, and a measurement pressure P is applied between the inside and outside of this cylindrical vibrator 1.
,, Po are introduced, and the differential pressure between the two pressures is measured. The cylindrical vibrator 1 has a thick flange portion 1
1, and in this flange portion 11, four counterbore holes 12, 13 to 15 extending from the outer peripheral surface to the vicinity of the inner wall are formed at 90 degrees apart. Piezoelectric elements 22 and 2 for driving the cylindrical vibrator 1 are provided at the bottoms of the counterbore holes 12 and 13.
3 are attached to the bottoms of the counterbore holes 14 and 15, and piezoelectric elements 24 and 3 for detecting vibrations of the cylindrical vibrator 1 are mounted on the bottoms of the counterbore holes 14 and 15, respectively.
25 is installed. The driving piezoelectric elements 22 and 23 are applied with output signals from the modulator MO, and the output signals from the detection piezoelectric elements 24 and 25 are applied to each phase comparator circuit P.
It is applied to one input device of D, -PDn. The operation of the device configured in this way will be described next. In the following explanation, in order to simplify the explanation, a case will be taken as an example in which the cylindrical vibrator 1 is simultaneously vibrated in two vibration modes, a secondary vibration mode and a quaternary vibration mode. In this case, in FIG. 1, only the phase lock loops PLL, , PLL2 are used. Here, the loop composed of the PLL, the converter M○, and the resonator MR forms a positive feedback oscillation circuit that vibrates the resonator 1 at a frequency f, and also the PLL, the modulator M○, and the resonator M The loop formed by the former forms a positive feedback oscillation circuit that causes the vibrator 1 to oscillate at a frequency. As a result, the vibrator 1
will oscillate in two vibration modes as shown in FIG. The operation of each positive feedback oscillation circuit is performed as follows.

The phase comparison circuit PD inputs the signal e from the oscillator 1 and the output signal eo of the voltage-controlled oscillator VO with limited bandwidth, and calculates, for example, the product of both signals. If the output signal eo of the tortoise pressure control oscillator VO is expressed by the equation '1}, and the output signal eo of the tortoise pressure control oscillator VO is expressed by the equation (2), then the output signal em2 of the phase comparison circuit PD is expressed by the equation.

e=A, cos(of, t+8,)+ncos(■2t10a2) [1) e.

NiBICOS's lt ■e
m2=e. eo (3' The signal eL, which has passed through the loop filter LF, can be expressed by the {4' formula. eL.=A.・B.cosa,
(2) Therefore, the oscillation frequency of the voltage controlled oscillator VO is proportional to cosa.

If the loop gain of the negative feedback from the voltage controlled oscillator VO to the phase comparison circuit PD is set sufficiently high, the voltage controlled oscillator V
The change in phase 8, required to synchronize the oscillation frequency of O with the input frequency, can be made sufficiently small, and the PLL
The phase difference between the input and output of is set to the center frequency of the voltage controlled oscillator VO. will be checked. Therefore, transducer MRI
In this case, we will manipulate the resonance point and phase key, so we set the oscillator M so that the output of the voltage controlled oscillator V becomes negative with respect to the input of the PLL, that is, to form a positive feedback loop.
By applying it to the eye, the phase conditions necessary for oscillation of the vibrator MR are satisfied. Further, regarding the amplitude condition, if the gain of the phase comparison circuit PD is selected to be sufficiently large, the output amplitude of the voltage controlled oscillator VO is constant, so the loop gain becomes 1 and stable oscillation can be maintained. Each PLL, PLL2
is phase-locked only at the input frequency within the frequency band range (IckRange) of the individually set voltage controlled oscillators V○,,V02, and the oscillator 1
oscillates simultaneously and stably in two vibration modes.

Note that by further providing a plurality of PLLs, it is possible to oscillate in a plurality of vibration modes. When the vibrator MR is vibrating in two vibration modes as described above,
If the natural frequency of the vibrator MR is f, (the frequency of the second-order vibration mode) and f2 (the frequency of the fourth-order vibration mode), then f, , and r' are both measured. Pressure (P
o-P, ), and also a function of the density of the fluid surrounding the vibrator MR, etc.

Therefore, these frequency signals f, , f2 are input to the arithmetic circuit CN, where, for example, the density function is eliminated, and a pressure signal that is not affected by the fluid density etc. can be obtained by calculation. Furthermore, if the pressure function is eliminated, the density signal can also be obtained by calculation. Note that various functions can be eliminated by further vibrating the vibrator MR in a plurality of vibration modes. Fourth
5 and 5 are block diagrams showing the main parts of other embodiments of the present invention, in which only one oscillation circuit is shown, but it is assumed that a plurality of oscillation circuits exist in parallel.

In the embodiment shown in FIG. 4, the signal from the resonator MR is applied to the phase comparison circuit PD, via the input filter LFO, and in the embodiment shown in FIG. A filter circuit LFO is provided on the output side, and its output signal is fed back to one input side of the phase comparison circuit PD.

The output signal of the voltage controlled oscillator V○ is sent to the PLL circuit by the IC.
When a converted wave is used, it is generally a rectangular wave and includes harmonics of amplitude Kozo's (young 10) order (n: integer) with respect to the fundamental wave.

Also, os(wit+6i) is applied to the signal A from the vibrator MR.
Since it also contains harmonics of Aimcos (mwit 18im), if o of (yo + 1) = i of m (o: fundamental frequency of voltage controlled oscillator VO), the phase difference signal is removed - Aim There is a drawback that the phase of the vibrator MR changes because the signal Saim is added.

In the embodiment of FIG. 4, the signal applied to the PLL' is filtered by an input filter LFO to remove the above-mentioned harmonic components, and in the embodiment of FIG.
The above-mentioned drawbacks are eliminated by converting the output signal of O into a sine wave using the filter circuit FLO. In the above embodiments, the vibrator has a thin cylindrical shape, but other shapes may be used.

As described above, according to the present invention, it is possible to realize a vibrating transducer that is simple to operate, vibrates stably in a plurality of modes, and is therefore capable of measuring various physical quantities with high precision.

[Brief explanation of the drawing]

FIG. 1 is a configuration block diagram showing one embodiment of the present invention, and FIG.
The figure is a configuration diagram showing an example of the mechanical vibrator in Figure 1.
3 is an explanatory diagram of the operation of the vibrator in FIG. 2, and FIGS. 4 and 5 are configurations of main parts of other embodiments of the present invention. It is a block diagram. MR...Mechanical vibrator, PD,, PD2...
・PDn・...'・Phase comparison circuit, LF,, LF2...
...LFn... Loop fill evening, V○,,V02......V
○n...Voltage controlled oscillator, M○...Modulator, PLL, PLL2...PLLn...Phase locked loop, CK...Kawasumi calculation circuit. Tsutomuso-zu younger brother / Box younger brother J-zo 4th Tsuyoshizume

Claims (1)

[Claims] 1. In a vibratory transducer that utilizes the fact that the natural frequency of a mechanical vibrator changes depending on the surrounding conditions of the vibrator and the tension applied to the vibrator, A plurality of phase comparator circuits to which a signal of A plurality of voltage controlled oscillators each outputting a different frequency signal, and feedback that applies the output signal of each of these voltage controlled oscillators to the other input terminal of a corresponding phase comparator circuit so as to configure a phased lock loop. A circuit means and a modulation means receiving each output signal from each of the voltage controlled oscillators as input are provided, and the output signal of the modulation means is applied to the vibrator to cause the vibrator to vibrate in a plurality of vibration modes. Vibratory transducer. 2. Each phase drop loop includes a filter between the voltage controlled oscillator and the feedback circuit means, which converts the output signal of the voltage controlled oscillator into a sine wave signal, and applies each output signal from each filter to the modulation means. A vibrating transducer according to claim 1, wherein the vibrating transducer is configured as follows.