JPS6055030B2 - Piezoelectric vibrator minute signal measurement device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a minute signal measuring device for a piezoelectric vibrator.

It has been known that the equivalent electrical constant of a piezoelectric vibrator changes depending on its excitation level.

Therefore, when a piezoelectric vibrator is used in an electric circuit, it must be designed in consideration of its excitation level and other conditions of use. That is, a circuit is designed with electrical equivalent constants at the level of steady use in an electric circuit, and operation as designed can be expected at the level of steady use. However, for example, in a feedback oscillator, when the oscillation starts, the excitation level is about the same as the extremely small white noise level.
In a circuit that gradually increases and reaches a steady state, simply having a piezoelectric vibrator constant at the excitation level in the steady state is insufficient.

This is because the resonance impedance (hereinafter simply referred to as Cl) of the piezoelectric vibrator increases to several times the normal level at a minute level below the measurement limit of the piezoelectric vibrator alone.
Alternatively, there may be a case where a frequency due to an unnecessary vibration mode such as sub-resonance exists near the desired vibration mode, and the Cl characteristic at a minute level is more linear than that of the desired vibration.
Even if such a piezoelectric vibrator is operated by connecting it to an oscillator whose circuit is designed with steady-state constants, the required vibration mode cannot reach the loop gain (μβ = 1) for a several-fold increase in Cl. First, even if the power supply voltage used by the oscillation circuit, that is, the gain (μ) of the amplifying section reaches the designed value, oscillation may not start, and conversely, it may start in an unnecessary mode such as the above-mentioned sub-resonance. An object of the present invention is to provide a minute signal from a piezoelectric vibrator that can detect piezoelectric vibrators having defects as described above.

That is, in the linear region of an oscillator that is configured to oscillate using a piezoelectric vibrator, which is the material to be measured, and has an amplifier circuit in which the gain and the amplitude of the output signal increase in one direction as the power supply voltage rises, the power supply voltage Changes in X-Y recorder
The oscillator output signal is rectified and applied to the Y-axis. Thereafter, the power supply voltage is automatically and continuously increased gradually, and when the gain of the amplifier increases and reaches μβ<1, the start of oscillation is depicted on the recorder. Conversely, when the power supply voltage is gradually lowered, the gain of the amplifier and the amplitude of the output signal decrease until μβ>1, and the oscillation stops, which is depicted on the recorder. This hysteresis phenomenon in which the oscillation starting voltage and the oscillation stopping voltage are different can be said to indicate that the CI of the piezoelectric vibrator exhibits a nonlinear shape depending on the excitation level. Therefore, by evaluating or standardizing this difference, the characteristics of the piezoelectric vibrator at a minute level, which has been difficult in the past, can be clarified, and non-oscillations in the oscillator can be drastically reduced. However, in this case, the speed at which the power supply voltage is increased must be sufficiently slower than the speed at which the oscillation rises.
The present invention will be explained in detail below using the drawings. FIG. 1 shows a piezoelectric vibrator constant measurement circuit that has been widely used in the past. 11 is an oscillator that oscillates a measurement frequency; 12 is a variable resistor that sets a measurement level; and 13 is an impedance of a piezoelectric vibrator to be measured 14 that obtains a measurement voltage.

CI excitation level (IQ
) characteristics are shown in Figure 2. With a general measuring circuit like the one shown in Figure 1, it is difficult to measure an IQ below point a in Figure 2;
Even if the CI characteristic curve following the point looks like a broken line, it cannot be detected. FIG. 3 is a circuit showing one embodiment of the present invention. 31 is a piezoelectric vibrator to be measured, 32
is an oscillator that oscillates with a piezoelectric vibrator 31; 33 is a power source that supplies DC voltage to the oscillator 32; the voltage automatically increases or decreases gradually over time;

34 is a rectifier that rectifies the output of the oscillator 32 and generates a DC signal in proportion to the increase or decrease in its input; 35 is an X-Y recorder that draws curves in the X and Y directions according to external signals.

Each of the curves in FIGS. 4a to 4c is a diagram for explaining the operation of the measuring circuit of FIG. 3, and will be used for each case in the explanation. In FIG. 3, it is assumed that the power supply voltage V of the power source 33 starts from point b (7) e in FIG. 4 and gradually increases.
The gain G and output amplitude A of the amplifier circuit are also shown in Fig. 4c (:I).
Assuming that the loop gain as an oscillator exceeds 1 when it gradually increases starting from point h and exceeds CI and reaches G, then when G exceeds G, that is, when it reaches VO, the oscillation stops. After startup, Lv shown in Fig. 4a appears, and v further rises, and as the amplitude A of the output signal increases, the excitation level of the vibrator also increases, and finally the gain and amplitude difference at point i (Cf) in Fig. 4. It reaches the linear region and reaches a steady state. Next, after V reaches the maximum g point, it starts to fall again, and even when V reaches the initially activated ■O, the gain G necessary for oscillation is sufficiently secured as shown in Figure 4 c, and oscillation does not occur. It persists. Then, as V further decreases, G decreases, and when GO is finally cut off, that is, when it falls below Vs, oscillation cannot be maintained and oscillation stops. Therefore, when observing the output level Lv, as shown in FIG. 4a, it is displayed that there is a slight difference between the voltage VO at which oscillation is started and the voltage Vs at which oscillation is stopped. The above-mentioned phenomenon occurs because the movement of the resonant impedance CI is non-linear with respect to the increase in the excitation level IQ. Therefore, using a measuring device with such a configuration, the fourth
By standardizing the sizes of ■S and VO in Figure a, the linearity of C■ depending on the excitation level IQ of the piezoelectric vibrator becomes clear, and it is possible to extract piezoelectric vibrators that exhibit large nonlinearity. Become. As a result, in circuit design, there is no need to provide an extra loop gain to cover large CI at a minute level stage, and an optimal design that reliably oscillates only at CI in a steady state becomes possible. Note that the following points need to be taken into consideration when implementing the present invention. (1) The rise and fall speed of the power supply voltage should always be set sufficiently slower than the oscillation startup speed. (11) The time constant of the rectifier that rectifies the output of the oscillator must be sufficiently small in the frequency range to be measured. (
111) Give sufficient consideration to the linearity of the amplifier circuit. The operating principle of the present invention has been explained above using one embodiment. However, as an applied means to obtain the same effect, a picture tube may be used instead of the XY recorder 35 in FIG. 3 to display the image as an image. Also good. In addition, as shown in Figure 5a, when a two-pen recorder is used to sweep the change in power supply voltage and the rectified signal of the oscillator output for a fixed time T, two curves as shown in Figure 5b are drawn. Thus, V when oscillation is started and V when oscillation is stopped can be obtained. Also, as shown in Figure 6a, by using a one-pen recorder, sweep only the rectified signal of the oscillator output for a certain period of time T to obtain a curve as shown in Figure 6b, and calculate the power supply voltage V with respect to the sweep time. If the value of is known, the same effects as in FIGS. 3 and 5 can be obtained.

[Brief explanation of drawings]

Fig. 1 is a diagram of a conventional piezoelectric vibrator constant measurement circuit, Fig. 2 is a diagram showing changes in impedance CI during resonance with respect to excitation level IQ measured with the circuit of Fig. 1, and Fig. 3 is an embodiment of the present invention. FIGS. 4a to 4c are diagrams illustrating the operation of the present invention, and FIGS. 5A and 6B and 6A and 6B are diagrams showing other embodiments of the present invention. In FIG. 3, 31...piezoelectric vibrator to be measured;
32... Oscillation circuit that oscillates by the piezoelectric vibrator to be measured, 33... Power supply for 32 oscillation circuit whose voltage automatically and continuously rises or falls, 34...
- Rectifier circuit that outputs a DC signal according to the amplitude of the oscillation output signal, 35... Recorder that automatically records voltage changes on the x-axis and the Y-axis.

Claims (1)

[Claims] 1. An oscillation circuit having a piezoelectric vibrator as a material to be measured;
An automatic power supply that provides an automatically and continuously changing DC voltage to the oscillation circuit, means for rectifying the output signal of the oscillation circuit, and a relationship between the DC signal of the rectification means and voltage changes of the automatic power supply. 1. A piezoelectric vibrator minute signal measuring device comprising: a recording means for automatically recording the relationship; and a display section for displaying the relationship. 2. The piezoelectric vibrator minute signal measuring device according to claim 1, wherein the recording means or the display means is swept at an arbitrary time. 3. The piezoelectric vibrator minute signal measuring device according to claim 2, wherein the recording means or the display section automatically records or displays only a DC signal obtained by rectifying the output signal of the oscillation circuit.