JPH0434090B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crystal thermometer using a crystal resonator as a temperature measuring element. For more details,
The present invention relates to a crystal thermometer having two crystal oscillators constructed from the same crystal wafer, one of which is used as a temperature measuring element, and the other oscillator is used as an oscillation element for obtaining a reference clock. It is something.

Since quartz crystal has crystal anisotropy, by appropriately selecting the cutting angle, the temperature coefficient can be reduced to zero, or conversely, the temperature coefficient can be increased. A crystal thermometer uses a crystal resonator with a large temperature coefficient as a temperature measuring element.
It has features such as high resolution, high stability, and frequency output.

In conventional crystal thermometers of this type, the crystal oscillator as the temperature measuring element and the crystal oscillator for obtaining the reference clock are constructed completely separately, so many temperature calibration points are required. It took a lot of effort to proofread it.

The present invention has been made in view of this point, and its purpose is to reduce the number of temperature calibration points and provide a highly accurate crystal thermometer.

The apparatus according to the present invention makes a pair of crystal resonators at an angle of ±60° to ±120° on a crystal wafer cut out at a rotation angle of 20° to 160° with respect to the X-axis or Y-axis. One crystal oscillator is used as a temperature measuring element,
The feature is that the other crystal oscillator is used as a crystal oscillator for obtaining a reference clock.

FIG. 1 is an electrical block diagram showing an example of a crystal thermometer according to the present invention. In this figure, 1
is the first crystal oscillator, which serves as a temperature measuring element. Although not shown, the crystal resonator 1 is installed in a metal case filled with an inert gas such as helium gas and having a high heat transfer coefficient in order to quickly transfer heat.

2 is a second crystal oscillator, which is used to obtain a reference clock. Reference numerals 31 and 32 denote amplifiers, which form oscillation circuits OS 1 and OS ₂ together with the first crystal oscillator ₁ and the second crystal oscillator 2, respectively, and the oscillation frequency is output from each oscillation circuit OS ₁ and OS ₂ . Signals ₁ and ₂ are obtained.

40 is a frequency divider that divides the oscillation frequency signal ₁ from the oscillation circuit OS ₁ ; 4 is a gate circuit that inputs the pulse from the frequency divider 40 and the oscillation frequency signal ₂ from the oscillation circuit OS ₂ ; 5 is a counter; 6 is an arithmetic and display circuit that inputs the signal from the counter 5.

2 and 4 are explanatory diagrams for explaining how to make the first crystal resonator 1 and the second crystal resonator 2. FIG.

As shown in FIG. 2, crystal resonators are made from crystal wafers cut at various rotation angles α relative to the X-axis (or Y-axis), and their temperature characteristics are determined as shown in FIG. 3. In FIG. 3, the vertical axis shows the change in resonance frequency Δ/.

First, in the present invention, the rotation angle α with respect to the X axis (or Y axis) is in the range of 20° to 160° in FIG. This method uses a crystal wafer W cut out in a range of 1.

Next, as shown in FIG. 4, a pair of crystal oscillators 1 and 2 are placed on this crystal wafer W using, for example, photolithography and etching so that their cut surfaces form an angle of θ to each other. Made by technology. Here, the first-order temperature coefficient with respect to the cutting angle ψ (see FIG. 4) of the crystal bending vibrator 1 (for example, a sound vibrator) formed on the crystal wafer W is as shown in FIG. That is, the temperature coefficient is the largest when the cutting angle ψ is 0° (when cutting parallel to the Y axis), whereas the temperature coefficient is small and close to zero when ψ is around 90°.

In the present invention, the bending vibrator 1 cut out at around ψ=0 is used as the first crystal resonator that serves as a temperature measuring element, and the angle at which ψ is around 90°, that is, the angle with respect to the bending vibrator 1 θ is ±
A bending oscillator 2 cut out at an angle of 60° to ±120°, preferably ±90°, is used as a second crystal oscillator for obtaining a reference clock.

The bending vibrator 1 and the bending vibrator 2 can be created using the same mask on the same crystal wafer cut out with a rotation angle α in the range of 20° to 160° with respect to the X axis or the Y axis, It can be made by aligning the angle θ between the two with high precision.

The characteristics of the resonance frequency ₁ of the bending vibrator 1 and the resonance frequency ₂ of the bending vibrator 2 manufactured in this manner with respect to temperature can be expressed by equations (1) and (2).

₁ ≒ ₁₀ {1+A ₁ (T-T ₀ ) +B ₁ (T-T ₀ ) ² +C ₁ (T-T ₀ ) ³ } ...(1) ₂ ≒ ₂₀ {1+A ₂ (T-T ₀ ) +B ₂ (T-T ₀ ) ² + C ₂ (T-T _{0 )} ³ } ...(2) However, ₁₀ , ₂₀ : Resonance frequency A ₁ , A ₂ , B ₁ , B ₂ , C ₁ , C at temperature T 0 ₂ : primary, 2
With the second and third order temperature coefficients, A ₂ , B ₂ , C ₂
is almost zero in this case. Returning to Figure 1, the oscillation circuit OS ₁ including the first crystal oscillator 1 outputs a frequency signal ₁ related to temperature, and the oscillation circuit OS 1 including the second crystal oscillator 2 outputs a frequency signal 1 related to temperature. Circuit OS ₂ outputs a frequency signal ₂ (reference clock signal) that is almost unaffected by temperature. Frequency divider 40 divides frequency signal ₁ and applies it to gate 4, which applies frequency signal ₂ to counter 5 while gate 4 is open. The counter 5 counts this signal, and its count value N is expressed by equation (3).

N= _1/2 = _10/20 {1+( _{A 1 −A 2} )t+
(B ₁ - B ₂ ) t ² + (C ₁ - C ₂ ) t ³ }...(3) However, t = (T - T ₀ ) The calculation display circuit 6 inputs the count value from the counter 5. , performs calculations to convert this into temperature, calculations for linearization, etc., and displays the calculation results.

In a crystal thermometer with such a configuration, the first crystal oscillator 1 and the second oscillator 2 are manufactured in the same process using the same mask on the same crystal wafer, and both crystal oscillators The angle θ formed by the cutting angle of
Can always maintain accurate values. Furthermore, since both vibrators are obtained in the same process, the effects of disturbances such as adhesion of electrodes and dust can be made almost the same. Therefore, by accurately determining only the cutting angle α of the crystal wafer W and obtaining _1/2 , it is possible to cancel the effects of various disturbances and achieve highly accurate crystal temperature with a small number of calibration points _. can be realized.

In addition, in the above, the crystal wafer W is first
Although a crystal wafer cut out at a rotation angle α relative to the axis has been described, a crystal wafer cut out at a rotation angle β relative to the Y axis in the range of 20° to 160° may also be used.

FIG. 6 is a diagram showing the first-order temperature coefficient with respect to the cutting angle ψ of a crystal bending vibrator manufactured on a crystal wafer rotated by β=50° with respect to the Y axis. In this case, a bending vibrator can be obtained that has a small temperature coefficient near ψ=0° and a large temperature coefficient near ψ=90°. Therefore, the bending vibrator cut out around ψ=90° can be used as a temperature measuring element, and the bending vibrator cut out around ψ=0° can be used to obtain the reference clock.

In the above, the first crystal oscillator 1 and the second crystal oscillator 2 are paired in the same shape on the same crystal wafer W at an angle of θ, as shown in FIG. It is assumed that the first
The shapes of the second crystal resonator and the second crystal resonator do not have to be the same, and the second crystal resonator 2 may be formed within the first crystal resonator 1.

FIGS. 7 and 8 are explanatory diagrams showing an example of the shape of each crystal resonator in this case.

In the example shown in FIG. 7, the first crystal oscillator 1 is a vibrating sound or oscillator as shown by the arrow, and a non-vibrating part of the crystal oscillator 1 has a shape smaller than that of the first crystal oscillator. The second crystal oscillator 2 is integrally formed with an acoustic vibrator so that the cutting direction forms an angle of θ=90° with respect to the cutting direction of the first crystal oscillator.

In the example of FIG. 8, the second vibrator 2 in FIG. 7 is a longitudinal vibrator that vibrates as shown by the arrow.

In FIG. 1, the oscillation frequency signal ₁ from the oscillation circuit OS ₁ and the oscillation frequency signal ₂ from the oscillation circuit OS ₂ are processed by signal processing including the calculation of _1/2 by the configuration shown in the figure _. However, instead of this, ₁ and ₂ are each counted by counters, and the digital signals from these counters are applied to a microprocessor, which performs predetermined calculations and displays the temperature. It is also possible to create a circuit that performs the following steps.

As described above, according to the present invention, a highly accurate crystal thermometer with fewer temperature calibration points can be realized.

[Brief explanation of drawings]

FIG. 1 is an electrical block diagram showing an example of a crystal thermometer according to the present invention, and FIGS.
An explanatory diagram for explaining how to make the second crystal resonator, Figures 3, 5, and 6 are all diagrams showing temperature characteristics with respect to the cutting angle, and Figures 7 and 8 are diagrams showing the temperature characteristics of the first , is an explanatory diagram showing an example of the shape of a second crystal resonator. 1... First crystal oscillator, 2... Second crystal oscillator, 31, 32... Amplifier, OS ₁ , OS ₂ ... Oscillation circuit, 40... Frequency divider, 5... Counter ,6...
...Arithmetic display circuit, W...Crystal wafer.

Claims (1)

[Claims] 1 A pair of crystal wafers are cut out from a crystal wafer cut out at rotation angles of 20° to 160° with respect to the A crystal thermometer in which a crystal oscillator is made, one crystal oscillator is used as a temperature measuring element, and the other crystal oscillator is used to obtain a reference clock. 2. The crystal thermometer according to claim 1, wherein the pair of crystal oscillators are formed using photolithography technology and etching technology. 3. The crystal thermometer according to claim 1, which is constructed by integrating a pair of crystal oscillators.