JPS60131434A - Temperature sensor - Google Patents

Abstract

PURPOSE:To detect temperature, and to divide the resonance frequency of flexural oscillation and display time by putting one crystal oscillation in flexural oscillation and torsional oscillation, and calculating the ratio of two kinds of frequency signal. CONSTITUTION:The crystal oscillator 1 is formed by rotating a two-cut crystal plate by + or -10 deg. around an X axis and by + or -10 deg. around an Y axis. This crystal oscillator 1 is put in flexural oscillation by the 1st self-oscillation loop OSC1 and in torsional oscillation by th 2nd self-oscillation loop OSC2. An arithmetic display circuits 5 performs specific arithmetics including the calculation of the ratio of both frequency signals from resonance frequency signals f1 and f2 from said self-oscillation loops OSC1 and OSC2 to output a measured temperature signal, and also counts a frequency signal relating to the resonance frequency signal f1 to output a time signal.

Description

DETAILED DESCRIPTION OF THE INVENTION 1 [Technical Field to which the Invention Pertains] The present invention is directed to a temperature sensor that detects temperature using a crystal resonator. For more details, □ and
・□ ″ ・ , □, , 1° The present invention relates to a temperature sensor that can display the time as well as the temperature.

Seimonrai Technology] □ □A temperature sensor using a conventional crystal resonator is described in Japanese Patent Application Laid-Open No. 57-26725.
There is 1.

□1 °-ri□・, ri'montokumeionmon9 Consists of two pot crystal oscillators and a reference crystal oscillator that is not affected.

Quartz has a well-known anisotropy, so if you select the cut tb L'angle' number i, then the temperature □
The coefficient number can be increased to 7, or it can be set to a value close to zero.
Ki-゛. In this device, a temperature-measuring crystal oscillator i is used with a large coefficient of coefficient □, and a reference crystal oscillator is used with a temperature coefficient of zero, resulting in high resolution.

Features include high stability and single frequency output.

However, in a conventional device with such a configuration, 2
Errors occur unless the temperature difference between the two crystal oscillators is kept constant or the temperature characteristics of the reference crystal oscillator are completely zero. There are drawbacks such as:

[Object of the present invention]

The present invention has been made in view of these drawbacks of conventional devices, and aims to realize a low power consumption temperature sensor that has a simple configuration, can display high resolution temperature and time.
[Summary of the present invention] The device according to the present invention uses one crystal resonator, causes it to simultaneously perform bending vibration and torsional vibration, and generates two types of frequency signals obtained. The device is characterized in that temperature is detected by calculating a ratio, and the time is displayed by dividing the resonance frequency signal of the bending vibration.

〔Example〕

FIG. 1 is a structural diagram showing an example of a temperature sensor according to the present invention. In the figure, reference numeral 1 denotes a crystal resonator installed at a temperature measurement location, which is manufactured from two crystal plates into a tuning fork shape.

This crystal oscillator is provided with an excitation electrode for exciting it and a detection electrode/pole for detecting vibration, as shown in the figure. For example, the crystal resonator 1 has a thickness t of 0.0
Approximately 25 to 0.2 mm, 1 arm, arm 1a, lb length t, approximately 2.5 to 20 mm (:LOO,t), both arms 1
The width W of a and lb is approximately 0.05 to 0.5 mm, and the manufacturing of the shape and the formation of each electrode required 8 photolithography steps.

This is done using amplifier technology. 21.22 is ml
Among the filter circuits coupled to the motion detection electrodes, one filter circuit 21 is a low-pass filter through which the bending vibration frequency f1 of the crystal resonator 1 passes, and the other filter circuit 22 is
It serves as a bandpass filter through which the screw vibration frequency f2 of the crystal resonator 1 passes. 31.32a Each filter circuit 21
．． This is an adder circuit that adds the signals from each of the four amplifiers 31 and 32, and outputs this added signal to the excitation electrode.

The loop formed including the low-pass filter circuit 21, the amplifier 31, and the adder circuit 4 constitutes a self-excited oscillation loop 08C1 that bends the crystal resonator 1, and includes the low-pass filter circuit 22, the amplifier 32, The loop formed including the pulse calculation circuit 4 constitutes a self-excited oscillation loop 08C2 that causes the crystal resonator 1 to vibrate in a circular motion.

5 is an arithmetic and display circuit that inputs the frequency signals f□ and f2 obtained from the two self-excited oscillation loops 08CI and 08C2 and calculates the ratio between the two; here, a frequency divider 51 that divides the frequency signal f□; , a counter 531 . . . which counts the frequency signal f2 while the gate 52 is open due to the signal from the frequency divider 51 . Counter 53. Enter the estimated value of
After performing certain calculations, it is safe to say! Temperature display 54 to display
and a time display 55 that counts the signal from the frequency divider 51 and displays the hour.

FIG. 2 is an explanatory diagram of the bending vibration of the crystal resonator 1. Flexural vibration is when the arms 1a and lb of the tuning fork-shaped crystal oscillator 1 vibrate as shown by the arrow (■) (the vibration mode is symmetrical vibration), and its resonant frequency f depends on each dimension of the oscillator 1. If we take K as shown in the diagram, we obtain the formula (1)% formula % (where α: characteristic coefficient, k: complementary coefficient ρ: density of crystal resonator S2□: value related to Young's modulus of crystal resonator S' 44: Value related to screw rigidity of crystal resonator.

FIG. 3 is an explanatory diagram of screw vibration of the crystal resonator 1. Both arms 1 and lb of the tuning fork-shaped vibrator 1 vibrate (the vibration mode may be symmetrical or asymmetrical) as shown by the arrow ■, which is screw vibration, and its resonant frequency f2 is (
2) It can be expressed by the following equation.

(2) However, β: Eigenvalue Sm: Value related to torsional rigidity of the crystal resonator n: Order of vibration mode In the present invention, two crystal substrates (two cut plates) are used for making the crystal resonator 1. Based on , the first rotation is
A range of ±10@ for the axis and ±10' for the Y axis is used.

FIG. 4 is a diagram showing the temperature characteristics of the resonant frequency f1 when the crystal resonator 1 is made in the shape of a tuning fork using the above-mentioned crystal substrate and subjected to bending vibration.

In this diagram, the change in the resonant frequency f of bending vibration with respect to temperature is small overall, and in particular the temperature coefficient α near normal temperature of 20°C to 30°C is very small, for example α1-0・O4ppm/°C2 It will be about.

Here, if we ignore the temperature coefficients after the second order, the resonance frequency f1 of the bending vibration and the first order temperature coefficient α1 of the bending vibration are:
For temperature T, there is a relationship shown in equation (3).

f1111fo□(1+α□(T-To) l (s>
However, f. 1: Temperature T. The frequency of bending vibration when
As is clear from equation (1), f□ changes depending on the shape and dimensions W/Z, etc., and it is important to select these to specific values. For example, it can be set to 32.768 kHz, which corresponds to 2n.

FIG. 5 is a diagram showing the temperature characteristics of the resonant frequency 12 when the crystal resonator 1 is subjected to torsional vibration. In this diagram, the change in the resonant frequency f2 of torsional vibration with respect to temperature is linear. For example, the size and shape of the crystal resonator are t/w#0.4+1.
= 2.5mm, α2 = 40ppm /'
It will be about c.

In FIG. 1, the crystal resonator 1 simultaneously performs bending vibration and torsional vibration through two self-excited oscillation loops 08CI and 08C2, and each self-excited oscillation loop 09CI,
08C2 outputs frequency signals f and f2.

Usually, the resonant frequency f2 of screw vibration is higher than the resonant frequency of bending vibration (f2 > fl), and these frequency signals are separated by a low-pass filter circuit 21 and a bandpass filter circuit 22, and i The self-oscillation loop connects the self-oscillations asynchronously to each other.

5 calculation display circuits, each with self-excited oscillation loop 05C1.

Input frequency signals f□ and f2 from 08C2, (5)
Performs expression-like operations. That is, in the example of Figure 1,
The count value (calculation result) Vc of the counter 53 is the result of equation (5).

2 (5) where f is a constant determined by the division ratio of frequency divider 51 In equation (5), substituting equations (3) and (4), we get
Equation (6) is obtained.

When formula (6) is rearranged, formula (7) is obtained.

The calculation display circuit 54 performs the calculation shown in equation (7) and displays the calculation result as the measured temperature T. Further, the time display circuit 55 receives the signal f/k from the frequency divider 51, counts it, and displays the time.

・In the above explanation, in order to simplify the explanation, we have omitted the second-order coefficients and subsequent temperature coefficients for bending vibration and torsional vibration, but if we take these coefficients into consideration, we can obtain even more accurate calculations. A temperature signal can be obtained.

FIG. 6 is a perspective view showing an example of the structure in which the crystal resonator 1 is enclosed.

In this example, a crystal resonator 1 is placed in a container 6 filled with a gas with low activity such as He, Ar, or N2 across a vacuum.

7 and 8 show examples of forming electrodes provided on the crystal resonator 1, in which (a) is a perspective view and (b) is a (
, ) is a sectional view taken along line xx in the figure.

In each case, opposing electrodes 15, 16 and 17° 18 are formed on both surfaces of both arms of the crystal resonator 1 in parallel to each other. As is well known, crystal is an elastic material, and is also a piezoelectric material.
By applying an excitation signal from the adder circuit 4 between them, bending vibration and torsional vibration are caused, and a voltage signal corresponding to the vibration of the crystal resonator 1 is generated between the electrodes 17 and 18.
.

Note that the electrodes may be provided on the sides of the six arms 1a and lb.

Further, the shape of the crystal resonator 1 does not have to be a tuning fork shape,
For example, it may have a rod-like shape with free polarity.

[Effects of the present invention]

As explained above, the present invention is based on two boards, and one
The second rotation is ±10' for the X axis and ±1 for the Y axis.
By using a single crystal resonator made from a 0° range crystal substrate, a temperature sensor with a simple configuration, accurate time display, and low power consumption can be realized.

[Brief explanation of the drawing]

Fig. 1 is a configuration block diagram showing an example of the device according to the present invention, Fig. 2 is an explanatory diagram of bending vibration of a crystal resonator, Fig. 3 is an explanatory diagram of torsional vibration of a crystal resonator, and Fig. 4 is an illustration of the present invention. Resonance frequency f of bending vibration of the crystal oscillator used in the invention
5 is a diagram showing the relationship between the resonant frequency f2 of torsional vibration and temperature, FIG. 6 is a perspective view of the configuration showing an example of a case where a crystal resonator is enclosed, FIGS. 7 and 8 are explanatory diagrams showing examples of forming electrodes provided on a crystal resonator. 1...Crystal resonator, 0sc1. osc2...Self-excited oscillation loop, 4...Addition circuit, 5...Calculation display circuit.

Claims (2)

[Claims] (1) A crystal resonator installed at the measurement temperature point made from a crystal substrate made by rotating a z-cut crystal plate by ±10° with respect to X@< and ±10″ with respect to the Y axis, this crystal resonator Input the resonant frequency signal f1 obtained from the self-excited oscillation loop of the mackerel 1 that bends and vibrates the crystal resonator, the resonant frequency signal f1 obtained from the self-excited oscillation loop, and the resonant frequency signal f2 obtained from the second self-excited i-loop. 1 calculation display circuit that performs predetermined calculations including calculations involving the ratio □ ′□ of image frequency signals and outputs a measured temperature signal, and also counts frequency signals related to the resonance frequency signal f□ and outputs a time signal; Temperature sensor equipped with (2) The temperature sensor according to claim 1, in which the thickness of the crystal oscillator is in the range of 0.025 to 0.2 mm.