JPS58155321A - Surface wave device for temperature sensor - Google Patents

Abstract

PURPOSE:To enhance productivity and conformity, by imparting a specified angle from a +Y axis to the phase propagating direction of the surface wave, which is generated by the excitation of electrodes provided on the surface of a substrate comprising an X cut crystal plate. CONSTITUTION:On the surface of a vibrator 1 comprising the X cut crystal plate, the cross finger type electrodes 2 and 3 constituting, e.g. an input and output transducer, are provided. A surface wave element 10 is combined with an amplifier 4 and a phase shifter 5. A resonant frequency (f) is extracted from a terminal 6. At this time, the angle between the phase propagating direction of the generated surface wave and the +Y axis of the vibrator 1 is specified in the range of 5-27 degrees in the counterclockwise direction.

Description

DETAILED DESCRIPTION OF THE INVENTION (a1 Technology of the Invention Public Funding) The present invention relates to a surface wave device using a highly accurate and sensitive crystal X-cut plate as a substrate for use as a temperature sensor.

伽）Technical Background Temperature sensors used for various monitoring or control purposes include those whose electrical resistance changes according to temperature changes (for example, thermistors), those whose generated voltage is carbonized (N-Ebo thermocouples), In addition, various types of devices such as those whose resonance frequency changes (for example, crystal oscillators) are selected and used depending on the purpose, but in any case, they must be able to quickly respond to temperature changes, have high precision, and high sensitivity. is desirable.

(C) Conventional technology and problems As a temperature sensor that requires high accuracy, a crystal oscillator is conventionally used, especially a crystal oscillator, which has a large first-order frequency temperature coefficient and a second-order
The following LC cut crystal resonators with small temperature coefficients have been used.

However, this LC cut crystal resonator has the disadvantage that it is extremely difficult to manufacture as it is necessary to select the cutting direction very strictly in order to make the second-order temperature coefficient near zero. Since it is housed in a holder, there is a time delay BE in responding to the outside temperature, making it difficult to measure in a short period of time.

ld1 Purpose of the Invention The present invention takes advantage of the high precision characteristics of a crystal resonator, and
The purpose of this invention is to obtain a novel temperature sensor suitable for this oak tree temperature sensor that eliminates the conventional drawbacks of cut vibrators, ie, the problem of productivity and lack of quick response.

tQ) Structure of the Invention In the present invention, the purpose is to use a crystal X-cut plate as a substrate, and to set the phase propagation direction of a surface wave generated by excitation of an electrode provided on the surface of the substrate to be 5 degrees counterclockwise from the +Y axis.
This is achieved by a surface wave device configured to be selected in the range of 10° to 30°.

In surface wave devices, surface waves literally occur only on the surface of the transducer, and the characteristics of the surface waves are not affected by the condition of the back surface, so the back surface is brought into direct contact with the outside air even when protecting the transducer. This allows the transducer temperature to become the outside temperature in a short time, allowing immediate measurement.

Also, according to the research of the present inventor, the phase propagation direction of the surface wave is
It was confirmed that this direction is significantly related to the first and second order temperature coefficients of the surface wave frequency as described below, and the direction is
In the range of 5° to 27° counterclockwise with respect to the Y-axis, the primary temperature coefficient is relatively large and the secondary temperature coefficient is extremely small, making it possible to obtain a temperature sensor with excellent linearity. .

(f1 Embodiment of the Invention As an embodiment of the present invention, as shown in FIG. 1(A), a cross-finger-shaped electrode 2. 3 is combined with an amplifier 4 and a phase shifter 5 as shown in FIG. The temperature coefficient of the resonant frequency of this oscillator 1 is shown in Figure 2, depending on the angle θ between the phase propagation direction of the oscillator 1 (perpendicular to the interdigitated electrodes 2.3 attached thereto) and the Y crystal axis of the oscillator 1. It changes like this.

In Figure 2, the horizontal axis is θ and the vertical axis is the primary frequency temperature coefficient Tri.
on a scale of 10/C, and the secondary temperature coefficient Tf2 is 10'
/"C" scale, and the first-order temperature coefficient, which is desirable for a temperature sensor, is relatively large, and the second-order temperature coefficient is within a small range where θ is approximately 5° to approximately 10°, especially 10°. ``It shows that the vicinity is optimal.

Figure 3 shows the resonant frequency change rate Δ in the temperature range -5°C to 55°C when using a vibrator with θ = 10°.
It shows f/f and shows approximately linearity. At this time, the ratio of deviation from the straight line is less than 1/8°O (approximately 1/150 for the LC cut vibrator), which is a remarkable improvement.

Figure 4 shows the above θ-5° to n°, which is suitable as a temperature sensor.
The beam steering angle is approximately 6° or less within the scope of the present invention, indicating that there is almost no problem in terms of characteristics.

Although the description has been made above using a surface wave device having an input/output transducer configuration as an example, it goes without saying that the gist of the present invention can be applied as is to a surface wave device having a resonator configuration.

(G1 As described in the detailed description of the invention, the surface wave device according to the present invention can be used with the back side exposed as it is, so the device (crystal substrate)
It does not require much time for the temperature of This makes it easy to use and provides remarkable effects.

[Brief explanation of drawings]

Figure 1 shows a surface wave device (a) with an input/output transducer configuration and its oscillation circuit (b) as an embodiment of the present invention.
Figure 2 shows the phase propagation direction (θ) of the resonant frequency and 1
Next, the relationship between the secondary frequency temperature coefficients Tf1 and Tf2 is expressed as
The figure shows the resonant frequency change rate Δf/f due to temperature change.
The figure is a characteristic curve showing the relationship between the phase propagation direction (θ) and the beam steering angle. In the figure, l is a crystal substrate, 2.3 is an interdigital electrode that constitutes the input/output transducer, 4 is an amplifier, 5 is a phase shifter, 6 is an output terminal, and 10 is composed of the components shown in FIG. 2 (A). A surface wave device is shown. Figure 1 "J 31121"

Claims (1)

[Claims] A crystal X-cut plate is used as a substrate, and the phase propagation direction of a surface wave generated by excitation of an electrode provided on the surface thereof is +
5° to υ counterclockwise from the Y axis. A surface wave device for a temperature sensor, characterized in that it is selected within the range of.