JPS61138131A - Crystal thermometer - Google Patents

Abstract

PURPOSE:To measure the temperature with high precision and high resolution in a very low temperature area by utilizing the insertion loss of a crystal resonator having the large temperature coefficient in the very low temperature area and improving the temperature resolution. CONSTITUTION:A crystal thermometer is composed of the crystal resonator 1 with about 40kHz of the natural frequency through a production process of photolithography, an AGC amplifier 2 generating the self-excited vibration for this crystal resonator 1, a counter 3 detecting the resonant frequency of the crystal resonator 1, an arithmetic circuit 4 detecting the insertion loss and an arithmetic circuit 5, etc. calculating the ambient temperature. Then, the crystal resonator 1 generates the self-excited vibration by the amplifier 2 and makes the bending vibration and the counter 3 detects its resonant frequency and the arithmetic circuit 4 detects the insertion loss. Further, the arithmetic circuit 5 calculates the ambient temperature from the natural frequency and in case the temperature is lower than 20 deg.K, the temperature can be measured with high precision by calculating the ambient temperature based on the insertion loss.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in the measurement range of a quartz I1 degree meter that measures ambient temperature by utilizing changes in the resonance frequency of a quartz crystal resonator.

(Prior art) When measuring ambient temperature using changes in the resonant frequency of a crystal resonator, the frequency contraction coefficient becomes small in the extremely low temperature region regardless of the cut angle or vibration mode of the crystal. High precision concentration measurement is difficult.

(@Illustration point to be solved by the invention) The present invention was made to solve the above problems, and the crystal temperature enables high-precision temperature measurement in a wide range of fA degrees including the cryogenic region. The aim is to realize the goal.

(Means for Solving the Problems) A crystal thermometer of the present invention includes a crystal resonator, means for generating self-excited vibration in the crystal resonator, and means for detecting a resonant frequency of the crystal resonator. The method includes means for detecting insertion loss of the crystal resonator, and calculation means for calculating temperature from the resonant frequency and insertion loss of the crystal sensor, and measures temperature from the resonant frequency and insertion loss of the crystal sensor. It is characterized by

(Function) According to the configuration of the present invention, by utilizing the insertion loss of the crystal resonator having a large temperature coefficient in the cryogenic temperature range, it is possible to perform temperature measurement with high precision and high resolution even in the cryogenic temperature range.

(Example) The present invention will be explained in detail below using the drawings.

FIG. 1 is a block diagram showing an embodiment of a crystal thermometer according to the present invention. 1 is a crystal resonator with a natural frequency of 40K 1-12 manufactured through a photolithography process, 2 is an AGO amplifier connected between the input and output terminals of this crystal resonator 1 to generate self-oscillation, and 3 is this AGC amplifier 2
4 is an arithmetic circuit that detects the insertion loss of the crystal sensor from the input/output signal of the crystal oscillator; 5 is the counter 3 and an arithmetic operation circuit; A second arithmetic circuit 6 calculates the ambient temperature from the output of the device 4, and 6 is a display means for displaying the temperature output from this arithmetic circuit.

The operation of the device having such a configuration will be explained next.

Crystal unit 1 and AGO (Automatic Ga1
The crystal resonator 1 generates self-oscillation at a resonant frequency corresponding to its ambient temperature due to the positive feedback loop formed with the amplifier 2. As a result, the crystal resonator 1 performs bending vibration (a type of bulk vibration). Counter 3 detects the frequency of output signal vO of AGC amplifier 2. The arithmetic circuit 4 receives the input signal vL of the AGC amplifier 2 described in iiO.
Then, V L /V o is determined from the output signal Va, and the insertion loss occurring in the crystal resonator 1 is detected. The calculation circuit 5 calculates the ambient temperature based on the resonance frequency of the crystal sensor output from the counter 3 in a first temperature range (described later), and also calculates the ambient temperature in a second temperature range (described in I).
Ambient temperature is calculated based on the insertion loss output from the calculation unit 4. The display means 6 displays the output contents of the arithmetic circuit 5.

FIG. 2 is a characteristic curve diagram showing the frequency change rate-temperature characteristic and the insertion loss-temperature characteristic of the crystal Tx shifter 1 of FIG. 1. Normally, the natural and active numbers of crystals are unrelated to insertion loss, but in the low temperature region there is a large absorption peak near the product of angular velocity (2π x natural frequency) and relaxation time of phonon scattering, thermal relaxation, etc. occurs. Therefore, the change in insertion loss becomes particularly steep when the ambient humidity is below 20°, and if this portion is used as one parameter for temperature measurement as shown below, temperature resolution can be improved.

Specific motion number f of the crystal resonator and ambient temperature T in Figure 2
, and the relationship between insertion loss ■ and ambient temperature T is as follows (1
) (2).

f=ΣAnT""(1)■-ΣBnT"-(2> However, An, Bn (n, = 1, 2.-) are constants determined by the cut angle and vibration mode.Here, af/aT is 20 ' Below K, the measurement resolution decreases.However, in this region, al/aT takes a large value, so if the temperature is determined from the value of ■, the measurement resolution does not decrease.

The arithmetic circuit 5 in FIG. 1 first calculates the temperature T from the specific imaging number f. This temperature T is a predetermined temperature To
(In the above embodiment, if the temperature is higher than 20'K>, the calculation result is output to the display 6, but if it is lower than the temperature To, the temperature is calculated from the insertion loss ■ and the result is output to the display 6.
Output to. At this time, the conversion formula from natural frequency f and insertion loss ■ to temperature is an inverse function of equations (1) and (2), and is a polynomial that satisfies the required accuracy as shown in equations (3) and (4). is expressed in

T=ΣAn′f”·=(3) T=Σan I”−(4) A spline function or the like is useful for function approximation when the temperature measurement range is wide.

In the above embodiment, the arithmetic circuit 4 calculates the insertion loss using the input/output signals of the AGC amplifier.
Since the amplitude of the output signal VO of the amplifier is kept constant, it is also possible to perform the process using only the input signal vL.

Further, in the above embodiment, the resonant frequency f is set at the temperature T0 as a boundary.
Although insertion loss I and insertion loss I are used separately, it is also possible to use both in coordination.

Furthermore, in the above embodiment, bending vibration is used as the i-mode of the crystal resonator, but the invention is not limited to this.
Various bulk vibration modes such as contour and m-vibration can be used.

(Effects of the Invention) As described above, according to the present invention, a crystal thermometer capable of high-accuracy and high-resolution temperature measurement in a wide range of temperature ranges including the cryogenic temperature range can be used with one (6) oscillators. This can be realized with a simple configuration using .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the crystal thermometer according to the present invention, and FIG. 2 is a characteristic curve diagram for explaining the operation of the device shown in FIG. 1... Crystal camera, 2... Means for generating self-excited vibration, 3... Means for detecting resonance frequency, 4... Means for detecting insertion loss, 5... Calculating temperature. calculation means. Figure 1 Figure 2

Claims (4)

[Claims] (1) a crystal resonator, means for generating self-excited vibration in the crystal resonator, means for detecting the resonant frequency of the crystal resonator, and means for detecting insertion loss of the crystal resonator;
A crystal thermometer comprising a calculating means for calculating temperature from the resonant frequency and insertion loss of a crystal resonator, and measuring temperature from the resonant frequency and insertion loss of the crystal resonator. (2) Crystal temperature according to claim 1, in which the temperature is measured mainly by using insertion loss from 0°K to 20°K, and mainly by using resonance frequency from 20°K to 700°K. Total. (3) The crystal thermometer according to claim 1, which utilizes bulk vibration of a crystal resonator. (4) The crystal thermometer according to claim 1, which uses a crystal resonator manufactured using photolithography.