JPS6013232A - Temperature detecting method wherein temperature-frequency characteristics of crystal oscillator is compensated - Google Patents

Abstract

PURPOSE:To make it possible to detect temperature accurately, by directly selecting a frequency region by the oscillating frequency of a crystal oscillator, reading the coefficient corresponding to the region, performing required operations, and detecting the temperature. CONSTITUTION:An input signal SIG is inputted to a counter CUNT through a gate GATE. The resonant frequency of a temperature sensor is counted. The result is sequentially inputted to an operating circuit CALC. Meanwhile, with frequency stored in a latch circuit LATCH as an address, the coefficient corresponding to the frequency is read out of an ROM, and inputted to the operating circuit as a series signal. The computed temperature is displayed on a display DISP, in which, e.g., a liquid crystal is used. Since there is no deterioration in accuracy accompanied by A-D conversion in this method, the temperature can be detected highly accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature detection method that compensates for the temperature-frequency characteristics of a crystal temperature sensor.

Conventional temperature sensors that use a thermistor etc. generally use an analog circuit to fully compensate for the non-linearity of the thermistor's temperature-resistance characteristics, but the design of the compensation circuit is extremely time-consuming and requires a large amount of circuitry. There was a drawback in that the characteristics of the operational amplifier used inside had a large effect on temperature detection accuracy.

For this reason, a method has been proposed in which the nonlinearity of the temperature-resistance characteristic is compensated for by digital calculation processing using a microprocessor, but this method also converts the resistance value converted into voltage into A.
-1) Conversion was required, and the cost and accuracy were not fully satisfactory.

The present invention has been made in view of the problems of conventional temperature sensors as described above, and it is an object of the present invention to set a frequency range corresponding to the temperature measurement range of the temperature-frequency characteristic curve of a crystal resonator as a temperature sensor to an appropriate number of frequencies. Divide into regions, set in advance an optimal approximate straight line for the curve of each divided region, memorize the coefficients of the approximate straight line equation in memory, and directly calculate the frequency using the oscillation frequency of the crystal oscillator. It is an object of the present invention to provide a temperature detection method that fully compensates for the temperature-frequency characteristics of a crystal resonator, by selecting a region, reading all the corresponding coefficients from the memory, and performing necessary calculations to detect the temperature.

Hereinafter, the present invention will be explained in detail with reference to embodiments shown in the drawings.

FIG. 1 is a diagram illustrating a temperature-frequency/wavenumber characteristic compensation method according to the present invention.

That is, assuming that the temperature-frequency characteristic curve of the crystal resonator frequency is as shown in the thick line in the figure, and when the temperature measurement range is set from to to t3, the frequency range corresponding to the temperature measurement range is fO to For example, divide f3 into three equal parts, fO to flO
The space between them is defined as a first region, and the regions between fl and fl and between fl and f3 are defined as regions ① and Ha, respectively. Also, the above f1 and f
Let the temperatures corresponding to l be t1 and t2, respectively.

An approximate straight line t=anf+b that approximates the characteristic curve with the least error for each of the frequency regions divided in this manner.
Determine n.

If the approximate straight line is determined as described above, the coefficients an and bn of the equation in each region are automatically determined, so these are stored in fR・OM and can be applied to changes in the temperature of the crystal oscillator serving as the temperature sensor. The region is directly selected from the oscillation frequency that fluctuates accordingly, and based on this, the coefficient corresponding to the selected region is read out from the B.OM, and the equation L=a
The temperature t'l can be found by performing the calculation nf+bn.

In order to carry out the above-mentioned calculations, it is sufficient to assemble all the calculation circuits as shown below.

FIG. 2 is a diagram showing an embodiment of a block diagram for realizing the temperature detection method according to the present invention.

That is, the input signal SIG is input to the counter CUNT via the gate GATEf, the resonant frequency of the temperature sensor is counted, this is temporarily stalled by the latch circuit LATCH, and converted into a serial signal by the shift register FAI (, A-8DR) to the arithmetic circuit. Input to CALC sequentially.

On the other hand, the frequency (
The coefficient an of the approximate straight line is calculated using the count number) as the address.
and bn (i7 remembers R, OM, reads out the coefficient of the area corresponding to the frequency, and also reads the coefficient from the other shift register P.
AB, A −+ S IHI (,) are input to the arithmetic circuit as a serial signal.

Since the operations performed here are not necessary other than addition and multiplication, for example, an IC for the four arithmetic operations of the simplest desktop electronic calculator.
Another feature of the present invention is that it can be constructed at an extremely low cost.

Now, the temperature calculated by the arithmetic circuit CALC may be displayed on a suitable display DISP using a liquid crystal, for example.

Same, the gate GATE and shift register P A R
, A-+8E R5 should of course be driven in synchronization with the clock CLOCK.

FIG. 3 shows the above-mentioned procedure in a flow chart. After determining the region to be selected, the frequency offset amount bn/an'fr and the temperature - Since the frequency compensation method is performed as explained above, there is no decrease in accuracy due to A-Dfi conversion, etc., and the calculation circuit can be used by using the four arithmetic ICi for calculators, so it is suitable for manufacturing high-precision and inexpensive thermometers. It has a remarkable effect.

Similarly, the number of frequency regions to be divided can be determined by taking into consideration the accuracy required for the thermometer, but increasing the number of regions improves accuracy, but requires a large capacity for B/OM, which increases cost. Needless to say, it has some impact. Further, the approximate straight line for the temperature-frequency characteristic curve of the crystal resonator does not necessarily have to connect the area division points, but may pass through all the intermediate points of the curve.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the temperature detection method according to the present invention, FIG. 2 is a block diagram showing an embodiment of an arithmetic circuit for realizing the temperature detection method according to the present invention, and FIG.
The figure is a flow chart. Patent applicant: Toyo Tsushinki Co., Ltd. Kaya 1 tA 1-209- Figure 3

Claims (1)

[Claims] The frequency fluctuation range corresponding to the side temperature range of the temperature-frequency curve of the crystal oscillator is divided into an appropriate number of regions in advance, and an approximate linear equation optimal for approximating the characteristic curve for each frequency region is calculated. By setting coefficients and storing them in all memories, by directly selecting the frequency range from the oscillation frequency of the crystal oscillator, reading out the coefficients to be used in the range from the memory, and solving the equation. A temperature detection method that fully compensates for the temperature-frequency characteristics of a crystal resonator, which is characterized by detecting temperature with high accuracy.