JPS6129653B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crystal thermometer that uses a piezoelectric vibrator such as a crystal vibrator as a temperature sensor.

The purpose of the present invention is to use a small oscillator commonly called a TM crystal oscillator, which has two vibration modes in one crystal oscillator, as a temperature sensor element.
The objective is to manufacture a small and simple thermometer and supply it to the market at low cost. Another object of the present invention is to construct a high-precision timepiece using the TM crystal oscillator having extremely excellent frequency-temperature characteristics as a time standard source;
It is an object of the present invention to provide on the market inexpensively and in large quantities a consumer device that includes the crystal thermometer of the present invention and displays the ambient temperature and time at the same time.

Conventionally, thermometers for the above purpose include a thermistor, a thermocouple, a base-emitter voltage of a transistor, a crystal resonator of a thickness-shear oscillation system, and the like as temperature sensor elements. All temperature sensor elements other than the crystal oscillator require an operation to convert voltage, which is an analog quantity corresponding to temperature, into a digital quantity by converting it into a digital quantity, and as a measuring instrument, it becomes large in terms of power and device size. Furthermore, when using a crystal resonator, it is basically possible to measure with a frequency counter because it can detect the frequency proportional to the temperature, but in the case of the thickness-shear type resonator, the size is large;
Furthermore, the frequency is as high as several MHz, which makes them unsuitable for the above purpose in terms of power consumption and the like. The present invention significantly improves the above-mentioned drawbacks, and the contents of the present invention will be explained in detail below using examples.

First, FIG. 1 shows the frequency-temperature characteristics of a crystal resonator used in a crystal thermometer according to the present invention. The crystal resonator has an ultra-small external size of φ'2 x 6 mm, and the shape of the crystal piece is a tuning fork type, and the frequency is usually determined by combining the bending and torsional vibration modes of the tuning fork type crystal piece. By compensating for temperature characteristics that are linear or quadratic functions with respect to temperature, extremely excellent frequency-temperature characteristics of cubic functions are obtained. In 1 diagram
_F indicates the frequency-temperature characteristic of vibration mainly consisting of this bending vibration. The third temperature coefficient γ of the frequency temperature characteristic (△/) is γ=2×10 ^-1 M/(℃) ³ and -
△ in the temperature range of 10 to 60°C corresponds to 1 to 2 ppM, and at an oscillation frequency of _F = 200 KHz, the amount of frequency change is about 0.4 Hz. On the other hand, the resonance frequency of torsional vibration, which is another vibration mode, is several KHz lower than that of bending vibration, and the frequency temperature characteristic can be approximated by a straight line over a considerable temperature range, and its first temperature coefficient αT is αT = 40 ~ It is sufficiently large at around 50ppM/℃. The above crystal oscillator is commonly called a TM crystal oscillator (abbreviation for twin mode crystal oscillator). The crystal thermometer according to the present invention uses the frequency _F of the vibrator as a frequency standard and a time standard, and uses _F or Δ= _F − _F as a temperature detection parameter.

Next, FIG. 2 shows an oscillation circuit capable of simultaneously oscillating two frequencies of the TM crystal resonator used in the crystal thermometer according to the present invention. The names and functions of each part in the diagram are as follows. 20
1,202,204,205 are C-M for amplifier
S inverter, 203 is C-MS2 input N
The R circuit serves as an amplitude modulator. 206,2
07, 209, 210, and 211, 212 are DC bias resistors that set the operation of the amplifier and vibration modulator. The capacitor 219 connecting one of the inputs of the NR circuit and the output terminal is 1KHz of △
This is a capacitor for attenuating the above frequency components. Also, the resistor 208, capacitor 216, trimmer capacitor 217 and TM resonator 200 are _F
forming a resonant circuit. Coupling capacitor 21
5,219, diode 220, resistor 213,2
14 and the capacitor 218 together constitute a detector. The operating principle of this oscillation circuit is as follows. The voltage waveform at the point is the carrier wave frequency _F subjected to amplitude modulation by the modulation frequency Δ.
The voltage waveform is filtered by a 200 TM crystal oscillator, and weight waveforms of _F , _F = _F - △ and _F + △ appear. is a loop in which the rectangular wave _F is amplified in two stages until it is saturated with the power supply voltage and returns to the input side of the amplitude modulator. It is divided into two loops that are amplified and returned to the amplitude modulator 203 in opposite phase. The voltage waveform of △ is characterized by being in phase between the terminals of the 200 TM crystal resonators.

Next, FIGS. 3 and 4 are block diagrams of a specific example of a crystal thermometer constructed using the above-mentioned oscillation circuit, and diagrams showing the operation timing between each block. First, explanation will be given starting from FIG. The names and functions of each part in Figure 3 are as follows. 301 is the oscillation circuit shown in FIG. 2, 302 is a frequency divider that divides the clock output _F of 301, 303 is a counter that measures seconds, minutes, hours, days, etc., and 304 is a liquid crystal display device 305. These are decoders and drivers that drive etc. The above series of blocks collectively constitute a clock function. On the other hand, the function of the crystal thermometer is configured as follows: △= _F − _T ≒ output from the 301 oscillator
The voltage waveform of the voltage wave number signal of the frequency signal of Const- _T is
If the series resonant resistance of the crystal resonator's _T oscillation is large, it will contain a large amount of _F component, but in order to prevent malfunction due to this, the △ waveform should be set at a frequency several times that of △.
Sampling is performed at a sampling frequency of 10 to 20 KHz, high frequency components are cut out, and a Δ signal whose phase fluctuates but whose average frequency is constant is obtained. This function is performed by a sampling circuit 308 in the figure consisting of a D-type FF.

306 and 307 are a timer and a timer time setting section, respectively, which output a timer time of time T every cycle of the clock Φ ₀₀ (see FIG. 4). Φ ₀₁ gives the minimum resolution of time T. The timer functions to adjust the variation in frequency temperature of _T of the TM crystal resonator. This adjustment is done as follows. First, the difference frequency Δ can be expressed by the following equation.

△=△O+ _T α(θ−θ.) (1) α=−αT=−40 to −50PPM/℃ However, here, θ is the temperature, and θ ₀ is, for example, θ ₀ =0
°C and α are the first-order temperature coefficients of Δ, and Δo and _T o are the difference frequency between _F and _T and the frequency of _T when θ=θ ₀ . At this time, the number N of output pulses of the AND circuit 309 is given by N=ΔT=ΔoT+ _ToTα (θ−θ ₀ )=No+ΔN(θ−θ ₀ ) (2). For example, in order to set the amount of change ΔN in the number of pulses per 1°C of N to 10, the time T should be set so that ΔN= _ToT ·1α1=10 (3). If we count this T in the case of a TN crystal resonator, α=40PPM/℃, 192KHz, so _T = 7.64Hz/℃, so T=1.31sec. In this case, it is sufficient that the input clock Φ ₀ J to the timer is 2 seconds, and the temperature measurement is repeated every 2 seconds. △
For N=10, the minimum resolution for temperature measurement is 0.1°C. From equation (3), it is clear that the variation in the primary temperature coefficient and _T o of the TM crystal resonator can be adjusted by changing the timer time T.

Next, 310 is an up-down counter that can be preset, and 312 is an external setting terminal of 310, which is expressed in equation (2).
Set NO value. 311 is a circuit that memorizes the presence or absence of the carry output of the 310 counter; 31
7 is a differentiation circuit that generates a differential pulse Φ ₁ at the falling edge of a binary digital signal of H (High) and L (Low) of the timer output T, and 316 is a delay circuit that further delays Φ ₁ in time. . 313,314 is D
A data latch circuit 315 is a type FF, and 315 is a decoder that converts the binary numbers 313 and 314 into decimal numbers, and a driver that drives the liquid crystal display device 318. The operations of blocks 310-318 are performed as follows. Referring to FIG. 4, first, the data number 312 is preset in the counter 310 by the clock pulse _Φ2 . The counter 310 starts counting from the moment the time T reaches the logic level.
At this time, the counter starts operating as a down counter. The number of pulses N during the time T shown by equation (2)
If N≧No, a carry is output from the counter 310, and at the same time, the counter becomes an up counter rather than a down counter. Also, the carry value is stored in 311. 311 may be a 1-bit counter.

If N<No, no signal is output from 310, and the internal state of 311 maintains the L level state at the time of reset. 310 counter and 3
The operation of the latch circuits 13 and 314 and the state of internal data are as shown in the lower part of FIG. In the figure, 41 indicates the count state, 42 indicates the data retention state, and 4
3 indicates a preset state. The output S of the memory circuit 311 corresponds to a positive temperature when it is at L level, and corresponds to a negative temperature when it is at H level. Finally, since the circuit in Figure 3 can be configured with C-MOS, the total current consumption is several μA.
Another feature is that only a small amount is required. From the above explanation, the flip-flop 308, timer 306, timer time setting section 307, AND circuit 309, counter 310, external setting terminal 312, memory circuit 31
1. A detection circuit 3 that detects the amount of change in the difference frequency signal Δ with respect to the frequency signal _F as a temperature using the delay circuit 316, the differentiation circuit 316, the differentiation circuit 317, and the data latch circuits 313 and 314 as a whole.
It can be seen that 20 are configured. Further, the decoder/driver 315 and the display 318 constitute a display means 321.

As explained in detail above, the thermometer of the present invention can obtain a resolution of about 0.1℃ with a relatively simple circuit, can be made compact, and can also be equipped with a clock function, so it will be used in many places in the future. It can be used and seems to be extremely effective. In this embodiment, a tuning fork type crystal resonator has been described, but the first vibration mode vibrates at a reference frequency that is stable with respect to temperature, and the second vibration mode vibrates at a frequency that fluctuates with respect to temperature. If piezoelectric vibrators are generated at the same time, a thermometer can be provided with a similar configuration. In particular, in the present invention, the frequency signal _F of the first vibration mode is divided into the frequency signal _F of the first vibration mode and the frequency signal _F of the second vibration mode.
A resonant circuit including a piezoelectric vibrator is excited by a signal vibration-modulated by the difference frequency signal Δ, and a detector detects the difference frequency signal Δ from the output signal of the resonant circuit. Since the temperature is displayed by detecting the amount of change in the difference frequency signal △ with respect to the frequency signal _of It can detect the temperature information signal △, making it easier to manufacture piezoelectric vibrators, and it can also be applied to vibrators that vibrate at low frequencies (where the frequency difference cannot be large), providing a thermometer with low power consumption. It is possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing frequency-temperature characteristics of a tuning fork type coupled mode crystal resonator commonly called a TM crystal resonator. FIG. 2 shows an oscillation circuit that can oscillate at two frequencies of the crystal resonator using a TM crystal resonator having the characteristics shown in FIG. 1 in the crystal thermometer according to the present invention. circuit diagram. Third
The figure is a block diagram showing the block configuration of a crystal thermometer according to the present invention. Furthermore, FIG. 4 is a timing diagram of operations between blocks in FIG. 200...TM crystal oscillator, 301... Oscillation circuit, 306... Timer, 310... Presetable up/down counter, 305, 318...
Display location.

Claims (1)

[Claims] 1 a first output signal _F having a first frequency and a second
An oscillation circuit that outputs a second output signal Δ having a frequency, a detection circuit that detects the amount of change in the second output signal Δ with respect to the first output signal _F , and a display means that displays a temperature according to the output of the detection circuit. The oscillation circuit includes an amplitude modulation circuit that modulates the first output signal _F with the second output signal Δ, a first vibration mode that vibrates at the first frequency, and a second vibration mode that vibrates at the third frequency. a resonant circuit formed by a piezoelectric vibrator and a codenser that are simultaneously generated and excited by the output signal of the amplitude modulation circuit; a detector that detects the second output signal Δ from the output signal of the resonant circuit; A first amplifier that amplifies the output signal of the circuit and inputs it to the amplitude modulation circuit, and a second amplifier that amplifies the output signal of the detector and inputs it to the amplitude modulation circuit, and the second output signal Δ is a difference frequency signal between the first vibration mode and the second vibration mode,
A thermometer characterized in that a signal obtained by amplifying the output signal of the resonant circuit is used as the first output signal _F , and a signal obtained by amplifying the output signal of the detector is used as the second output signal Δ.