JPS6248174B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a quartz crystal thermometer. Furthermore, the present invention particularly provides that the heat-sensitive element is a crystal resonator,
The present invention relates to a thermometer in which a vibrator is in a vibrating state by an oscillation circuit and generates an electrical frequency signal representing the temperature experienced by the vibrator.

Temperature measuring devices using quartz crystals as sensors (sensing elements) are already well known. It is a known fact that the frequency of such a vibrator changes with temperature. The relationship between the oscillation frequency of the crystal and the temperature is expressed by the following polynomial.

f _T = f _Tp [1+α(T-To)+β(T-To)] where f _Tp and To are constants, T is the temperature to be measured, f _T is the frequency of the crystal oscillator at temperature T, or α and β are coefficients independent of temperature.

In general, it is not sufficient for the frequency to simply depend on the temperature T; it is desirable that this dependence be as linear as possible. The main advantage of this type of thermometer compared to all other known devices is that it has a direct temperature-frequency conversion, in other words the information about the temperature It is mostly expressed in numerical form. Another advantage of this type of thermometer is that frequency is a physical quantity that can be measured with the required degree of resolution even though the measurement time is reduced.

In the general market, thermometers with probes having oscillating quartz crystals with very good linear characteristics and whose frequency depends on the temperature are available. The first device, manufactured by Heuretsu Pats Card Company in the United States, was designed to excite (apply vibrational energy) at a frequency of 28 MHz.
A crystal with an LC cut plane is used. This instrument has a sensitivity of 1000Hz per degree Celsius. The device manufactured by Tokyo Denpasha uses an oscillating crystal with an YS-cut plane, which is excited at frequencies around 10 MHz. This device has a similar degree of sensitivity as the previous device.

These high-precision instruments have the disadvantage that they are extremely expensive, and are extremely difficult to handle because the crystal oscillator used as the heat-sensitive element is manufactured using a technical method that does not permit easy miniaturization.
Furthermore, the methods for making them are not suitable for mass production. Finally, because they are arranged to oscillate at a frequency equal to or above 10 MHz, the electronic circuitry for processing the signals generated by the crystal oscillators consumes a relatively large amount of electrical energy.

In order to overcome these drawbacks, a first object of the present invention is to provide a quartz thermometer which has good linearity with respect to temperature and which can be made relatively compact.

A second object of the invention is to provide a quartz thermometer with an oscillator that can be easily made by modern manufacturing methods, such as chemical etching.

A third object of the invention is to provide a quartz thermometer with a relatively simple electronic circuit.

A fourth object of the invention is to provide a crystal thermometer that operates at a lower frequency than in prior art devices in order to save the electrical energy consumption of the circuit coupled to the vibrator.

A fifth object of the present invention is to provide a crystal thermometer with a vibrator having a dynamic capacitance C ₁ sufficient to allow stable oscillation of the vibrator with acceptably low electrical energy consumption.

To achieve these objectives, the present invention utilizes a crystal whose length is substantially parallel to the X-axis of the crystal. The vibrator is provided with electrodes and supplied with current so that the vibrator vibrates torsionally.

This transducer can be configured either in the form of a tuning fork or in the form of a bar.

According to a first embodiment, the normals of the upper and lower major surfaces of the tuning forks or bars are at an angle θ in the range of −30° to +30° with respect to the Z axis of the crystal.
is doing. The electrodes are provided parallel to the length direction of the vibrator. Two electrodes are provided on the upper surface of the teeth of the tuning fork and two electrodes are also provided on the lower surface. These electrodes are supplied with a current that causes torsional vibrations. The oscillator outputs an electrical signal having a frequency variation that is substantially linear with temperature.

According to a second embodiment, the perpendiculars of the upper and lower major surfaces of the tuning fork or bar lie within a range of +30° to +50° or - with respect to the Z-axis of the crystal.
The angle θ ranges from 30° to -50°.

The electrodes are provided parallel to the length direction of the vibrator.
Each major surface of the tooth of the tuning fork or bar is provided with a respective electrode, and likewise each edge of the tooth of the tuning fork or the edge of the bar is provided with a respective electrode. A current is supplied to these electrodes to cause the vibrator to vibrate torsionally. The oscillator outputs an electrical signal with a frequency that is a substantially linear function of temperature.

The term "linear" should be understood as follows. In the polynomial between frequency and temperature, the coefficient α of the first-order term is much larger than the coefficient β. This means that the coefficient β does not need to be zero. For example, the ratio of these two coefficients is 10 ² to 10 ³
That's about it.

The ratio of the thickness e and the length W of the crystal element is preferably selected such that the absolute value of α is sufficient in order to make the oscillator highly dependent on temperature, i.e. to obtain high sensitivity. . This ratio is 0.1 to 0.8
It is desirable to be between.

Some embodiments of the invention will be described by way of example with reference to the accompanying drawings, in which: FIG.

As already explained, the thermometer according to the invention comprises:
On the one hand, a quartz crystal oscillator provided with electrodes and supplied with an electric current so that the quartz crystal element is torsionally excited, and on the other hand an electronic circuit for producing the temperature indication measured by the oscillator. have

With reference to FIGS. 1, 1a and 3, a first embodiment of the invention relating to a vibrator constituted by a tuning fork 2 will first be described. Tuning fork 2 has a base 4,
This fixes it to the pedestal 6. The tuning fork naturally has two teeth 8 and 10 whose cross section is rectangular. This cross section has a short side length e equal to the thickness of the tuning fork and a long side length W equal to the width of each tooth of the tuning fork. Each tooth 8 and 10 of the tuning fork thus has a parallelepiped shape. The directions corresponding to the length L, width W and thickness e of each tooth of the tuning fork are indicated in FIG. 1a as axes X', Y' and Z', respectively. Figure 1a also shows the axis of the oscillator,
The directions of Y' and Z' are shown with respect to the crystal axes X, Y and Z.

The tuning fork shown in FIG. 1 was cut by the following method. That is, its length is substantially along the X axis of the crystal, in other words, the directions of X and X' are substantially equal. However, the axis Z' of the tuning fork is tilted by an angle θ with respect to the optical axis of the crystal. Of course, the same applies to axis Y' with respect to axis Y.

As already explained, this tuning fork is excited to twist. For this purpose, a metal coating is applied along the width W of the teeth of the tuning fork to the main surface 9,
9' and 11, 11'.

In particular, each main surface of each tooth of the tuning fork is provided with two electrodes extending parallel to the length of the tooth at the ends of said main surface, ie near the sides of each tooth. As shown in FIG. 1a, the eighth main surface 9 is provided with electrodes 12 and 13, and one surface 9' is provided with electrodes 12' and 13'. Similarly, the main surfaces 11 and 11' of the teeth 10 are provided with electrodes 14, 15 and 14', 15', respectively. Further, the electrodes on the same major surface of each tooth are at different potentials, and the electrodes on the opposite major surface of each tooth are at different potentials as well. Finally, the two inner electrodes on the same (upper or lower) main surface are at the same potential. Thus, in FIG. 1a the electrodes 12,1
3', 14' and 15 are kept at positive potential, and one electrode 12', 13, 14 and 15' is kept at negative potential. The two teeth 8 and 10 of the tuning fork are thus made torsionally vibrate.

Furthermore, this arrangement causes the teeth 8 and 10 of the tuning fork to vibrate asymmetrically, compensating for their dynamic moments.

FIG. 1 shows the practical arrangement of conductive metal coatings to form electrodes with connections between the electrodes to be maintained at the same potential.

In this figure, the accuracy of proportions in the dimensions of the tuning fork has been ignored for the purpose of clearly depicting the placement of the metal coating. Electrodes 12 and 14 each have a conductive coating 16 forming positive and negative potential contacts.
and 17 extend from the base. Electrodes 13 and 15 are coated with metal coatings 18 and 19 located on the free ends of the teeth of the tuning fork.
It will be extended to. In addition, metal coating 2
0 connects electrodes 13 and 14. On the lower major surface of the tooth, a metal coating is provided correspondingly on the upper surface. Electrodes 13' and 1
5' extends from the base 4 by conductive coatings 16' and 17'. Electrodes 12' and 1
4' extends to metal coatings 18' and 19' opposite metal coatings 18' and 19'. Electrode 13' is connected to electrode 14' by a metal coating 20'. Electrical coupling between the metal coatings on the two major surfaces is provided by metal coatings on the edges and ends of the teeth and base. More specifically, metal coatings 18 and 18' are metal coatings 18 and 18'.
8″ and metal coatings 19 and 1
9' are connected by a metal coating 19''. In the base 4, the metal coating 16''
and 16' by metal coating 16'',
On the one hand, the metal coatings 17 and 17' are connected by a metal coating 17''. These metal coatings are formed by conventional methods such as depositing layers of chromium, gold, aluminum or other metals. Strictly speaking, only the metal coatings thus produced on the edges do not constitute electrodes, and it should be noted that the areas in which these metal coatings are to be formed are relatively free (the distal ends of the teeth and the lateral edges of the base). ) It is interesting that there are no major problems in manufacturing all of these metal coatings.

In addition, in order to obtain a good linear relationship between the temperature and the signal frequency output by the thermometer, the angle θ on the one hand and the value of the ratio e/W on the other hand should be kept within one constant limit. It is necessary to select accordingly. For ideal response linearity, as defined earlier, the value chosen for the angle θ and the ratio e/W
It is necessary to consider the relationship between

Furthermore, with the type of electrode selected, the angle θ must be between -30° and +30°. Furthermore, it is necessary that the value of the ratio e/W lies between 0.4 and 0.8.

Figure 3 shows the value (curve) of the coefficient β expressed as 10 ^-9 °C ^-2 and 10 ^-6 °C ^-1 at θ = +2°.
The value of the coefficient α (curve) expressed as is expressed with respect to different values of the ratio e/W. These curves show that it is possible to manufacture a vibrator with a coefficient β of zero. The thermometer response is completely linear in this case. This curve also shows that it is possible to choose a ratio e/W with a large value of α while keeping the coefficient β very small, i.e. in this case the thermometer is very High sensitivity.

Furthermore, the length L of the teeth of the tuning fork is such that the frequency of the tuning fork is several 100K.
The frequency is chosen to be on the order of Hz, typically the frequency used as the time base.
It is assumed to be an integral multiple of 32738KHz.

For example, a thermometer resonator manufactured using a torsionally excited quartz tuning fork has the following characteristics:

θ=+2゜W=0.230mm e=0.125mm e/W=0.55 L=2.75mm (length of one tooth of tuning fork) In this case, the excite frequency is 262144KHz, and the coefficient of the thermometer is as follows. become that way.

α=35×10 ^-6 ℃ ^-1 β=20×10 ^-9 ℃ ^-2 The cut angle θ=+2° is a typical cut angle used to manufacture the crystal resonator that makes up the time base of an electronic wristwatch. This is important because it is a cut angle. More desirably, such manufacturing methods are controlled, for example by chemical attack. Furthermore, the dynamic capacitance of this tuning fork is 0.33 fF, which is a large value for a crystal in a torsional vibration state. It should also be noted that the oscillation frequency of 262144 KHz is extremely low compared to the frequency of several MHz in known oscillators of thermometers based on conventional vibration technology. Finally, if we take into account the equations used in this description, it can be seen that this oscillator has very good linearity with respect to temperature. That is, even if β is not zero, the value of the function α/β is 1.75×10 ³ . The influence of the first term is much larger than that of the second term. Moreover, the absolute value of α is 35
×10 ^-6 °C ^-1 , which is extremely large and provides extremely high sensitivity to temperature. The two prerequisites for a good thermometer collector are thus combined.

Figure 3 shows that when the ratio e/W is chosen equal to 0.68, the coefficient β becomes zero and the coefficient α becomes 20×
This shows that the value slightly exceeds 10 ^-6 °C ^-1 . It should be pointed out again that this is the case in which very satisfactory values for α are obtained.

It has been made clear in the above description that the angle θ is in the range of −30° to +30°. However, −
It should be clearly stated that by limiting the angle to the range between 10° and +10°, the cleavage plane close to the Z plane is maintained at the same time, and the temperature characteristics are maintained. This is a suitable angle for a transducer that can be easily manufactured by chemical attack. Note that if the angle θ is slightly negative,
For example, between 0° and -10°, and the ratio e/W remains in the range already specified, the coefficient β becomes zero or almost zero, and the coefficient α becomes substantially 20 × 10 ^-6 °C.
It is possible to set it to a value larger than ^-1 , for example, at least about 30×10 ^-6 °C ^-1 . Furthermore, the fact that the length of the tuning fork is substantially parallel to the X-axis means that after rotation by an angle θ about the It means it's possible.

FIG. 2 shows another vibrator that can be used in a thermometer according to the invention. Oscillator 2' is length
It has the shape of a parallelepiped bar of W' and thickness e'.

This crystal bar 21 has a longitudinal dimension along the X-axis of the crystal, and the perpendicular Z' with respect to its upper and lower main surfaces is + with respect to the Z-axis of the crystal.
It is tilted by an angle θ between 30° and -30°.

The electrodes are provided on the two half bars, 21a and 21b. These half bars are 1 in the diagram.
They are virtually separated by a nodal plane N represented by a dotted chain line. Electrodes 22 and 23 are located near the edges on the upper major surface of half bar 21a. Similarly, electrodes 22' and 23'
are arranged opposite electrodes 22 and 23, respectively, on the lower surface of a. In the case of half bar 21b, electrodes 24 and 25 are on the upper surface and electrode 2
4' and 25' respectively have electrodes 24 on the lower surface.
and 25 are provided oppositely. Since the bar vibrates in a twisting manner, as in one tooth of the tuning fork 2 shown in Figs. 1 and 1a,
Each half-bar has a similar electrode arrangement and, furthermore, the two electrodes symmetrical about the nodal plane must be kept at opposite potentials. For this purpose, electrodes 23 and 2
4 are interconnected by a metal coating 26 across the nodal plane. In addition, electrodes 22 and 2
4' are interconnected by a metal coating 27 that crosses the nodal plane, and electrodes 23 and 25' are interconnected by a metal coating 27 that also crosses the nodal plane.
7'. These metal coatings 27 and 27' are provided on the edges of the bar. Further, electrodes 24' and 25 are interconnected by metal coatings 28 and 29, respectively, provided on the lower surface and one edge near the end of half-bar 21b, and one-sided electrodes 22' and 23 are , respectively, are interconnected by metal coatings 28' and 29' provided on the lower surface and one edge near the distal end of half-bar 21a.

Finally, leads 31a and 31'a are fixed onto metal coatings 26 and 27 to keep electrodes 22', 23, 24 and 25' at a positive potential.
Lead wires 31a, 31'a, 31b and 31'b
are all placed in the selected plane of the torsionally vibrating crystal to ensure support for the crystal bar.

Figures 7, 7a and 8 depict a second embodiment of a transducer for a thermometer in which different cleavage angle ranges are used with different electrode configurations. .

7 and 7a show the case where the vibrator 2 has a tuning fork shape. This tuning fork naturally has a base 4' as a means for fixing to the support 6' and two teeth 8' and 10' substantially parallel to the X-axis of the crystal. As seen in FIG. 7a, the upper surfaces 102 and 104 and the lower surfaces 102' and 104' of the teeth 8' and 10' of the tuning fork are referenced 106, 108 and 106', 108', respectively. A longitudinally extending electrode is provided as depicted. Similarly, electrodes 118 and 118 are provided at edges 110 and 112 of tooth 8' and edges 114 and 116 of tooth 10', respectively.
118' and 120, 120' are provided. In each tooth, the electrodes opposite each other are at the same potential, and the electrodes located on tooth 8' have a different potential than the electrodes located similarly on other teeth.
For example, electrodes 106, 106', 120 and 1
20' is at a positive potential, and electrodes 118, 11
8', 108 and 108' are at negative potential. Torsional vibration of the vibrator is obtained in this way. In addition, teeth 8' and 10' vibrate asymmetrically to balance their respective operating moments.

FIG. 7 shows the arrangement of metal coatings to create the electrodes and to make electrical connections between the electrodes. In this figure, the electrode 10 on the lower surface
6' and 108' are not visible. The electrodes on the upper and lower major surfaces terminate short of the ends of teeth 8' and 10', with metal coatings 122 and 123 extending a short distance to the ends of these teeth and on the upper and lower major surfaces. This makes it possible to install it in an overhanging shape. metal coating 1
22 interconnects electrodes 118 and 118';
On the other hand, the metal coating 124 is connected to the electrodes 120 and 12.
0'. metal coating 126
interconnects electrodes 106 and 120, and metal coating 128 interconnects electrodes 108 and 118. The metal coating 130 is the electrode 11
8' to electrode 108', which is not visible in FIG. Finally, a metal coating (not shown) provided on the lower major surface of base 4' includes electrode 106' and electrode 12, which are not visible in the figure.
0'. On the upper major surface of base 4', contacts 132 and 134 are connected to electrodes 118 and 120', respectively. By connecting contact 132 to a negative voltage and contact 134 to a positive voltage, the electrode potentials shown in FIG. 7a are obtained.

FIG. 8 shows the structure and arrangement of a bar-shaped vibrator in a second embodiment of the present invention. In this figure, the relationships between the width W', the thickness e' and the length do not correspond to reality for the sake of clarity. Functionally, the bar 150 is a nodal plane.
Two half bars 150a and 150 by N'
It is divided into b. In half bar 150a, electrodes 152, 152' and 154, 154' are provided on the major surface and edges of the half bar, respectively. Similarly, half-bar 150b has electrodes 156 and 156' on its major surface and electrodes 158 and 158' on its edges. Electrode 152
and 152' are interconnected by a metal coating 160. Electrodes 152' and 158 are interconnected by a metal coating 162, and electrodes 158 and 158' are interconnected by a metal coating 164 disposed on the end of the upper major surface of half bar 150b. Similarly, electrode 15
6 and 154 are metal coating 166,
Electrodes 156 and 154' are metal coatings 16
8 and electrodes 154' and 156' are interconnected by a metal coating 170. Thus, half bar 150a has a configuration similar to tooth 8' of the tuning fork of FIGS. 7 and 7a, and half bar 150b has a configuration similar to tooth 10' thereof. Powering the bar and supporting the bar are
This is done by means of four conductive lines placed in the nodal plane. In particular, lines 172 and 172' are connected to electrode 15
6 and 154' and connected to a negative potential, and one-way wires 174 and 174' are welded to electrodes 158 and 152' and connected to a positive potential.

In this electrode arrangement, the cut angle θ should have a different value in order to take advantage of the piezoelectric coupling. In this case, the angle θ lies in the range between -50° and -30° or between +30° and +50°. It is clear that these limits are not absolute, but are chosen according to the configuration according to practical circumstances. For this electrode type,
e′/W′ is between 0.1 and 0.8. Figure 1 and 1
As in the case of the example in figure a, the parameters θ and e′/W′ are set so that β is zero, while α is an acceptable value, or even if β has a small non-zero value, α and β becomes extremely large.

For example, the following quartz tuning fork having the electrode system shown in FIGS. 7 and 7a can be obtained.

θ=-40゜e/W=0.3 α=50×10 ^-6 ℃ ^-1 β=0 Furthermore, in general, the curves shown in FIGS. This is the case when the relationship between temperature and frequency is specified to be completely linear. Figure 9 shows that a β of zero can be obtained for values of θ between -42° and +28° and for values of e/W between 0 and 0.7. . Figure 10 shows that α is 20 × 10 ^-6 °C ^-1 to 40 × 10 ^-6 in the above cleavage angle (cut angle) range.
It shows that the temperature changes up to ℃ ^-1 .

With reference to FIG. 4, the form of the electronic processing circuit that together with the vibrator constitutes the thermometer will be explained. In one general method, the thermometer has an oscillating measuring circuit A including a temperature pickup composed of a vibrator, an oscillating reference circuit B, a comparator circuit C, and a display and zero reset circuit D. .

The oscillation measurement circuit A consists of the oscillation measurement element 2 described above and a oscillation sustaining circuit of known form. The circuit comprises an amplifier 30 in whose feedback path the vibrating element 2 is arranged. capacitor 3
2 and 34 are respectively provided between the input and output of the amplifier on the one hand and ground on the other hand. This circuit is completed by a buffer amplifier 36.

Oscillation reference circuit B is also arranged in a similar manner,
An amplifier 38 including an oscillation reference element 40 is provided in the feedback path. This circuit also includes capacitors 42 and 44. Capacitor 44 is variable and allows the reference frequency to be adjusted as will be explained later.

The comparator circuit C basically consists of two counters of capacitance M (M being an integer), indicated by reference symbols 46 and 48 respectively, a third counter and an electrical pulse generator with adjustable frequency. Vessel 52
It consists of. In particular, clock inputs 46a and 48a of counters 46 and 48 are
It receives pulses generated by oscillator circuits A and B. Output 46b of counters 46 and 48
and 48b are respectively connected to two inputs of exclusive-or gate 54. The variable frequency source 52 is suitably constituted by a generator 52a supplying a fixed high frequency pulse signal and a programmable divider 52b connected to its output. At the output of divider 52b, the signal has a frequency f _c stabilized by the division ratio of divider 52b. It is clear that this generator 52 can alternatively be constructed by a variable frequency generator.

The output of generator 52 and the output of gate 54 are each connected to two inputs of AND gate 56. Clock input 50a of third counter 50 is connected to the output of AND gate 56. The outputs of counters 46 and 48 are connected to D flip-flop input D and clock input 58a, respectively. The function of this flip-flop is to give the sign of the temperature measured at the oscillator. That is, it shows the order in which the leading edges of the signals generated by counters 46 and 48, respectively, appear.

The display and zero reset circuit D has a latch 60 whose input is connected to the binary outputs ₅₀₁ to _50o of the counter 50. This latch 6
0 is itself connected to a decoding and display mechanism 62. This display mechanism 62 has a special input 62a connected to the output of the bistable (flip-flop) 58 for displaying the sign of the temperature centered around 0°C.

Outputs 46b and 48b of counters 46 and 48 are similarly connected to two inputs of AND gate 64, respectively. The output of gate 64 is connected to the input of non-reexcitable monostable 66.
The output 66a of the monostable 66 is a control signal.
Supply LD. This signal is connected to the input of the second monostable 68 on the one hand and to the latch 60 on the other hand.
control input 60a. Monostable 68 provides zero reset inputs 46c, 48c and 50 for counters 46, 48 and 50, respectively.
Generates a zero reset pulse that is applied to 0c.

The thermometer described herein operates as follows. Counter 46 counts the pulses provided by measurement oscillator A. When this counter has counted M pulses, its output goes to logic state 1, as shown in FIG. 1 in FIGS. 5a and 5b.

At the same time, counter 48 is counting the pulses provided by reference oscillator B. When this counter counts M pulses, its output is 5a
A logic state 1 is obtained as shown in FIG. 2 of the figure and FIG. 5b. ps in Figures 5a and 5b is
It means previous sign. Tt is counter 46
represents the time required to count M pulses, and Tn represents the time required for the counter 48 to count M pulses.
The signal L appearing at the output of the exclusive OR gate 54 is generated during the period when one of the outputs of the counters 46 and 48 is in the logic state 1, i.e. t ₁
The logic state is 1 only for the time between and t ₂ . This signal L maintains the logic state 1 for a period of Tt-Tn. In the case of FIG. 5a, time Tt is shorter than time Tn. That is, the measured temperature is higher than the reference temperature. Conversely, in the case of FIG. 5b, the time Tt is longer than the time Tn, so that the measured temperature is equal to the reference temperature T ₀
It is known that it is lower than

Counter 50 receives at its input the pulses of signal P generated by AND gate 56. That is, the counter 50 will receive the pulses generated by the generator between T ₁ and T ₂ . As a result, after T ₂ (FIG. 5a) the content of counter 50 is equal to the number N of pulses generated by the generator during the time interval Tt-Tn. This numerical value N represents the measured temperature T, as will be explained later. In addition, T ₂
In (FIG. 5a), the output of the AND gate 64 is in the logic state 1, producing the signal LD only for a time period τ ₁ defined by the time constant of the circuit. Signal generated by monostable 66
LD controls the release of latch 60, which also applies a number N of pulses to decode and display device 62. The falling edge of the signal LD changes the output of the monostable 68 to logic state 1 for a period of time τ ₂ .
change to This pulse is counter 46,4
8 and 50 are reset to zero. When the falling edge of this pulse appears, the device is ready for a new temperature measurement.

Eventually, counter 50 counts the pulse signals provided by pulse generator 52 during a period defined by t ₁ and t ₂ . The number of pulses N represents the measured temperature T. The relationship between N and T becomes substantially linear depending on the selection of the vibrator.

Adjustment of this thermometer is accomplished by manipulating the frequency f _c of the signal generated by generator 52 and the value of reference oscillator capacitor 44.

FIG. 6 shows a graph for different adjustments, D ₁ , D ₂ and D ₃ , which shows a substantially linear relationship between the temperature T and the number of pulses N counted by the counter 50. Changing the frequency f changes the proportionality constant between the temperature T and the number of pulses counted. That is, this affects the angle Y (Y ₁ , Y ₂ . . . ). On the other hand, adjusting the capacitor 44 changes the reference value, ie the number of pulses No corresponding to 0°C. In Figure 6, the straight line D ₁ corresponds to ideal adjustment, and No = 0 when T = 0°C, and the angle Y = Y ² represents good sensitivity characteristics with respect to temperature. It is something.

To adjust the capacitance of capacitor 44, this thermometer (oscillator A) is placed in a 0°C environment.
At this time, time Tt corresponds to temperature To. Capacitor 44 is adjusted until counter 50 no longer counts pulses from generator 52. Under this condition, Tn=Tt and oscillator B has T=
A signal having a reference frequency corresponding to 0° C. is generated. This adjustment step is of course separate from the adjustment of the frequency f _c .

The value of angle Y is adjusted by changing the frequency f _c without adjusting capacitor 44.

If the oscillator is 30×10 ^-6 ℃ as the coefficient of the first term.
^-1 and M (counting capacity of counters 46 and 48) has a value of 2×10 ⁵ , an increase in temperature of 1° C. will appear as a decrease of 10 μs in counting time. If frequency f _c is 10MHz (period Tc = 0.1μ
s), N is 100. As a result, if the frequency of the vibrator 2 is 300KHz at T=0℃, this thermometer is 0.01KHz.
It is possible to measure temperature differences in °C.

For example, two consecutive measurements are separated by a time interval of less than 400 mS if the monostable time constants τ ₁ and τ ₂ are chosen properly.

The circuit described is only one example of a circuit that can be well applied to handle the problem to be solved. It is clear that other circuits could be used instead. These circuits may include a device capable of measuring the frequency difference between the signal generated by the measuring oscillator and the signal generated by the reference oscillator, and a device for displaying the result of this measurement, preferably in numerical form. It is sufficient.

As a result of the foregoing description, the selection of the oscillator and its exciting method result in a thermometer according to the invention that is simple and therefore of inexpensive construction.

The tuning fork or bar is aligned with the Z axis (first
1a and 3)
It is equally clear that the manufacture of the crystal is simplified if the plane is chosen to be cut relatively close to the plane containing the . The processing circuit is extremely simple, and thermometer adjustment becomes easy. Additionally, electricity consumption is low due to the fact that the vibrator operates at a frequency of around 300KHz.

Furthermore, despite these simple low frequency values, this thermometer allows temperature measurements with good resolution (0.01°C) and with sufficiently short repetition rates for rapid monitoring of temperature changes. It has a measurement cycle (about 400mS).

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a tuning fork-shaped first vibrator that can be used in the present invention,
FIG. 1a is a cross section of the tuning fork taken along line A-A in FIG. 1, and FIG. 2 is a diagram showing a first crystal bar that can be used in the present invention,
Figure 3 shows the cleavage angle θ=+2 with respect to the optical axis Z of the crystal.
The first of the torsionally excited oscillators in the case of ゜
Figure 4 shows a curve representing the following temperature coefficient α and the second temperature coefficient β as a function of the ratio e/W of the thickness and length dimensions of the crystal element. Figures 5a and 5b are time diagrams illustrating how the processing circuit operates;
The figures are diagrams depicting different adjustments of the thermometer, and FIG.
Figure a is a cross-sectional view of the tuning fork taken along line A-A in Figure 7, Figure 8 is a diagram showing a second crystal bar that can be used in the present invention, and Figure 9 is a diagram showing a second crystal bar that can be used in the present invention.
The figure shows the ratio e/W at β=0 as a numerical value of the cleavage angle, and FIG. 10 shows the value of α at β=0 as a function of the angle θ. 2... Tuning fork, 4... Bass,
6... Pedestal, 8, 10... Teeth, 9, 11... Main surface, 12, 13, 14, 15... Electrode, 16, 1
7, 18, 19... conductive coating, 21...
Crystal bar, 22, 23, 24, 25...electrode, 2
6, 27, 28, 29... conductive coating, 1
02,104...main surface, 106,108...electrode, 110,112,114,116...edge, 118,120...electrode, 150...crystal bar, 152,154,156,158...electrode,
160, 162, 164, 166, 168, 17
0... Conductive coating, A... Oscillation measurement circuit,
B...Oscillation reference circuit, C...Comparison circuit, D...Display/zero reset circuit.

Claims (1)

[Scope of Claims] 1. A quartz crystal thermometer whose length is substantially parallel to the X-axis of the quartz crystal, and which has two main surfaces that are substantially parallel to each other and further parallel to the length. at least one elongated quartz crystal element delimited by an edge, and an electric field provided on the elongated element parallel to the length for producing an electric field in the quartz crystal which causes the element to vibrate torsionally; a vibrator having a plurality of electrodes and generating a signal whose frequency change is a substantially linear function of temperature; an electronic circuit for producing at an output a quantity having a magnitude representative of the temperature experienced by the oscillator, the substantially parallel major surfaces being at an angle of from +30° with respect to the optical axis Z of the quartz crystal; perpendicular to the axis Z' inclined by an angle θ between -30°, and each electrode is provided close to the edge of the element on one of the two major surfaces of the element. A crystal thermometer characterized in that the ratio of the length of the short side to the long side of the cross section of the vibrator is between 0.4 and 0.8. 2. The vibrator is comprised of a single element in the shape of a parallelepiped crystal bar having a substantially rectangular cross section and having a long side and a short side provided on the main surface. Thermometer according to item 1. 3. The vibrator has two elements, each element being one of the teeth of a tuning fork, each tooth having a rectangular cross section with a long side and a short side provided on said main surface. The thermometer according to claim 1, having a parallelepiped shape. 4. The thermometer according to claim 1, wherein the angle θ is between +10° and -10°. 5 such that the angle θ is substantially +2° and the ratio of the length of the short side to the long side is substantially equal to 0.68,
A thermometer according to any one of claims 1 to 4. 6 Electrodes are supplied with currents with two different voltages, two electrodes on the same side of the same tooth are kept at different voltages, and two electrodes located opposite each other on the same tooth are kept at different voltages. Thermometer according to claim 1 or 3, which is maintained at a voltage. 7 A quartz crystal thermometer, the length of which is substantially parallel to the at least one elongated quartz crystal element with defined limits, and a plurality of electrodes disposed on the elongated element parallel to the length for creating an electric field in the quartz crystal that causes the element to torsionally oscillate. , an oscillator for generating a signal whose frequency change is a substantially linear function of temperature; an electronic circuit for producing a quantity having a magnitude representative of the temperature experienced by the quartz crystal;
perpendicular to the axis Z' inclined by an angle between -30° and -50°, and each edge and each major surface is provided with at least one electrode. , the ratio of the length of the short side to the long side of the vibrator is 0.
A crystal thermometer characterized by a temperature between 1 and 1. 8. The vibrator is formed of a single element in the shape of a parallelepiped crystal bar having a substantially rectangular cross section with a long side provided on the main surface and a short side provided on one of the edges. The thermometer according to claim 7, wherein: 9. The vibrator has two elements, each element being one of the teeth of a tuning fork, each tooth having a long side provided on the main surface and a short side provided on the edge. 8. Thermometer according to claim 7, having a parallelepiped shape with a substantially rectangular cross section. 10 Each major surface and each edge of the two teeth is provided with an electrode, the electrodes on the major surfaces of the same tooth being held at a first voltage, and the electrodes on the edges of the same tooth being held at a second voltage. 10. A thermometer as claimed in claim 9, wherein: 11. Apparatus for said electronic circuit to compare the frequencies of signals generated by said oscillator and said reference oscillator with an adjustable reference frequency oscillator and to generate a temperature expression from the difference between the frequencies of these signals. and a device for displaying the temperature representation. 12 said comparator device for counting M pulses generated by said transducer and generating a first signal when these M pulses are counted; and a device for generating a first signal generated by said reference frequency oscillator; a device for simultaneously counting M pulses and generating a second signal when these M pulses are counted, a device for providing a measurement signal of adjustable frequency, and between said first and second signals; and a device for counting pulses of the measurement signal.