JP2012032194A - Probe for crystal temperature measurement, and crystal temperature measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress generation of a measurement error due to a secular change in temperature measurement based upon an oscillation frequency of a crystal vibrator, to use a variety of cables other than a coaxial cable as a cable for connecting a probe for crystal temperature measurement and a measurement device body to each other, and to relax necessary precision of a reference clock signal that a frequency counter uses to measure a sensor frequency signal without lowering measurement precision.SOLUTION: A crystal vibrator 31 (Y cut) has temperature characteristics such that an oscillation frequency varies largely with temperature, and a crystal vibrator 32 (AT cut) has temperature characteristics such that an oscillation frequency is stable with respect to temperature. The crystal vibrators 31, 32 are cut out of materials of the same kind, and formed to have substantially the same shape, material, and size. A difference frequency generation circuit 35 generates a signal of a frequency component (35 kHz) of the difference in oscillation frequency between crystal oscillation circuits 33, 34, and this signal is output to the measurement device body to calculate measured temperature.

Description

  The present invention relates to a crystal temperature sensor, a crystal temperature measuring probe, and a crystal temperature measuring device for measuring temperature based on an oscillation frequency of a crystal resonator.

The crystal resonator has a specific oscillation frequency (vibration frequency) determined by the shape and the like. This oscillation frequency is known to be expressed by the following equation.

Here, each variable is as follows.
f: Intrinsic oscillation frequency n: Overtone order t: Quartz crystal thickness ρ: Density Cij: Elastic constant

  In general, a crystal resonator is used as a frequency source for a radio communication device, various measuring instruments, and the like as an oscillating element that generates a most stable frequency with low frequency temperature characteristics. However, depending on the cutting angle (cutting orientation), which is the angle cut from the crystal, there are those having the characteristic that the oscillation frequency changes greatly depending on the temperature. Typical examples include Y-cut and LC-cut.

  Temperature measurement that measures the temperature by measuring the oscillation frequency of the crystal resonator using a crystal resonator with a cutting orientation that makes the frequency change with temperature linear. An apparatus is used (for example, refer to Patent Documents 1 and 2). Since the frequency can be measured with a high resolution, a temperature measurement device using such a crystal resonator can realize a temperature measurement with a high measurement accuracy such as a resolution of 1/10000 ° C. .

  However, the frequency-temperature characteristics of the quartz resonator vary with time. In a temperature measuring device using a crystal resonator, the temperature measurement is performed based on a relationship between a preset oscillation frequency and temperature. It will shift.

  In order to prevent measurement errors due to changes in frequency temperature characteristics due to such secular changes, it is usual to perform periodic maintenance and calibrate the equipment to recalculate the coefficient for converting frequency to temperature. Yes.

  In recent years, changes in the global environment such as global warming have become a problem. Therefore, in order to observe crustal deformation, changes in seawater temperature, etc. and observe changes in the global environment over a long period of time, using the crystal temperature measuring device as described above, groundwater, deep wells, crustal heat, deep seawater Measuring temperature etc. is performed. Moreover, it is used also for the use which measures the seawater temperature unattended by installing the crystal temperature measuring apparatus as mentioned above for the weather and sea state observation on the ocean.

  However, when the crystal temperature measuring device is installed in such a place, it may be impossible to remove the device once installed because it takes a lot of work. Therefore, the quartz temperature measuring device cannot be calibrated after installation, and there arises a problem that it is impossible to prevent the measurement accuracy from deteriorating due to secular change.

  In addition, when you want to measure seawater temperature and crustal heat in the deep sea using a crystal temperature measuring device, a crystal temperature measuring probe is installed on the deep sea floor or in an observation mine, and the measuring device main body (frequency counter) ) Must be connected with a cable. Depending on the measurement environment, the length of this cable may be several hundred meters. In such a case, in order to transmit a high frequency signal of about 10.6 MHz generated by the crystal temperature measurement probe without loss for several hundred meters, use a general measurement cable other than a coaxial cable with a large attenuation. In the prior art, only a coaxial cable was used.

  In recent years, however, the number of items for observing changes in the global environment has increased, and the system has been unified to measure various measurement items other than temperature. Therefore, in the system for measuring such measurement items, the cables to be used have been similarly unified. And about these cables, the cable for a measurement occupies many. Therefore, the use of crystal temperature measuring devices that require a coaxial cable only for temperature measurement has been limited, and there is a flexible and diverse technology that can use cables other than coaxial cables. It was sought after.

Furthermore, in the conventional crystal temperature measuring device, since the sensor signal frequency from the temperature measuring probe is high, higher resolution and accuracy are required for the reference clock signal used by the frequency counter for measuring the sensor signal frequency. In some cases, a high precision was required, and it was necessary to use a ± 1 × 10 ⁻⁹ (10 MHz) OCXO (quartz crystal oscillator with constant temperature bath) or a rubidium frequency standard, which deteriorated the economy.

JP 2003-23339 A JP 2003-149058 A

  As described above, when the frequency temperature characteristics of the crystal unit fluctuate due to secular change, there is a problem that an error occurs in the measured temperature when calibration is difficult. It was.

  Further, the above-described conventional technique has a problem that a coaxial cable needs to be used for connection between the crystal temperature measurement probe and the measurement apparatus main body.

  Further, the above-described prior art has a problem that a high-precision reference clock signal used by a frequency counter for measuring a sensor frequency signal from the crystal temperature measurement probe is required.

  An object of the present invention is to provide a crystal temperature sensor capable of suppressing the occurrence of measurement errors due to aging even when calibration cannot be performed when performing temperature measurement based on the oscillation frequency of a crystal resonator, To provide a crystal temperature measuring probe and a crystal temperature measuring device.

  Another object of the present invention is to provide a crystal temperature sensor and a crystal that can use various cables other than a coaxial cable as a cable for connecting the crystal temperature measuring probe and the measuring device main body. It is to provide a temperature measurement probe and a crystal temperature measurement device.

  Another object of the present invention is to reduce the accuracy required for the reference clock signal used by the frequency counter for measuring the sensor frequency signal from the crystal temperature measurement probe without degrading the measurement accuracy. A crystal temperature sensor, a crystal temperature measuring probe, and a crystal temperature measuring device are provided.

[Crystal temperature sensor]
The crystal temperature sensor of the present invention includes a first crystal unit having a temperature characteristic in which an oscillation frequency is stable with respect to temperature,
Compared with the first crystal unit, a second crystal unit having temperature characteristics such that the oscillation frequency changes greatly with respect to temperature is provided.

  In the quartz temperature sensor according to the present invention, the first crystal unit and the second crystal unit may be cut from the same type of raw material and have substantially the same shape and material. Also good.

  Furthermore, in the crystal temperature sensor of the present invention, the first crystal unit is an AT-cut crystal unit, and the second crystal unit is a Y-cut or LC-cut crystal unit. You may make it a child.

[Crystal temperature measurement probe]
A crystal temperature measuring probe according to the present invention includes a first crystal resonator having a temperature characteristic in which an oscillation frequency is stable with respect to temperature,
Compared with the first crystal unit, a second crystal unit having a temperature characteristic such that the oscillation frequency changes greatly with respect to temperature, and the first crystal unit using the first crystal unit as an oscillation element A first oscillation circuit for generating a signal having an oscillation frequency;
A second oscillation circuit that generates a signal of a specific oscillation frequency using the second crystal resonator as an oscillation element;
A differential frequency generation circuit that generates a signal having a frequency component that is a difference between the oscillation frequency of the first oscillation circuit and the oscillation frequency of the second oscillation circuit;

  The crystal temperature measuring probe according to the present invention may further include an output circuit that outputs a signal generated by the difference frequency generation circuit as a two-wire signal.

  The crystal temperature measuring probe according to the present invention may further include an output circuit that outputs a signal generated by the difference frequency generation circuit as a three-wire signal.

Further, another crystal temperature measuring probe of the present invention includes a first crystal resonator having a temperature characteristic in which an oscillation frequency is stable with respect to temperature,
A plurality of second crystal resonators having a temperature characteristic such that the oscillation frequency changes greatly with respect to temperature compared to the first crystal resonator;
A first oscillation circuit that generates a signal of a specific oscillation frequency using the first crystal resonator as an oscillation element;
A plurality of second oscillation circuits that generate signals of a specific oscillation frequency using the plurality of second crystal resonators as oscillation elements;
A differential frequency generation circuit that generates a signal having a frequency component that is a difference between an oscillation frequency of the first oscillation circuit and an oscillation frequency of the plurality of second oscillation circuits.

  The crystal temperature measuring probe according to the present invention may further include an output circuit that outputs a plurality of signals generated by the differential frequency generation circuit as a two-wire signal.

  The crystal temperature measuring probe of the present invention may further include an output circuit that outputs a plurality of signals generated by the difference frequency generation circuit as a three-wire signal.

[Crystal temperature measuring device]
The crystal temperature measuring device of the present invention includes a first crystal resonator having a temperature characteristic in which the oscillation frequency is stable with respect to temperature, and the oscillation frequency is larger than the temperature of the first crystal resonator. A second crystal resonator having temperature characteristics that change, a first oscillation circuit that generates a signal of a specific oscillation frequency using the first crystal resonator as an oscillation element, and the second crystal A second oscillation circuit that generates a signal having a specific oscillation frequency using an oscillator as an oscillation element; and a frequency component of a difference between an oscillation frequency of the first oscillation circuit and an oscillation frequency of the second oscillation circuit A quartz temperature measuring probe comprising a differential frequency generating circuit for generating a signal and an output circuit for outputting a signal generated by the differential frequency generating circuit;
A frequency counter for measuring the frequency of the signal received from the crystal temperature measuring probe, a conversion means for converting the frequency measured by the frequency counter into a measurement temperature, and a display for displaying the measurement temperature obtained by the conversion means A measuring device main body provided with a measuring instrument.

  In the present invention, in the crystal temperature measurement probe, a signal having a frequency difference between the signals generated based on the first and second crystal resonators having different temperature characteristics is generated. A measured temperature is calculated based on the frequency. In general, a crystal resonator changes in characteristics in the same direction as time passes. Therefore, by taking the difference between the oscillation frequencies of the first and second crystal resonators, the characteristic change is canceled out. Therefore, according to the present invention, when temperature measurement is performed based on the oscillation frequency of the crystal resonator, it is possible to suppress generation of measurement errors due to aging.

  In particular, the first and second crystal resonators are cut out from the same type of raw material, and the crystal resonators having substantially the same shape and material can be made closer to changes in characteristics over time. It is possible to more effectively suppress the occurrence of measurement errors due to changes.

  In the present invention, the frequency of the signal transmitted from the crystal temperature measurement probe to the measuring device main body is significantly lower than the oscillation frequency of the first and second crystal units. The cable for connecting between the temperature measurement probe and the measurement apparatus main body need not be a cable having a low loss in a high frequency band such as a coaxial cable. Therefore, according to the present invention, it is possible to use a general cable other than the coaxial cable as a cable for connecting the crystal temperature measurement probe and the measurement apparatus main body.

  Furthermore, in the present invention, since the frequency of the sensor signal from the crystal temperature measuring probe measured by the frequency counter of the measuring device main body is a low frequency, the frequency counter is used without reducing the measurement accuracy of the temperature measurement. It becomes possible to relax the accuracy required for the reference clock signal.

The crystal temperature measuring device of the present invention further includes an output circuit in which the crystal temperature measuring probe outputs a signal generated by the differential frequency generation circuit as a two-wire signal,
The frequency counter may measure the frequency of a two-wire signal received from the crystal temperature measuring probe.

The crystal temperature measuring device of the present invention further includes an output circuit in which the crystal temperature measuring probe outputs a signal generated by the difference frequency generation circuit as a three-wire signal,
The frequency counter may measure the frequency of a three-wire signal received from the crystal temperature measuring probe.

In addition, according to another crystal temperature measuring apparatus of the present invention, the oscillation frequency of the first crystal resonator having a temperature characteristic that the oscillation frequency is stable with respect to temperature is higher than that of the first crystal resonator. A plurality of second crystal resonators having temperature characteristics that vary greatly with respect to the first oscillation circuit, and a first oscillation circuit that generates a signal of a specific oscillation frequency using the first crystal resonator as an oscillation element; , A plurality of second oscillation circuits that generate signals of a specific oscillation frequency using the plurality of second crystal oscillators as oscillation elements, the oscillation frequency of the first oscillation circuit, and the plurality of second oscillation circuits A crystal temperature measuring probe comprising: a differential frequency generating circuit that generates a signal having a frequency component that is different from the oscillation frequency of the oscillation circuit; and an output circuit that outputs a plurality of signals generated by the differential frequency generating circuit; ,
Obtained by the frequency counter for measuring the frequencies of the plurality of signals received from the quartz temperature measuring probe, the conversion means for converting the frequencies measured by the frequency counter to measured temperatures, respectively, and the conversion means A measuring device main body having a display for displaying a plurality of measured temperatures.

  According to the present invention, even when performing multipoint measurement such as measuring temperatures at a plurality of measurement points, the effects described above can be obtained.

The crystal temperature measuring device of the present invention further includes an output circuit in which the crystal temperature measuring probe outputs a plurality of signals generated by the difference frequency generating circuit as a two-wire signal,
The frequency counter may measure the frequencies of a plurality of two-wire signals received from the crystal temperature measurement probe.

The crystal temperature measuring device of the present invention further includes an output circuit in which the crystal temperature measuring probe outputs a plurality of signals generated by the difference frequency generating circuit as a three-wire signal,
The frequency counter may measure the frequencies of a plurality of three-wire signals received from the crystal temperature measuring probe.

  According to the present invention, when temperature measurement is performed based on the oscillation frequency of the crystal resonator, it is possible to obtain an effect that it is possible to suppress the occurrence of measurement errors due to secular change.

  In addition, according to the present invention, it is possible to obtain an effect that a general cable other than the coaxial cable can be used as a cable for connecting the crystal temperature measurement probe and the measurement apparatus main body. it can.

  Furthermore, according to the present invention, it is possible to relax the accuracy required for the reference clock signal used by the frequency counter for measuring the sensor frequency signal from the crystal temperature measurement probe without reducing the measurement accuracy. The effect that can be obtained.

It is a figure which shows the system configuration | structure of the crystal temperature measuring device of the 1st Embodiment of this invention. It is a figure which shows the external appearance of the crystal temperature measuring device of the 1st Embodiment of this invention. It is a block diagram which shows the structure of the probe 11 for crystal temperature measurement in FIG. It is a figure which shows an example of the frequency temperature characteristic of the crystal oscillator of AT cut, and the crystal oscillator of Y cut. 3 is a diagram illustrating an example of a structure of a quartz temperature sensor 41. FIG. It is a figure which shows the structure of the probe 11a for crystal temperature measurement used when connecting between the measuring device main-body parts 10 with a coaxial cable. It is a figure for demonstrating an example of how the oscillation frequency of the crystal oscillator 31 (Y cut) and the crystal oscillator 32 (AT cut) changes based on temperature. It is a flowchart which shows the operation | movement for calculating measured temperature in the crystal temperature measuring device of the 1st Embodiment of this invention. It is a figure for demonstrating the actual mode that an oscillation frequency changes with time passage of a Y-cut crystal resonator. It is a figure for demonstrating a mode that the difference frequency (DELTA) f changes when the oscillation frequency of the crystal oscillators 31 and 32 is fluctuate | varied by secular change. It is a figure which shows an example of a secular change of the sensor signal frequency from the probe 11 for quartz temperature measurement measured in the quartz temperature measuring device of one Embodiment of this invention. It is a figure which shows the structure of the probe 111 for quartz temperature measurement in the quartz temperature measuring device of the 2nd Embodiment of this invention. It is a figure which shows the structure of the measuring device main-body part 110 in the crystal temperature measuring device of the 2nd Embodiment of this invention. It is a figure which shows an example in the case of displaying eight measurement temperature measured with the crystal temperature measuring device of the 2nd Embodiment of this invention.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

[First embodiment]
FIG. 1 is a system diagram showing a configuration of a crystal temperature measuring apparatus according to a first embodiment of the present invention.

  As shown in FIG. 1, the crystal temperature measuring apparatus according to the present embodiment is measured based on a crystal temperature measuring probe 11 installed at a place where temperature is to be measured and a signal from the crystal temperature measuring probe 11. It comprises a measuring device main body 10 for calculating and displaying temperature, and a three-wire cable 12 for connecting the crystal temperature measuring probe 11 and the measuring device main body 10.

  As shown in FIG. 1, the measurement apparatus main body 10 includes sensor signal amplification circuits 13 and 13 a, sensor power supply circuits 14 and 14 a, a frequency count circuit 15, a CPU 16, and a reference clock generation circuit 17. , Display 18, communication interface (IF) circuit 19, storage device 20, three-wire connection terminal 21, and BNC connector 22.

  The three-wire cable 12 connecting the quartz temperature measuring probe 11 is connected to the three-wire connection terminal 21 of the measuring device main body 10. The three-wire connection terminal 21 is configured to connect three wires of a signal output, a common wire, and a sensor power supply.

  The BNC connector 22 is used when the crystal temperature measuring probe 11 and the measuring apparatus main body 10 are connected by a coaxial cable. The crystal oscillator temperature measurement device of the present embodiment is configured such that either a three-wire cable or a coaxial cable can be connected between the crystal temperature measurement probe 11 and the measurement device main body 10.

  The sensor signal amplifier circuits 13 and 13 a amplify the signal output from the three-wire connection terminal 21 or the signal output from the BNC connector 22 and output the amplified signal output to the frequency count circuit 15. The frequency Δf of the signal amplified in the sensor signal amplifier circuits 13 and 13a is 35 kHz / 25 ° C. This signal output will be described later. Here, the notation “/ 25 ° C.” means the frequency when the measurement temperature is 25 ° C.

  The sensor power supply circuits 14 and 14 a are circuits for supplying sensor power used in the crystal temperature measurement probe 11. In the present embodiment, as an example, the sensor power supply circuit 14 supplies 5 V power as a sensor power supply to the crystal temperature measurement probe 11 via the three-wire connection terminal 21. The sensor power supply circuit 14a supplies sensor power to the signal line of the BNC connector 22, and this sensor power is superimposed on the signal line of the coaxial cable and transmitted to the crystal temperature measuring probe.

  The frequency count circuit 15 operates as a frequency counter that measures the frequency of the signal received from the crystal temperature measurement probe 11 and amplified by the sensor signal amplification circuits 13 and 13a.

  The CPU 16 functions as a conversion unit that converts the frequency measured by the frequency count circuit 15 into a measured temperature. A specific method for converting the measured frequency into the measured temperature will be described later. Then, the CPU 16 displays the obtained measured temperature on the display 18 or outputs it to the outside via the communication IF circuit 19. Further, the CPU 16 may store the obtained measured temperature in the storage device 20.

  The reference clock generation circuit 17 generates, for example, a 10 MHz clock signal and supplies it to the frequency count circuit 15 and the CPU 16 as an operation clock.

  FIG. 2 shows the appearance of the crystal temperature measuring apparatus of the present embodiment configured as described above. In the example shown in FIG. 2, a case where a personal computer (hereinafter referred to as a personal computer) 40 is connected to the outside of the measuring apparatus main body 10 is shown. As shown in FIG. 2, in the crystal temperature measuring device according to the present embodiment, the measuring device main body 10 is connected to the crystal temperature measuring probe 11 via a three-wire cable 12, and a personal computer 40, for example, Are connected by an RS232C cable or the like. In the measuring device main body 10, the measured temperature is displayed on the display 18.

Next, the configuration of the crystal temperature measuring probe 11 shown in FIG. 1 will be described with reference to FIG.
As shown in FIG. 3, the crystal temperature measurement probe 11 includes a crystal temperature sensor 41, crystal oscillation circuits 33 and 34, a difference frequency generation circuit 35, and a three-wire output circuit 36. The crystal temperature sensor 41 includes a crystal resonator 31 and a crystal resonator 32.

  The crystal unit 32 is a crystal unit having a temperature characteristic such that the oscillation frequency does not depend on temperature, that is, a temperature characteristic in which the oscillation frequency is stable with respect to temperature. It is.

  The crystal unit 31 is a crystal unit having a temperature characteristic that the oscillation frequency depends on temperature, that is, a temperature characteristic that the oscillation frequency changes greatly with respect to the temperature as compared with the crystal unit 32. In the present embodiment, description will be made using a crystal resonator having a cutting orientation of Y cut. In addition, a crystal resonator having a temperature characteristic whose oscillation frequency depends on temperature can be used in the same manner. As another specific example of this, a crystal resonator whose cutting direction is LC cut can be given. Can do.

  The crystal resonator has a frequency-temperature characteristic that changes depending on a cutting orientation (cutting angle) that is an angle cut from the crystal. As such cutting directions, various cut names such as AT cut, BT cut, CT cut, SC cut, LC cut, and Y cut are given. The crystal resonator has various frequency temperature characteristics according to the cutting direction.

  For example, an example of frequency temperature characteristics of an AT-cut quartz crystal resonator that is widely used as having high frequency stability with respect to a temperature change and a Y-cut quartz crystal resonator whose frequency changes greatly with respect to the temperature change. 4 shows. In FIG. 4, the oscillation frequency of the crystal resonator is f, and the frequency variation with respect to the temperature change is Δf.

  As can be seen from FIG. 4, the oscillation frequency of the Y-cut crystal resonator changes almost linearly with respect to the temperature change, whereas the oscillation frequency of the AT-cut crystal resonator is It can be seen that within a certain narrow range, there is almost no change with respect to temperature change and is constant.

  Further, the crystal resonators 31 and 32 are cut out from the same type (grade) of raw material, and are configured to have substantially the same shape, material, and size. The crystal units 31 and 32 are created by the same manufacturing method and process as possible. This is because the crystal resonators 31 and 32 preferably have the same characteristics with respect to the aging characteristics other than the frequency temperature characteristics. The reason for this will be described in detail later.

  Then, the crystal oscillation circuit 33 generates a signal of 10.595 MHz / 25 ° C. (f (Y)) using the crystal resonator 31 as an oscillation element. The crystal oscillation circuit 34 generates a signal of 10.56 MHz / 25 ° C. (f (AT)) using the crystal resonator 32 as an oscillation element.

  The difference frequency generation circuit 35 is a signal having a frequency component of 35 kHz / 25 ° C. (Δf) as a difference between the oscillation frequency of 10.595 MHz / 25 ° C. of the crystal oscillation circuit 33 and the oscillation frequency of 10.56 MHz / 25 ° C. of the crystal oscillation circuit. Is generated.

  The three-wire output circuit 36 outputs a 35 kHz signal generated by the difference frequency generation circuit 35 to the measuring device main body 10 as a three-wire signal and is supplied from the measuring device main body 10. 5 V sensor power supply is supplied to the crystal oscillation circuits 33 and 34, the difference frequency generation circuit 35, etc.

  The crystal temperature sensor 41 having the crystal resonator 31 and the crystal resonator 32 is provided at the tip of the crystal temperature measuring probe 11. An example of the structure of the crystal temperature sensor 41 is shown in FIG. Referring to FIG. 5, it can be seen that the crystal resonators 31 and 32 are held so as to have the same positional relationship with respect to the place where the temperature is to be measured.

  Next, FIG. 6 shows the configuration of the crystal temperature measuring probe 11a used when the measuring apparatus main body 10 is connected by a coaxial cable. This crystal temperature measurement probe 11a differs from the crystal temperature measurement probe 11 for the 3-wire cable shown in FIG. 3 only in that the 3-wire output circuit 36 is replaced with a 2-wire output circuit 36a. ing.

  The two-wire output circuit 36a outputs the 35 kHz signal generated by the difference frequency generation circuit 35 to the measuring device main body 10 via a coaxial cable, and from the measuring device main body 10 to the signal line of the coaxial cable. The 5V sensor power supplied in a superimposed manner is supplied to the crystal oscillation circuits 33 and 34, the differential frequency generation circuit 35, and the like.

  When the crystal temperature measuring probe 11a shown in FIG. 6 is used, the crystal temperature measuring probe 11a and the measuring apparatus main body 10 are connected by a coaxial cable, and this coaxial cable is connected to the measuring apparatus main body 10 side. Connected to the BNC connector 22.

  In the crystal temperature measuring device according to the present embodiment, a signal transmitted between the crystal temperature measuring probe and the measuring device main body 10 has a low frequency of about 35 kHz / 25 ° C., and thus a coaxial cable is not used. However, it is possible to use a coaxial cable to prevent external noise from entering the signal output and achieve more accurate temperature measurement. it can.

Next, the operation at the time of performing temperature measurement by the crystal temperature measuring device of the present embodiment will be described in detail.
First, FIG. 7 shows an example of how the oscillation frequencies of the crystal resonator 31 (Y cut) and the crystal resonator 32 (AT cut) installed in the crystal temperature sensor 41 change based on temperature.

  Referring to FIG. 7, the oscillation frequency f (Y) of the Y-cut crystal resonator 31 is 10,570,031 Hz as the temperature changes from 0 ° C., 20 ° C.,. It can be seen that there are significant changes such as 10,588,924 Hz,..., 10,649,914 Hz. On the other hand, the oscillation frequency f (AT) of the AT-cut crystal resonator 32 is 10,558, despite the fact that the temperature changes to 0 ° C., 20 ° C.,. It can be seen that there is little change such as 258 Hz, 10,558,265 Hz,..., 10,558,387 Hz.

  Therefore, the difference frequency Δf (f (Y) −f (AT)) between the oscillation frequency f (Y) of the crystal unit 31 and the oscillation frequency f (AT) of the crystal unit 32 is substantially the oscillation of the crystal unit 31. It can be seen that the frequency is equal to the change.

  Next, a specific method for calculating the measurement temperature based on the frequency Δf transmitted from the crystal temperature measurement probe 11 in the measurement apparatus main body 10 will be described.

  However, first, a calculation method in the case of calculating the measurement temperature based on the measured frequency in a conventional crystal temperature measurement apparatus that performs temperature measurement using only a Y-cut crystal resonator alone will be described. When performing this calculation, the calculation formula shown in the following formula (1) is used.

f _T −f ₀ = f ₀ (AT + BT ² + CT ³ ) (1)

Here, each variable is as follows.
T: Measurement temperature f _T : Oscillation frequency with respect to measurement temperature T f ₀ : Oscillation frequency of reference temperature A: Sensor coefficient (linear function)
B: Sensor coefficient (quadratic function)
C: Sensor coefficient (cubic function)

As a precondition for temperature measurement, crystal temperature sensors have different temperature characteristics, so check the temperature measurement range, the number of calibration points and the temperature in advance, and calibrate with a crystal temperature measuring device (use a reference thermometer in the temperature chamber to The frequency with respect to the temperature of the temperature probe is checked), and the oscillation frequency f ₀ of the reference temperature and sensor coefficients A, B, and C are obtained.

In the actual temperature measurement, when f _T is given, the measured temperature T can be calculated using f ₀ , A, B, and C determined in advance and the above equation (1). it can.

  Next, a calculation method for calculating the measurement temperature from the obtained frequency Δf in the crystal temperature measurement device of the present embodiment will be described. Since the CPU 16 in the measurement device main body 10 of the crystal temperature measurement device of the present embodiment shares the same calculation method as the case where the temperature measurement is performed with a Y-cut crystal resonator alone, it is actually obtained by the frequency count circuit 15. The measured temperature is calculated by adding 10.56 MHz to the obtained frequency Δf and using the equation (1) described above based on the obtained frequency.

  Therefore, in the following description, the case where the measured temperature is calculated by adding 10.56 MHz to the frequency Δf obtained by the frequency counting circuit 15 will be described, but the present invention is limited to such a case. is not. The present invention is also applicable to the case where the measured temperature is directly calculated using the obtained frequency Δf.

The operation for calculating the measured temperature in the crystal temperature measuring apparatus of this embodiment is shown in the flowchart of FIG.
First, in the measurement apparatus main body 10, the frequency Δf of the signal transmitted from the crystal temperature measurement probe 11 is measured by the frequency count circuit 15 (step S101).

Then, the CPU 16 adds 10.56 MHz to the measured frequency (step S102), and calculates the measured temperature T using the obtained frequency f _T and the above-described equation (1) (step S103). ).

  Then, the CPU 16 displays the obtained measured temperature on the display 18 to update the temperature display, to output the measured temperature to a personal computer 40 or the like connected to the outside, or to store the measured temperature in the storage device 20. Etc. are executed (step S104). If the measurement has not been completed, the processes in steps S101 to S104 are repeated (step S105).

  Next, advantages of the quartz crystal temperature measuring device of the present embodiment over the conventional quartz crystal temperature measuring device that measures temperature with only one quartz crystal resonator will be described below.

  First, an actual state in which the oscillation frequency of the Y-cut crystal resonator changes with time will be described with reference to FIG.

  The measurement data shown in FIG. 9 shows the result of measuring the change in the oscillation frequency of the same crystal resonator by an actual measurement engine. Referring to this result, the oscillation frequency has changed from 10,570,079 Hz to 10,570,032 Hz with the lapse of about 7 years from January 19, 2001 to March 17, 2008. I understand that. That is, it can be seen that the frequency is -47 Hz and the ratio is -4.45 ppm (-47 Hz / 10,570,079 Hz).

  That is, it can be said that the secular change has occurred by −0.64 ppm (−4.45 ppm / 7 years) in about one year. Referring to FIG. 9, since the oscillation frequency is already 10,570,031 Hz as of December 22, 2005, approximately −1 ppm / year when focusing on the first four years. It can be said that this is an age-related change.

  In addition, as described above, the Y-cut crystal resonator 31 and the AT-cut crystal resonator 32 in the crystal temperature measuring device of the present embodiment are the same in size, shape, raw material, manufacturing method and process other than the cutting orientation. It is comprised so that.

  Therefore, it is considered that the secular change in the AT-cut quartz resonator has the same property as that of the Y-cut quartz resonator. In other words, the oscillation frequency of the Y-cut quartz crystal unit decreases with time, but the oscillation frequency of an AT-cut crystal unit with similar characteristics other than the cutting direction increases with time. This is usually unthinkable.

  For the reasons described above, it is considered that the oscillation frequency of the Y-cut quartz crystal resonator and the oscillation frequency of the AT-cut quartz crystal resonator change in the same direction due to secular change.

  Next, how the difference frequency Δf changes when the oscillation frequency of the crystal resonators 31 and 32 fluctuates due to aging in the crystal temperature measuring device of the present embodiment will be described with reference to FIG. Note that FIG. 10 shows virtual numbers for the sake of simplicity, and does not measure actual frequency changes. Therefore, in the example shown in FIG. 10, description will be made assuming that the first oscillation frequency of the crystal unit 31 is 10,595,000 Hz and the first oscillation frequency of the crystal unit 32 is 10,560,000 Hz.

  First, FIG. 10A shows how the difference frequency Δf changes when the oscillation frequencies of the crystal resonators 31 and 32 both change by −1 ppm due to secular change.

  In this case, the oscillation frequency of the crystal unit 31 changes to 10,594,989 Hz, and the oscillation frequency of the crystal unit 32 changes to 10,559,989 Hz. However, the frequency Δf of these differences is 10,594,989 Hz−10,559,989 Hz = 35,000 Hz. That is, even if both the quartz vibrators 31 and 32 change by the same amount, the difference is canceled out by taking the difference frequency, and it is understood that the change with time does not affect the measured temperature.

  However, since both the crystal resonators 31 and 32 do not change exactly the same, the oscillation frequency of the crystal resonator 31 varies by −1 ppm due to secular change, and the oscillation frequency of the crystal resonator 32 varies by −0. An example in the case of 5 ppm fluctuation is shown in FIG.

  In this case, the oscillation frequency of the crystal unit 31 changes to 10,594,989 Hz, and the oscillation frequency of the crystal unit 32 changes to 10,559,995 Hz. However, the frequency Δf of these differences is 10,594,989 Hz-10,559,995 Hz = 34,994 Hz. In other words, even if the crystal resonators 31 and 32 change over time by different amounts, if the crystal resonators 31 and 32 change in the same direction, a part of the change cancels out by taking the difference frequency, and the change over time with respect to the measured temperature. It can be seen that the impact is reduced. Specifically, although the oscillation frequency of the crystal unit 31 has changed by −1 ppm, the frequency of the difference has changed only by −0.5 ppm (−1 ppm−0.5 ppm). It can be seen that the measurement error due to the secular change is halved compared to the case where the temperature is measured with the crystal unit alone.

  An example of the secular change of the sensor signal frequency from the crystal temperature measuring probe 11 measured in the crystal temperature measuring device of this embodiment is shown in FIG.

  In the example shown in FIG. 11, the result of measuring the sensor signal frequency before and after the passage of about one year, January 23, 2009 and February 19, 2010, using the same crystal temperature measuring probe. It is shown. In addition, this measurement result is a measurement result performed in Toa Keiki Seisakusho Co., Ltd., and was measured using a temperature at a triple point of water of 0.01 ° C. as a standard temperature. In FIG. 11, the numbers in parentheses are values after adding 10,560,000 Hz to the sensor signal frequency.

  Referring to the measurement result of FIG. 11, it can be seen that the sensor signal frequency changes only from 2 Hz from 17,832 Hz to 17,830 Hz with the passage of time for one year. That is, when compared with a conventional quartz temperature measuring device that measures temperature with a Y-cut quartz crystal unit alone, the secular change in one year can be suppressed to 0.189 ppm (2/10, 577, 832). I understand that.

  As described above, according to the crystal temperature measuring apparatus of the present embodiment, the measurement temperature is calculated based on the difference frequency between the two crystal resonators 31 and 32 configured to have the same aging characteristics. Therefore, when temperature measurement is performed based on the oscillation frequency of the crystal resonator, even when the oscillation frequency of the crystal resonator changes with time, it is possible to suppress the occurrence of measurement errors.

  Further, in the crystal temperature measuring device of the present embodiment, the difference frequency between the crystal resonators 31 and 32 is obtained in the crystal temperature measuring probe 11, and a signal of this frequency is transferred to the measuring device main body 10 to calculate the measured temperature. It is carried out. Therefore, according to the crystal temperature measuring device of the present embodiment, the frequency of the signal transmitted between the crystal temperature measuring probe 11 and the measuring device main body 10 becomes a low frequency signal of about 35 kHz, and the crystal temperature measuring device is used. It is not necessary to use a coaxial cable as a cable for connecting between the probe 11 and the measuring apparatus main body 10.

  Furthermore, in the crystal temperature measuring device of the present embodiment, it is not necessary to count a signal with a high frequency such as 10.56 MHz / 25 ° C. in the measuring device main body 10, and a signal with a low frequency of 35 kHz / 25 ° C. is counted. Just get better. Therefore, it is not necessary to use a high-resolution circuit capable of measuring a high frequency as the frequency count circuit 15, and the cost of the apparatus can be reduced by simplifying the circuit configuration.

That is, in the crystal temperature measuring device of this embodiment, the sensor signal frequency is about two orders of magnitude lower than the sensor signal frequency in the conventional crystal temperature measuring device, so (10,595.000 kHz / 25 ° C. to 35.000 kHz). / 25 ° C.), it is possible to improve the economics of the crystal temperature measuring device. Further, the reference clock signal of the frequency count circuit 15 having a temperature characteristic that is two digits lower can be used. Specifically, as the reference clock generation circuit 17, for example, ± 1 × 10 ⁻⁹ (10 MHz) OCXO (quartz crystal oscillator) or rubidium frequency standard has been used until now, but ± 1 × 10 ^-7 (10 MHz) TCXO (temperature compensated crystal oscillator) can be used. As a result, it is possible to measure temperature with higher accuracy and higher resolution than before in a long time in a special place such as the deep sea.

  In the crystal temperature measuring apparatus of the present embodiment, since temperature measurement with high accuracy is not possible unless the oscillation frequency of the AT-cut crystal resonator 32 is changed, temperature measurement is performed using a single crystal resonator. Compared to the case, the measurable temperature range becomes narrow. However, when measuring seawater temperature, crustal heat, groundwater temperature, etc., the temperature range to be changed is limited, so even if the measurable temperature range is somewhat narrow, it does not pose a major problem.

[Second Embodiment]
Next, a crystal temperature measuring apparatus according to a second embodiment of the present invention will be described.
The crystal temperature measuring device according to the first embodiment described above is a device for measuring the temperature at one location, but the crystal temperature measuring device according to the present embodiment is for measuring the temperatures at a plurality of locations simultaneously. This is a case where the present invention is applied to a crystal temperature measuring apparatus for multipoint measurement.

  FIG. 12 shows the configuration of the crystal temperature measuring probe 111 in the crystal temperature measuring device of this embodiment, and FIG. 13 shows the configuration of the measuring device main body 110. The crystal temperature measuring device of this embodiment is an example of a measuring device having a configuration capable of measuring temperatures at eight locations.

Crystal Temperature measuring probe 111 in the lens temperature measuring device of the present embodiment, as shown in FIG. 12, and eight crystal oscillator 31 _{1-31 8} Y-cut, one of the AT cut crystal oscillator 32 If a crystal oscillator circuit 34, and a eight of the crystal oscillation circuit 33 _to 333 _8, a difference frequency generation circuit 135, and an output circuit 136.

  The crystal oscillation circuit 34 generates a signal of 10.56 MHz / 25 ° C. (f (AT)) using the crystal resonator 32 as an oscillation element.

Crystal oscillator circuit 33 _to 333 _8, respectively, to generate a signal of 10.595MHz / 25 ℃ (f (Y1 ) ~f (Y8)) using a crystal oscillator 31 _{1-31 8} as an oscillation element.

Difference frequency circuit 135, the oscillation frequency 10.595MHz / 25 ℃ crystal oscillation circuit 33 _to 333 ₈ and (f (Y1) ~f (Y8 )), the oscillation frequency 10.56MHz / 25 ℃ crystal oscillation circuit 34 Of the frequency components of 35 kHz / 25 ° C. (Δf1 to Δf8) are respectively generated.

  That is, Δf1 = f (Y1) −f (AT), Δf2 = f (Y2) −f (AT),..., Δf8 = f (Y8) −f (AT).

  Then, these eight differential frequencies (Δf1 to Δf8) are transmitted to the measuring apparatus main body 110 by the output circuit 136.

  The measurement apparatus main body 110 of the present embodiment is the same as the measurement apparatus main body 10 of the first embodiment shown in FIG. 1 except that the changeover switch (SW) circuit 91 is provided. Description is omitted.

  The changeover switch (SW) circuit 91 in the present embodiment sequentially switches the eight differential frequencies (Δf1 to Δf8) transferred from the crystal temperature measuring probe 111 and outputs them to the sensor signal amplifier circuit 13. Therefore, the CPU 16 can sequentially calculate the measured temperatures at the eight locations.

  An example in the case of displaying eight measured temperatures measured in this way is shown in FIG. The display example shown in FIG. 14 is an example when eight measured temperatures are displayed on the display screen of a personal computer connected to the outside of the measuring apparatus main body 110. As described above, according to the crystal temperature measuring apparatus of the present embodiment, it is possible to check the temperatures at eight locations measured at the same time in a list.

[Modification]
In the above embodiment, the case where the crystal temperature measuring probe installed at the measurement target location and the measuring device main body portion are connected by a three-wire cable or a coaxial cable has been described. The present invention is not limited, and the same applies to the case where the quartz temperature measuring probe and the measuring device main body are connected by a wireless line and the differential frequency Δf is transmitted by wireless communication without using a cable. It is something that can be done.

DESCRIPTION OF SYMBOLS 10 Measurement apparatus main-body part 11, 11a Crystal temperature measurement probe 12 3-wire type cable 13, 13a Sensor signal amplification circuit 14, 14a Power supply circuit for sensors 15 Frequency count circuit 16 CPU
17 Reference clock generation circuit 18 Display 19 Communication interface (IF) circuit 20 Storage device 21 3-wire connection terminal 22 BNC connector 31, 31 _{1 to} 3 ₈ Crystal resonator (Y cut)
32 Crystal resonator (AT cut)
33, 33 _{1 to} 33 ₈ Crystal oscillation circuit 34 Crystal oscillation circuit 35 Difference frequency generation circuit 36 3-wire output circuit 36a 2-wire output circuit 40 Personal computer 41 Crystal temperature sensor 91 Changeover switch (SW) circuit 111 For crystal temperature measurement Probe 135 Difference frequency generation circuit 136 Output circuit

Claims (15)

A first crystal unit having a temperature characteristic in which an oscillation frequency is stable with respect to temperature;
A second crystal unit having a temperature characteristic such that the oscillation frequency changes greatly with respect to temperature, as compared to the first crystal unit;
Crystal temperature sensor with   2. The crystal temperature sensor according to claim 1, wherein the first crystal unit and the second crystal unit are cut from the same type of raw material and have substantially the same shape and material. The first crystal unit is a crystal unit whose cut orientation is AT cut,
The quartz crystal temperature sensor according to claim 1 or 2, wherein the second quartz crystal resonator is a quartz crystal resonator whose cutting direction is Y cut or LC cut. A first crystal unit having a temperature characteristic in which an oscillation frequency is stable with respect to temperature;
A second crystal unit having a temperature characteristic such that the oscillation frequency changes greatly with respect to temperature, as compared to the first crystal unit;
A first oscillation circuit that generates a signal of a specific oscillation frequency using the first crystal resonator as an oscillation element;
A second oscillation circuit that generates a signal of a specific oscillation frequency using the second crystal resonator as an oscillation element;
A difference frequency generation circuit for generating a signal having a frequency component of a difference between an oscillation frequency of the first oscillation circuit and an oscillation frequency of the second oscillation circuit;
Crystal temperature measurement probe with   The crystal temperature measuring probe according to claim 4, further comprising an output circuit that outputs a signal generated by the differential frequency generation circuit as a two-wire signal.   The crystal temperature measuring probe according to claim 4, further comprising an output circuit that outputs a signal generated by the differential frequency generation circuit as a three-wire signal. A first crystal unit having a temperature characteristic in which an oscillation frequency is stable with respect to temperature;
A second crystal unit having a temperature characteristic such that the oscillation frequency changes greatly with respect to temperature, as compared to the first crystal unit;
A first oscillation circuit that generates a signal of a specific oscillation frequency using the first crystal resonator as an oscillation element;
A plurality of second oscillation circuits that generate signals of a specific oscillation frequency using the plurality of second crystal resonators as oscillation elements;
A difference frequency generation circuit that generates a signal of a frequency component of a difference between an oscillation frequency of the first oscillation circuit and an oscillation frequency of the plurality of second oscillation circuits;
Crystal temperature measurement probe with   The crystal temperature measurement probe according to claim 7, further comprising an output circuit that outputs a plurality of signals generated by the difference frequency generation circuit as a two-wire signal.   The crystal temperature measurement probe according to claim 7, further comprising an output circuit that outputs a plurality of signals generated by the difference frequency generation circuit as a three-wire signal. A first crystal unit having an oscillation frequency that is stable with respect to temperature, and a first crystal unit having such a temperature characteristic that the oscillation frequency changes greatly with respect to temperature as compared with the first crystal unit. A second oscillation unit, a first oscillation circuit that generates a signal having a specific oscillation frequency using the first crystal unit as an oscillation element, and a second oscillation unit that uses the second crystal unit as an oscillation element. A second oscillation circuit that generates a signal having an oscillation frequency of the first oscillation circuit, a differential frequency generation circuit that generates a signal having a frequency component that is the difference between the oscillation frequency of the first oscillation circuit and the oscillation frequency of the second oscillation circuit, and A crystal temperature measuring probe comprising: an output circuit that outputs a signal generated by the differential frequency generation circuit;
A frequency counter for measuring the frequency of the signal received from the crystal temperature measuring probe, a conversion means for converting the frequency measured by the frequency counter into a measurement temperature, and a display for displaying the measurement temperature obtained by the conversion means A measuring device main body provided with a measuring instrument,
A quartz crystal temperature measuring device. The crystal temperature measurement probe further includes an output circuit that outputs a signal generated by the differential frequency generation circuit as a two-wire signal,
The crystal temperature measuring device according to claim 10, wherein the frequency counter measures a frequency of a two-wire signal received from the crystal temperature measuring probe. The crystal temperature measurement probe further includes an output circuit that outputs a signal generated by the differential frequency generation circuit as a three-wire signal,
The crystal temperature measurement device according to claim 10, wherein the frequency counter measures a frequency of a three-wire signal received from the crystal temperature measurement probe. A first crystal unit having an oscillation frequency that is stable with respect to temperature, and a plurality of temperature characteristics that cause the oscillation frequency to vary greatly with respect to temperature as compared with the first crystal unit. A second oscillation unit, a first oscillation circuit that generates a signal having a specific oscillation frequency using the first quartz crystal unit as an oscillation element, and the plurality of second crystal units as oscillation elements. A plurality of second oscillation circuits that generate a signal having a specific oscillation frequency, and a signal of a frequency component of a difference between the oscillation frequency of the first oscillation circuit and the oscillation frequency of the plurality of second oscillation circuits A crystal frequency measuring probe comprising: a differential frequency generating circuit for generating a plurality of signals; and an output circuit for outputting a plurality of signals generated by the differential frequency generating circuit;
Obtained by the frequency counter for measuring the frequencies of the plurality of signals received from the quartz temperature measuring probe, the conversion means for converting the frequencies measured by the frequency counter to measured temperatures, respectively, and the conversion means A measuring device main body comprising a display for displaying a plurality of measured temperatures;
A quartz crystal temperature measuring device. The crystal temperature measurement probe further includes an output circuit that outputs a plurality of signals generated by the difference frequency generation circuit as a two-wire signal,
14. The crystal temperature measuring device according to claim 13, wherein the frequency counter measures frequencies of a plurality of two-wire signals received from the crystal temperature measuring probe. The crystal temperature measurement probe further includes an output circuit that outputs a plurality of signals generated by the difference frequency generation circuit as a three-wire signal,
14. The crystal temperature measuring device according to claim 13, wherein the frequency counter measures frequencies of a plurality of three-wire signals received from the crystal temperature measuring probe.

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