JP2604181B2 - Non-contact temperature / pressure detection method using ultrasonic waves - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention detects a resonance frequency of a temperature / pressure sensor positioned in an object to be measured by using ultrasonic waves, thereby enabling non-contact temperature / pressure detection. A method for measuring

(Prior art) In recent years, a non-powered sensor and an in vitro measuring instrument embedded in a living body for a long period of time to measure the temperature or pressure of various parts in the living body for the purpose of biological and medical research, particularly for the treatment of cancer, etc. There has been proposed a method of performing measurement without connecting a wire between the two.

Surgically in the desired position as temperature measuring or pressure measuring method described above in vivo a sensor connected to a crystal resonator X and ultrasonic transducer SW to the antenna coil L ₁ as shown in FIG. 2 (a) driving the ultrasonic transducer SW by a current when the vibrator applied to the crystal resonator X the energy irradiated with electromagnetic energy required frequency from outside the embedded living body through the antenna coil L ₁ resonates to There is a method of observing an ultrasonic wave generated during control from outside the living body (see Japanese Patent Application No. 60-021542). In this case, a temperature or pressure measuring device shown in FIG. 2 (b) is generally used. .

That SEN In the figure a sensor shown in the second diagram (a), the quartz crystal resonator X and the antenna coil L ₁ as forming the mochi this closed loop series resonance point 8MHz vicinity ultrasonic connect the transducer SW is obtained by the sensor, a variable frequency oscillator which generates an electromagnetic wave of 8MHz near thereto allowed position of the antenna coil L ₂ in the biological surface closer to the sensor is buried in a required portion of the living body 1
And a transmitting unit including a frequency meter 2 and an ultrasonic microphone 3, a high-frequency amplifier 4, a level meter 6, and the like.

The output of the measurement when the variable frequency oscillator 1 and the electrical signal received by the microphone 3 ultrasound emitted from the ultrasound transducer SW of the sensor irradiates the sensor SEN described above through the antenna coil L ₂ to the high-frequency amplifier 4 After amplification to a required level, the level is monitored by a level meter 6. Further, in this state, if the oscillation frequency of the variable frequency oscillator 1 is changed and a point at which the reading of the level meter becomes maximum is found, the irradiation electromagnetic wave frequency at this time becomes the resonance frequency of the quartz oscillator of the above-described sensor. (See FIG. 2 (c)).

Therefore, if the relationship between the resonance frequency and the temperature or the pressure of the quartz oscillator X incorporated in the above-described sensor is known, the temperature or the pressure in the living body can be accurately measured.

However, in the method of irradiating an electromagnetic wave from the outside and detecting the ultrasonic wave from the sensor as described above, the configuration of the sensor is inevitably complicated, and there is a limit to miniaturization.

In other words, the sensor for this is the minimum antenna coil,
A quartz oscillator and an ultrasonic transducer are indispensable, and the shape must be large.

Further, since electromagnetic waves are used, there is a possibility that a malfunction may occur due to strong electromagnetic waves from other electronic devices, particularly an electromagnetic heating device used for thermal treatment of a gun.

In addition, since the living body has a conductive component, absorption or attenuation of electromagnetic waves is large, and there is a problem that the distance between the sensor coil and the external antenna coil cannot be increased.

There has been proposed a method of measuring the temperature of cooling water or the like of a power reactor or a nuclear fuel reactor using only ultrasonic waves without using electromagnetic waves (Japanese Patent Laid-Open No. 59-100831). Thus, mechanical vibration is applied to the ultrasonic sensor, and an ultrasonic signal generated by the mechanical vibration is extracted. Therefore, the ultrasonic sensor cannot be used in an environment where there is no medium that vibrates the ultrasonic sensor, such as in a living body.

(Object of the Invention) In order to solve these problems, the same applicant has already proposed a sensor useful for measuring temperature / pressure by irradiating a sensor with ultrasonic waves instead of electromagnetic waves (Japanese Patent Application No. 61-21
1888).

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the conventional temperature and pressure measurement. For example, by using a temperature / pressure sensor which has already been filed by the same applicant, it is possible to eliminate the need for using electromagnetic waves. In addition, the size of the sensor can be small and the non-contact temperature /
It is an object to provide a pressure detection method.

(Summary of the Invention) As a means for achieving this object, as a sensor used in the present invention, an ultrasonic transducer whose resonance frequency changes with temperature or pressure and generates ultrasonic waves of the resonance frequency in response to a harmonic wave It is configured to measure the temperature / pressure of a desired object by irradiating an ultrasonic wave to the sensor and detecting an ultrasonic frequency as a response signal using a piezoelectric vibrator or a mechanical vibrator having the function of Things.

(Examples) Hereinafter, the present invention will be described in detail with reference to the illustrated examples, but before that, in order to help understanding of the present invention,
The sensor proposed by the same applicant will be described in detail.

In a mechanical vibrator represented by a conventional quartz oscillator, the resonance sharpness Q value is increased as much as possible. In order to reduce the leakage of acoustic energy from the supporting portion, which is a main cause of the deterioration of the Q value, the vibration displacement is minimized. Whereas it was common to select the part as the support, the same applicant has proposed that the vibrator of the earlier proposal transmit an ultrasonic energy by transmitting a portion of its acoustic energy to the container through the support. We will give and receive.

That is, as shown in FIG. 3 (a), the specific structure thereof is such that the base height (H) and the base bottom (D) of the tuning-fork type quartz vibrator 7 are formed.
Is set to be about 3 or less. By doing so, it becomes possible to transmit a part of the acoustic energy to the container 9 via the holder 8 of the vibrator 7.

FIG. 4B is a diagram of an experimental result showing the relationship between the H / D and the leakage energy. The required excitation electrode is provided on the vibrator 7 of the sensor shown in FIG. It is excited and its acoustic leakage energy is measured with a microphone.

From the above experimental results, the sensor constructed as shown in FIG. 1 (a) can excite the vibrator 7 by applying ultrasonic energy from the outside and extract the signal through the electrode. It is also possible to re-emit the ultrasonic wave via the container 9, and in this case, it is obvious that the vibrator 7 does not need an electrode.

The present invention measures temperature / pressure by using a sensor which is excited by the above-described ultrasonic wave and emits an ultrasonic wave having a frequency at which the ultrasonic wave resonates.

FIG. 1A is a system configuration diagram showing an embodiment of the present invention.

In the figure, M is a microphone for transmitting and receiving an ultrasonic signal, and the input / output signal of the microphone is passed through a changeover switch S and one of the received signals is transmitted to a band-pass filter FIL.
The output of the FIL is compared with the phase comparator PD and the voltage controlled oscillator VCO.
The output of the voltage-controlled oscillator VCO is input to a frequency counter / count and the transmission terminal of the changeover switch S, respectively.

The changeover switch S is controlled by a timing circuit TIME, and alternately switches between a transmission side and a reception side at predetermined time intervals.

A method of detecting the temperature or the resonance frequency of the pressure sensor SENS positioned in a living body or the like and using the device to measure the temperature / pressure will be described.

FIG. 1 (b) is a diagram for explaining signal waveforms at various parts. First, a timing circuit TIME generates a rectangular wave signal having a predetermined period as shown in FIG.
And reception R alternately.

On the other hand, part of the output of the voltage-controlled oscillator VCO in the phase-locked loop PLL block is transmitted to the microphone M via the transmission end T of the changeover switch S, and is converted into an ultrasonic signal by the microphone as shown in FIG. Irradiate the sensor SENS intermittently as shown in ()). The sensor SENS is configured as shown in FIG. 3, and the internal vibrator is excited by the ultrasonic signal, and the reverberation continues for a certain period of time even after the applied ultrasonic wave is stopped as shown in FIG. An ultrasonic signal is emitted as vibration.

Therefore, while the changeover switch S is connected to the receiving side R,
The ultrasonic reverberation component shown in FIG. 4D is converted into an electric signal by the microphone M, and reaches the phase lock loop PLL via the filter FIL.

As is well known, a phase locked loop PLL is a filter FIL
The VCO oscillation frequency is automatically adjusted so that the phase difference between the signal input via the VCO and the feedback output of the voltage controlled oscillator VCO becomes zero. It becomes the same as the ultrasonic signal frequency extracted from.

At this time, the ultrasonic signal frequency becomes the self-resonant frequency of the sensor itself. If the resonance frequency is configured to change depending on the temperature, the ultrasonic signal frequency from the sensor is detected to detect the part to be measured. Temperature can be detected.

In the above-mentioned PLL, there is a period during which the input signal from the filter FIL is interrupted, during which the output of the phase comparator PD does not occur and a feedback loop is not formed. Switch S
In this case, the signal of the transmitting end T may be partially leaked to the filter FIL, or the VCO control voltage may be fixed to the value immediately before the period.

According to such a method, it is possible to measure the temperature in an object to be measured such as in a living body by using only ultrasonic waves without using electromagnetic waves.

Although the present invention has been described by taking the case of using a temperature sensor as an example, the present invention is not limited to this. For example, the present invention is applied to a case using a pressure sensor connected to a pressure sensitive application bellows as the sensor. Obviously, in this case the pressure can be measured.

Further, the sensor is not limited to the above-mentioned example, but may be one in which a quartz oscillator X and an ultrasonic transducer ST are connected in a loop as shown in FIG. 4 (a) in order to obtain a stronger ultrasonic response. May be further connected between them by an impedance matching transformer T as shown in FIG.

(Effect of the Invention) As described above, the present invention irradiates an ultrasonic wave to a temperature / pressure sensor and directly obtains an ultrasonic signal having a resonance frequency of the sensor. Temperature / pressure can be measured by contact, and accurate measurement can be performed even in an environment with a lot of electromagnetic noise.

Furthermore, the distance between the sensor and the external device can be remarkably increased as compared with electromagnetic waves in a liquid or a substance having excellent ultrasonic wave propagation characteristics in a living body or the like.

[Brief description of the drawings]

1 (a) and 1 (b) are a block diagram and a waveform diagram of a measuring apparatus showing an embodiment of the present invention, and FIGS. 2 (a), 2 (b) and 2 (c).
Is a block diagram showing a conventional temperature measuring device, a sensor configuration diagram and a characteristic diagram of the sensor, FIG. 3 is a diagram showing a sensor structure proposed by the same applicant and a diagram showing the relationship between dimensions and ultrasonic leakage energy, and FIG. 4 (a) and (b) are circuit diagrams showing another embodiment of the sensor used in the present invention. SENS: Sensor, M: Microphone, S: Changeover switch, PLL: Phase lock loop, count: Frequency counter, TIME: Timing circuit.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location G01K 11/26 G01K 11/26 G01L 1/10 G01L 1/10 Z 11/04 11/00 C

Claims (2)

(57) [Claims] 1. A piezoelectric vibrator sensor or a mechanical vibrator sensor comprising a vibrator and a container for accommodating the vibrator and having a resonance frequency dependent on temperature / pressure, is located in the object to be measured, and Exciting the sensor by intermittently irradiating an ultrasonic signal to the sensor from the outside, receiving the reverberation vibration of the sensor during the ultrasonic signal is interrupted,
By inputting the received signal to a phase locked loop (PLL) including a phase comparator and a voltage controlled oscillator, the frequency of the reverberation is detected to detect the temperature / pressure of the device under test, A non-contact temperature / pressure detection method using ultrasonic waves, comprising irradiating an output to the sensor as the ultrasonic signal. 2. A period in which the input to the phase lock loop is interrupted, a part of the ultrasonic signal to be irradiated is input to the phase lock loop, or the control voltage of the voltage controlled oscillator is set to a value immediately before the period. 2. A non-contact temperature / pressure detecting method using ultrasonic waves according to claim 1, wherein the non-contact temperature / pressure detecting method is fixed.