JPS635228A - Temperature or pressure sensor - Google Patents

Abstract

PURPOSE:To obtain a sensor having circuit constitution having function defined by the self-resonance frequency and Q-value of a quartz vibrator and capable of enhancing a SN ratio, by constituting a closed circuit by connecting a piezoe lectric vibrator and an ultrasonic transducer in parallel to an antenna coil. CONSTITUTION:An ultrasonic transducer SW is connected to an antenna coil L1 and a quartz vibrator X in parallel to both of them. By this constitution, since electromagnetic wave energy received by the coil L1 is absorbed in the vicinity of the resonant point of the electromagnetic wave energy vibrator X by the vibrator X, the ultrasonic energy sent out from the transducer SW is reduced and becomes min at a series resonant point. That is, the operation mechanism of a measuring system using this sensor is substantially same to a conventional one and the relation between the max. and min of a detection level may be merely made reverse. The impedance matching between parts is easy to take and the resonant point of the vibrator X can be utilized as temp. or pressure information as it is and, since a Q-value is not lowered to a large extent, stable measurement can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a temperature or pressure sensor. In particular, it relates to a chamber for measuring temperature or pressure inside a living body.

(Prior art) In recent years, unpowered cells have been implanted into living bodies for long periods of time to measure the temperature or pressure of various parts of the living body for the purpose of biological and medical research or especially for cancer treatment. A method has been proposed in which measurements can be made without a wired connection to an external measuring device.

As a method of measuring temperature or pressure as described above.

A sensor in which a crystal oscillator and an ultrasonic transducer are connected to an antenna coil is surgically implanted at a desired position within a living body, and electromagnetic energy of a desired frequency is irradiated from outside the living body, and the energy is transmitted through the antenna coil. There is a method of observing the ultrasonic waves generated from outside the living body by controlling the ultrasonic transducer using a current applied to the crystal oscillator and causing the oscillator to empathize with the current (see Japanese Patent Application No. 60-021542). .

The temperature or pressure sensor used at this time and the pickup device for detecting the ultrasonic waves emitted from the sensor from outside the living body are generally those shown in FIG. 2 (al).

That is, in the figure, X is a crystal oscillator with a series resonance point near 8MH2, and an antenna coil L1 and an ultrasonic transducer SW are connected to this in a closed loop to be used as a sensor. Antenna coil L2 is embedded in the required part, and an antenna coil L2 is placed on the surface of the living body closest to the sensor.A transmitter section consisting of a variable frequency oscillator 1 and a frequency meter 2 that generate electromagnetic waves in the vicinity of 8 MHz, and an ultrasonic microphone 3 are installed. ．． A measurement system is composed of a receiving section consisting of a high frequency amplifier 4, a level meter 6, and the like.

In the measurement, the output of the variable frequency excavator 1 is irradiated to the above-mentioned area through the antenna coil L2 connected thereto, and the ultrasonic waves oscillated by the sensor are received by the microphone 3, and the electrical signals are converted into high frequency signals. After amplifying to a required level in the amplifier 4, the excavation frequency of the variable frequency excavator 1 is changed while being monitored by the level meter 6, and the resonance of the crystal oscillator of the sensor is detected at the point where the reading of the level meter becomes maximum. The frequency can be detected (see FIG. 2(c)).

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

Furthermore, the configuration of a processor for implantation in a living body used for such measurements has conventionally been generally as shown in FIG. 2 (bl).

However, in a sensor having such a configuration, since the crystal oscillator X is connected to the ultrasonic transducer SW and the antenna coil L1 or 11, the maximum point of the current flowing through this closed circuit is The frequency is lower than the series resonance frequency (fS) of the child. As described above, since the resonant frequency of the sensor cannot be defined by the self-resonant frequency of the crystal oscillator incorporated therein, measurements such as frequency calibration are required, complicating the inspection process and increasing costs. In addition, if the I/V dance of the ultrasonic transducer, especially the series resistance component, is high, the Q value of the closed circuit will be significantly reduced, which will not only deteriorate the function as a sensor but also affect the ability of the sensor to be implanted in the living body. When such a compact device is required, it is necessary to downsize the ultrasonic transducer, but this has the disadvantage that its 1-beadance increases, making it more susceptible to noise.

(Object of the Invention) The present invention has been made in order to eliminate the defects of the conventional ultrasonic sensor as described above.

It is an object of the present invention to provide a temperature or pressure case sensor whose sensor function is defined by the self-resonant frequency and Q value of a crystal oscillator incorporated therein, and which has a circuit configuration that makes it possible to improve S/N.

(Summary of the Invention) In order to achieve the above object, a sensor according to the present invention connects a piezoelectric vibrator such as a crystal vibrator and an ultrasonic transducer in parallel with the antenna coil of the sensor to form a closed circuit.

In addition, we can control the resonance characteristics by performing impedance matching between the antenna coil and the ultrasonic transducer, and adjusting the combined impedance and pressure of both. The structure is such that the ratio to the series resonance impedance of the vibrator is appropriately selected.

(Embodiments of the Invention) The present invention will be described in detail below based on illustrated embodiments. Figure 1 (al is a circuit diagram showing one embodiment of the present invention. In the figure, L! is an antenna coil, in which a ceramic resonator is used in parallel with a crystal resonator X whose resonance frequency is around 8 MHz. Connect the ultrasonic transducer SW.

The frequency characteristic of the ultrasonic output of the sensor configured in this way is opposite to that of the conventional one, as shown in Figure 1 (bl).In other words, the electromagnetic wave energy received by the antenna coil L1 resonates with the crystal oscillator Near this point, the ultrasonic energy sent out from the ultrasonic transducer SW decreases because it is absorbed by this crystal oscillator, and becomes the minimum at the series resonance point of the crystal oscillator X. This characteristic is the resonance characteristic of the crystal oscillator Since this directly appears as a dip phenomenon, the operating mechanism of a measurement system using this sensor is substantially the same as the conventional one, and it is only necessary to reverse the relationship between the maximum and minimum detection levels.

FIG. 3 (at, '(b) and (cl) are diagrams showing other embodiments of the present invention, in which FIG. 3(a) is a diagram in which a condenser C is inserted in parallel to the antenna coil L1 and paralleled. By configuring a resonant circuit and tuning to the frequency near the resonance point of the crystal oscillator By appropriately selecting the ratio of , the dip in the dip phenomenon can be made deep.

Father, $3 Figures (bl and (C)) are circuits used when the impedance of the ultrasonic transducer is relatively low, and impedance matching is performed by attaching the antenna coil L1 to the secondary coil L3 or with a tap. This is an example.

In such a parallel circuit, in order to use the crystal oscillator without reducing its Q, the antenna coil L1 should have a parallel resistance as high as possible, and in order to further increase the sensitivity of the sensor, the antenna coil L1 should have the highest possible parallel resistance. It is important to match the impedance between L/L1 and the ultrasonic transducer SW.

Similarly, the specific configuration of the sensor is the fourth sensor in the case of a temperature sensor.
As shown in the figure, a coil L1 wound around a ferrite core 7 may be placed between the ultrasonic transducer SW and the crystal oscillator X, and its surroundings may be coated with a biocompatible material coating 9 such as Teflon. In the case of a pressure sensor, Fig. 5 (a
), a metal diaphragm 10 is fixed to the outer periphery of both main surfaces of a general crystal oscillator These may be replaced with the temperature detecting crystal oscillator X shown in FIG. 4 in order to utilize resonance frequency fluctuations based on compression or tension.

(Effect of the invention) The present invention is constructed in accordance with the above explanation.9
Impedance matching between components is easy, the resonance point of the crystal oscillator can be directly used as temperature or pressure information, and the Q value does not drop significantly, making it effective for stable measurements.

[Brief explanation of the drawing]

Figures 1(a) and (bl) are circuit diagrams and frequency characteristic diagrams showing one embodiment of the present invention, respectively, and Figures 2 (1al to (cl) are principle diagrams showing one embodiment of in-vivo temperature measurement, respectively. Conventional Sensor circuit diagram and frequency characteristic diagram, Figure 3 (a)
, (bl and (cl are respectively circuit diagrams showing other embodiments of the present invention, FIG. 4 is a sectional view showing an embodiment of a specific configuration of the temperature sensor according to the present invention, and FIG. 5 is a circuit diagram showing another embodiment of the present invention. bl are cross-sectional views showing different configurations of crystal oscillators to be used as pressure sensors.L1 and L2...Antenna coil L
3... Secondary coil X... Piezoelectric resonator (crystal resonator) SW.
・・・・・・・・・Ultrasonic transducer patent applicant Toyo Tsushinki Co., Ltd. SW Part 4 Diagram ぢ

Claims (2)

[Claims] (1) A temperature or pressure sensor characterized in that an antenna coil and an ultrasonic transducer are each connected in parallel to a piezoelectric vibrator whose resonance frequency is temperature or pressure dependent. (2) A tap or a secondary coil is provided in the antenna coil to match the internal impedance of the antenna and the coil with the impedance of the ultrasonic transducer. pressure sensor.