JP2003032043A - Oscillation circuit for crystal vibrator and crystal vibrator sensor employing the circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crystal vibrator use oscillation circuit that can contribute to practical use of a crystal vibration sensor vibrated in a thickness torsional vibration mode and the crystal vibration sensor that can contribute to the measurement accuracy by using it. SOLUTION: A 1st winding 15 of a 1st common mode choke 13 is inserted between an input terminal 101 of an inverting amplifier 1 and a 1st electrode 3 provided to a crystal vibration plate 5, a 4th winding 18 of a 2nd common mode choke 14 is inserted between an output terminal 102 of the inverting amplifier 1 and a 2nd electrode 4 of the crystal vibrator plate 5, and a 2nd winding 16 of the 1st common mode choke 13 and a 3rd winding 17 of the 2nd common mode choke 14 are inserted between the output terminal 102 of the inverting amplifier 1 and the input terminal 101 so that the natural frequency of the crystal vibration plate 5 is changed as a single-valued function attended with a change in the physical characteristic of the measured object.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillator circuit for a crystal unit and a crystal unit type sensor using the same, and more specifically, an oscillator capable of vibrating the crystal unit in a thickness torsion vibration mode. Circuit, and a crystal oscillator type using the circuit, which is suitable for detecting the concentration of solute in an electrically conductive solution such as an electrolytic solution and the viscosity of the solution by the change in natural frequency of the thickness torsional vibration mode It is about sensors.

[0002]

2. Description of the Related Art A solution in which a solute is dissolved in a solvent changes in viscosity and density depending on the amount of the solute dissolved. Therefore, the viscosity and density of the solution depend on the natural frequency of the piezoelectric vibrator brought into contact with the solution. It is known that it can be detected by a change, and that the concentration of a solute dissolved in the solution can also be detected.

Such a detection method is disclosed in International Publication Number WO
93/06452. The above publication discloses the use of a crystal oscillator, which is a kind of piezoelectric oscillator, for detecting the viscosity and density of a solution and the concentration of a solute dissolved in the solution. This crystal oscillator has a structure in which a first electrode and a second electrode are attached to two surfaces of a plate-shaped AT-cut crystal diaphragm, and the viscosity and density of the solution and the solution are dissolved in the solution. The solute concentration is detected by changing both natural frequencies when the second electrode is in contact with a solution, both electrodes are connected to an oscillation circuit, and the oscillation circuit is oscillated at a high frequency. .

In the above method of bringing the crystal oscillator into contact with the solution, it is essential that one electrode is brought into contact with the solution. After the electrodes are processed on both sides of the crystal oscillator, both electrodes are further contacted. It is necessary to pull out each lead wire from.

There is also a method described in Japanese Patent Laid-Open No. 9-89740. This method can be applied only when a conductive solution such as an electrolytic solution is to be measured, and a pair of electrodes are provided in parallel in the Z-axis direction only on one surface of the AT-cut quartz crystal diaphragm. It oscillates in the thickness torsional vibration mode. In such a crystal oscillator sensor that oscillates in the thickness torsion vibration mode,
Since a pair of electrodes can be provided in parallel in the Z-axis direction only on one surface of the T-cut crystal diaphragm, and the other surface without electrodes can be brought into contact with the solution, the lead wire from the electrode in contact with the solution There is an advantage in that it is possible to avoid the difficulty of taking out the electrode and the problem that the electrode itself is corroded by the solution.

[0006]

As described above, the crystal oscillator type sensor that oscillates in the thickness torsional vibration mode has some advantages, but the impedances of the pair of electrodes with respect to the solution or the ground are matched and balanced. If it is not oscillated in such a state, there is a problem that the measurement result is sensitively affected by changes in the measurement environment and disturbances. That is, FIG.
As shown in FIG. 2, a crystal oscillator sensor 2 is provided with an inverting amplifier 1 having an input terminal 101 and an output terminal 102.
The first and second electrodes 3 and 4 are provided on one surface, the other surface is in contact with the object to be measured 8, and the crystal oscillator plate 5 attached to the insulating container 6 is provided. 1 is connected to the first electrode 3 provided on the crystal resonator plate 5, and the output terminal 102 of the inverting amplifier 1 is connected to the resistor 12
Is connected to the second electrode 4 provided on the crystal oscillator plate 5 via the, and the natural frequency of the crystal oscillator plate 5 is the measured object 8
Even if it changes in a monovalent function with the change of the physical characteristics of the inverting amplifier 1, the input impedance of the input terminal 101 of the inverting amplifier 1 to which the electrode 3 is connected and the output terminal of the inverting amplifier 1 to which the electrode 4 is connected. Since the output impedance of 102 is different, it is impossible to oscillate in the above-mentioned balanced state.

Therefore, in the crystal oscillator type sensor which oscillates in the thickness torsional vibration mode and the oscillation circuit therefor described in Japanese Patent Application Laid-Open No. 9-89740, the input terminal and the output terminal of the amplifier are the two crystal oscillators. Since the feedback circuit is formed by connecting to each of the electrodes to oscillate, the essential problem that the input terminal and the output terminal have different impedances with respect to the ground is solved, that is, two electrodes. As long as you can not match the impedance when looking at each amplifier from,
There is a problem in that it is difficult to put a quartz oscillator sensor that oscillates in the thickness torsional vibration mode into practical use.

[0008]

In order to solve the above-mentioned problems, the invention according to claim 1 has an inverting amplifier having an input terminal and an output terminal, and a first inverting amplifier having first and second windings.
Common mode choke, a second common mode choke having third and fourth windings, and a crystal resonator plate provided with first and second electrodes on one surface thereof, and the input of the inverting amplifier The first winding of the first common mode choke is inserted between the terminal and the first electrode provided on the crystal oscillator plate, and the output terminal of the inverting amplifier and the second electrode of the crystal oscillator plate are provided. And a fourth winding of the second common mode choke, and a second winding of the first common mode choke and a second winding between the output terminal and the input terminal of the inverting amplifier.
3. An oscillation circuit for a crystal resonator, wherein the third winding of the common mode choke according to claim 1 is inserted, and the invention according to claim 2 is an inverting amplifier having an input terminal and an output terminal; A first common mode choke having two windings, a second common mode choke having third and fourth windings, and first and second electrodes provided on one surface,
A crystal oscillator plate having the other surface in contact with the object to be measured, and a first common mode choke between the input terminal of the inverting amplifier and the first electrode provided on the crystal oscillator plate. The first winding is inserted, and the fourth winding of the second common mode choke is inserted between the output terminal of the inverting amplifier and the second electrode of the crystal resonator plate, and Between the output terminal and the input terminal, the second winding of the first common mode choke and the third winding of the second common mode choke
A crystal oscillator type sensor characterized in that a natural frequency of the crystal oscillator plate is changed in a monovalent function according to a change in physical characteristics of the object to be measured by inserting a winding. Therefore, by adding a filter having a balanced / unbalanced conversion function configured by using a common mode choke to the crystal oscillator and the amplifier that oscillate in the thickness torsional vibration mode, the above-mentioned impedance becomes unbalanced. Solve the problem.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on its embodiments.

FIG. 1 is a diagram showing an oscillator circuit for a crystal oscillator that oscillates in a thickness torsional vibration mode and a crystal oscillator type sensor using the same according to an embodiment of the present invention.

FIG. 1 shows an input terminal 101 and an output terminal 1.
Inverting amplifier 1 having 02 and first and second windings 1
A first common mode choke 13 having 5, 16;
A second common mode choke 14 having third and fourth windings 17, 18 and first and second electrodes 3, 3 on one side.
4, a crystal oscillator plate 5 having the other surface in contact with the object to be measured 8, the input terminal 101 of the inverting amplifier 1 and the first electrode 3 provided on the crystal oscillator plate 5. The first winding 15 of the first common mode choke 13 is inserted between the first common mode choke 13 and the second common between the output terminal 102 of the inverting amplifier 1 and the second electrode 4 of the crystal oscillator plate 5. The second winding 16 of the first common mode choke 13 and the second common mode choke are inserted between the output terminal 102 and the input terminal 101 of the inverting amplifier 1 with the fourth winding 18 of the mode choke 14 interposed. It is shown that 14 third windings 17 are inserted so that the natural frequency of the crystal oscillator plate 5 changes in a monovalent function according to the change in the physical characteristics of the DUT 8. There is. In FIG. 1, the connection point between the first winding 15 of the first common mode choke 13 and the third winding 17 of the second common mode choke 14 is grounded via the capacitor 10 and the second common Mode choke 1
The connection point between the fourth winding 18 of No. 4 and the second winding 16 of the first common mode choke 13 is grounded through the capacitor 11, and the resistor 12 is connected between the output terminal 102 of the inverting amplifier 1 and the output terminal 102. Interposed, second common mode choke 1
Capacitors 19 and 20 are connected in series between the third winding 17 of No. 4 and the second winding 16 of the first common mode choke 13, and the capacitors 19 and 20 are connected together.
The connection point with is grounded.

With the above configuration, when a current flows from the output terminal 102 of the inverting amplifier 1 through the resistor 12, the second winding 16 of the first common mode choke 13 and the capacitor 19, the first common mode choke 13 is formed. First winding 1
Currents of the same magnitude are induced in 5 due to the characteristics peculiar to the common mode choke, and the floating impedance 9, the conductive container 7, the DUT 8, the crystal oscillator plate 5, and the first
Through the electrode 3 of the inverting amplifier 1 from the input terminal 101 of the inverting amplifier 1, from the output terminal 102 of the inverting amplifier 1 to the resistor 12, the fourth winding 1 of the second common mode choke 14.
When a current flows through 8, the second electrode 4, the crystal oscillator plate 5, the DUT 8, the conductive container 7, and the floating impedance 9, the third winding 17 of the second common mode choke 14 A current of the same magnitude is induced by the characteristic peculiar to the common mode choke and flows from the ground to the input terminal 101 of the inverting amplifier 1 through the capacitor 20.

As a result, the first electrode 3 and the second electrode 4 of the crystal resonator plate 5 are driven by the oscillating currents having the same size but opposite phases, which cancel each other out. Therefore, the current flowing through the floating impedance 9 is always zero, and even if the floating impedance 9 is affected by mounting conditions, operating conditions, etc., the oscillation operation is not affected.

Further, the crystal oscillator oscillation circuit vibrating in the thickness torsional vibration mode shown in FIG. 1 is seen from the output terminal 102 and the input terminal 101 side of the inverting amplifier 1 and has the first and second common modes. The chokes 13 and 14 are connected in parallel to each other, and the first and second common mode chokes 13 and 14 between the first electrode 3 and the second electrode 4 of the crystal resonator plate 5 are connected in series. Therefore, the crystal impedance of the crystal resonator plate 5 viewed from the output terminal 102 and the input terminal 101 side of the inverting amplifier 1 effectively acts as a half of the actual value.
Will need to drive a load that is one half of the actual crystal impedance, and there will be a margin in oscillation capability.

[0015]

EXAMPLES A 10 MHz, AT-cut quartz resonator plate is provided with two electrodes arranged in parallel on one side to form a thickness torsional vibration mode quartz resonator which is housed in an insulating container, an inverting amplifier or a common mode choke. When the crystal unit type sensor having the structure shown in FIG. 1 is provided and the crystal unit type sensor having the structure shown in FIG. 2 except the common mode choke is operated and compared, FIG. The oscillating frequency of the thing of FIG. 1 fluctuated in the unit of several kilohertz when approaching a human hand, but that of FIG. 1 was several hertz.

[0016]

As described above, according to the oscillator circuit for a crystal resonator of the present invention, it has features such as ease of manufacture and improved durability due to the absence of electrodes that come into contact with liquid, and mounting conditions and operating conditions. The crystal oscillator type sensor vibrates in the thickness torsional vibration mode, which has been hindered from being put into practical use due to the problem that the oscillation frequency fluctuates. Greatly contributes to the improvement of.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a crystal oscillator oscillation circuit of the present invention and a crystal oscillator sensor using the same.

FIG. 2 is a diagram showing a configuration of a conventional crystal oscillator oscillator circuit and a crystal oscillator sensor using the same.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Inversion amplifier 2 Crystal oscillator type sensor 3, 4 1st, 2nd electrode 5 Crystal oscillator plate 6 Insulating container 7 Conductive container 8 DUT 9 Floating impedance 10, 11 Capacitor 12 Resistor 13, 14 1st and Second common mode choke 15, 16 First of common mode choke 13,
The second winding 17, 18, the third of the second common mode choke 14,
Fourth winding 19, 20 Capacitor

Claims (2)

[Claims] 1. An inverting amplifier having an input terminal and an output terminal, a first common mode choke having first and second windings, and a second common mode choke having third and fourth windings. A crystal oscillator plate having first and second electrodes provided on one surface thereof, and a first common mode choke between the input terminal of the inverting amplifier and the first electrode provided on the crystal oscillator plate. And the fourth winding of the second common mode choke is interposed between the output terminal of the inverting amplifier and the second electrode of the crystal oscillator plate.
A first terminal is provided between the output terminal and the input terminal of the inverting amplifier.
2. An oscillation circuit for a crystal unit, wherein the second winding of the common mode choke and the third winding of the second common mode choke are inserted. 2. An inverting amplifier having an input terminal and an output terminal, a first common mode choke having first and second windings, and a second common mode choke having third and fourth windings. A crystal oscillator plate provided with first and second electrodes on one surface and having the other surface in contact with the object to be measured, the first terminal provided on the crystal oscillator plate and the input terminal of the inverting amplifier; The first winding of the first common mode choke is interposed between the first common mode choke and the second common mode choke between the output terminal of the inverting amplifier and the second electrode of the crystal resonator plate. And a second winding of the first common mode choke and a third winding of the second common mode choke between the output terminal and the input terminal of the inverting amplifier. The natural frequency of the crystal oscillator plate is the physical frequency of the measured object. A crystal oscillator sensor characterized in that it changes monotonically as the characteristics change.