JPH04289438A - Minute-amount measuring sensor and minute-amount measuring apparatus - Google Patents

Abstract

PURPOSE:To eliminate noises and disturbances, to stabilize oscillation and to make it possible to measure the minute amount of change by providing a sensor electrode on the surface of a quartz resonator which is in contact with an object to be measured, and providing a pair of oscillating electrodes on the surface different from the sensor electrode. CONSTITUTION:A sensor electrode 2 is provided on one surface of a quartz resonator 1 which is in contact with an object to be measured. A pair of oscillating electrodes 3a and 3b are provided on the other surface of the resonator 1. The electrode 2 of the resonator 1 is arranged in a liquid phase or in a gaseous phase and brought into contact with solution or gas. The electrodes 3a and 3b are not in contact with the liquid-phase solution or the gaseous-phase gas. Therefore, a solid product material is attached to the electrode 2 and is not attached to the electrodes 3a and 3b. Therefore, the resonator 1 is oscillated without generating noises and disturbances caused by the inflow of current. The oscillating frequency is changed with the attached amount of the solid product material which is attached to the electrode 2. When the frequency is read on a counter 5 which is connected to a transmitting circuit 4, the mass of the minute amount of the solid product material which is attached to the electrode 3 can be measured.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor and a micrometer measuring device used for measuring ultra-trace amounts of solid products produced by chemical reactions in solutions.

0002

2. Description of the Related Art A sensor for measuring a small amount is formed from a piezoelectric material such as a crystal, and after the piezoelectric material is placed in contact with a solution as described later, the piezoelectric material is caused to oscillate. Thereafter, when a small amount of solid product adheres to the electrode surface of the piezoelectric body, the resonant frequency of the piezoelectric body decreases. The above sensor is used in a device that can measure the weight of solid product deposited by detecting this decrease in resonance frequency with a counter or the like.

Currently, a quartz crystal microbalance (hereinafter referred to as QCM) is used as the sensor for measuring a small amount, and this QCM is used as a measurement cell for liquid phase QCM. Typical examples thereof are shown in FIGS. 3 to 6. Figures 3 to 6
In this method, one side of the crystal oscillator is placed in contact with the solution, but other than this point, the principle is similar to vacuum and gas phase microbalance. The crystal resonator is fixed to the cell using an O-ring or silicone rubber adhesive, avoiding the vibration electrode part so as not to interfere with vibration.
Connected to an oscillation circuit (not shown).

[0004] The shape of the measurement cell differs depending on the object to be measured, and FIGS. 3 and 4 are of a flow-through type in which a solution can flow. In FIG. 3, reference numeral 11 denotes a crystal oscillator holder in which a solution passage 12 is formed, and one side of the quartz crystal oscillator 13 is exposed to the solution passage 12 of this holder 11. With this configuration, one side of the crystal resonator 13 comes into contact with the solution. Further, in FIG. 4, an O-ring 14 is provided between the crystal resonator 13 and the retainer 11.

FIG. 5 is for the purpose of electrochemical measurement.
It consists of a container 15 that can be connected to an electrolytic cell (not shown) incorporating a counter electrode and a reference electrode. Also,
FIG. 6 shows a configuration in which a gap 16 is provided on the back side of a crystal resonator 13 so that the entire resonator can be immersed in a solution.

[0006] The vibrator system manufactured as described above can obtain frequency stability of about several Hz/hr even in a solution under constant temperature conditions. The accuracy with which the QCM produced in this manner follows the "Suerbray" equation in the liquid phase can be calibrated by electrochemically depositing a metal on an electrode in contact with the solution layer. That is, by using a metal (Ag, Cu, etc.) that can be quantitatively deposited, and comparing the mass change calculated from the electrical quantity and the frequency change, the quantitative accuracy of the prepared QCM is checked. Can be done.

[0007]

[Problems to be Solved by the Invention] Usually, an AT-cut thickness shear vibrator is used in a QCM measurement cell. FIG. 7 shows the relationship between such a vibrator and electrodes. Reference numeral 21 is a crystal vibrator, and oscillation electrodes 22 and 23 are provided on both sides of the crystal vibrator 21 to face each other. These oscillation electrodes 22 and 23 have an oscillation circuit 2 as shown in FIG.
4 is connected. The oscillation frequency of the oscillation circuit 24 is measured by the counter 25. In the case of liquid phase QCM, one of the opposing electrodes 22 and 23 (electrode 23) comes into contact with the solution, and a small amount of solid product adheres to the electrode. do. As a result,
Since a change occurs in the resonant frequency of the crystal resonator 21, the mass can be measured from this change. In this case, since the electrode 22 for vibration and the electrode 23 to which the solid product adheres (hereinafter referred to as sensor electrode) are the same, the following problem arises.

When the purpose is electrochemical measurement, the vibration electrode 22 and the sensor electrode 23 are shared, and the power supplies for each (oscillator power supply and electrochemical power supply) cannot be made independent. generation of noise,
Oscillation instability and oscillation active elements were likely to be destroyed.

The present invention has been made in view of the above circumstances, and is capable of stabilizing the oscillation by eliminating noise and disturbance to the oscillation of the vibrator, making it possible to measure minute changes, and making it easy to manufacture. The purpose of the present invention is to provide a sensor for measuring a small amount and a device for measuring a small amount.

0010

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a crystal resonator, a sensor electrode provided on a surface of the crystal resonator that comes into contact with an object to be measured, and a The device is characterized in that it includes a pair of vibration electrodes provided on a different surface from the sensor electrode so as to be sandwiched therebetween. Further, the sensor electrode is placed in a liquid phase or a gas phase.

[0011]

[Operation] The sensor electrode to which solid products adhere is placed in the liquid phase or gas phase, but since the vibration electrode is on the back side of the sensor electrode, no solid products, etc. adhere to it. As a result, the vibration electrode does not pick up noise or generate disturbances due to current looping.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIGS. 1A, 1B, and 1C, 1 is a crystal resonator, and a sensor electrode 2 is provided on one surface of the crystal resonator 1 that is in contact with the object to be measured. Also, crystal oscillator 1
A pair of vibration electrodes 3a and 3b are provided on the other surface of the oscillator. The vibration electrodes 3a, 3b are connected to an oscillation circuit 4 shown in FIG. The oscillation frequency of the oscillation circuit 4 is measured by a counter 5.

The micro-quantity measurement sensor using the crystal oscillator constructed as described above is disposed in a liquid phase or a gas phase. At this time, the sensor electrode 2 of the crystal resonator 1 is configured to be in contact with the liquid phase or the gas phase, but the vibration electrodes 3a and 3b are configured so that the liquid phase solution or gas phase does not come into contact with them. be done. By configuring like this,
Since the solid product adheres only to the sensor electrode 2, the crystal resonator 1 oscillates without noise or disturbance due to current looping occurring in the vibration electrodes 3a, 3b. Since this oscillation frequency changes depending on the amount of solid products deposited on the sensor electrode 2, by reading this frequency with a counter 5 connected to the oscillation circuit 4, a trace amount of solid products deposited on the sensor electrode 2 can be detected. Can measure mass.

Furthermore, since the vibration electrodes 3a and 3b are arranged on one side of the crystal resonator 1, the manufacturing process as a sensor for measuring a small amount becomes capacitive. In the above embodiment, a crystal resonator was used as the QCM, but other piezoelectric crystals may also have vibration modes where the frequency is determined by the thickness, such as thickness vibration or thickness shear vibration. All can be applied to.

[0015]

[Effects of the Invention] As described above, according to the present invention,
Since the electrode for vibration and the electrode for sensor are separated, there is no disturbance due to noise or current wrap-around to the oscillation of the vibrator, which makes it possible to stabilize the oscillation and prevent the formation of minute solids. You can also measure objects accurately. Further, according to the present invention, since an oscillation circuit can be connected to the electrode on one side of the vibrator, it becomes easy to manufacture a sensor for measuring a small amount.

[Brief explanation of the drawing]

FIG. 1(a) is a front view showing one embodiment of the present invention;
b) is a side view of the same embodiment, and (c) is a view of the same embodiment seen from below.

FIG. 2 is an explanatory diagram of an embodiment using the present invention as a measuring device.

FIG. 3 is an explanatory diagram of a liquid phase QCM measurement cell.

FIG. 4 is an explanatory diagram of a liquid phase QCM measurement cell.

FIG. 5 is an explanatory diagram of a liquid phase QCM measurement cell.

FIG. 6 is an explanatory diagram of a liquid phase QCM measurement cell.

FIG. 7(a) is a front view showing the relationship between a crystal resonator and electrodes, and FIG. 7(b) is a side view showing the relationship between the crystal resonator and electrodes.

FIG. 8 is a diagram explaining the principle of QCM.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Crystal resonator, 2... Sensor electrode, 3a, 3b... Vibration electrode, 4... Oscillation circuit, 5... Counter.

Claims (2)

[Claims] 1. A crystal resonator, a sensor electrode provided on a surface of the crystal resonator that contacts a measurement object, and a pair of sensor electrodes provided on a different surface from the sensor electrodes so as to sandwich the crystal resonator. A sensor for measuring a small amount, comprising: a vibration electrode. 2. The micro-quantity measuring device according to claim 1, wherein the sensor electrode is located in a liquid phase or a gas phase.