JP3488554B2 - Solution sensor system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solution sensor system for simultaneously measuring the viscosity, conductivity and relative permittivity of a solution, and more particularly to a solution sensor system using a sliding surface acoustic wave (SH-SAW).

[0002]

2. Description of the Related Art An ultrasonic measurement sensor has been proposed which measures mechanical quantity (viscosity) and electric quantity (conductivity and relative permittivity) of a liquid by using a surface acoustic wave.

[0003]

However, since the mechanical quantity and electric quantity measuring sensors according to the prior art use individual sensor cells, it is not possible to measure both physical quantities at the same time. Further, since the conventional measuring system is composed of a combination of a signal generator and a vector voltmeter, it requires a long time for measurement in addition to high cost.

An object of the present invention is to provide an inexpensive automatic measuring system which enables simultaneous measurement of a mechanical quantity and an electric quantity in a solution sensor system.

[0005]

A solution sensor system according to the present invention as set forth in claim 1 stores a liquid in each of the first to third channels formed on the surface of a single piezoelectric element. Possible first to third three sensor cells are arranged in parallel,
An opening window exposing the piezoelectric element is formed in the sensor cell in the third channel, and a pair of transmitting electrode and receiving electrode is directly fixed to the piezoelectric element on both sides of each sensor cell, and is common to the transmitting electrode. The high-frequency oscillator is selectively connected corresponding to the sensor cell, and a common propagation characteristic measuring instrument is connected to the transmitting electrode and the receiving electrode together with the formation of a measurement system including a combination of the high-frequency oscillator and the sensor cell selectively connected to the high-frequency oscillator. It is configured so that it can be selectively connected.

According to the present invention of claim 2, in addition to the invention of claim 1, the reference liquid is further stored in any one of the first and second sensor cells, and the remaining two sensor cells are loaded with the measurement liquid. Then, each change and amplitude of the oscillation frequency of the slip surface acoustic wave propagating between the transmitting electrode and the receiving electrode of each sensor cell is measured, and the measured liquid is compared from the measured data obtained for the reference liquid and the measured liquid. The viscosity, conductivity and relative permittivity of are simultaneously measured.

According to a third aspect of the present invention, in addition to the first or second aspect of the present invention, a feedback oscillation loop is formed by a signal amplifier, a slip surface acoustic wave sensor, and an automatic gain control circuit, and a transmission electrode is always provided. The circuit configuration is such that the received voltage and the oscillation frequency are measured while a constant voltage is applied to, and the slip surface acoustic wave can be attenuated and the sound velocity can be continuously measured.

The present invention according to claim 4 provides the invention according to claims 1 to 3.
In any one of the present inventions, the piezoelectric element is composed of a 36-degree rotating Y plate X propagating Li Ta O ₃ .

The present invention according to claim 1 has the following effects. The first to third three sensor cells are arranged in parallel in each of the first to third three channels formed on the surface of a single piezoelectric element, and the liquid can be stored in each sensor cell. An opening window exposing the piezoelectric element is formed in the corresponding third sensor cell in each of the three channels.

The slip surface acoustic wave (SAW) can change the physical quantity to be measured depending on the state of the sensing surface (SAW propagation surface), and the first and second sensor cells (first,
When the propagation surface is electrically short-circuited as in the second channel), the mechanical quantity is electrically opened like in the third sensor cell (third channel) (there is an opening window and is directly connected to the piezoelectric element). In the case of, the amount of electricity is measured.

According to the second aspect of the present invention, the following operational effects are obtained. The reference liquid (standard liquid) stored in the sensor cell of the first (or second) channel and the propagation characteristics of the slipping surface acoustic waves of the measurement liquid stored in the second (or first) and third channels have the same measurement circuit. Enables simultaneous measurement of the mechanical quantity and the electric quantity of the measurement liquid by switching and comparing with.

The present invention according to claim 3 has the following operational effects. By using a feedback oscillation circuit including the propagation path of the slip surface acoustic wave in the measurement circuit, automation of measurement and cost reduction can be achieved.

According to the present invention described in claim 4, there are the following operational effects. When the 36-degree rotating Y-plate X-propagation LiTaO ₃ is used for the sensor substrate, unnecessary acoustic waves (spurious vibrations of longitudinal liquid, etc.) other than the target slip surface acoustic wave do not occur, and compared with other elements Since the coupling coefficient is large, a highly sensitive sensor can be realized.

[0014]

1 is a schematic diagram showing an embodiment of a solution sensor system according to the present invention, FIG. 2 is a measurement system diagram of the solution sensor system according to the present invention, and FIG. 3 is a sound velocity and attenuation of an aqueous solution. FIG. 4 is a diagram showing a measurement example of velocity change due to electric characteristics with respect to the concentration of an aqueous solution, and FIG. 5 is a diagram showing a relative permittivity-conductivity diagram as an example of change due to an electric quantity.

As shown in FIG. 1, the solution sensor 40 comprises a single piezoelectric element 41 having three channels of transmission / reception sensors (10, 20, 30).

In FIG. 1, reference numerals 11, 21, and 31 are transmission electrodes, and 1
2, 22, 32 are short-circuit electrodes, 13, 23, 33 are receiving electrodes, 14, 24, 34 are sensor cells, and 35 is a short-circuit electrode 3.
4 is an opening window in which the piezoelectric element 41 is exposed through a part of the through holes. Reference numerals 42 and 43 in the sectional view are pool outer walls of the sensor cell.

Each electrode (sending / receiving electrode and short-circuit electrode) is
It is formed by a Cu / Au vapor deposition film on the surface (sensing surface) of the piezoelectric element 41 of the 36-degree rotating Y plate X propagation Li Ta O ₃ .

When the standard solution for reference is loaded into the sensor cell 14 of the first channel and the measurement fluid is loaded into the sensor cells 24 and 34 of the second and third channels, the measured amounts of the first and second channels are processed by computer. The mechanical quantity of the measured liquid,
The amount of electricity of the measurement liquid can be measured by computer processing of the measured amounts of the first and third channels.

In this case, since the same measurement liquid is loaded on the sensor cells 24 and 34 of the second and third channels, the sensor cells 24 and 34 can be a common pool as shown by the broken line in FIG. .

FIG. 2 shows the case of the first channel (Ch.1) measurement, and the transmission voltage is applied to the first channel corresponding transmission electrode 11 of the solution sensor 40 by the automatic gain control circuit 52. A slip surface acoustic wave having a center frequency of 50.2 MHz is generated in the transmitting electrode 11, propagates in the corresponding sensor cell 14, and transmits information on the standard solution to the corresponding receiving electrode 13.
The received signal is amplified by the signal amplifier 51 and fed back to the automatic gain control circuit 52.

Automatic gain control circuit 52 → solution sensor 40 →
The measurement system configured by the closed circuit of the signal amplifier 51 → the automatic gain control circuit 52 forms an oscillation loop, oscillates at a repetition frequency corresponding to the sound velocity of the solution, and the transmission voltage is controlled to a constant amplitude. Therefore, when the output of the signal amplifier 51 is detected by the detection circuit 53, the amplitude of the standard solution is measured by the digital multimeter 54 and input to the computer 55.

On the other hand, the oscillation frequency of the oscillation loop is mixed with the reference frequency of the crystal oscillator 56 by the mixer circuit 57, and the difference frequency is measured by the frequency counter 58, and the frequency corresponding to the sound velocity characteristic of the standard liquid is stored in the computer 55. Is entered. All the series of operations from the above measurement to computer input are automatically performed.

The same measurement is automatically and repeatedly carried out on the second and second channels (Ch.2, Ch.3), and the amplitude and frequency of the (a) first and second channels input to the computer 55. The mechanical quantity of the measurement liquid is calculated from each of the above, and the electric quantity of the measurement liquid is calculated from the comparison of each of the amplitudes and frequencies of the first and third channels (b).

As specific examples, measurement examples of glycerin and four kinds of alcohols will be shown. Each sample was prepared by diluting 10% to 88% by weight of glycerin and 10% to 100% by volume of alcohol with distilled water, using a commercially available JIS special grade reagent as 100%.

FIG. 3 shows an example of measurement of each aqueous solution of glycerin and methanol. In the figure, the horizontal axis is the propagation velocity change ΔV / V obtained by the frequency change, and the vertical axis is the attenuation change Δα / k.

FIG. 3 (a) shows the characteristics of an aqueous glycerin solution.
61 is an electric quantity and 62 is a mechanical quantity. FIG. 3B shows the characteristics of the aqueous methanol solution, where 63 is an electric quantity and 64 is a mechanical quantity.

From FIG. 3, the change of the mechanical quantity (viscosity) (62, 6)
In 4), glycerin goes up to the left and methanol goes down to the right. This is consistent with the change in viscosity from distilled water. From the changes (61, 63) depending on the amount of electricity, it can be seen that the permittivity greatly changes.

FIG. 4 shows the concentrations of the four alcohols.
This is a speed change (corresponding to the amount of electricity) characteristic.

In the figure, 71 is methanol, 72 is ethanol, 73 is 1 propanol, and 74 is 2 propanol. There is no clear difference between 1-propanol 73 and 2-propanol 74, which have similar molecular structures, but there is a difference between them and ethanol 72 and methanol 71.

FIG. 5 is a graph showing the changes in the above-mentioned five types of samples depending on the amount of electricity on the relative permittivity-conductivity chart.

From the figure, the change in conductivity (σ / f) is obtained for each sample.
× 10 ^-8 s · m ^-1 H ₂ ^-1 ) is minute and the relative permittivity (ε _r ') is greatly changed.

[0032]

As described above, according to the solution sensor system of the present invention, the mechanical quantity (viscosity) and the electric quantity (conductivity and relative permittivity) of the solution can be simultaneously measured with high accuracy. .

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a solution sensor system according to the present invention.

FIG. 2 is a measurement system diagram of a solution sensor system according to the present invention.

FIG. 3 is a diagram showing a measurement example of sound velocity and attenuation of an aqueous solution.

FIG. 4 is a diagram showing an example of measurement of velocity change due to electrical characteristics with respect to the concentration of an aqueous solution.

FIG. 5 is a diagram showing an example of a change with an electric quantity in a relative permittivity-conductivity diagram.

[Explanation of symbols]

10, 20, 30 Send / receive sensors 11, 21, 31 Transmitting electrode 12, 22, 32 short-circuit electrodes 13, 23, 33 receiving electrodes 14, 24, 34 sensor cells 35 open window 40 Solution sensor 52 Automatic gain control circuit 54 Digital Multimeter 55 Computer 58 frequency counter

Front page continuation (56) References JP-A-6-109710 (JP, A) JP-A-6-194346 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01N 29 / 00-29 / 28 G01N 11 / 00-11 / 16 JISST file (JOIS)

Claims (4)

(57) [Claims] 1. A first piezoelectric device formed on the surface of a single piezoelectric element.
To each of the third to third channels, first to third sensor cells capable of storing liquid are arranged in parallel, and an opening window exposing the piezoelectric element in the sensor cell is formed in the third channel, A pair of transmitting electrode and receiving electrode is directly fixed to the piezoelectric element on both sides of the sensor cell, and a common high-frequency oscillator is selectively connected to the transmitting electrode corresponding to the sensor cell, and the transmitting electrode and the receiving electrode are connected to each other. A solution sensor system configured so that a common propagation characteristic measuring device can be selectively connected in conjunction with the formation of a measuring system including a high frequency oscillator and a sensor cell selectively connected to the high frequency oscillator. 2. A slip elastic surface which stores a reference liquid in one of the first and second sensor cells and loads the remaining two sensor cells with a measurement liquid to propagate between a transmission electrode and a reception electrode of each sensor cell. Claims configured to measure the change and amplitude of the oscillating frequency of the wave respectively and to simultaneously measure the viscosity, conductivity and relative permittivity of the measurement liquid by comparing the measurement data obtained for each of the reference liquid and the measurement liquid. 1. The solution sensor system according to 1. 3. A slipping surface acoustic wave is formed by forming a feedback oscillation loop with a signal amplifier, a slipping surface acoustic wave sensor, and an automatic gain control circuit, and measuring a reception voltage and an oscillation frequency with a constant voltage constantly applied to the transmission electrode. 3. The solution sensor system according to claim 1, wherein the solution sensor system has a circuit configuration capable of continuously measuring attenuation of sound and sound velocity. 4. The Y-plate X-propagation Li of the Y-plate rotated by 36 degrees.
The solution sensor system according to any one of claims 1 to 3, which is composed of Ta O ₃ .