JPS60164256A - Salt concentration sensor for sea water - Google Patents

Abstract

PURPOSE:To stabilize a continuous measurement for a long time by measuring the salt concentration of sea water based on an oscillation frequency. CONSTITUTION:A salt concentration sensor is made up of an operation amplifier 1 comprising a C-MOSIC and the like and an oscillation circuit 10 composed of a feedback circuit 4 comprising a resistance 2 and a capacitor 3 connected between input and output terminals 1A and 1B of the amplifier. A pair of electrodes 5A and 5B as opposed to each other being isolated and made immersible into sea water W serve as a resistance element of the circuit 4. When the electrodes 5A and 5B are sunk into sea, current flows between the electrodes according to salt concentration of sea water and the sensor makes an oscillation.

Description

[Detailed description of the invention] This invention relates to a seawater salinity sensor.

The salinity of seawater represents the properties of seawater, and organisms living in the ocean depend on it. Therefore, measurement of seawater salinity is an essential requirement for the investigation and exploration of fisheries resources.

Conventionally, electrical measurement methods that utilize the conductivity of seawater have been known as a means of measuring the salinity of seawater.This method uses a DC bridge to measure the electrical resistance between a pair of electrodes isolated and facing each other in seawater. In particular, devices that measure salinity concentration are generally known.

However, since this type of measurement device uses DC voltage, seawater is electrolyzed between the electrodes, and as a result, suspended matter in the seawater is electrically attached to the surface of the negative electrode, which increases the resistance between the electrodes. It was causing an increase.

For this reason, the above-mentioned measuring device has the disadvantage that the electrode surface must be frequently cleaned and polished, maintenance is troublesome, and continuous measurement cannot be performed for a long period of time.

Furthermore, when measuring salt concentration in the sea, a long conductor is required depending on the depth of the water, which has the disadvantage that the resistivity of these conductors can be ignored, and adjustments to ensure accurate measurements are troublesome. Ta.

In view of the above-mentioned drawbacks, it is an object of the present invention to provide a seawater salinity sensor that does not cause electrode contamination due to electrolysis, can perform continuous measurement over a long period of time, and can easily measure salinity in the deep sea. This is an oscillation circuit that is made for this purpose and consists of a feedback circuit consisting of a resistor and a capacitor connected between the input and output of an IC circuit that performs a positive feedback action. The pair of electrodes made possible are used as resistance elements of the return circuit,
The device is characterized in that the oscillation circuit is configured to oscillate at a frequency corresponding to the conductive resistance when the pair of electrodes are immersed in seawater.

The present invention will be explained below using examples.

FIG. 1 is a configuration block diagram of the present invention.

The seawater salinity sensor A of the present invention consists of an operational amplifier or logic circuit composed of one or more C-MOs, SICs, etc., and input/output terminals IA and IB of the C-MO5ICI.
In an oscillation circuit 10 formed by connecting a return circuit 4 consisting of a resistor 2 and a capacitor 3 between them, they are isolated and opposed to each other,
A pair of electrodes that can be immersed in seawater W5. A,
5B is a resistance element of the return circuit 4, which together with the resistance 2 forms a circuit 4A, and the pair of electrodes 5A,
The oscillating circuit 1o is configured to oscillate at a frequency T corresponding to the conductive resistance R' when the oscillator 5B is immersed in seawater.

FIG. 2 shows two c-
A circuit configuration diagram in the case of using u, o s inverter 11.12 is shown, in which input and output terminals IA and IB of two directly connected C-MOS inverters are connected by a capacitor 3, and the first stage The input/output terminals IA and 113' of the second C-MOS inverter 11 are connected to the resistor 2 and the electrodes 5'A and 5B.
It is configured by being connected by a circuit 4A consisting of.

Next, the operation of the above embodiment will be explained.

When the electrodes 5A and 5B are in the air, the return circuit 4 is cut off, so the seawater salinity sensor A does not oscillate, and the C-MOS inverters 11 and 12 have extremely small resting currents. Flows and stays.

However, when the electrodes 5A and 5B are submerged in the sea, a current flows between the electrodes depending on the salt concentration of the seawater, and the electrodes 5A and 5B
B essentially acts as a resistance.

Therefore, the return circuit 4 is closed and the seawater salinity sensor A oscillates.

At this time, the oscillation period T is as follows: VTur: threshold voltage of the first stage C-MOS inverter, VDD: c-MOS ybar#) is the original voltage, R: actual resistance between electrodes 5A and 5B. value R' and the resistance value R of resistor 2
"Sum C: Can be expressed as the capacitance of capacitor 3.

In the above equation, since VTHI vDD and CFi can be set as constant values when configuring the circuit, the oscillation period T will vary depending on the conductivity depending on the salinity concentration of seawater. The oscillation period T output from the circuit indicates the salt concentration of seawater.

During this oscillation operation, the electrodes 5A and 5B immersed in seawater have VTHI and VDD + V
A varying alternating current flows through Tux and UVTHI-VDD.

Moreover, since the conductivity between the electrodes 5A and 5B is caused by the concentration of positive ions and negative ions dissociated in seawater, the period of the alternating current is also related to the ion concentration, and specifically, the period of the alternating current is related to the ion concentration. Glass ions and negative ions in a dissociated state during W move in a direction to neutralize the potential applied between the pair of electrodes 5A and 5B,
In this way, when the potential between both electrodes is neutralized to VTHI, the potential is suddenly reversed, and positive ions and negative ions move in the opposite direction to that described above. Therefore,
This also prevents suspended matter in seawater from adhering to the electrodes 5A and 5B.

In the above embodiment, the C-MOS inverter has a two-stage configuration, but as shown in FIGS. It is also possible to have a multi-stage configuration.

In each example, the case where the resistor 2 is a variable resistor is shown, but this is because the frequency can be determined with the standard solution or the span can be adjusted in response to the ion concentration of seawater. Therefore, in practical terms, it is possible to substitute a certain standard resistance.

For each of the above examples, a salt concentration detection test was conducted continuously for one week on three types of liquids: seawater, tap water, and distilled water, and the measurement accuracy was 4 digits and stable for seawater and tap water. It was found that the product showed excellent long-term stability.

As described above, this invention has a configuration in which the salinity concentration of seawater can be measured by the oscillation frequency, so that specific ions are attached to specific electrodes due to the alternating current flowing between the electrodes that are immersed in the sea. It is possible to perform continuous measurements over a long period of time, and the trenches, equipment, and I
By using the C circuit, it is possible to significantly reduce the size, and therefore, a pressure-resistant and watertight container can be easily obtained, and measurements in the deep sea can be easily performed.

Note that the present invention can be used not only for measuring salinity concentration but also for seawater detection switches and the like.

[Brief explanation of drawings]

FIG. 1 is a configuration block diagram showing a circuit of an embodiment of the present invention, FIG. 2 is a configuration block diagram of a tenth embodiment, and FIG.
The figure is an explanatory diagram of the operation of FIG. 2, and FIGS. 4(a) and 4(b) are block diagrams of the configuration of still another embodiment. A...Seawater salinity sensor, l...1c inverter, 2...resistor, 3...capacitor, 4...return circuit, 5A, 5B...pair of electrodes, 10...transmission Circuit, 11.12- C-MOS inverter. 118 72/B 41fl

Claims (1)

[Claims] (1) In an oscillator circuit consisting of a feedback circuit consisting of a resistor and a capacitor connected between the input and output of an IC circuit that performs positive feedback, a pair of isolated and opposing elements that can be immersed in seawater. The electrode is used as a resistance element of the return circuit, and the oscillation circuit is configured to oscillate at a frequency corresponding to the conductive resistance when the pair of electrodes is immersed in seawater. sensor.