pH electrode

Abstract

To provide a pH electrode capable of detecting that surface stain and the like deteriorate responsiveness and accuracy of measurement and removing the surface stain.SOLUTION: A pH electrode including a glass film 4 provided at a tip of a probe 1 comprises, in the probe 1, a light-emitting element 21 for irradiating the glass film 4 with light, and a light receiving element 22 for receiving reflected light from the glass film 4, and is configured to detect stain attached to the glass film on the basis of an amount of received light of the light receiving element 22. The glass film 4 includes photocatalyst on its outer surface and is irradiated by the light-emitting element 21 with UV light. UV emission amount is increased when the amount of received light of the light receiving element 22 is large.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pH electrode, and more particularly to a pH electrode in which a photocatalyst such as titanium oxide is attached to the outer surface of a glass membrane. [Background technology]

[0002] If dirt adheres to the glass membrane of a pH electrode, the sensitivity of the pH electrode will decrease and errors in the measurement values ​​will increase. As a countermeasure, Patent Document 1 and Non-Patent Document 1 describe a method of attaching titanium oxide to the outer surface of the glass membrane of a pH electrode to give the pH electrode a self-cleaning function.

[0003] Non-Patent Document 1 further describes that an LED is placed inside a pH electrode, and UV (ultraviolet light) is irradiated onto titanium oxide to promote the photocatalytic reaction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4876123 [Non-patent literature]

[0005] [Non-Patent Document 1] Journal of the academic journal "EICA" Vol. 23, No. 2 & 3 (2018) P. 69 Summary of the Invention [Problem to be solved by the invention]

[0006] Even if titanium oxide or even UV LEDs are provided on the glass film, it is not possible to completely prevent the glass film from becoming dirty, and dirt will gradually accumulate on the surface of the glass film.

[0007] An object of the present invention is to provide a pH electrode that can detect a decrease in measurement response or accuracy due to surface contamination of the glass membrane, and can remove the surface contamination. [Means for solving the problem]

[0008] [1] In a pH electrode where a glass membrane is provided at the tip of the probe, a light-emitting element for irradiating light toward the glass film and a light-receiving element for receiving light reflected from the glass film are provided within the probe; A pH electrode that detects the adhesion of dirt to a glass membrane based on the amount of light received by a light-receiving element.

[0009] [2] The pH electrode according to [1], wherein the light-emitting element is a UV light-emitting element and a photocatalyst is attached to the outer surface of the glass film.

[0010] [3] The pH electrode of [2], further comprising a control means for comparing the amount of light received by the light-receiving element with a reference value and increasing the amount of UV light emitted by the light-emitting element when the amount of light received is equal to or greater than the reference value.

[0011] [4] A pH measurement method using the pH electrode of [3], in which the light-emitting element is constantly operated during pH measurement, and the amount of light emitted by the light-receiving element is increased for a predetermined period when the amount of light received by the light-receiving element exceeds a reference value.

[0012] [5] The pH measurement method using the pH electrode according to [3], wherein the light-emitting element is intermittently operated during pH measurement; A pH measurement method in which the light-emitting element's light-emitting time is extended when the amount of light received by the light-receiving element during operation of the light-emitting element exceeds a reference value. [Effects of the Invention]

[0013] In the present invention, a light-emitting element and a light-receiving element are provided inside the pH electrode, and the light-receiving element receives reflected light from the glass film. If the amount of light received increases to or exceeds a predetermined value, it is determined that contamination has occurred on the glass film.

[0014] In one embodiment of the present invention, a photocatalyst is provided on the glass film, and when a predetermined level of contamination is detected, the amount of UV radiation from the UV light-emitting element provided in the pH electrode to the glass film is increased, thereby enhancing the self-cleaning function of the photocatalyst and restoring the cleanliness of the glass film. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 2 is a cross-sectional view of a probe of a pH electrode according to an embodiment. [Figure 2] FIG. 2 is a block diagram of an LED control system of a pH electrode according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment will be described with reference to FIGS.

[0017] FIG. 1 shows the structure of a probe 1 of a pH electrode according to an embodiment, and is a cross-sectional view excluding an end portion 8 on the base end side.

[0018] The probe 1 has an outer tube 2 and an inner tube 3, each made of glass, and a glass membrane 4. The tips of the outer tube 2 and the inner tube 3 are sealed by a sealing part 3a, which separates a chamber 5 between the outer tube 2 and the inner tube 3 and a chamber 6 inside the inner tube 3. A liquid junction 7 is provided in the outer tube 2. The chamber 6 extends into the glass membrane 4 and into the tip of the probe.

[0019] Silver / silver chloride internal electrodes (internal electrodes) 11 and 13 are disposed in the chambers 5 and 6, respectively, and their detected potentials are taken out via lead wires 11a and 13a.

[0020] A temperature compensation temperature sensor 12 is also disposed in the chamber 5, and a detection signal is taken out via a lead wire 12a.

[0021] Titanium oxide is attached to the outer surface of the glass film 4 as a photocatalyst. The titanium oxide may be in the form of fine particles or a porous film. The photocatalytic action of this titanium oxide provides a self-cleaning function to the outer surface of the glass film 4. In particular, in this embodiment, the self-cleaning function is enhanced by irradiation with UV light from a light-emitting element 21, which will be described next. On the inner side of the glass film 4, there are disposed a light-emitting element 21 that irradiates UV light toward the glass film 4, and a light-receiving element (photodiode) 22 that receives light reflected from the glass film 4. Lead wires 21a and 22a are connected to each element 21 and 22.

[0022] The chambers 5 and 6 are filled with a potassium chloride solution adjusted to pH 7. The pH is detected based on the outputs of the internal electrodes 11 and 13 and the temperature detected by the temperature sensor 12.

[0023] 2 is a block diagram showing a drive system for the light-emitting element 21 and the light-receiving element 22. An oscillation frequency signal from an oscillator 31 provided in the converter 30 and a light-emitting intensity instruction signal from a calculation unit 34 are supplied to a driver 32, and a drive current is supplied from the driver 32 to the light-emitting element 21 via a lead wire 21a, causing the light-emitting element 21 to irradiate UV light toward the inner surface of the glass film 4.

[0024] When there is no dirt on the outer surface of the glass film 4, the amount of light reflected from the glass film 4 is small. As the amount of dirt on the outer surface of the glass film 4 increases, the amount of light reflected from the glass film 4 increases.

[0025] The light receiving element 22 transmits a light receiving signal corresponding to the amount of reflected light via the lead wire 22a. This light receiving signal is transmitted to the band pass filter 23 in the end portion 8, and the signal in a predetermined frequency band passes through the band pass filter 23 and is amplified by the amplifier 24, after which it is converted into a digital signal by the A / D converter 33 and input to the calculation unit 34. The calculation unit 34 provides a control signal to the driver 32 based on the light receiving amount signal.

[0026] An oscillation signal of a specific frequency (for example, 1 kHz) is output from oscillator 31 to driver 32. In response to a signal from calculation unit 34, a current signal of a specific level sufficient for light-emitting element 21 to emit light is modulated by the frequency from oscillator 31 and sent to light-emitting element 21, causing light-emitting element 21 to emit light.

[0027] The UV light emitted from the light-emitting element 21 activates the photocatalyst on the outer surface of the glass film 4, suppressing the adhesion or proliferation of organic matter and microorganisms on the outer surface of the glass film 4. When this self-cleaning function is fully effective, the outer surface of the glass film 4 is kept clean, and most of the UV light from the light-emitting element 21 is transmitted through the glass film 4 and released into the water, so the level of scattered light generated at the boundary between the glass film 4 and the water is weak.

[0028] If, for some reason, the rate at which organic matter and other substances adhere or multiply on the surface of the glass film 4 exceeds the self-cleaning function due to the oxidation action of the photocatalyst, and the amount of organic matter and other contaminants adhering to the surface of the glass film 4 increases, the amount of scattering on the surface of the glass film 4 increases due to these contaminants, the amount of light received by the light receiving element 22 increases, and the output signal level from the light receiving element 22 increases.

[0029] In general, in environments where pH electrodes are used, natural light or indoor light may be incident on the measurement environment, and UV light with the same wavelength as UV may also be present. However, because the output signal is a signal modulated at a specific frequency as described above, only scattered light is extracted by a filter 23 that extracts only specific frequencies. This is then amplified by an amplifier 24, converted into a digital signal by an A / D converter 33, and input to a processing unit (CPU) 34.

[0030] The calculation unit 34 compares this input signal level with a predetermined threshold level. If the level of scattered light from the surface of the glass film 4 rises above the threshold level, it is determined that the contamination on the surface of the glass film 4 has increased above a predetermined value. The calculation unit 34 then instructs the driver 32 to increase the output current to increase the irradiation amount, or, if UV irradiation is being performed intermittently, to extend the irradiation time (increase the light emission duty ratio).

[0031] This operation increases the amount of UV light irradiated from the light emitting element 21 onto the surface of the glass film 4, improving the activity of the photocatalytic oxidation on the surface of the glass film 4 and removing the dirt. After a predetermined time, the irradiation unit 34 repeats the operation of determining the state of dirt based on the amount of scattered light from the surface of the glass film 4.

[0032] In the above embodiment, a photocatalyst is provided on the glass film 4, but the photocatalyst may be omitted in the present invention. In this case, the light-emitting element 21 and the light-receiving element 22 can still detect dirt on the outer surface of the glass film 4. In this case, the light-emitting element may be one that emits visible light. [Explanation of symbols]

[0033] 1 probe 2 outer tube 3 Inner tube 4 Glass membrane 11,13 Internal electrode 12 Temperature sensor for temperature compensation 21 Light-emitting element 22 Photodetector

Claims

1. In a pH electrode in which a glass membrane is provided at the tip of the probe, a light-emitting element for irradiating light toward the glass film and a light-receiving element for receiving light reflected from the glass film are provided within the probe; A pH electrode characterized in that it detects the adhesion of dirt to a glass membrane based on the amount of light received by a light-receiving element.

2. 2. The pH electrode according to claim 1, wherein said light-emitting element is a UV light-emitting element, and a photocatalyst is attached to the outer surface of said glass film.

3. 3. The pH electrode according to claim 2, further comprising a control means for comparing the amount of light received by said light receiving element with a reference value, and increasing the amount of UV light emitted by said light emitting element when the amount of light received is equal to or greater than the reference value.

4. 4. A method for measuring pH using a pH electrode according to claim 3, wherein the light-emitting element is constantly operated during pH measurement, and when the amount of light received by the light-receiving element exceeds a reference value, the amount of light emitted by the light-emitting element is increased for a predetermined period of time.

5. 4. The method for measuring pH using a pH electrode according to claim 3, further comprising intermittently activating the light-emitting element during pH measurement, A pH measurement method in which the light-emitting element's light-emitting time is extended when the amount of light received by the light-receiving element during operation of the light-emitting element exceeds a reference value.

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