JPH0412454Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a composite electrode for concentration detection, and particularly to a composite electrode for concentration detection having a sensing electrode and a reference electrode connected to a female coaxial connector.

Conventional technology PH for process control and water quality monitoring of water and sewage water, etc.
Meters and other densitometers are widely used. Sensing electrodes and reference electrodes used in concentration meters such as PH meters inevitably deteriorate in characteristics with use, so it is necessary to make both electrodes convertible. Generally, sensitive electrodes (eg, glass electrodes) have very high output impedances, so that highly insulated cables must be used to connect the electrodes to the transducer. However, the conventional structure has the drawback that during cable wiring work, the cable ends and terminals, which should be highly insulated, are touched by hands or dirt is deposited on them, degrading the insulation and causing measurement errors.

To avoid this drawback, sensitive electrodes, reference electrodes,
A composite electrode has been proposed in which all of the temperature-sensitive resistance elements for temperature compensation are detachable. However, since the stability of the temperature-sensitive resistance element is very high, if the temperature-sensitive resistance element was also made detachable, the structure would be unduly complicated and handling would be inconvenient. Additionally, although there is an advantage in terms of parts economy in replacing the sensitive electrode and reference electrode individually, it is difficult to judge which electrode should be replaced if you are not skilled in measuring concentrations such as PH. In reality, both electrodes are often replaced at the same time, and maintenance is time-consuming, which is not necessarily advantageous. Further, in conventional composite electrodes, the terminal of the element to be replaced is male, and the terminal on the main body side that is to hold the element is female, so that the main body terminal cannot be easily cleaned.

The combination of sensitive and reference electrodes is used to detect concentrations other than PH, especially ionic indices. pH
The above-mentioned drawbacks that are particularly recognized regarding the electrodes of the meter are:
Similar conditions exist in the case of other concentration detection electrodes.

Purpose of the Invention Accordingly, the purpose of the present invention is to solve the above-mentioned drawbacks of the prior art by providing a composite electrode for concentration detection that is detachable and easy to maintain.

Structure of the invention In order to achieve the above object, the composite electrode for concentration detection according to the invention includes a cylindrical electrode element having a glass membrane at the tip and a built-in reference electrode and a sensitive electrode; an outer cylinder to be held; a female coaxial connector fixed to a sealing cover at one end of the outer cylinder and connected to the sensing electrode and the reference electrode; and a female coaxial connector detachably connected to the other end of the outer cylinder and facing the glass membrane. a holding member having an opening for opening, a liquid junction held between the holding member and the vicinity of the tip of the electrode element and defining a closed space between the outer cylinder and the reference electrode, and the inside of the closed space. A configuration comprising an intermediate internal liquid filled with a liquid is used.

EXAMPLE The present invention will be explained in detail below with reference to the attached drawings in the case of a composite electrode for PH detection.
It is not limited to PH detection. The embodiment shown in the schematic cross-sectional view of FIG. 1 is a signal conversion type PH detector using a composite electrode according to the present invention. A converter chamber 4 is provided. Electrode chamber 3
holds the cartridge-shaped composite electrode 5 of the present invention in a detachable manner. In the illustrated embodiment, in order to securely hold the composite electrode 5, the threaded portion 6a of the electrode cover 6 is screwed into the threaded portion 1a of the casing 1.
An inner protrusion 7 of the electrode cover 6 keeps the enlarged portion 8 of the composite electrode 5 in a position in contact with the lower end of the casing 1.

FIG. 2 shows an example of the composite electrode 5 according to the present invention. An electrode element 10 is attached to an O-ring 11 inside the outer cylinder 9.
are held coaxially through the An example of the electrode element 10 shown in FIG. 3 will be described, but the present invention is not limited to the electrode element 10 having the structure shown in FIG.
The outer tube 12 of the electrode element 10 has an inner tube 13 at its lower end.
A buffer solution 14, such as a potassium chloride solution, is sealed in the inner tube 13. The inner pole 15a of the sensitive electrode 15 is in contact with the buffer solution 14 in the inner tube 13, and the glass membrane 16 is attached to the lower end of the inner tube 13. The outer tube 12 is provided with a pinhole 17 (exaggerated) through which an internal liquid 18, such as a potassium chloride solution, sealed in the outer tube 12 communicates with the outside of the electrode element 10. be done. It is sufficient that the pinhole 17 connects the inside and outside of the electrode element 10, and does not necessarily need to be a liquid junction with low internal liquid consumption. The inner electrode 19a of the comparison electrode 19 is placed within the internal liquid 18. A voltage is generated between the sensitive electrode 15 and the reference electrode 19, which is substantially related only to the difference in hydrogen ion activity between the inside and outside of the glass membrane 16.

Both inner poles 15a, 19a of the electrode element 10 are connected to the core wire 21 and outer circumferential conductor 22 of the female coaxial connector 20 of the composite electrode 5 via lead wires 15b, 19b. In the illustrated example, the sensitive electrode lead wire 15b within the internal liquid 18 is protected by a protective tube 15c. In the example of FIG. 2, the sensitive inner pole 15a is connected to the core wire 21, and the comparison inner pole 19a is connected to the outer conductor 22.
By connecting the terminal to the reference electrode 19, the terminal of the sensitive electrode 15, which has a high internal impedance, is covered with the terminal of the comparison electrode 19, thereby preventing induction interference from the outside as much as possible.

The female coaxial connector 20 is attached to the sealing cover 2 of the outer cylinder 9.
3. Preferably, an insulator 24 such as epoxy resin is sealed between the top of the electrode element 10 and the sealing cover 23. In order to prevent the test liquid from entering the female coaxial connector 20, an O-ring 25 is appropriately fitted around the outer periphery of the outer cylinder 9, if necessary.

In the illustrated composite electrode 5, a preferably ceramic liquid junction 26 is formed between the lower end of the outer cylinder 9 and the electrode element 10. According to the present invention, the liquid junction portion 26 is detachably held by a restraining member 37 shown in FIG. Electrode element 10 above this liquid junction 26
The electrode element 1 is preferably placed in the space between the outer cylinder 9 and the outer cylinder 9.
An intermediate internal liquid 28, such as a potassium chloride solution, is filled with the same internal liquid 18 in 0. The inner electrode 19a of the comparison electrode 19 is connected to the test liquid via both the internal liquid 18 in the electrode element 10 and the intermediate internal liquid 28,
When the pinhole 17 is a liquid junction, a so-called double junction structure is formed. In the case of a double junction structure, the intermediate internal liquid 28
For example, the liquid may be ammonium nitrate and may be different from the internal liquid 18 in the electrode element 10. The electrode cover 6 has an opening 29 (FIG. 1) through which the test liquid passes.

To explain how it is used, when the composite electrode 5 is inserted into the casing 1 as shown in FIG. 1, the male coaxial connector 30 attached to the wall 2 and the female coaxial connector 20 of the composite electrode 5 are fitted, and the core wire 21 and outer conductor 22 of the female coaxial connector are connected to the core wire 31 and outer conductor 32 of the male coaxial connector 30, respectively. The signal converter 33 arranged in the converter chamber 4 of the casing 1 generates a potential difference between the sensitive electrode 15 and the reference electrode 19 that is proportional to the pH value of the test liquid and has a high internal impedance. , which converts the signal into a signal with low internal impedance. For temperature compensation of measured values, a temperature-sensitive resistance element 34 such as a thermistor is installed on the outer peripheral wall of the casing 1.
This temperature-sensitive resistance element 34 and the coaxial connector 30 are connected to the signal converter 33 by the lead wire 35.
Connect to. A pull-out cable 36 is directly connected to the signal converter 33 , and driving power is supplied to the signal converter 33 and output is sent from the signal converter 33 via the pull-out cable 36 .

In the present invention, the restraining member 37 shown in FIG.
This makes the liquid junction part 26 detachable, protects the glass membrane 16 during transportation, and facilitates replenishment of the internal liquid 18. That is, screws 9a and 37a are attached to the lower end of the outer cylinder 9.
A removable restraining member 37 is attached using a method such as the following, and a packing 38 is inserted between the ceramic liquid junction 26, the electrode element 10, and the outer cylinder 9. The holding member 37 is provided with an opening 37b to ensure contact between the glass membrane sensitive electrode and the test liquid.

Effects of the invention As explained above, the composite electrode according to the invention has
Since the sensing electrode and the reference electrode are connected to a female coaxial connector, the following effects are achieved.

(a) Since the connector of the composite electrode on the side to be replaced is a female type, and the connector on the side that is used repeatedly and is difficult to move is a male type, cleaning and other maintenance work is easy.

(b) It is possible to provide a composite electrode in which the sensitive electrode glass membrane, which is easily damaged, is protected by the holding member and the electrode cover, and which is easy to handle.

(c) Composite electrodes whose characteristics inevitably change due to use can be easily replaced while maintaining high measurement accuracy.

(d) It can be easily made into a shape that is convenient to handle, such as a cartridge type, and can be easily incorporated into various pH meters.

(e) Since the liquid junction is made of relatively large ceramic and has a surface area several hundred times larger than that of conventional liquid junctions, clogging is less likely to occur.

(f) The structure can be such that the liquid junction itself can be easily replaced.

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view of a signal conversion type pH detector.
FIG. 2 is a schematic sectional view of one embodiment of the composite electrode, FIG. 3 is a schematic sectional view of an electrode element, and FIG. 4 is an explanatory diagram of another embodiment of the composite electrode. 5...Composite electrode, 6...Electrode cover, 7...Inner projection, 8...Enlarged portion, 9...Outer tube, 10...Electrode element, 11, 25...O ring, 12...Outer tube , 13... Inner tube, 14... Buffer solution, 15... Sensitive electrode, 16... Glass membrane, 17... Pinhole, 18... Internal solution, 19... Reference electrode, 20...
... Female coaxial connector, 21 ... Core wire, 22 ... Outer conductor, 23 ... Sealing cover, 24 ... Insulator,
26...Liquid junction, 28...Intermediate internal liquid, 29...
Opening, 37... Retaining member, 38... Packing.

Claims (1)

[Scope of utility model registration request] A cylindrical electrode element having a glass film at the tip and containing a comparison electrode and a sensitive electrode, an outer cylinder that concentrically holds the electrode element, a sealing cover at one end of the outer cylinder, and a cylindrical electrode element that is fixed to a sealing cover at one end of the outer cylinder and includes the sensitive electrode and a female coaxial connector connected to a reference electrode; a holding member detachably connected to the other end of the outer cylinder and having an opening facing the glass membrane; and a space between the holding member and the vicinity of the tip of the electrode element. A composite electrode for concentration detection, comprising: a liquid junction held in the outer tube to define a closed space between the outer cylinder and the reference electrode; and an intermediate internal liquid filled in the closed space.