JPH0417378B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a PH meter. In particular, the present invention
A signal conversion type PH detector in which a composite electrode having a sensing electrode and a reference electrode connected to a female coaxial connector is detachably held is sealed at one end of a cylindrical holder,
Relating to a PH meter in which an indicating regulator having an adjusting means and an indicator is attached to the other end of a cylindrical holder, and a cable between the signal conversion type PH detector and the indicating regulator is inserted into the cylindrical holder. .

Conventional technology In conventional PH meters, the PH detector and indicator controller are installed separately without being mechanically connected, in order to facilitate replacement of the glass electrode, etc., and the two are electrically connected using a highly insulated cable. It is customary to do so. If the PH detector is located far from the indicator controller, calibration using a standard solution is performed using the PH detector immersed in the standard solution.
Because there is a distance between the detector position and the indicator controller position that monitors and adjusts the calibration status, some means of communication is required between the two positions, which not only makes the calibration work troublesome but also requires a single worker. The disadvantage arises that it is difficult to calibrate. Furthermore, the PH detector is susceptible to induction due to its high internal impedance, but it has the disadvantage of being exposed to many noise sources and increasing induction disturbances, especially when the distance between the PH detector and the indicating controller is long.

OBJECTS OF THE INVENTION Accordingly, an object of the present invention is to provide a PH meter with an integral structure in which a signal conversion type PH detector and an indicating regulator, which detachably hold a composite electrode, are combined by a cylindrical holder. The aim is to solve the above-mentioned drawbacks of the prior art.

Structure of the Invention In order to achieve the above object, the present invention includes the following:
A sensing electrode and a reference electrode are connected to a female coaxial connector to form a composite electrode, and the composite electrode is detachably connected to a casing having a temperature-sensitive resistance element and a signal converter to form a signal conversion type PH detector. do. Here, the signal converter converts the potential difference between the sensitive electrode and the reference electrode, which is proportional to the pH value of the test liquid and has a high internal impedance, into a low internal impedance signal, and also Temperature compensation is performed using a resistance element. This signal conversion type PH detector is sealed at one end of a cylindrical holder. At the other end of the cylindrical holder, an indicating regulator consisting of an asymmetric potential difference adjusting means, a span adjusting means, and an indicator is attached. Further, a cable between the signal conversion type PH detector and the indicating regulator is inserted into the inside of the cylindrical holder to form an integrally constructed PH meter.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In FIG. 1 showing a schematic cross-sectional view of one embodiment, the PH meter includes a signal conversion type PH detector E, an indicating regulator I, and a tube connecting the signal converting type PH detector E and indicating regulator I. It consists of a shaped holder H.

In the embodiment shown in the figure, an electrode chamber 3 and a converter chamber 4 separated by a wall 2 are provided inside a casing 1 of a signal conversion type PH detector E. The electrode chamber 3 holds a cartridge-shaped composite electrode 5 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
is screwed onto the threaded portion 1a of the casing 1, and the enlarged portion 8 of the composite electrode 5 is kept in a position in contact with the lower end of the casing 1 by the inward protrusion Z of the electrode cover 6.

FIG. 2 shows an example of the cartridge-type composite electrode 5. A plastic sleeve 9 coaxially holds an electrode element 10 therein. Preferably O
The ring 11 seals the contact portion between the upper part of the electrode element 10 and the outer tube 9 . O-ring 11 may be omitted if sufficient sealing is achieved with adhesive.

Although FIG. 3 shows one example of the electrode element 10, the present invention is not limited to the electrode element 10 having the structure shown in the figure. The outer tube 12 of the electrode element 10 holds an inner tube 13 at its lower end, and a buffer solution 14 such as a potassium chloride solution is sealed in the inner tube 13 . Buffer solution 14 in inner tube 13 and inner pole 15 in contact with it
a, and a glass film 16 attached to the lower end of the inner tube 13 constitute a sensitive electrode 15. Outer tube 12
A liquid junction 17 is provided in the outer tube 12 , and the internal liquid 18 sealed in the outer tube 12 is communicated with the outside of the electrode element 10 via the liquid junction 17 . An inner electrode 19a is placed in the internal liquid 18 to form a comparison electrode 19. 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 appropriately 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 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 cover 23 of the outer cylinder 9. Preferably, an insulator 24 such as epoxy resin is placed between the top of the electrode element 10 and the cover 23.
Enclose. To prevent the test liquid from entering the female coaxial connector 20, install the O-ring 25 as necessary.
is fitted to the outer periphery of the outer cylinder 9 as appropriate.

In the illustrated composite electrode 5, an auxiliary liquid junction 26, preferably of ceramic type, is formed between the lower end of the outer cylinder 9 and the electrode element 10. An intermediate internal liquid 28 such as ammonium nitrate is sealed in the space between the electrode element 10 and the outer cylinder 9 above the auxiliary liquid junction 26 . In this case, the inner pole 19a of the comparison electrode 19
However, the internal liquid 18 in the electrode element 10 and the intermediate internal liquid 2
A so-called double junction structure is used in which the test liquid is communicated through both of the two. The electrode cover 6 has an opening 29 (first
Figure). The composite electrode 5 in FIG.
Although two liquid junction parts, ie, the liquid junction part 7 and the auxiliary liquid junction part 26, are provided, the present invention is not limited to this embodiment. That is, only the liquid junction 17 may be used, or the liquid junction 17 may be omitted and only the auxiliary liquid junction 26 may be used as the liquid junction.

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 fit together, and The core wire 21 of the coaxial connector and the outer conductor 22 are the core wire 3 of the male coaxial connector 30.
1 and the outer circumferential conductor 32, respectively. In the illustrated example, the metal pipe 33 is connected to the converter chamber 4 of the casing 1.
The signal converter 34 is disposed therein. If the casing 1 is made of metal, the liquid earthing described below may be performed directly through the casing 1, and the metal pipe 33 may be omitted. In the illustrated example, a temperature-sensitive resistance element 35 such as a thermistor is attached to the outer peripheral wall of the casing 1 for temperature compensation of measured values. This temperature-sensitive resistance element 35 and the coaxial connector 30 are connected to the signal converter 3 by a lead wire 36.
Connect to 4. In the embodiment shown in FIG. 1, the metal case 37 holding the temperature-sensitive resistance element 35 is
3, and the metal case 37 is liquid grounded to the test liquid L as shown in FIG. 5, so the signal converter 34 is electrically protected from external noise.

In the illustrated example, the metal case 37, which is embedded in the wall surface of the casing 1 around the converter chamber 4 and holds the temperature-sensitive resistance element 35, transmits the temperature of the test liquid L to the temperature-sensitive resistance element 35. Preferably, metal pipe 33
The interior is filled with an insulating material 38 such as epoxy resin.
A pull-out cable 39 is directly connected to the signal converter 34, and the drive power supply to the signal converter 34 and the output output from the signal converter 34 are carried out by this pull-out cable 3.
9. Signal converter 3 if necessary
4 and the extraction cable 39 may be provided with a suitable connector (not shown).

FIG. 5 is an electrical circuit diagram showing the basic configuration of this PH meter, in which the sensitive electrode 15 is connected to one input of the amplifier A1 of the signal converter 34, and the reference electrode 19 is connected to one input of the amplifier A1 of the signal converter 34.
is connected via a resistor R to the other input of the amplifier A1. A temperature-sensitive resistance element 3, such as a thermistor, which is connected to the output of the amplifier A1 through series resistors _R1 and _R2 to the other input of the amplifier A1, and has a resistance value Rt.
5 is connected in parallel to the resistor _R1 via a resistor _R3 .
Resistance values of the above resistors R ₁ , R ₂ , R ₃ and thermistor
Since Rt is essentially a pure resistance, it is clear that they can be converted into a single equivalent resistance value Rf as shown in FIG.

Further referring to FIG. 1, the signal conversion type PH detector E having the above configuration is sealed at the lower end of the cylindrical holder H with a sealing portion 40. As shown in FIG. This sealing portion 40 prevents the test liquid from entering into the cylindrical holder H. The upper end of the cylindrical holder H has an instrument case 4 of the indicator controller I.
1 are screwed together, and the screwing is reinforced by a cap nut 42. In order to prevent water from entering the inside of the cylindrical holder H from this threaded portion, a packing 43 is inserted between the upper edge of the cylindrical holder H and the instrument case 41.

The instrument case 41 has an internal space that is closed by an instrument cover 44, preferably via an O-ring 44a. Two printed wiring boards 46 are held in this internal space by studs 45. The upper end of the lead-out cable 39 from the signal converter 34 of the signal conversion type PH detector E is connected to an internal connection terminal 47 fixed to one printed wiring board 46. An internal connector 48 connects the internal connection terminals 47 to the other printed wiring board 46 with an indication adjustment circuit 49.
and connected to the indicator 50.

Referring to FIG. 4, the value indicated by the liquid crystal of the indicator 50 is displayed on the transparent window 5 made of glass or plastic.
It is read externally through 1. An asymmetric potential difference adjustment resistor Z and a span adjustment resistor S (FIG. 1), which constitute a part of the indication adjustment circuit 49 attached to the other printed wiring board 46, are located below the transparent window 51 of the instrument case 41. It has an adjustment screw 52 protruding from the surface.

As shown in FIGS. 1 and 4, the extraction cable 39 is also connected to an external output circuit 53 and an external connection terminal 54 via an internal connection terminal 47.
From this external connection terminal 54, an external cable (not shown) can be led out of the PH meter via a cable hole 55 and a conduit 56.

Still referring to FIG. 5, the signal from the signal converter 34 of the PH detector E is connected via a span adjustment resistor S to one input of the amplifier A2. The output of amplifier A2 is applied to indicator 50 and also to external output circuit 53. Amplifier A2
has a negative feedback resistor Ro. An asymmetric potential difference adjusting resistor Z, which is a voltage dividing resistor, is connected to the other input of the amplifier A2. The power supply V1 is connected to the amplifier A2 of the indication adjustment circuit 49 and the amplifier A1 of the signal converter 34. In the case of the configuration shown in FIG. 5, the number of core wires of the pull-out cable 39 is sufficient to be four.

To explain the operation with reference to FIGS. 5 and 6,
When the PH detector E of the PH meter in FIG. 1 is immersed in the test liquid L, the glass membrane 16 of the sensitive electrode 15 comes into contact with the test liquid, and the reference electrode 19 It is connected to the test liquid L via the junction 17 , the intermediate internal liquid 28 , and the auxiliary liquid junction 26 . Therefore, the glass film 16 shown in FIG.
A potential difference corresponding to the difference in PH value between both sides, that is, the difference between the known PH of the buffer solution 14 and the PH of the test solution, is generated, and this potential difference is the input potential difference Vi of the amplifier A1 of the signal converter 34 in FIG. becomes. Since the internal resistance of the sensitive electrode 15 is extremely high and its output current is extremely small,
The output voltage Vo of the signal converter 34 is given by the following equation.

Vo={1+(Rf/R)}Vi (1) As is clear from equation (1), the output Vo of the signal converter 34 is the difference between the PH value of the test liquid and the PH value of the known buffer solution 14. Since it is proportional to the potential difference Vi, this output Vo indicates the PH value of the test liquid.

Furthermore, as is clear from the Nernst equation, the change in the output of the PH detector with the above configuration due to temperature change is given as a change in the slope of the potential difference Vi line passing through the isothermal intersection, so the temperature compensation of the PH measurement value is , is achieved by changing this slope depending on the temperature of the sample liquid at the time of measurement. As shown in equation (1), the output Vo of the signal converter has a slope proportional to the equivalent resistance value Rf with respect to the potential difference Vi. If it is changed appropriately, the above-mentioned potential difference Vi that is changed in accordance with the temperature of the test liquid can be represented as a straight line as the output Vo. Temperature-sensitive resistance element 35 such as a thermistor
Since the resistance value Rf changes in response to changes in the temperature of the test liquid, if the equivalent resistance value Rf is set to an appropriate value by selecting the resistances _R1 to _R3 , the test liquid after temperature correction The PH value can be shown as the output Vo. Therefore, the signal converter 34 in FIG. 5 generates, as the output voltage Vo, a value obtained by adding temperature correction to the measured potential difference between the sensitive electrode 15 and the comparison electrode 19, which is proportional to the PH value of the sample liquid.

The output Vo of the signal converter 34 is transmitted to the indicator 50 via the pull-out cable 39, internal connection terminal 47, internal connector 48, and indicator adjustment circuit 49 shown in FIG.
The value of the output Vo is read as a digital display on, for example, a liquid crystal display in front of the indicating controller I in FIG.

In the above description, a thermistor was used as an example of the temperature-sensitive resistance element 35, but the temperature-sensitive resistance element 35 of the present invention is not limited to a thermistor.
However, it goes without saying that the circuit configuration and circuit constants shown in FIG. 5 are changed depending on the temperature characteristics of the resistance value change of the temperature-sensitive resistance element 35.

Referring to FIG. 7, the asymmetric potential difference adjustment is performed by immersing the signal conversion type PH detector E in a standard solution of PH7, and turning the adjusting screw 52 of the asymmetric potential difference adjusting resistor Z in front of the indicating controller I. This can be easily done by translating the unadjusted characteristic shown by the dotted line in the figure to the characteristic shown by the chain line. This asymmetric potential difference adjustment is
This is carried out periodically during preparation for and during measurement. Furthermore, for span adjustment, the signal conversion type PH detector E is immersed in a standard solution of the required PH value, and the adjustment screw 5 of the span adjustment resistor S is inserted in front of the indicator controller I.
This can be easily done by rotating the chain line and tilting the characteristic shown by the chain line to the required characteristic shown by the solid line.

Effects of the Invention As explained above, the PH meter according to the present invention includes a specific PH detector in which a composite electrode having a sensing electrode and a reference electrode is removably fitted, and a specific indication adjustment device in which an adjusting means and an indicator are attached. Since the container is integrally connected with the cylindrical holder, the following effects are achieved.

(a) Since the PH detector and indicator controller are integrated, calibration work using standard solutions can be easily performed by a single worker.

(b) In a PH meter in which a PH detector and an indicating regulator are integrally connected by a cylindrical holder, the PH detector and indicating regulator can be connected with an economical low-insulation cable.

(c) The output from the PH detector is converted into a signal and has a low internal impedance, and the lead-out cable between the PH detector and indicator controller has low insulation and is short, so this part Measurement errors due to insulation deterioration in the sensor reduce externally induced errors, and their synergistic effect makes it possible to obtain high measurement accuracy.

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

(e) A highly reliable connection can be obtained if the pull-out cable is directly connected to the signal converter.

(f) It can be easily applied to the measurement of ion indices other than PH by simply replacing the electrode element.

[Brief explanation of drawings]

Fig. 1 is a schematic sectional view of the PH meter, Fig. 2 is a schematic sectional view of the composite electrode, Fig. 3 is a schematic sectional view of the electrode element, Fig. 4 is a schematic front view of the indicating regulator, and Fig. 2 is a schematic sectional view of the composite electrode. 5
6 and 6 are explanatory diagrams of the electric circuit, and FIG. 7 is an explanatory diagram of the adjustment operation. DESCRIPTION OF SYMBOLS 1... Casing, 2... Wall, 3... Electrode chamber, 4... Transducer chamber, 5... Composite electrode, 6... Electrode cover, 7... Inner projection, 8... Enlarged part, 9 …
... Outer cylinder, 10 ... Electrode element, 11, 25 ... O ring, 12 ... Outer tube, 13 ... Inner tube, 14 ... Buffer solution, 15 ... Sensitive electrode, 16 ... Glass membrane, 1
7... Liquid junction, 18... Internal liquid, 19... Reference electrode, 20... Female coaxial connector, 21, 31...
Core wire, 22, 32... Outer conductor, 23... Cover, 24, 38... Insulator, 26... Auxiliary liquid junction, 28... Intermediate internal liquid, 29... Opening, 30...
...Male coaxial connector, 33...Metal pipe, 34
...Signal converter, 35...Temperature-sensitive resistance element, 36...
... Lead wire, 37 ... Metal case, 39 ... Pull-out cable, 40 ... Sealing part, 41 ... Instrument case, 42 ... Cap nut, 43 ... Packing, 4
4...Instrument cover, 45...Stud, 46...
Printed wiring board, 47...Internal connection terminal, 48...Internal connector, 49...Indication adjustment circuit, 50...Indicator, 51...Transparent window, 52...Adjustment screw, 53
...External output circuit, 54...External connection terminal, 5
5... Cable hole, 56... Conduit, E...
Signal conversion type PH detector, G... Cylindrical holder, I...
Indication regulator, S...span adjustment resistance, Z...asymmetric potential difference adjustment resistance.

Claims (1)

[Claims] 1 PH detection consisting of a composite electrode having a sensing electrode, a reference electrode, and a female coaxial connector connected to both electrodes, and a casing that detachably holds the composite electrode and has a temperature-sensitive resistance element and a signal converter. an indicating regulator having an asymmetric potential difference adjusting means, a span adjusting means, and an indicator; and the PH detector is sealed at one end, the indicating regulator is coupled to the other end, and the PH detector and the indicating regulator are sealed inside. A PH meter comprising a cylindrical holder into which a cable is inserted for connecting to the indicator controller.