JPS5940258B2 - electrolyte analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrolyte analyzer, and more particularly to an electrolyte analyzer equipped with an ion-selective electrode suitable for measuring test liquids containing various ions.

FIG. 1 is a schematic configuration diagram for explaining the principle of an electrolyte analyzer.

An ion selective electrode 2 having an ion detection membrane 10 and a reference electrode 4 having a liquid junction 9 are inserted into a sample liquid 1 contained in a container 8 . The ion selective electrode 2 is connected to an amplifier 6 via a signal line 3, and the comparison electrode 4 is connected to an amplifier 6 via a signal line 5. The potential difference generated between the ion selective electrode 2 and the comparison electrode 4 depending on the ion concentration contained in the sample liquid 1 is displayed on the display device T. When operating an electrolyte analyzer having such a configuration, the operator himself becomes a source of noise, and the operator's actions cause measurement errors.

The reason for this is that the internal resistance of the ion-selective electrode is extremely high. Table 1: Internal resistance of ion-selective electrodes Table 1 shows examples of internal resistances of ion-selective electrodes, but even though the internal resistance of the signal line is this high, the level of the output signal based on the sample is is small.

Therefore, induced noise due to changes in various external electromagnetic fields entering the signal line is too large to be ignored as a measurement error. On the other hand, since an ion-selective electrode can speed up the response time by rapidly performing ion exchange in the ion-selective membrane, the sample solution is stirred during measurement.

However, devices that stir the sample liquid generally involve temporal changes in the electromagnetic field. In addition, when an analyzer is operated automatically, a sample liquid suction/drainage mechanism, a sample liquid transfer mechanism, etc. are installed, and these also cause temporal changes in the electromagnetic field, which can cause noise. /N decreases. As described above, electrolyte analyzers are strongly affected by externally induced noise, so countermeasures such as shielding the ion-selective electrode podium with a metal membrane, etc. are taken to reduce this effect. There is.

However, even if such measures are taken, the induced noise from the outside cannot be sufficiently removed, and measurements with large noise differences have been forced. The present invention has been made in view of the above-mentioned points, and its object is to provide an electrolyte analyzer that can significantly reduce noise and, therefore, significantly improve measurement accuracy.

The electrolyte analyzer to which the present invention is applied is equipped with an ion-selective electrode having an electrode body containing an ion-sensing membrane and an internal liquid, and an electrode wire immersed in the internal liquid. It is configured to determine the concentration of electrolyte contained in the test liquid from the potential difference generated between the test liquid and the electrode.

In order to achieve the above object, the present invention shields the electrode body with a conductive material, leads a signal conductor connected to the electrode wire to one input side of the difference comparator, and connects the signal conductor wire connected to the electrode wire to the other input side of the difference comparator. It is characterized in that a shield conductor connected to a conductive substance is guided on the side, and the signal conductor and shield conductor are twisted together.

When the inventors were struggling with the noise problem mentioned above, they proposed the use of wires twisted together in phase U (hereinafter sometimes referred to as twisted wires) used for digital signal transmission to eliminate noise. After getting a hit that it could be used, and after trial and error, it was discovered that the configuration of the present invention is extremely effective.

The use of the well-known twisted wire mentioned above will be explained with reference to FIG.

In general, digital signals have low impedance in signal lines, so noise due to external induction is not a problem over short distances, but when transmitting signals over long distances, there is a high possibility of malfunctions due to the influence of external induction. In order to eliminate this influence, a configuration as shown in FIG. 2 is adopted. That is, 31 is a driver circuit, 32 is a receiver circuit, and 33 is a driver circuit.
is a twisted wire. As understood from FIG. 2, one end of the twisted wire 33 is connected to ground, thereby providing a shielding effect. However, even if the use of twisted wires as shown in FIG. 2 is directly applied to an ion-selective electrode that can obtain a high impedance signal, the expected effect will not be obtained. The inventors believe that the reason for this is that the internal resistance of the ion-selective electrode is extremely high, so that the voltage generated by the inductance of the shield wire jumps into the signal wire through the stray capacitance. Noise once on the signal line becomes the second noise.
It cannot be removed depending on the configuration shown in the figure. Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a schematic diagram showing an embodiment of the present invention. In this example, a polymer membrane type ion-selective electrode is used to measure ions such as sodium, potassium, and chlorine in a blood sample. In FIG. 3, the ion selection electrode 20 has an outer cylinder formed by an electrode body 13 made of an electrically insulating material, and inside the body 13 is a metal layer 1 in a tubular shape.
5 is provided.

The body 13 may be constructed so that an inner cylinder and an outer cylinder fit together, and in this case, a shielding film may be formed by coating the outer surface of the inner cylinder with metal. Shield body 15 made of conductive material
is connected via the cap 18 to a shield conductor 27 forming one of the two-core twisted wires. Electrode body 1
A polymer membrane-type ion detection membrane 14 containing an ion-sensitive substance is provided at the lower end of the body 13, and an internal liquid 1 is disposed within the body 13.
2 is accommodated. A silver chloride-coated silver wire 11 serving as an electrode wire is immersed in the internal liquid 12, and this silver wire 11 is connected to a two-core twisted wire signal conductor 30.
The signal conducting wire 30 is connected to the differential amplifier 40 via the amplifier input terminal 23 and the resistor R1, and the shielding conducting wire 27 is connected to the differential amplifier 40 via the amplifier input terminal 24. .

The shield conductor 27 and the signal conductor 30 are vertically and closely twisted together, and a shield coating material 25 made of a conductive material is provided to cover the outside of these.
5 is connected to the ground terminal 28 of the amplifier 21. Further, an insulating material covering material 26 is provided outside the shield covering material 25. 22 is a guard ring, R2,
R3 is a resistance.

During measurement, the ion selective electrode 20 and the reference electrode 29 are brought into contact with the test sample liquid 16 containing an electrolyte contained in the test phase container 17 .

The signal line 41 of the comparison electrode 29 is connected to the ground terminal 28, but the signal line 41 may be twisted together with the shield conductor 27 and the signal conductor 30. The minute signal voltage generated between the ion selection electrode 20 and the comparison electrode 29 is guided to the amplifier 21 via the twisted wire and amplified. Externally induced noise transmitted by leaking through the shield covering material 25 rides on the twisted wire, but due to the effect of twisting, it becomes substantially equal in magnitude, and is differentially amplified by the amplifier 21 to increase the externally induced noise. Output with the influence canceled is obtained. By connecting the shield body 15 to the amplifier input terminal 24 and to the guard ring 22 to shield the amplifier manual terminal 23, current leakage from the power supply is prevented and the storage capacitance of the twisted wire is reduced. is lowering.

FIG. 4 and FIG. 5 are data comparing cases where the present invention is applied and cases where the present invention is not applied.

FIG. 4 shows the state of an analog signal obtained based on the embodiment shown in FIG. 3, and FIG. Indicates the state of the signal. The electrode used in the experimental example from which the data shown in Figure 5 was obtained was the core wire of a coaxial cable connected to the electrode wire immersed in the internal liquid, which was led to the human power terminal of the amplifier. The one without was used. However, in this example, the shield wire of the coaxial cable is connected to the ground terminal in the same way as the covering material 25 made of a conductive material in FIG. In this way, in the embodiment shown in FIG. 3, the shield conductor 27 of the shield body 15 is led to the input side of the differential amplifier, and the shield conductor 27 and the signal branch conductor 30 are twisted together, so that noise can be reduced. It is easily seen that the level is reduced by a factor of 10 or more.

As described above, according to the present invention, measurement accuracy is significantly improved as noise is reduced, and its practical effects are enormous.

[Brief explanation of drawings]

Figure 1 is a diagram explaining the principle of an electrolyte analyzer, Figure 2 is a diagram explaining how to use a conventional twisted wire, Figure 3 is a schematic diagram of an embodiment of the present invention, and Figure 4 is Figure 3. FIG. 5 is a state diagram of an analog signal obtained based on the conventional example. 11... Electrode wire, 12... Internal liquid, 1
3... Electrode body, 14... Ion detection membrane, 15... Shield body, 20...
Ion selective electrode, 21...... amplifier, 23, 24
...Input terminal, 25...Shield covering material, 27...Shield conductor, 28...
・Earth terminal, 29... Reference electrode, 30...
...Signal conductor.

Claims (1)

[Claims] 1. An ion-selective electrode having an electrode body containing an ion detection membrane and an internal solution, and an electrode wire immersed in the internal solution, and a reference electrode, and both electrodes are brought into contact with a test solution containing an electrolyte. In an electrolyte analyzer configured to measure the potential difference that occurs between two electrodes when and a shielding conductor connected to the conductive substance to the other input side of the difference comparator, and the signal conductor and the shielding conductor are twisted together. electrolyte analyzer.