JP3263446B2 - Electrode ion concentration meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode type ion concentration meter such as a tabletop pH meter and an ion selective electrode type analyzer, and more particularly to an electrode type ion concentration meter capable of simultaneously measuring a plurality of channels.

[0002]

2. Description of the Related Art In this type of ion concentration meter, the pH value and other ion concentrations in the same test solution are measured simultaneously, and the same type of test solution is used for a plurality of types of test solutions. In the case of simultaneously measuring the ion concentration, it is necessary to provide a plurality of measurement electrode sections including an ion electrode (ion-selective electrode) such as a glass electrode and a reference electrode for measurement. In this case, when measurement is performed for a plurality of channels by an amplifier that uses the comparison electrode as a common potential of the circuit among the measurement electrode portions of each channel, a difference in a generated potential of each comparison electrode, a difference in output impedance, and the like affect other channels, There is a case where a difference is generated in the potential of the comparison electrode of each channel, so that the potential difference between the ion electrode and the comparison electrode cannot be measured accurately.

[0003] In order to solve the above-mentioned inconvenience, there is provided a method in which an insulating amplifier is individually provided for each channel as in an industrial pH meter, and the potential between an ion electrode and a reference electrode is measured via these insulating amplifiers. However, according to this method, since an insulating amplifier is required for the number of measurement channels, there is a problem that the circuit configuration becomes complicated and the cost increases.

On the other hand, there is also known a method in which an amplifier for amplifying the output voltage of the measurement electrode section is provided for only one channel, and the measurement electrodes for a plurality of channels are sequentially switched and connected to always measure only one channel. However, in this method, simultaneous measurement of a plurality of channels is impossible, and it takes a long time to measure all of the plurality of channels.

Therefore, in order to simultaneously measure a plurality of channels without using an insulating amplifier, it is necessary to use, for example, Japanese Laid-Open Utility Model Application No.
A method of performing measurement using a differential amplifier for each channel as disclosed in Japanese Patent Application Publication No. 254 and Japanese Utility Model Application Publication No. 50-124346 is effective. However, in this case, in addition to the ion electrode and the comparison electrode, the measurement electrode unit connected to the differential amplifier of each channel must include a ground electrode that serves as a reference for these potentials. Depending on the type of the measurement electrode unit possessed by the user, there may be a disadvantage that the measurement electrode unit cannot be used as is.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide various connection modes on the input side of a differential amplifier for a plurality of channels according to the configuration of a measurement electrode unit. An object of the present invention is to provide an electrode type ion densitometer for simultaneous measurement of a plurality of channels, which is changeable and has improved versatility and usability.

[0007]

In order to achieve the above object, the present invention provides an input terminal for connecting a glass electrode or another ion electrode, an input terminal for connecting a comparison electrode, an input terminal for connecting a ground electrode, and an output. In the first invention, a differential amplifier having terminals is provided for a plurality of channels. In the first invention, switch means for connecting / disconnecting a plurality of input terminals for connection of a comparison electrode is provided. Connect multiple input terminals for electrode connection to ground potential point common to each differential amplifier /
It comprises switch means for separation and a control circuit such as a microcomputer for operating these switch means. Here, each of the switch means is constituted by, for example, a relay and its contact.

[0008] By combining the first and second inventions, a first switch means for connecting / disconnecting a plurality of input terminals for connection of a reference electrode, and a plurality of inputs for connection of a reference electrode are provided. Both a terminal and a second switch for connecting / disconnecting a ground potential point common to each differential amplifier may be provided together with these control circuits.

[0009]

According to the first aspect of the present invention, the input terminals for connection of the comparison electrode of each channel are separated or connected to each other by the switch means in accordance with the configuration of the measurement electrode section connected to each channel. As a result, a connection state equivalent to the case where all the measurement electrode units have the comparison electrode and the ground electrode is realized, and the potential difference between the ion electrode and the ground electrode and between the comparison electrode and the ground electrode is applied to the differential amplifier for each channel. The ion concentration of a plurality of channels is measured simultaneously by taking in and differential mode. Therefore, it is possible to share the reference electrode of the measurement electrode unit of an arbitrary channel with another channel. In the second invention, by connecting the input terminal for connecting the comparison electrode of each channel to the ground potential point by the switch means, it is possible to cope with the simultaneous measurement of the ion concentration in the non-differential mode in each channel. Can be.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a main part of an electrode type ion densitometer of this embodiment, which is constructed by combining the embodiments of the first and second inventions. In the figure, 10,
Reference numerals 20, 30, and 40 denote differential amplifiers corresponding to the first to fourth channels, respectively. Each of the channels is connected to various measurement electrode units of an electrode type ion concentration meter, such as a pH electrode. Here, the differential amplifiers 10 to 40 are operational amplifiers 11 to 13, 21 to 23, 31 to 33, 41 to 41, respectively.
43 and a plurality of resistors and capacitors. The power supply of each operational amplifier is not shown.

Next, the configuration of the differential amplifier will be briefly described.
Since the configurations of the differential amplifiers 10 to 40 are the same, the first channel differential amplifier 10 will be described below as an example. The non-inverting input terminal of the operational amplifier 11 is connected to a first input terminal W ₁ via the resistor r _1, r _2, common resistor r _1, the connection point of r ₂ is the ground potential via the capacitor C ₁ (circuit (Potential) point. A feedback resistor r ₃ is connected between the output terminal of the operational amplifier 11 and the inverting input terminal.
The output terminal of the operational amplifier 11 through a resistor r _4, is connected to the inverting input terminal of the operational amplifier 13 having a feedback resistor r _9.

On the other hand, a non-inverting input terminal of the operational amplifier 12 is connected to a second input terminal R ₁ via resistors r ₅ and r ₆ ,
Connection point of the resistors r _5, r ₆ is connected to the ground potential point via the capacitor C _2. Feedback resistor r ₇ is connected between the output terminal of the operational amplifier 12 and the inverting input terminal. The output terminal of the operational amplifier 12 is connected via a resistor r ₈ to the non-inverting input terminal of the operational amplifier 13, together with the non-inverting input terminal is connected to the ground potential point through a resistor r _10, the operational amplifier 13 an output terminal connected via a resistor r ₁₁ to the output terminal O _1. One end of the resistor r ₁₁ is connected to the ground potential point via a capacitor C _3. With the above configuration, a voltage proportional to the difference between the output voltages of the first-stage operational amplifiers 11 and 12 is output from the last-stage operational amplifier 13.

In the same manner, the differential amplifiers 20 to 40 of the second to fourth channels are constructed,
30 and 40 respectively have a first and a second input terminal W ₂ ,
R ₂ , W ₃ , R ₃ , W ₄ , R ₄ are connected to output terminals O ₂ , O ₃ , O ₄ . Although not shown, a multiplexer and an A / D are provided after the output terminals O ₁ , O ₂ , O ₃ and O _4.
A converter and a microcomputer are sequentially connected, and the output signals from the output terminals O ₁ , O ₂ , O ₃ , and O ₄ are successively taken into the A / D converter by a multiplexer at a fixed period, and are converted into digital signals. The microcomputer executes the calculation of the pH value and various ion concentrations. here,
By shortening the cycle of scanning the output signal via the multiplexer, the output signal of each channel, that is, the ion concentration, can be simultaneously measured almost in real time. Of course, the A / D converter may be provided for each channel.

The second input terminals R ₁ , R ₂ ,
The contacts S ₁₁ , S ₁₂ , S ₁₃ , S _{14 of} the relay Ry ₁ shown in the lower part of FIG. 1 are connected to R ₃ , R ₄ , and these contacts S ₁₁ , S ₁₂ , S ₁₃ , The input terminals R ₁ , R ₂ , R ₃ , R ₄ and the ground potential point are connected / disconnected by turning on / off S ₁₄ . Further, the second input terminals R ₁ ,
Contact S ₂ of the relay Ry ₂ between R ₂ is likewise R _2,
R _3, between the R ₄ and the contact S _31, S ₃₂ of the relay Ry ₃ is connected, the input terminal R _1, R ₂ Dooshi are connected / separated by the on / off contacts S _2, contact S _31, S ₃₂
The input terminals R ₂ , R ₃ , R ₄ are connected / disconnected by turning on / off.

[0015] Here, the relay Ry ₂ and its contacts S ₂ and relay Ry ₃ and its contacts S _31, S ₃₂ is the connecting / separating the input terminals R ₁ to R ₄ Dooshi for comparison electrode connection 1 grounding switch means to configure the relay Ry ₁ and its contacts _{S 11, S 12, S 13} , S 14 includes an input terminal R ₁ to R ₄ of the comparative electrode connected in common to the differential amplifiers 10-40 It constitutes a second switch means for connecting / disconnecting the potential point. The relay Ry ₁ to Ry ₃ is to operate by a control signal applied from the control circuit in the microcomputer via the gate circuit. Note that the first and second
The switch means may be an analog switch such as an FET controlled to be opened and closed by an analog control circuit.

In this embodiment configured as described above, for example, a pH electrode is connected as a measurement electrode section to the first channel, and a measurement electrode section for measuring another ion concentration is provided to the second to fourth channels. The operation will be described as a connection. Note that the correspondence between the channel and the type of the measurement electrode unit is not particularly limited to the present embodiment. In connecting the measuring electrode units, the first input terminals W ₁ , W ₂ , W ₃ , and W ₄ of the respective channels are connected to ion electrodes (ion-selective electrodes) constituting the respective measuring electrode units. It is assumed that a comparison electrode is connected to at least one of the second input terminals R ₁ , R ₂ , R ₃ and R ₄ . In addition, each channel is provided with an input terminal to which a ground electrode constituting the measurement electrode unit is connected, and these input terminals are connected to a ground potential point.

Hereinafter, an example of connection between each channel and the measurement electrode unit will be described with reference to FIGS. First, FIG. 2 to FIG. 4 show a case where a pH electrode is connected as the measurement electrode unit 100 to the first channel. Measurement electrode part 1
00 is an ion electrode (glass electrode) 101, a comparative electrode 10
2 and a ground electrode 103, and are usually of a composite type.

In FIG. 2, measurement electrode units 200A, 300A, and 400A for measuring ion concentrations other than pH are connected to the other second to fourth channels, respectively. These measurement electrode units 200A, 300A, 40
OA is composed of ion electrodes 201, 301, 401 and comparative electrodes 202, 302, 402, each of which is usually a single-function electrode. The connection example of FIG. 2 can be realized by opening all the contacts S ₁₁ , S ₁₂ , S ₁₃ , S ₁₄ , S ₂ , S ₃₁ , and S ₃₂ in FIG. In this state, the ground electrode 103 of the first channel is shared by the other second to fourth channels, so that the measurement electrode units 200A, 300A, 400
A is equivalent to each having a ground electrode.

According to this connection example, the pH value is measured by the measuring electrode unit 100, and the other ion concentrations are measured by the measuring electrode units 200A, 300A, 300A, and 300A, which do not have the ground electrode.
With 400A, both can be measured simultaneously in the differential mode. Although the figure shows a case where one type of test solution a is measured by four channels, different types of test solutions are measured for each channel, or two types or one type are measured by each channel. It is also possible to measure with three types of combinations.

FIG. 3 shows a case where the measurement electrode section 100 is used for the first channel, and the measurement electrode sections 200B, 300B and 400B which are composed only of the ion electrodes 201, 301 and 401 are used for the other second to fourth channels, respectively. This is an example of connection. In this connection example, the contacts S ₂ , S ₃₁ , S in FIG.
By closing the contact ₃₂ and opening the contacts S ₁₁ , S ₁₂ , S ₁₃ , S ₁₄ , the comparison electrode 102 and the ground electrode 103 of the first channel are shared by the other second to fourth channels, respectively. Therefore, the measurement electrode units 200B, 300B, 400
B is equivalent to having a reference electrode and a ground electrode, respectively.

According to this connection example, the measurement electrode unit 100 for the pH value and the measurement electrode units 200B, 30 without the reference electrode and the ground electrode for other ion concentrations.
With 0B and 400B, both can be measured simultaneously in the differential mode. Also in this example, various combinations are possible for the correspondence between each channel and the type of the test liquid.

FIG. 4 shows a case where the measurement electrode unit 100 is used for a first channel, and a measurement electrode unit 200A including an ion electrode 201 and a comparison electrode 202 is used for a second channel.
The third and fourth channels respectively have ion electrodes 301,
This is an example in which measurement electrode units 300B and 400B consisting of only 401 are connected. In this connection example, the contact S in FIG.
₂ , the contacts S ₃₁ and S ₃₂ are closed, and the contacts S ₁₁ and S ₃₂ are closed.
By opening S ₁₂ , S ₁₃ , and S ₁₄ , the comparison electrode 202 of the second channel is shared by the third and fourth channels, and the first and second channels are shared.
The ground electrode 103 of the channel is shared by the other second to fourth channels. Thereby, the measurement electrode unit 200A,
300B and 400B each have a ground electrode, and
The measurement electrode units 300B and 400B are equivalent to having a comparison electrode.

According to this connection example, the pH value is measured by the measurement electrode unit 100, and the other ion concentrations are measured by the measurement electrode unit 200A without the ground electrode and the measurement electrode unit 300B without the comparison electrode and the ground electrode. , 400B can be simultaneously measured in the differential mode.
Also in this example, various combinations are possible for the correspondence between each channel and the type of the test liquid.

FIGS. 5 to 7 show an ion electrode (glass electrode) 101 and a comparison electrode 102 in the first channel.
This is an example in which a pH electrode is connected as a measurement electrode unit 100A made of the following. In each of these connection examples, measurement in a non-differential mode (normal mode) is assumed. First,
The connection example of FIG. 5 corresponds to the contacts S ₁₁ , S ₁₂ , S ₁₃ ,
Close S _14, by opening the contact _{S 2, S 31, S 32} ,
This is realized by connecting all input terminals for the comparison electrode of each channel to the ground potential point. In this connection example, one kind of the test liquid a is measured by the measuring electrode unit 100A having no ground electrode.
This is effective when measuring the H value or when measuring one type of ion concentration other than the pH value.

FIG. 6 shows that the measurement electrode section 100A is connected to the first channel, and the ion electrodes 201, 301, 401 and the comparison electrode 202, respectively, are connected to the second to fourth channels, respectively.
Measuring electrode units 200A, 300 comprising 302, 402
A, 400A, and contacts S ₁₁ , S ₁₂ ,
S ₁₃ , S ₁₄ , S ₂ , S ₃₁ , and S ₃₂ are opened and closed in the same manner as in FIG.
2, 402 are all connected to the ground potential point.
In this connection example, different types of test liquids a to d are measured for each channel, and the pH values and various values of the test liquids a to d are measured by the measurement electrode units 100A, 200A, 300A, and 400A having no ground electrode. Suitable for measuring ion concentration at the same time.

[0026] In this particular example, there is no need to measure a differential mode for the sample liquid a~d Dooshi are insulated from each other, the relay Ry ₁ and its contacts _{S 11, S 12, S 13} , S ₁₄
By unifying the potentials of the comparison electrodes of all the channels to the ground potential by the action of (1), simultaneous measurement in the non-differential mode is enabled. In this connection example, the measurement object was one type of test solution, and the pH was measured by the measurement electrode unit 100A.
The value is measured, and the other measurement electrode units 200A, 300A, 40
The ion concentration other than the pH value may be measured by 0A.

FIG. 7 shows a case where the measurement electrode section 100A is connected to the first channel, and the measurement electrode sections 200B, 300B, and 400B, each of which comprises only the ion electrodes 201, 301, and 401, are connected to the second to fourth channels. , 5 contacts _{S 11, S 12, S 13} , S 14, S 2, S 31, S 32,
In this case, all the input terminals for the comparison electrode of each channel are connected to the ground potential point in the same open / close state as in FIG.
In this connection example, one type of test liquid a is used for each channel.
Is measured, and the pH is measured by the measuring electrode unit 100A.
The value is measured, and the other measurement electrode units 200B, 300B, 40
This is suitable when simultaneously measuring ion concentrations other than the pH value by using 0B. In the connection examples of FIGS. 6 and 7, various combinations are possible for the correspondence between each channel and the type of the test liquid.

FIGS. 8 to 10 show connection examples in the case of measuring the pH value and various ion concentrations in a differential mode using a measurement electrode section having an ion electrode, a reference electrode and a ground electrode. 8 shows the measurement electrode unit 1 having the ion electrode 101, the comparison electrode 102, and the ground electrode 103.
PH of one kind of test liquid a by pH electrode as 00
A connection example when measuring value is achieved by opening all of the contacts _{S 11, S 12, S 13} , S 14, S 2, S 31, S 32 in FIG. 1. In this connection example, the measurement electrode unit 1
This is effective when measuring the pH value of one type of the test liquid a by the use of 00 or when measuring one type of ion concentration other than the pH value in the differential mode.

FIG. 9 shows all the measuring electrode sections 100 and 20.
0, 300, and 400 are the ion electrodes 101, 20 respectively.
1, 301, 401, comparative electrodes 102, 202, 30
2,402 and ground electrodes 103,203,303,40
3 shows a case where test liquids a to d of different types are measured for each channel, and FIG. 10 also shows a case where one type of test liquid a is measured. These connection examples also, the contact _{S 11, S 12, S 13} , S 14,
This is realized by setting S ₂ , S ₃₁ , and S ₃₂ to the same open / close state as in FIGS. 8 and 2.

That is, FIG. 10 shows a measurement electrode section 100, 200, 3 having an ion electrode, a reference electrode, and a ground electrode.
A connection example equivalent to that of FIG. 2 is realized using 00 and 400, and FIG. 9 can be said to be applied to a plurality of types of test liquids a to d. That is, when using the measurement electrode part 100, 200, 300 and 400 shown in FIGS. 9 and 10, the contact _{S 11, S 12, S 13} , S 14, S 2, S 31,
By opening and closing state of S ₃₂ the same as FIG. 2, it is possible to simultaneously measure the pH values and various ion concentrations in the differential mode for multiple channels. Here, FIG. 9 and FIG.
In the connection example described above, various combinations are possible for the correspondence between each channel and the type of the test liquid.

As described above, according to this embodiment, the contacts S ₁₁ , S ₁₂ , S ₁₃ , S ₁₄ , S ₂ , S ₃₁ , S ₃₂ according to the configuration of the measurement electrode unit prepared on the user side. By changing the open / closed state, the ion concentration in a plurality of channels can be measured simultaneously in the differential mode or the non-differential mode. In particular, when measuring in differential mode,
As shown in FIG. 2 to FIG. 4, the measurement electrode section of the second to fourth channels, which does not have a ground electrode or a reference electrode, can be used, so that the versatility as an ion concentration meter is enhanced, and the user side is easy to use. Is also good. As a user, a relatively inexpensive measurement electrode unit can be used.

Further, in the above embodiment, the connection example at the time of measurement has been described. However, the present invention is also applicable to the case where the standard solution of the measuring electrode portion is calibrated. Or if there is one that can be used in common depending on the ion species to be measured, a common standard solution may be used to select each of the above connection examples.

FIGS. 11 to 14 show display examples of the respective connection examples on a digital display provided in the ion concentration meter of this embodiment. In FIG. 11, CH indicates a channel display section, RC indicates a connection state display section of a comparison electrode, EC indicates a connection state display section of a ground electrode, and MD indicates a mode display section. FIG. 11 corresponds to the connection example of FIG. 8, FIG. 9, FIG. 10 or FIG. 2, in which the comparison electrode of each channel is separated from the ground electrode, and the ground electrodes of all channels are connected to each other. Equivalent status is displayed in the connection status display sections RC and EC
Is indicated by. On the mode display section MD, a numeral “1” indicating that this mode is the first mode as a differential mode is blinkingly displayed.

FIG. 12 corresponds to the connection example of FIG. 3 and shows a connection state equivalent to a state where the comparison electrodes of all channels are connected to each other and the ground electrodes of all channels are connected to each other. This is indicated by the display units RC and EC. On the mode display section MD, a number "2" indicating that this mode is the second mode as a differential mode is blinkingly displayed.

FIG. 13 corresponds to the connection example of FIG. 4, and is equivalent to the case where the comparison electrodes of the second to fourth channels are connected to each other and the ground electrodes of all the channels are connected to each other. The status is indicated by the connection status display sections RC and EC. On the mode display section MD, a numeral "3" indicating that this mode is the third mode as a differential mode is blinkingly displayed.

FIG. 14 corresponds to the connection example of FIG. 5, FIG. 6, or FIG. 7, in which the comparison electrode and the ground electrode of all the channels are respectively connected, and the ground electrode of all the channels is mutually connected. The connection state display section R
Indicated by C and EC. On the mode display section MD, a numeral “4” indicating that this mode is the fourth mode as a non-differential mode is blinkingly displayed.

Since these display examples correspond to the connection examples of the respective electrodes, various displays according to the connection examples are possible. For example, although not shown, when the comparison electrodes are connected by two channels and the ground electrodes of all channels are connected to each other, the connection between the second and third channels in the connection state display part RC of the comparison electrodes in FIG. May be removed. By performing the display as described above, the connection state of each measurement electrode unit can be immediately grasped visually, which is extremely convenient for the user.

It is to be noted that the present invention aims at making it possible to measure the potential difference in the differential mode or the non-differential mode by sharing the reference electrode and the ground electrode constituting the measuring electrode section. Since the type and the measurement target are not particularly limited, the measurement is not limited to an electrode type ion concentration meter such as a pH meter, and may be a measurement using a redox potential measurement or an enzyme membrane electrode.
The present invention can be applied to various types of potentiometric measuring devices.

[0039]

As described above, according to the present invention, according to the configuration of the measurement electrode section connected to each channel by the user,
In the first invention, connection / separation between the reference electrode connection input terminals of an arbitrary channel is determined, and in the second invention, connection / separation between the comparison electrode connection input terminal of an arbitrary channel and the ground potential point is determined. Is realized by the switch means and the control circuit.

For this reason, if at least one measurement electrode section has a comparison electrode, each differential amplifier has a common ground potential point. Can realize a connection state equivalent to that in which all measurement electrode units have a comparison electrode and a ground electrode, and can simultaneously measure ion concentration and the like in a differential mode for each channel. Further, according to the second aspect, by connecting the input terminal for connection of the comparison electrode of each channel to the ground potential point, simultaneous measurement of a plurality of channels in the non-differential mode becomes possible.

Therefore, the configuration of the measuring electrode unit usable on the user side is diversified, and the degree of freedom of measurement is greatly improved, so that versatility, usability and economy are improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a main part of an embodiment of the present invention.

FIG. 2 is a diagram illustrating a connection example of a measurement electrode unit in the embodiment.

FIG. 3 is a diagram showing a connection example of a measurement electrode unit in the embodiment.

FIG. 4 is a diagram showing a connection example of a measurement electrode unit in the embodiment.

FIG. 5 is a diagram showing a connection example of a measurement electrode unit in the embodiment.

FIG. 6 is a diagram showing a connection example of a measurement electrode unit in the embodiment.

FIG. 7 is a diagram showing a connection example of a measurement electrode unit in the embodiment.

FIG. 8 is a diagram illustrating a connection example of a measurement electrode unit in the embodiment.

FIG. 9 is a diagram illustrating a connection example of a measurement electrode unit in the example.

FIG. 10 is a diagram showing a connection example of a measurement electrode unit in the embodiment.

FIG. 11 is a diagram illustrating a display example of a connection example of a measurement electrode unit in the embodiment.

FIG. 12 is a diagram illustrating a display example of a connection example of measurement electrode units in the example.

FIG. 13 is a diagram illustrating a display example of a connection example of measurement electrode units in the example.

FIG. 14 is a diagram illustrating a display example of a connection example of measurement electrode units in the example.

[Explanation of symbols]

10, 20, 30, 40 Differential amplifier 11, 12, 13, 21, 22, 23, 31, 32, 3
3, 41, 42, 43 operational amplifiers 100, 100A, 200, 200A, 200B, 30
0,300A, 300B, 400,400A, 400B
Measuring electrode portion 101,201,301,401 ion electrode 102, 202, 302, and 402 reference electrode 103,203,303,403 ground electrode _{W 1, R 1, W 2} , R 2, W 3, R 3, W 4 , R ₄ input terminals _{O 1, O 2, O 3} , O 4 output terminals Ry _1, Ry _2, Ry ₃ relay _{S 11, S 12, S 13} , S 14, S 2, S 31, S 32 contacts

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Satoshi Ito 4-13-14 Kichijoji Kitamachi, Musashino City, Tokyo Electrochemical Instruments Co., Ltd. (56) References JP-A-62-851 (JP, A) JP-A Sho 60-174945 (JP, A) JP-A-60-143756 (JP, A) JP-A-60-22654 (JP, A) JP-A-5-45326 (JP, A) U) Japanese Utility Model Showa 50-124346 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 27/27 G01N 27/416

Claims (2)

(57) [Claims] 1. A measuring electrode part is immersed in a test liquid, and a potential difference between an ion electrode and a reference electrode constituting the measuring electrode part is measured by a differential amplifier to measure an ion concentration in the test liquid. A differential amplifier having an input terminal for connecting an ion electrode, an input terminal for connecting a comparison electrode, an input terminal for connecting a ground electrode, and an output terminal for a plurality of channels; An electrode type ion densitometer comprising: switch means for connecting / disconnecting a plurality of input terminals for connection; and a control circuit for operating the switch means. 2. An ion concentration in the test solution is measured by immersing the measurement electrode portion in the test solution and measuring a potential difference between an ion electrode and a reference electrode constituting the measurement electrode portion by a differential amplifier. A differential amplifier having an input terminal for connecting an ion electrode, an input terminal for connecting a comparison electrode, an input terminal for connecting a ground electrode, and an output terminal for a plurality of channels; An electrode type ion densitometer comprising: switch means for connecting / disconnecting a connection input terminal and a ground potential point common to each differential amplifier; and a control circuit for operating the switch means.