JP2015155894A - Electric characteristics measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow electric characteristics such as a specific resistance of a liquid specimen high in insulation property to be measured using an operational amplifier so as to reduce a risk of an electric shock.

SOLUTION: An electric characteristics measurement device includes: a pair of electrodes 21, 22 forming a storage space S of a liquid specimen; a circuit body 3 including a power supply circuit 31 for applying a voltage to the pair of electrodes 21, 22 and a detection circuit 32 for measuring a specific resistance of the liquid specimen or a physical quantity relating to the specific resistance; two connection lead wires 41, 42 for connecting the pair of electrodes 21, 22 and the circuit body 3; and coated conductors 5 for coating the two connection lead wires 41, 42 and connected to the common or an electric shock prevention resistor 313 disposed in a wiring line 312 on the high voltage side of the power supply circuit 31. The detection circuit 32 detects an electric current flowing between the paired electrodes 21, 22, and calculates the specific resistance or the physical quantity relating to the specific resistance from the electric current detected by the detection circuit 32.

COPYRIGHT: (C)2015,JPO&INPIT

Description

  The present invention relates to an electrical property measuring apparatus that measures a specific resistance of a liquid sample or a physical quantity related to the specific resistance.

  Conventionally, what is shown in patent document 1 is considered as what measures the specific resistance of the liquid sample which has insulation. This specific resistance measuring apparatus measures the specific resistance of a liquid sample located between an external electrode and an internal electrode by applying an alternating voltage to the external electrode and the internal electrode.

  However, in order to measure the specific resistance of an insulating liquid sample, a high voltage must be applied to the external electrode and the internal electrode. The voltage applied to both electrodes becomes higher as the distance between the outer electrode and the inner electrode is larger. This increases the risk of electric shock. Here, it is conceivable to reduce the distance between the external electrode and the internal electrode, but it is easily affected by measurement errors caused by external vibration.

  Furthermore, in the conventional specific resistance measuring apparatus, for example, as shown in FIG. 5, the specific resistance is calculated by detecting a voltage generated between a pair of electrodes using an operational amplifier. However, in the configuration in which a high voltage is applied to the external electrode, in the circuit configuration in FIG. 5A, a voltage can be applied only to the pair of electrodes within the operating voltage range of the operational amplifier. 5 becomes difficult to measure, and in the circuit configuration of FIG. 5B, the input voltage to the non-inverted inverting input terminal of the operational amplifier becomes large. In either case, the operational amplifier should be used. I can't.

Japanese Patent No. 3769119

  Therefore, the present invention has been made to solve the above problems, and it is possible to measure the electrical characteristics such as the specific resistance of a liquid sample with high insulation using an operational amplifier, and to reduce the risk of electric shock. This is the main issue.

  That is, the electrical characteristic measuring apparatus according to the present invention includes a pair of electrodes that contact a liquid sample, a power supply circuit for applying a voltage to the pair of electrodes, and a detection circuit that detects a current flowing between the pair of electrodes. A circuit body, two connection conductors connecting the pair of electrodes and the circuit body, a coated conductor covering the two connection conductors and connected to a common, or a high voltage of the power supply circuit A resistance for preventing electric shock that causes a current value flowing to a person to be 3 A or less when an electric shock is received, and calculates a specific quantity related to the specific resistance or specific resistance from the current detected by the detection circuit. It was configured as described above.

In the case of the electrical characteristic measuring apparatus having the coated conductor, since the two connecting conductors connecting the pair of electrodes and the circuit body are covered with the coated conductor, when measuring a liquid sample with high insulation, Even when a high voltage is applied to the pair of electrodes, the risk of electric shock can be reduced. Further, since the coated conductor is connected to the common, noise detected by the detection circuit can be reduced, and the specific resistance of the liquid sample or a signal indicating a physical quantity related to the specific resistance can be easily extracted. The measurement accuracy of the physical quantity related to the specific resistance or specific resistance of the liquid sample can be improved. Furthermore, since the charge current of the stray capacitance formed in the connection conductor and the current detected by the detection circuit can be separated, the specific resistance or the current without waiting for the charge current of the stray capacitance to reach a steady state can be obtained. A physical quantity related to the specific resistance can be measured. In addition, because the detection circuit is configured to detect the current flowing between a pair of electrodes, the voltage input to the operational amplifier that configures the detection circuit can be reduced, and conventional operational amplifiers can be used without difficulty. can do.
In the case of the electrical characteristic measuring apparatus having the electric shock prevention resistance, even when a high voltage is applied to the pair of electrodes when measuring a liquid sample having high insulation, the current flowing through the human body due to the electric shock prevention resistance Can be limited to 3 A or less, and the risk of electric shock can be reduced.

  As an aspect in which the coated conductor is provided, it is desirable that the coated conductor is provided independently of each of the two connecting conductors. If this is the case, an inexpensive double coaxial cable can be used, and noise can be reduced while avoiding the risk of electric shock without using an expensive highly insulated cable.

  In the power supply circuit, it is preferable that the wiring between the high voltage power supply and the external terminal connected to the connection conductor is an aerial wiring. In this case, since the high-voltage power supply and the external terminal are wired in the air, it is possible to ensure the insulation of the wiring board constituting the main circuit unit.

  In order to reduce noise superimposed on the current detected by the detection circuit, the pair of electrodes includes a cylindrical external electrode and a cylindrical internal electrode arranged inside the external electrode. It is desirable that the high voltage of the power supply circuit is applied to the external electrode, and a current flowing between the electrodes is detected from the internal electrode to the detection circuit.

  According to the present invention configured as described above, electrical characteristics such as specific resistance of a liquid sample having high insulation can be measured using an operational amplifier, and the risk of electric shock can be reduced. In particular, it is possible to safely measure the specific resistance of a liquid sample having a high insulating property or a physical quantity related to the specific resistance.

The schematic diagram which shows the structure of the electrical property measuring apparatus of 1st Embodiment. The figure which shows the structure of the specific resistance measurement circuit containing the detection circuit of 1st Embodiment. The schematic diagram which shows the structure of the electrical property measuring apparatus of deformation | transformation embodiment. The schematic diagram which shows the structure of the electrical property measuring apparatus of 2nd Embodiment. The figure which shows the structure of the conventional specific resistance measuring circuit.

<First Embodiment>
Hereinafter, a first embodiment of an electrical property measuring apparatus according to the present invention will be described with reference to the drawings.

  The electrical property measuring apparatus 100 according to the first embodiment continuously sets the specific resistance (electrical resistivity) of the liquid sample in order to detect deterioration of a liquid such as a fluorinated liquid used for a temperature adjustment mechanism on a wafer support, for example. It is a specific resistance measuring device to measure. The liquid sample to be measured by the specific resistance measuring apparatus 100 includes lubricating oil, liquid organic medium for lubrication, rust preventive oil, electric discharge machining oil, hydraulic working fluid, edible oil and other oils, and heat medium fluid. , Hydrocarbon solvents for diluting varnishes, pigments, agricultural chemicals, hydrocarbon solvents for cleaning, greases having fluidity, and the like.

  Specifically, the specific resistance measuring apparatus 100 is of a two-electrode system, and as shown in FIG. 1, a voltage is applied to the pair of electrodes 21 and 22 that are in contact with the liquid sample and the pair of electrodes 21 and 22. Circuit body 3 having a power supply circuit 31 and a detection circuit 32 for measuring the specific resistance of the liquid sample, and a pair of electrodes 21 and 22 and two connecting conductors 41 and 42 for connecting the circuit body 3. ing.

  The pair of electrodes 21, 22 are arranged in a cell space between the inner peripheral surface of the outer electrode 21 and the outer peripheral surface of the internal electrode 22 by disposing the cylindrical inner electrode 22 inside the cylindrical outer electrode 21. S is formed. That is, the pair of electrodes 21 and 22 of the present embodiment constitutes a measurement cell. In addition, the electrode 21 having a flat plate shape and the electrode 22 having a flat plate shape may be arranged to face each other. The pair of electrodes 21 and 22 is inserted into, for example, a side wall of the storage container 200 that stores the liquid sample, and is attached to the storage container 200 so as to contact the liquid sample in the storage container 200.

  The circuit body 3 is configured by forming a power supply circuit 31, a detection circuit 32, and the like on a wiring board 301. The circuit body 3 has external terminals 3a and 3b for connecting the connecting conductors 41 and 42. The circuit body 3 is housed in a housing 302, and the housing 302 is provided with external terminals 3a and 3b.

  The wiring 312 between the high voltage power supply 311 of the power supply circuit 31 and the external terminal 3a is an aerial wiring. As described above, since the high-voltage side wiring 312 is an aerial wiring, insulation can be ensured with a wiring connected to an inverting input terminal of the operational amplifier 32a, which will be described later, and is detected by the operational amplifier 32a. Noise can be reduced. Further, since the high voltage power supply 311 of this embodiment does not need to consider the electrolysis of the liquid sample, a DC power supply (for example, 500 V) is used. Even when a DC power supply is used, it is preferable to periodically set the DC power supply to 0V. At this time, the zero output of the detection circuit 32 described later can be confirmed, or the electric charge accumulated in the circuit can be discharged.

  The detection circuit 32 measures the specific resistance of the liquid sample by detecting a current flowing between the external electrode 21 and the internal electrode 22.

Specifically, as shown in FIG. 1, the detection circuit 32 is configured using an operational amplifier 32a to detect a current flowing between the external electrode 21 and the internal electrode 22, and the inverting input of the operational amplifier 32a. The terminal is connected to the external terminal 3b by wiring. The non-inverting input terminal of the operational amplifier 32a is connected to the common. Note that the non-inverting input terminal of the operational amplifier 32a may be grounded. A detection resistor 32b is connected in parallel with the operational amplifier 32a between the inverting input terminal and the output side of the operational amplifier 32a. With such a configuration, an output voltage (V _out ) corresponding to the current flowing between the external electrode 21 and the internal electrode 22 is output from the operational amplifier 32a. The detection circuit 32 includes a specific resistance calculation unit 32c that calculates the specific resistance (R ₂ ) of oil using the output voltage from the operational amplifier 32a. The calculation of the specific resistance (R ₂ ) by the specific resistance calculation unit 32c is R ₂ = R ₁ × V ₁ / V _out . Here, V ₁ is a DC voltage applied to the external electrode 21 and the internal electrode 22, and R ₁ is a resistance value of the detection resistor 32 b.

  And the specific resistance measuring apparatus 100 of this embodiment is equipped with the covering conductor 5 connected to the common while covering the two connection conducting wires 41 and 42. Here, one connection conductor 41 connects the external terminal 3 a and the internal electrode 22, and the other connection conductor 42 connects the external terminal 3 b and the external electrode 21. In the present embodiment, a high voltage is applied to the internal electrode 22. This is because the external electrode 21 is directly attached to the grounded conductive storage container 200 (without an insulator).

  The coated conductor 5 is provided on each of the two connecting conductors 41 and 42 independently of each other. That is, the covered conductor 5 covers the periphery of one connection conductor 41 and is provided separately from the first covered conductor 51 connected to the common and the first covered conductor 51, and surrounds the other connection conductor 42. And a second covered conductor 52 which is covered and connected to the common. That is, one connection conductor 41 is accommodated inside the first covered conductor 51, and the other connection conductor 42 is not accommodated. Further, the other connecting conductor 42 is accommodated inside the second covered conductor 52, and the one connecting conductor 41 is not accommodated. A common connected to each of the covered conductors 51 and 52 is provided in the main body circuit unit 3. Each of the covered conductors 51 and 52 may be grounded. Further, the other connecting conductor 42 and the second covered conductor 52 are connected to the common so as to be equipotential to each other, and no current flows between the other connecting conductor 42 and the second covered conductor 52. It is configured as follows.

  As a specific configuration, one connecting conductor 41 and the first covered conductor 51 are provided with an insulating resin between them, and an insulating resin is also provided around the first covered conductor 51. It is composed of a coaxial cable. Further, the other connecting conductor 42 and the second covered conductor 52 are provided by a coaxial cable in which an insulating resin is provided therebetween, and an insulating resin is provided around the second covered conductor 52. It is configured. That is, the pair of electrodes 21 and 22 and the main body circuit unit 3 are connected by two coaxial cables. In addition, the resin provided around the first covered conductor 51 and the resin provided around the second covered conductor 52 may be shared to form a single cable configuration.

  According to the specific resistance measuring apparatus 100 configured as described above, the two connecting conductors 41 and 42 that connect the pair of electrodes 21 and 22 and the circuit body 3 are covered with the covered conductors 51 and 52, respectively. Even when a high voltage is applied to the pair of electrodes 21 and 22 when measuring a highly insulating liquid sample, the risk of electric shock can be reduced. Further, since the detection circuit 32 is configured to detect the current flowing between the pair of electrodes 21 and 22, the voltage input to the operational amplifier 32a constituting the detection circuit 32 can be reduced, and the operational amplifier 32a. Can be used to measure the specific resistance of a highly insulating liquid sample. Further, since the coated conductors 51 and 52 are connected to the common, noise detected by the detection circuit 32 can be reduced, and a signal indicating the specific resistance of the liquid sample can be easily extracted, and the liquid The measurement accuracy of the specific resistance of the sample can be improved. In addition, since the charge current of the stray capacitance formed in the connection conductor 41 and the current detected by the detection circuit 32 can be separated, without waiting for the charge current of the stray capacitance to reach a steady state, The specific resistance can be measured.

  Further, since each of the connecting conductors 41 and 42 is provided with the covering conductors 51 and 52 connected to the common, a double coaxial cable composed of one inexpensive core wire and one seal conductor should be used. The noise can be reduced while avoiding the risk of electric shock without using an expensive high-insulation cable.

The present invention is not limited to the first embodiment.
For example, in the first embodiment, two coaxial cables each having the covering conductors 51 and 52 provided on each of the two connecting conductors are used. However, as shown in FIG. You may comprise with a cable. Specifically, the connection lead 41 on the high voltage side is covered with the connection lead 42 on the low voltage side, and the periphery of the connection lead 42 on the low voltage side is covered with the covering conductor 5 connected to the common. Conceivable. In this case, current leakage may occur between the two connection conductors 41 and 42, so that a resin having high insulation is required between the two connection conductors 41 and 42. However, the risk of electric shock can be reduced and noise detected by the detection circuit can be reduced. Also, the wiring can be simplified.

  Further, for the purpose of reducing the risk of electric shock and reducing the noise detected by the detection circuit to improve the measurement accuracy, the electrical characteristic measuring device includes a pair of electrodes that contact a liquid sample and the pair of electrodes. A circuit body having a power supply circuit for applying a voltage to the electrodes and a detection circuit for detecting a current flowing between the pair of electrodes, and two connecting conductors connecting the pair of electrodes and the circuit body. Any one may be used as long as it covers the two connecting conductors and has a covering conductor connected to the common.

Second Embodiment
Next, a second embodiment of the electrical property measuring apparatus according to the present invention will be described with reference to the drawings. The same reference numerals are used for members that are the same as or correspond to those in the first embodiment.

  As shown in FIG. 4, the electrical characteristic measuring apparatus 100 according to the second embodiment is different from the first embodiment in that an electric shock prevention resistor 313 is provided on the high-voltage side wiring 312 of the power supply circuit 31. . The electric shock prevention resistor 313 is a current limiting resistor (for example, several MΩ) that limits the current flowing to the person when the person touches the external terminals 3 a and 3 b provided on the housing 302. Specifically, it is a resistance that limits the current value flowing to a person to 3 A or less when an electric shock is received, preferably a resistance that limits to 50 mA or less, and more preferably a resistance that limits to 10 mA or less. The resistance value of the electric shock prevention resistor 313 is determined by using the current value flowing through the person and the DC voltage value of the DC power supply 311 as parameters.

  In the specific resistance measuring apparatus 100 of the present embodiment, one connection conductor 41 connects the external terminal 3a and the external electrode 21, and the other connection conductor 42 includes the external terminal 3b and the internal electrode 22. Are connected. In the present embodiment, a high voltage is applied to the external electrode 21. As a result, the current flowing between the external electrode 21 and the internal electrode 22 is extracted from the internal electrode 22 and input to the operational amplifier 32a of the detection circuit 32. At this time, since the internal electrode 22 is accommodated in the external electrode 21, the internal electrode 22 is not in direct contact with surrounding members such as the storage container 200, so that noise superimposed on the current can be reduced and the ratio of the liquid sample can be reduced. Resistance measurement accuracy can be improved.

  According to the specific resistance measuring apparatus 100 configured as described above, even when a high voltage is applied to the pair of electrodes when measuring a liquid sample having high insulation properties, the current flowing through the human body by the electric shock prevention resistor 313. The risk of electric shock can be reduced.

The present invention is not limited to the second embodiment.
For example, in the second embodiment, similarly to the first embodiment, the two connecting conductors 41 and 42 may be covered and a covering conductor connected to the common may be provided. With this configuration, the risk of electric shock can be further reduced.

  Further, from the viewpoint of noise removal, the connection conductor 42 of the two connection conductors 41 and 42 may be covered with a covered conductor. With this configuration, it is possible to remove noise with the coated conductor while preventing electric shock with the electric shock prevention resistor.

  Moreover, although the electrical characteristic measuring apparatus of each said embodiment measures a specific resistance, it may measure an electrical conductivity as a physical quantity relevant to a specific resistance, for example.

  In addition, it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

100: Specific resistance measuring device (electric property measuring device)
21, 22... A pair of electrodes S... Accommodating space 3... Circuit body 3 a, 3 b... External terminal 31. Wiring 313... Electric shock prevention resistor 32... Detection circuit 41, 42... Connection conductor 5.

Claims (4)

A pair of electrodes in contact with the liquid sample;
A circuit body having a power supply circuit for applying a voltage to the pair of electrodes and a detection circuit for detecting a current flowing between the pair of electrodes;
Two connecting conductors connecting the pair of electrodes and the circuit body,
For electric shock prevention, which covers the two connecting conductors and is provided on the covering conductor connected to the common or on the high voltage side wiring of the power supply circuit, and the electric current flowing to the person when electric shock is reduced to 3 A or less With resistance,
An electrical characteristic measuring apparatus configured to calculate a specific resistance or a physical quantity related to a specific resistance from a current detected by the detection circuit.   The electrical property measuring device according to claim 1, wherein the coated conductor is provided independently of each other for the two connecting conductors.   The electrical characteristic measuring device according to claim 1 or 2, wherein in the power supply circuit, a wiring between a high-voltage power supply and an external terminal connected to the connection conductor is an aerial wiring. The pair of electrodes includes a cylindrical external electrode and a columnar internal electrode disposed inside the external electrode,
The high voltage of the said power supply circuit is applied to the said external electrode, The electric current which flows between electrodes is comprised so that the said detection circuit may detect from the said internal electrode. Electrical property measuring device.