JP5509358B1 - Specific resistance measuring circuit, specific resistance measuring apparatus, liquid sample management method, and liquid sample management system - Google Patents

Abstract

The specific resistance of a liquid sample can be measured continuously and accurately, and deterioration such as alteration of the liquid sample accompanying measurement is prevented.
A specific resistance measuring circuit C for measuring a specific resistance to detect deterioration of a liquid sample, and detecting a voltage generated between an external electrode 21 and an internal electrode 22 to detect the specific resistance of the liquid sample. A rectangular wave AC voltage having an amplitude of 1 V to 42 V and a frequency of 0.5 Hz to 30 Hz is applied between the external electrode 21 and the internal electrode 22.
[Selection] Figure 4

Description

  The present invention relates to a specific resistance measuring device for measuring a specific resistance of a liquid sample such as a lubricating oil, a specific resistance measuring circuit used in the specific resistance measuring device, a liquid use management method using the specific resistance measuring device, and a liquid sample. It relates to the management system.

  Conventionally, what is shown in patent document 1 is considered as what measures the specific resistance of IPA (isopropyl alcohol) which is an insulating liquid. This specific resistance measuring apparatus measures the specific resistance of IPA located between an external electrode and an internal electrode by applying an alternating voltage to the external electrode and the internal electrode.

  Here, the specific resistance of IPA is about 1000 MΩ · cm, and the AC voltage applied to the external electrode and the internal electrode is one having an amplitude of about 2 V and a frequency of 100 Hz. In addition to IPA, the specific resistance of pure water or the like is generally measured using a similar AC voltage.

  On the other hand, in order to measure the specific resistance of the oil in order to detect the deterioration of the oil such as lubricating oil, it is considered to use the specific resistance measuring device.

  However, the specific resistance of oil is several tens to several hundreds times larger than the specific resistance of IPA, so that the current flowing through the measurement circuit having the external electrode and the internal electrode is small, making measurement difficult, and the stray capacitance of the measurement circuit. As a result, the response due to the AC voltage is deteriorated. Then, when an AC voltage having a frequency of 100 Hz is applied, the positive / negative of the AC voltage is switched before the signal output from the measurement circuit (for example, the output voltage) is stabilized. Therefore, the specific resistance of the oil is accurately measured. There is a problem that can not be.

  In order to measure the specific resistance of oil, it is conceivable to increase the detection current by setting the voltage applied to the external electrode and the internal electrode to a high voltage such as 1000 V, for example. In the conventional measurement of the specific resistance of oil, it is common to apply a high voltage.

  However, when a high voltage of, for example, 1000 V is applied to the oil, the oil is oxidized and denatured, and there is a problem that the measurement causes deterioration of the oil.

Japanese Patent No. 3769119

  Therefore, the present invention has been made to solve the above problems all at once, and it is possible to continuously measure the specific resistance of a liquid sample with high accuracy and to prevent deterioration of the liquid sample due to measurement. This is the main desired issue.

  That is, the specific resistance measurement circuit according to the present invention is a specific resistance measurement circuit that measures specific resistance in order to detect liquid sample deterioration, and detects a voltage generated between the pair of electrodes, thereby detecting the pair of electrodes. A specific resistance of a liquid sample in between is measured, and a rectangular wave AC voltage having an amplitude of 1 V to 42 V and a frequency of 0.5 Hz to 30 Hz is applied between the pair of electrodes. Here, liquid samples include lubricating oil, liquid organic medium for lubrication, rust preventive oil, electric discharge machining oil, hydraulic working medium liquid, cooking oil and other oils, heat medium liquid, heat treatment liquid, varnish / pigment / pesticide, etc. Examples include hydrocarbon solvents for dilution, hydrocarbon solvents for cleaning, greases having fluidity, and alcohols such as IPA (isopropyl alcohol).

  In such a case, since the rectangular wave AC voltage as described above is applied, the formation of an electric double layer at the boundary between the electrode and the liquid sample is suppressed, and the specific resistance of the liquid sample is continuously measured. can do. Further, since a voltage of 1 V to 42 V is applied, deterioration due to measurement such as alteration of the liquid sample being measured can be prevented. Here, since the AC voltage is 1 V to 42 V, the power source can be configured at a low cost, and the danger to the human body can be reduced even when there is an electric shock. Furthermore, since the frequency is 0.5 Hz to 30 Hz, the signal output from the measurement circuit can be stabilized before switching the AC voltage, so that the specific resistance of the liquid sample can be accurately measured, and the liquid sample Can be accurately detected. This liquid sample measuring cell can measure not only the specific resistance of liquid samples such as oil, which is several tens to several hundred times larger than the specific resistance of IPA, but also of liquid samples with a specific resistance of less than 10 GΩ · cm such as IPA. The specific resistance can also be measured naturally.

  When a DC voltage is applied to the external electrode and the internal electrode, electric charges accumulate in the electric double layer at the boundary between the electrode and the liquid sample, and the potential between the electrodes gradually increases as the electric double layer potential increases. The gradient decreases, the ion movement decreases, and the specific resistance increases. Accordingly, when a DC voltage is used when continuously measuring the specific resistance of the liquid sample, it is difficult to accurately measure the specific resistance of the liquid sample.

  It is desirable to have a shield drive circuit using an operational amplifier in which the potential difference of the stray capacitance formed between the wirings connected to the pair of electrodes is zero. If this is the case, the stray capacitance formed between the wirings connected to the pair of electrodes can be separated from the measurement circuit, the response of the signal indicating the specific resistance of the liquid sample can be accelerated, and the extraction can be performed. Can be easily. Therefore, the specific resistance of the liquid sample can be measured with high accuracy, and deterioration of the liquid sample can be detected with high accuracy.

  According to the present invention configured as described above, it is possible to continuously and accurately measure the specific resistance of the liquid sample while preventing deterioration such as deterioration of the liquid sample accompanying the measurement.

The longitudinal cross-sectional view of the oil measurement cell which concerns on one Embodiment of this invention. The cross-sectional view of the oil measurement cell of the same embodiment. The functional block diagram of the control apparatus of the specific resistance measuring apparatus of the embodiment. The schematic diagram which shows the specific resistance measurement circuit of the embodiment. The schematic diagram which shows the time-dependent change of the specific resistance of oil. The schematic diagram which shows the specific resistance and temperature relationship in several oil. The figure which shows the time chart until the measurement of the embodiment. The schematic diagram which shows the oil management system using the specific resistance measuring apparatus of the embodiment. The functional block diagram of the control apparatus of the specific resistance measuring apparatus of deformation | transformation embodiment.

  An embodiment of a specific resistance measuring apparatus according to the present invention will be described below with reference to the drawings.

  The specific resistance measuring apparatus 100 according to the present embodiment uses the oil (liquid sample) in order to detect deterioration of hydraulic oil (hereinafter simply referred to as oil) used in a lubricating oil or a hydraulic device used in a bearing, a gear, or the like. ) Is continuously measured.

  Specifically, this is a two-electrode type, and as shown in FIGS. 1 to 3, a cylindrical internal electrode 22 is arranged inside a cylindrical external electrode 21, and these electrodes 21 are arranged. , 22 between the external electrode 21 and the internal electrode 22, the oil measuring cell 2 in which the cell space S is formed, the heater 3 that is provided in the external electrode 21 and heats the oil contained in the cell space S The specific resistance measuring unit 4 that measures the specific resistance of the oil by detecting the voltage generated in the oil, the heating temperature setting signal receiving unit 5 that receives the heating temperature setting signal indicating the heating temperature of the oil, and the heating temperature setting signal And a heater control unit 6 for controlling the heater 3 based on the above. In the present embodiment, the specific resistance measuring unit 4, the heating temperature setting signal receiving unit 5, and the heater control unit 6 are configured by a control device 10. Hereinafter, each part will be described.

  As shown in FIGS. 1 and 2, the oil measurement cell 2 includes a cylindrical external electrode 21, a cylindrical internal electrode 22 that is inserted into the external electrode 21 and provided coaxially with the external electrode 21, An insulating member that fixes the electrode 21 and the internal electrode 22 to each other, closes both end openings of the external electrode 21, and forms a cell space S that contains oil between the inner surface of the external electrode 21 and the outer surface of the internal electrode 22. 23.

  The external electrode 21 and the internal electrode 22 of this embodiment are formed from stainless steel.

  The insulating member 23 has an annular shape, and the axial end of the internal electrode 22 is inserted into the opening via a seal member 24 such as an O-ring, and the axial end surface of the insulating member 23 is the external electrode 21. It is closely attached to the axial end face via a seal member 25 such as an O-ring. The insulating member 23 is fixed to the external electrode 21 by an annular fixing member 26. Thus, since the insulating member 23 fixes the external electrode 21 and the internal electrode 22 at both ends in the axial direction, the insulation member 23 is resistant to vibration and can suppress fluctuations in the gap between the internal surface of the external electrode 21 and the external surface of the internal electrode 22. Therefore, the gap between the inner surface of the external electrode 21 and the outer surface of the internal electrode 22 can be reduced, and the cell constant can be reduced to about 1/10 of the conventional one. In the present embodiment, the cell constant of the oil measurement cell 2 can be set to 0.001 / cm, for example.

  In the oil measuring cell 2, an oil introduction path L1 for introducing oil into the cell space S is formed in the internal electrode 22 on one axial end side, and the internal electrode 22 on the other axial end side An oil lead-out path L2 for leading oil from the cell space S is formed. External pipes H1 and H2 made of an insulating material such as PFA are connected to the inlet port P1 of the oil inlet path L1 and the outlet port P2 of the oil outlet path L2. In this way, by configuring the external pipes H1 and H2 with insulating pipes, the noise current can be reduced by being insulated from the outside and can be measured stably. These external pipes H1 and H2 are connected to bearings, gears, or a hydraulic device or the like directly or via other connecting pipes. The external pipe H1 is provided with a flow meter (not shown).

  The oil introduction path L1 is formed at one end of the internal electrode 22 in the axial direction, and the oil introduction path L1 has a plurality of oil introduction ports L1a communicating with one end of the cell space S in the axial direction. The oil outlet passage L2 is formed at the other axial end portion of the internal electrode 22, and the oil outlet passage L2 has a plurality of oil outlet ports L2a communicating with the other axial end portion of the cell space S. Yes. Note that one end and the other end in the axial direction of the internal electrode 22 are portions extending outward from the external electrode 21. Thus, since the oil introduction path L1 and the oil lead-out path L2 are formed in the insulating member 23, there is no need to provide the introduction port P1 and the lead-out port P2 in the external electrode 21 and the internal electrode 22, and the external electrode 21 and The facing area of the internal electrode 22 can be increased, and the cell constant can be reduced. In addition, since the oil introduction path L1 has a plurality of oil introduction ports L1a, the oil can be evenly distributed in the circumferential direction in the cell space S, and the oil outlet path L2 has a plurality of oil outlets L2a. Further, oil can be prevented from staying inside the cell space S and can be efficiently derived. Therefore, the specific resistance of oil can be measured with high accuracy.

  Further, in the oil measurement cell 2 of the present embodiment, the oil inlet L1a is formed at the lowermost end of the cell space S, and the oil outlet L2a is formed at the uppermost end of the cell space S. Thereby, the dead space of the lower end part and upper end part of the cell space S can be made as small as possible, and the accumulation of bubbles can be prevented. Furthermore, the plurality of oil inlets L1a and the plurality of oil outlets L2a are formed at equal intervals in the circumferential direction of the cell space S. The cell space S can be uniformly filled with oil, and the oil can be uniformly discharged from the cell space S in the circumferential direction, so that the accumulation of bubbles can be further prevented.

  Therefore, in the oil measurement cell 2 of the present embodiment, the heater 3 for heating the oil accommodated in the cell space S is provided on a part of the outer peripheral surface 21a of the external electrode 21. The heater 3 is, for example, a sheet-like member configured by incorporating a heating resistor in a flexible member such as silicon. The heater 3 is provided in close contact with the outer peripheral surface 21 a of the external electrode 21. Specifically, the heater 3 is provided corresponding to substantially the entire inner cell space S in the axial direction, and is provided in a part of the outer peripheral surface 21a in the circumferential direction. Is provided so as to be exposed to the outside. This externally exposed portion 21b functions as a heat radiating portion. Since the external electrode 21 is made of stainless steel and has excellent thermal conductivity, the entire cell space S can be heated by the partially provided heater 3, and the external exposed portion 21 b Cooling of the cell space S can also be facilitated. In addition, the current flowing through the heater 3 is controlled by a heater control unit 6 of the control device 10 described later.

  Further, a temperature sensor 7 for detecting the temperature of the external electrode 21 is provided on a portion of the outer peripheral surface 21a of the external electrode 21 where the heater 3 is not provided, that is, on the externally exposed portion 21b. Here, the temperature sensor 7 is provided on the bottom surface of the recess 21M formed in the externally exposed portion 21b. Thereby, the temperature of the external electrode 21 can be detected with high accuracy. In consideration of the vertical symmetry of the external electrode 21, the temperature sensor 7 is provided on the external electrode 21 at the axial center. The detection signal obtained by the temperature sensor 7 is acquired by the control device 10.

  The control device 10 controls the heater 3 using the temperature detected by the temperature sensor 7 so that the temperature of the external electrode 21 is constant, and measures the specific resistance of the oil flowing through the oil measuring cell 2. is there. Specifically, the control device 10 functions as the specific resistance measuring unit 4, the heating temperature setting signal receiving unit 5, the heater control unit 6, and the like. The control device 10 is constituted by a digital or analog electric circuit having a CPU, a memory, an A / D converter, a D / A converter, etc., and may be a dedicated device or a part thereof. Alternatively, a general-purpose computer such as a personal computer may be used for all. Further, it may be configured such that the functions of the respective units are achieved by using only an analog circuit without using a CPU, and need not be physically integrated, but includes a plurality of devices connected to each other by wire or wirelessly. It may be a thing.

  The specific resistance measuring unit 4 measures the specific resistance of oil by detecting a voltage generated between the external electrode 21 and the internal electrode 22.

Specifically, the specific resistance measuring unit 4 has a specific resistance measuring circuit C shown in FIG. This specific resistance measurement circuit C applies a reference resistance Ca (R ₁ ) having a known resistance value connected in series to the internal electrode 22, and an alternating voltage (V ₁ ) to the pair of electrodes 21, 22 and the reference resistance Ca. AC power source Cb, a detection unit Cc that detects an inter-electrode voltage (V ₂ ) generated between the pair of electrodes 21 and 22, and an oil specific resistance (R ₂ ) using an output voltage from the detection unit Cc. A signal processing unit (not shown) for calculation. The detection unit Cc of the present embodiment is configured by an operational amplifier OP that performs impedance conversion and outputs an interelectrode voltage (V ₂ ). In addition, the calculation of the resistance (R ₂ ) by the signal processing unit uses an expression of V ₂ / R ₂ = V ₁ / (R ₁ + R ₂ ).

Then, the AC power source Cb is a rectangular wave AC voltage between the external electrode 21 and the internal electrode 22 with any amplitude within the range of 1 V to 42 V and any frequency within the range of 0.5 Hz to 30 Hz ( V ₁ ) is applied. Here, the frequency of the rectangular wave AC voltage is more preferably 2 Hz or more for securing the response speed, and more preferably 15 Hz or less for securing the measurement accuracy. Further, the amplitude of the rectangular wave AC voltage is more preferably 15 V or less because an existing circuit element is used. The signal processing unit uses the stable output voltage to obtain a specific resistance at a timing when the output voltage output from the detection unit Cc is stabilized with the application of the rectangular wave AC voltage (V ₁ ) by the AC power source Cb. It is comprised so that it may calculate. The signal processing unit calculates the specific resistance using a stable output voltage. (1) After a predetermined time has passed since the output voltage in the latter half of the rectangular wave, that is, the positive / negative of the AC voltage is switched (in other words, For example, a configuration for calculating the specific resistance using the output voltage acquired immediately before switching between positive and negative of the AC voltage, or (2) determining whether the output voltage is stable by calculating the fluctuation amount, A configuration in which the specific resistance is calculated using the output voltage when it is determined to be stable can be considered.

Further, the specific resistance measuring circuit C is provided with a shield drive circuit C1 in which the potential difference of the stray capacitance Cd formed between the wiring CL1 connected to the external electrode 21 and the wiring CL2 connected to the internal electrode 22 is zero. It has been. The shield drive circuit C1 is configured using an operational amplifier OP that constitutes the detection unit Cc. As a result, the charge / discharge current to the stray capacitance Cd formed between the wiring CL1 connected to the external electrode 21 and the wiring CL2 connected to the internal electrode 22 can be reduced, and an electric current exhibiting a true specific resistance can be obtained. Signal extraction can be facilitated. Further, the time constant of the specific resistance measuring circuit C can be reduced, and the time until the interelectrode voltage (V ₂ ) is stabilized can be shortened. Therefore, the specific resistance of oil can be measured with high accuracy, and oil deterioration can be detected with high accuracy.

  The heating temperature setting signal receiving unit 5 receives a heating temperature setting signal indicating a heating temperature suitable for measuring the specific resistance of the oil stored in the oil measuring cell 2. This heating temperature setting signal is generated when the user inputs using a keyboard, a mouse, a touch panel, a temperature setting button or other input means or a communication system of the oil management system 100Z described later. Moreover, the heating temperature setting signal reception part 5 transmits the received heating temperature setting signal to the heater control part 6 described later. Here, as shown in FIG. 5, the specific resistance of the oil decreases with time, that is, with deterioration (oxidation) of the oil. As shown in FIG. 6, the specific resistance varies depending on the type and temperature. The specific resistance of oil is greatest when not in use. For this reason, the heating temperature of various oils is set so that the specific resistance when the various oils are not used is within the measurement range of the oil measurement cell 2.

  The heater control unit 6 acquires a heating temperature setting signal from the heating temperature setting signal receiving unit 5 and also acquires a detection signal from a temperature sensor 7 provided in the oil measurement cell 2 and measures the temperature (measurement) indicated by the detection signal. Temperature) and the temperature (set temperature) indicated by the heating temperature setting signal are compared, and the current flowing through the heater 3 is controlled so that the temperature measured by the temperature sensor 7 becomes the set temperature.

  Next, an example of a time chart up to the measurement of the specific resistance measuring apparatus 100 configured as described above will be described with reference to FIG.

  First, the user turns on the power of the specific resistance measuring apparatus 100. And a user sets the heating temperature suitable for the specific resistance measurement of the oil which is a measuring object by an input means. A heating temperature setting signal indicating the heating temperature set here is acquired by the heating temperature signal setting reception unit 5 and transmitted to the heater control unit 6. The heater control unit 6 acquires a heating temperature setting signal and starts temperature control of the heater 3. Thereby, the oil measuring cell 2 is warmed up by the heater 3. As the heater 3 warms up, the measured temperature obtained by the temperature sensor 7 increases toward a desired heating temperature. Further, when the oil measurement cell 2 reaches a constant temperature after the elapse of the temperature raising period, the specific resistance measuring unit 4 starts measuring the specific resistance of the oil.

  Note that the warm-up lamp provided in the control device 10 is lit until the oil measurement cell 2 reaches a certain temperature after the heater control unit 6 starts the temperature control of the heater 3, and the user prepares for measurement. It is set as the structure which alert | reports that it is in.

Further, the timing of starting the specific resistance measurement by the specific resistance measuring unit 4 may be, for example, the following (1), (2), and (3).
(1) A user who has confirmed that the warm-up lamp has been switched from lighting to extinguishing operates a measurement start switch or the like provided separately to transmit a measurement start signal to the specific resistance measuring unit 4 Is done. And the specific resistance measurement part 4 starts a specific resistance measurement, when the said measurement start signal is acquired.
(2) The heater control unit 6 is configured to transmit a determination signal to the specific resistance measurement unit 4 when it is determined that the measured temperature of the temperature sensor 7 is the same as the set temperature. Then, the specific resistance measurement unit 4 starts the specific resistance measurement when the determination signal is acquired.
(3) The specific resistance measuring unit 4 acquires the heating temperature setting signal from the heating temperature setting signal receiving unit 5 or the heater control unit 6, and also acquires the detection signal from the temperature sensor 7, and the temperature indicated by the detection signal ( The measurement temperature) is compared with the temperature (set temperature) indicated by the heating temperature setting signal. When the specific resistance measuring unit 4 determines that the measured temperature and the set temperature are the same, the specific resistance measurement is started.
(4) The start of specific resistance measurement or the validity determination of acquired data may be performed by a computer or the like that has received a signal via an oil management system 100Z described later.

  Next, an oil management system 100Z using the specific resistance measuring apparatus 100 of the present embodiment will be described with reference to FIG. Since the target device X managed by the specific resistance measuring apparatus 100 has a different relationship between the degree of deterioration, the specific resistance value, and the temperature depending on the type of the used liquid such as lubricating oil, the specific resistance measurement of the used liquid of the target device X is performed in advance. It is desirable to confirm the behavior in the apparatus 100 and use a working solution whose behavior has been confirmed.

  The oil management system 100Z includes a transmission system (not shown) that automatically transmits the specific resistance value and temperature obtained by the specific resistance measurement device 100 to a management device (user terminal) on the manager side via a communication line. The oil management can be performed over time by acquiring the specific resistance value and the temperature as signals. In addition to the signal from the specific resistance measuring device 100, the management device also receives a signal from a measuring device that measures other measurement target items such as moisture and light transmittance. Therefore, the used liquid can be managed.

  Specifically, the oil management system 100Z includes an oil supply pipe 11 (corresponding to the external pipe H1 described above) for supplying the used liquid from the used liquid tank X1 of the target device X to the oil measuring cell 2 of the specific resistance measuring apparatus 100. , An oil drain pipe 12 (corresponding to the above-described external pipe H2) for returning the oil from the oil measuring cell 2 back to the working liquid tank X1 is provided. The use liquid tank X1 is provided with a purification line X2 for purifying the oil stored in the use liquid tank X1, and the purification line X2 is used for circulating oil through the line X2. A pump X21 and a filter X22 for removing foreign matters such as contaminants and wear powder contained in the oil are provided.

  And the oil collection site | part by the oil introduction port of the oil supply pipe | tube 11 is the use liquid tank X1, and is the downstream of the filter X22 in the purification line X2 in detail. As a result, the use liquid purified by the filter X22 can be supplied to the oil measurement cell 2. In the case where the purification line X2 is not provided, it is conceivable that the oil introduction port is provided in a portion in contact with the use liquid in the use liquid tank X1.

  Further, the oil supply pipe 11 is provided with a supply pump 13 for supplying oil collected by the oil introduction port to the oil measurement cell 2. The supply pump 13 may be provided in the oil drain pipe 12.

  A foreign matter removing mechanism 14 is preferably provided on the upstream side of the oil measuring cell 2. The foreign matter removing mechanism 14 is a collection unit made of a filter, a magnet, or the like that collects impurities or wear powder contained in the oil. And this collection unit 14 is made detachable with respect to the oil supply pipe 11, and performs strict oil management by analyzing the collected matter collected by the collected collection unit 14 It is configured to be able to.

  The foreign matter removing mechanism 14 of the present embodiment is a filter, and pressure sensors 15 and 16 are provided on the upstream side and the downstream side of the filter 14. The pressure from the pressure sensors 15 and 16 is acquired as a signal and The differential pressure is used so that filter management such as clogging of the filter 14 can be performed together with oil management.

  Further, the oil drain pipe 12 is provided with a sampling line 16, and when the specific resistance value obtained by the specific resistance measuring device 100 becomes an abnormal value, the use liquid indicating the abnormal specific resistance value is sampled. The container 17 can be collected. Furthermore, when this system is operated in a portable manner, a number of devices are measured with one system per day to obtain quick results, and detailed analysis using actual samples for each device and results. Therefore, the sampling mechanism functions extremely effectively.

  Specifically, the sampling line 16 is a sampling pipe that is branched in the middle of the oil drain pipe 12, and a sampling container 17 is provided at the outlet of the sampling pipe 16. Further, a switching valve 18 is provided on the downstream side of the branch point in the oil drain pipe 12 and the sampling pipe 16 for switching the pipe through which the used liquid flows. This switching valve 18 may be an electromagnetic valve that can be switched automatically, or a manual valve that can be switched manually.

  Furthermore, the sampling container 17 is provided so as to be detachable from the sampling tube 16, and the abnormal use liquid stored in the sampling container 17 is analyzed by an analyzer such as an elemental analyzer. Note that an oil pan 19 is provided below the sampling container 17 for collecting the used liquid overflowing from the sampling container 17, and the collected used liquid is used for the used liquid. A return pipe 20 for returning to the tank X1 is provided.

<Effect of this embodiment>
According to the specific resistance measuring apparatus 100 of the present embodiment configured as described above, since the rectangular wave AC voltage is applied, it is possible to suppress the formation of the electric double layer at the boundary between the electrodes 21 and 22 and the oil, The specific resistance of oil can be continuously measured. Moreover, since the voltage of 1V-42V is applied, degradation by measurement, such as quality change of the oil under measurement, can be prevented. Here, since the AC voltage is 1 V to 42 V, the AC power source can be configured at low cost, and the danger to the human body can be reduced even when an electric shock is received. Furthermore, since the frequency is 0.5 Hz to 30 Hz, the signal output from the specific resistance measuring circuit C can be stabilized before switching between positive and negative of the AC voltage, so that the specific resistance of oil can be measured with high accuracy. Oil degradation can be detected with high accuracy.

  Moreover, since the temperature of the oil accommodated in the cell space S is adjusted to a predetermined heating temperature, it can be set to a temperature suitable for measuring the specific resistance of each oil, and the ratio of various oils The resistance can be made measurable. In addition, since the temperature of the oil stored in the cell space S is controlled to be constant, measurement errors due to temperature fluctuations of the oil can be reduced without necessarily relying on temperature compensation, and the specific resistance of the oil can be measured with high accuracy. be able to. Therefore, it is possible to accurately detect oil deterioration of various oils. Furthermore, in the case of particularly high-viscosity oil, since the viscosity is lowered by heating, the oil can be easily distributed to the oil measurement cell 2.

The present invention is not limited to the above embodiment.
For example, the specific resistance measuring apparatus 100 according to the embodiment may further include a deterioration determination unit. The deterioration determination unit is configured by the control device 10. The deterioration determination unit performs deterioration determination by comparing the specific resistance obtained by the specific resistance measurement unit 4 with a predetermined threshold (reference specific resistance). Here, the reference specific resistance is set for each of various oils. For example, the user may be able to set and input the threshold, or threshold data indicating threshold values set for each of the various oils may be stored in the memory. The user may be able to select it. In addition, as a method for determining deterioration, the deterioration determination may be performed based on the relationship with the initial value (specific resistance) of the measured oil, for example, the ratio to the initial value.

  Further, the deterioration determination unit outputs a deterioration determination signal to the notification unit control unit provided in the control device 10 when the calculated specific resistance is lower than the threshold value. The notifying unit control unit controls a notifying unit such as a lamp or a display provided in the control device 10 to notify the user of oil deterioration.

  In the embodiment, the configuration is such that the user sets the heating temperature, but the heating temperature may be automatically set on the control device 10 side when the user inputs the oil type. In this case, as shown in FIG. 9, the control device 10 includes a data storage unit 8 that stores heating temperature setting data indicating the heating temperature set for each type of oil, and the oil stored in the oil measurement cell 2. It is conceivable to include an oil selection signal receiving unit 9 that receives an oil selection signal indicating the type.

  The data storage unit 8 stores heating temperature setting data indicating the heating temperature set for each type of oil. Here, the heating temperature setting data indicates, for example, the heating temperature set so that the specific resistance of each oil when not in use is within the measurement range of the oil measurement cell 2. The heating temperature setting data is stored in advance in the data storage unit 8 by the user.

  The oil selection signal reception unit 9 receives an oil selection signal indicating the type of oil to be measured that is stored in the oil measurement cell 2. The oil selection signal is generated when the user inputs using an input means such as a keyboard, a mouse, a touch panel, an oil setting button, or the communication system of the oil management system 100Z. In addition, the oil selection signal receiving unit 9 transmits the received oil selection signal to the heater control unit 6.

  The heater control unit 6 acquires an oil selection signal from the oil selection signal receiving unit 9, and based on the oil selection signal and the heating temperature setting data stored in the data storage unit 8, the heating temperature of the heater 3 (set temperature) ) Is set. And the heater control part 6 acquires a detection signal from the temperature sensor 7 provided in the oil measurement cell 2, and compares the temperature (measurement temperature) which the detection signal shows with the set heating temperature (setting temperature). Then, the current value flowing through the heater 3 is controlled so that the temperature indicated by the detection signal of the temperature sensor 7 becomes the set heating temperature.

  In such a case, in addition to the effects of the above embodiment, the user can adjust the temperature to a temperature suitable for measuring the specific resistance of the oil only by inputting the type of the oil. Each temperature can be set to a temperature suitable for measuring the specific resistance of the oil, and the specific resistance of various oils can be measured.

  In the above embodiment, the heating temperature is set before the start of the temperature control of the heater. However, the setting is set before (for example, before the start of the temperature control) after the start of the temperature control of the heater or during the specific resistance measurement. You may comprise so that temperature can be changed.

  Further, instead of setting the set temperature as a single value, the upper limit value and the lower limit value of the heating temperature can be set, and the temperature of the oil measurement cell 2 is controlled between the upper limit value and the lower limit value of the heating temperature. You may comprise as follows. In this case, the specific resistance calculated by the specific resistance measurement unit may be configured to be temperature compensated using the detected temperature obtained by the temperature sensor.

  In addition, although the oil introduction path L1 and the oil lead-out path L2 of the embodiment are provided in the internal electrode 22, they may be provided in the insulating member 23.

  The oil measurement cell 2 and the control device 10 may be accommodated in one casing and unitized. In this case, it is conceivable to make the casing portable by providing a carrying handle. In addition, the casing has a supply port to which piping for supplying oil such as an external bearing and a hydraulic device is connected to the oil measurement cell, and an external bearing for discharging the measured oil from the oil measurement cell to the outside. It is conceivable to provide a discharge port to which a pipe for returning measured oil is connected to a hydraulic device or the like.

In addition, in the embodiment, the specific resistance is calculated by detecting the voltage (V ₂ ) between the external electrode 21 and the internal electrode 22, but the specific resistance is calculated by detecting the voltage applied to the reference resistor Ca. You may make it do. In this case, detecting the resistance value R ₁ of the reference resistor Ca with differential circuits.

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

100: Specific resistance measuring device 2 ... Oil measuring cell (liquid sample measuring cell)
21 ... External electrode 22 ... Internal electrode 4 ... Specific resistance measuring unit C ... Specific resistance measuring circuit Ca ... Reference resistance Cb ... AC power supply OP ... Operational amplifier CL1 ... External Wiring CL2 connected to electrode ... Wiring C1 connected to internal electrode ... Shield drive circuit Cd ... Floating capacitance

Claims (8)

A specific resistance measurement circuit that measures specific resistance to detect deterioration of a liquid sample,
By detecting the voltage generated between the pair of electrodes, the specific resistance of the liquid sample between the pair of electrodes is measured,
A shield drive circuit using an operational amplifier, in which the potential difference of the stray capacitance formed between the wires connected to the pair of electrodes is zero;
A specific resistance measurement circuit, wherein a rectangular wave AC voltage having an amplitude of 1 V to 42 V and a frequency of 0.5 Hz to 30 Hz is applied between the pair of electrodes. A specific resistance measuring device comprising the specific resistance measuring circuit according to claim 1 . A liquid sample management method for performing liquid sample management over time by acquiring a specific resistance value and a temperature as signals using the specific resistance measuring apparatus according to claim 2 . A transmission system for automatically transmitting the specific resistance value and temperature acquired as signals for the liquid sample management method according to claim 3 to the manager side via a communication line;
A liquid sample management system comprising a supply pump for supplying a liquid sample to a measurement cell having the pair of electrodes. The liquid sample management system according to claim 4 , wherein the supply pump is provided in at least one of a supply pipe that supplies the liquid sample to the measurement cell and a discharge pipe that discharges the liquid sample from the liquid sample measurement cell. 6. The liquid sample management system according to claim 4 or 5, wherein a signal or data is input to the specific resistance measuring device via a communication system. Liquid sample management system according to any one of claims 4 to 6 foreign matter removing mechanism is provided in the supply pipe for supplying the liquid sample to the measurement cell. The foreign matter removing mechanism in the liquid sample management system according to claim 7 is a filter.
A liquid sample management method comprising performing a filter management together with a liquid sample management by providing a pressure sensor at least upstream of the filter and acquiring the pressure from the pressure sensor as a signal.