JP2005114356A - Instrument and method for measuring ultra-high resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an instrument and method for measuring an ultra-high resistance, enabling continuous measurement under environmental stress, and allowing the measurement up to 10<SP>18</SP>to 10<SP>20</SP>Ω of ultra-high resistance. <P>SOLUTION: This ultra-high resistance measuring instrument is provided, in parallel with a background measuring side magnetic levitation electrode ionization chamber 1a with a magnetically levitated electrode 3a, and a resistance-measuring side ionization chamber 1b where an electrode 3b is connected with an external electrode with a sample 13. The electrodes 3a, 3b of the respective ionization chambers are charged; the potentials of the respective electrodes 3a, 3b are measured by a Faraday cage 5; a reduction in charge for each of the electrodes is found, based on a variation per a unit time of each of the potentials, currents are found based thereon to find a difference therebetween; and the voltage in the sample 13 is divided by the difference so as to measure the electrical resistance of the sample 13. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to an ultra-high resistance measuring apparatus capable of measuring an electrical resistance of an insulator having a resistance of 10 ¹⁵ Ω to 10 ²⁰ Ω, particularly an insulator having a resistance of 10 ¹⁸ Ω to 10 ²⁰ Ω, and an ultra-high resistance measuring method for implementing the same. Is.

Conventionally, as a method of measuring a high resistance of 10 ¹² Ω or more, a galvanometer method, a method using a DC amplifier, a super insulation meter, or an ultra high resistance measurement method for measuring a high resistance up to about 10 ¹⁴ Ω, etc. are known. (See Non-Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3). However, in these measurement methods, 10 ¹⁵ Ω is the limit of measurement. In addition to this, there is an ionization chamber method in which an ionization chamber filled with an isotope having a long half-life is constant regardless of a change in voltage, and this is used as a stable constant current source and a high resistance standard ( Non-patent document 4). In this method, measurement up to 10 ¹⁷ Ω is possible.

In the information electronics field, it is necessary to accurately measure the surface resistance value of glass, thin film components, etc., and in a typical case measured in accordance with JIS-C-2141 that defines this method, the surface resistance value is The resistance value (5 × 10 ¹⁵ Ω) is the measurement limit, and it has been reported that the surface resistivity can be measured at about 10 ¹⁷ Ω / cm.

  Normally, electric devices are used in a state of being energized for a long time, and therefore, the characteristics of electric resistance also change depending on the use environment and its change over time. For this reason, reliability evaluation of electronic devices is indispensable and environmental tests are often performed. However, in most cases, intermittent measurements are performed in each case to compare measured values before and after each test. This is because various environmental stresses such as temperature, X-rays, radiation, etc. not only change these characteristics, but also mix noise in the measurement results. This is because the measurement data becomes meaningless data due to fluctuations. This tendency becomes more pronounced as the measurement with higher sensitivity is required and the ratio of measured value / noise is deteriorated.

In this way, there is a contradiction that continuous measurement increases noise when sensitivity is increased, but if there is a method that can perform continuous measurement without being affected by environmental stress, the reliability evaluation of electronic equipment will be much more effective. Become. For example, Non-Patent Document 5 reports this effectiveness. Non-Patent Document 5 is obtained by continuously measuring fluctuations in characteristic values using a sample obtained by subjecting a glass epoxy substrate having an electrical resistance of about 10 ¹¹ Ω to a surface treatment of printed wiring. And we have concluded that continuous measurement under actual environmental stress is effective for reliability evaluation to find the cause of deterioration and failure. However, the direct current used in the measurement for this report was greater than 3 × 10 ⁻¹² A, and the resistance measured 10 ⁶ Ω to 10 ¹² Ω. Since the measurement is relatively low in sensitivity, the above contradiction is small and the noise is small, so it is considered that continuous measurement is possible. Therefore, the method of Non-Patent Document 5 has no suggestion for a continuous measurement for a long time of 10 ¹⁸ Ω or more, a minute current of 10 ⁻¹⁵ A or less that requires high-sensitivity measurement.

  Although not related to the resistance measurement apparatus described above, one of the inventors of the present invention has proposed a radiation detection apparatus that measures radiation with high sensitivity together with other inventors (see Patent Document 1). An electromagnet is arranged on the top of the ionization chamber body, an electrode is magnetically levitated inside the ionization chamber body, and an electrostatic charger for charging the electrode is installed. The Faraday cage is moved in and out from the shutter at the bottom of the ionization chamber body. It is what it is. The Faraday cage can read out charges without contact and improves sensitivity.

Japanese Patent No. 3061798 Denshu Shoin editorial department “Denki Handbook”, Denki Shoin, July 1968, p. 345-p. 358 Supervised by Jiro Yamauchi, “Electrical Measurement Handbook”, Ohmsha, May 1971, p. 390-p. 394 The 6th edition of the "Electronic Engineering Handbook" edited by the Institute of Electrical Engineers, Ohmsha, February 2001, p. 249 Konnobu Nobunobu, “Electrical Measurement”, Kyoritsu Shuppan, July 1969, p. 259 Tanaka Hirokazu et al. "A Study on Reliability Evaluation Method for Electronic Components", ESPEC Technical Information, No. 3, Tabai Espec Co., Ltd., September 1995, p. 4-p. 7

  The accuracy of electronic equipment depends on the performance and reliability of the electronic components used there, and also on environmental stress, which is an external factor. For example, high-sensitivity electrometers and picoammeters are required to have the performance and reliability of being able to measure extremely small currents and voltages. As a precondition for realizing this performance, the high resistance and ultrahigh resistance that constitute the measurement system Must be tested reliably in various environments.

When such high resistance is measured by the conventional galvanometer method, DC amplifier method, superinsulator, ultrahigh resistance measurement method, ionization chamber method, etc., measurement of about 10 ¹⁷ Ω is the limit. It was difficult to measure an ultrahigh resistance exceeding 10 ¹⁸ Ω to 10 ²⁰ Ω. Development of a measurement method that can measure such ultra-high resistance is desired, but such a measurement method is highly sensitive. The higher the sensitivity, the greater the influence of environmental stress on the surroundings. The contradiction of being buried inside arises. This cannot meet the need for continuous measurement with high sensitivity. Although non-patent document 5 also performs continuous measurement, it measures a resistance of 10 ⁶ Ω to 10 ¹² Ω and is not suggested for continuous measurement of ultrahigh resistance.

  Regarding the ionization chamber, the ionization chamber proposed by one of the present inventors is a highly sensitive radiation detection device, not a resistance measurement device capable of measuring ultrahigh resistance. It is not a constant current source and cannot be used in the conventional ionization chamber method.

Therefore, the problem to be solved by the present invention is that the resistance is continuously increased to an ultrahigh resistance of 10 ¹⁸ Ω to 10 ²⁰ Ω under an environmental stress such as a long-time energization state or use under X-ray irradiation. It is the point which implement | achieves the ultrahigh resistance measuring apparatus which can be measured, and an ultrahigh resistance measuring method.

The present invention is continuously under environmental stress, and to provide a 10 ¹⁸ Ω~10 ²⁰ Ω and resistance measurement method capable of measuring resistance measuring device to ultra-high resistance.

  The present invention includes a first internal electrode and a first external electrode which are provided in a container containing an ionizing gas and are electrically connected by setting a sample. A resistance measurement-side ionization chamber that measures the potential of the first internal electrode, which decreases in accordance with the background radiation dose and the electrical resistance of the sample, with a first Faraday cage, and a container that contains an ionizing gas, are magnetically levitated. A second Faraday cage is used to measure the potential of the second electrode, which includes a second internal electrode and a second external electrode provided in the container, and the charge charged by a predetermined amount during measurement decreases according to the amount of background radiation. The first current value is calculated based on the background measurement side magnetically levitated electrode ionization chamber and the change amount of the potential of the first internal electrode per time, and the change of the potential of the second internal electrode per time A calculation unit for calculating the second current value based on the difference between the first and second current values and a control unit for magnetically levitating the second internal electrode and controlling each Faraday cage. The main feature of the ultrahigh resistance measurement device is that the calculation unit obtains the electrical resistance of the measurement sample based on the voltage applied to the sample and the difference between the first and second current values.

According to the ultra-high resistance measuring apparatus and ultra-high resistance measuring method of the present invention, when background current is mixed into the measurement result due to environmental stress such as long-time energization and X-ray / radiation irradiation, it becomes noise Even so, it can be measured continuously and can be measured up to an ultrahigh resistance of 10 ¹⁸ Ω to 10 ²⁰ Ω.

In order to solve the above-mentioned problems, a first embodiment for carrying out the present invention includes a first internal electrode and a first internal electrode which are provided in a container containing ionizing gas and are electrically connected by setting a sample. A resistance measurement-side ionization chamber comprising a first external electrode and measuring the potential of the first internal electrode with a first Faraday cage in which the charge charged by a predetermined amount during measurement decreases according to the background radiation dose and the electrical resistance of the sample; A second internal electrode provided in a container containing an ionizing gas and magnetically levitated, and a second external electrode provided in the container, and a charge charged by a predetermined amount at the time of measurement becomes a background radiation dose The first current value is calculated based on the background measurement side magnetic levitation electrode ionization chamber that measures the potential of the second electrode that decreases in accordance with the second Faraday cage, and the amount of change in the potential of the first internal electrode per hour. And calculating a second current value based on the amount of change of the potential of the second internal electrode per time and obtaining a difference between the first and second current values, and magnetically levitating the second internal electrode. And an ultra-high resistance measuring device including a control unit for controlling each Faraday cage, wherein the arithmetic unit measures based on the voltage applied to the sample and the difference between the first and second current values. This is an ultra-high resistance measuring device that determines the electrical resistance of a sample. The internal electrode of the ionization chamber on the resistance measurement side is charged, the total current of the background current and the current flowing through the sample is measured by a Faraday cage, and the magnetic levitation on the background measurement side The current flowing through the sample can be calculated by charging the internal electrode of the electrode ionization chamber, measuring the background current, and calculating the difference between the total current and the background current. The resistance value can be calculated by dividing the voltage between the samples by this current value. With this apparatus and method, even when there is the environmental stress, it is possible to continuously measure to an ultrahigh resistance of 10 ¹⁸ Ω to 10 ²⁰ Ω. The conventional ionization chamber method is one in which an isotope is enclosed and the ionization chamber is used as a current source and high resistance standard. The resistance measurement side ionization chamber and the background measurement side magnetic levitation electrode ionization chamber of the present invention are also used as a current source. It is not a high-resistance standard but for removing environmental stress.

  According to a second embodiment for implementing the present invention, in the first embodiment, the sample holder is electrically connected to the first internal electrode and the first external electrode, and the resistance is measured by setting the sample in the sample holder. This is a resistance measurement device to be used, and since a sample holder is provided, resistance can be easily measured by simply setting a sample.

  A third embodiment for carrying out the present invention is a resistance measurement device in which the external electrode is grounded in the first or second embodiment, and the circuit configuration is simplified and the handling is facilitated.

According to a fourth embodiment for carrying out the present invention, a resistance measurement side ionization chamber containing an ionizing gas and a background measurement side magnetic levitation electrode ionization chamber are provided close to each other. And external electrodes are electrically connected by a sample. In the background measurement side magnetic levitation electrode ionization chamber, internal electrodes are magnetically levitated, and each internal electrode is charged a predetermined amount, and then ionizing gas is ionized by the action of background radiation. Then, the potential of each internal electrode is measured by a Faraday cage, the current value is calculated based on the amount of change in the potential of each internal electrode per hour, the difference between the two is calculated, and the voltage applied to the sample is calculated based on the difference. This is a resistance measurement method that measures the electrical resistance of a sample by splitting. The internal electrode of the resistance measurement side ionization chamber is charged and the background current and sample flow through the Faraday cage. Measure the total current, charge the internal electrode of the magnetic levitation electrode ionization chamber on the background measurement side, measure the background current, and calculate the difference between the total current and the background current to calculate the current flowing through the sample. It can be calculated. The resistance value can be calculated by dividing the voltage between the samples by this current value. It can be measured continuously under environmental stress, and can be measured up to an ultrahigh resistance of 10 ¹⁸ Ω to 10 ²⁰ Ω.

(Embodiment)
Hereinafter, the ultrahigh resistance measuring device and the ultrahigh resistance measuring method of the present invention will be described. The ultra-high resistance measuring device includes an ionization chamber having electrodes capable of magnetic levitation and an ionization chamber for setting a sample and measuring current. The former is used to measure the background current due to radiation injected into this location, and the latter is used to measure the sum of the current flowing through the sample and the background current. By taking the difference between the two currents, the background current is removed, and the resistance from high resistance to ultra-high resistance can be measured using the resulting current flowing through the sample and the applied voltage applied to the sample. To do. FIG. 1 is a configuration diagram of an ultrahigh resistance measurement device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of a background measurement side magnetic levitation electrode ionization chamber of the ultrahigh resistance measurement device according to an embodiment of the present invention, and FIG. These are explanatory drawings of the resistance measurement side ionization chamber of the ultrahigh resistance measurement device in the embodiment of the present invention.

  In FIG. 1, 1a is a background measurement side magnetic levitation electrode ionization case outer case, 1b is a resistance measurement side ionization case outer case for setting a measurement sample and measuring a current to obtain a resistance value, and 2a is external radiation. Background measurement-side magnetic levitation electrode ionization chamber that accommodates air that can be ionized by the like (ionizing gas of the present invention) in the container, 2b is air that can be ionized by external radiation or the like (ionizing gas of the present invention) The resistance measurement side ionization chamber 3a accommodated in the container is an electrode that collects negative ions (or cations) ionized by radiation by magnetic levitation in the background measurement side magnetic levitation electrode ionization chamber 2a. (Internal electrode), 3b is an electrode (second internal electrode of the present invention) that is suspended in a resistance measurement side ionization chamber 2b via a sample 13 described later, and 4 is an electromagnet for magnetically levitating the electrode 3a.The background measurement side magnetic levitation electrode ionization chamber 2a and the resistance measurement side ionization chamber 2b are both external electrodes formed by applying a conductive material to the inner surface of the cylindrical portion of the container. An external electrode, and a second external electrode of the present invention), and is appropriately grounded. Moreover, the volume of the ionization part of two ionization chambers is the same.

  5 is a Faraday cage that reads and charges the charges on the electrodes 3a and 3b as a cage voltage by moving up and down into the background measurement side magnetic levitation electrode ionization chamber 2a and the resistance measurement side ionization chamber 2b. This is an electrostatic charger (charging means of the present invention) that charges a predetermined amount of charge on the electrode 3. Reference numeral 9a denotes a light-emitting element that constitutes the position detection sensor, and reference numeral 9b denotes a light-receiving element of the position detection sensor that receives light emitted from the light-emitting element 9a. Reference numeral 10 denotes a background measurement side magnetic levitation electrode outer case 1a, an openable / closable shutter provided on the bottom plate of the resistance measurement side ionization case 1b, 11 an electrometer for measuring a voltage, and 12 an elevator for the Faraday cage 5. It is an actuator for doing. The shutter 10 can be opened and closed by sliding, or can be removed or opened by a hinge. For automation, opening and closing by slide or hinge is preferable. The size of the shutter 10 may be any size as long as the Faraday cage 5 can be inserted into the ionization chamber 2a2b.

  The anions (or cations) ionized by radiation are collected on the electrodes 3a and 3b charged by the electrostatic charger 8, and the charge amount of the charges on the 3a and 3b decreases according to the radiation dose. After a certain period of time, the shutter 10 is opened, the Faraday cage 5 is raised, and the cage voltage is read by the electrometer 11. If the difference between the cage voltages before and after the lapse of this fixed time is obtained, the average value of the current flowing during this time can be calculated using the capacitance of the Faraday cage 5 and the measurement time interval.

  Reference numeral 13 denotes a sample for measuring electric resistance, and 18 denotes a levitation driver means for levitation of the electrode 3a of the background measurement side magnetic levitation electrode ionization chamber 2a to the position of the position detection sensor. A difference from the target position detected by the position detection sensor is fed back to the levitating driver means 18, and the electrode 3 a is kept in a levitating state by balancing the gravity of the electrode 3 a and the magnetic force of the electromagnet 4. When the balance is broken, feedback is applied by the position detection sensor, and the electrode 3a rises to a predetermined position.

  Reference numeral 19 denotes an arithmetic unit that calculates analog data detected by the electrometer 11 after A / D conversion. In the calculation unit 19, the cage voltage of the Faraday cage 5 of the background measurement side magnetic levitation electrode ionization chamber 2a and the resistance measurement side ionization chamber 2b read by the electrometer 11, and each Faraday cage 5 input from the input unit 23 described later. Based on the capacitance and the measurement time interval, an average current value in this measurement time is calculated.

  20 is a control unit that controls the system of the ultrahigh resistance measurement device, and 20a is a resistance to the background measurement side magnetic levitation electrode ionization chamber 2a and the resistance measurement side ionization chamber 2b in order to automatically perform measurement by the ultrahigh resistance measurement device. Measurement management means for controlling the measurement, 20b is an elevation control means for controlling the actuator 12, 20c is a calculation processing means for calculating in the calculation unit 19, 21 is a measurement result, an input screen, and an error occurrence is displayed on the display. It is a display part to do.

  22 is a storage unit for storing data and a control program, 23 is an input unit such as a keyboard, 24 is a time counting means for counting a predetermined time in order to detect charges by the electrometer 11, and 25 is a total number of data Counting means. The control unit 20 is configured as a function realizing unit by reading a control program stored in the storage unit 22 into a central processing unit (hereinafter referred to as CPU). The measurement management means 20a, the elevation control means 20b, and the arithmetic processing means 20c are all functional means configured as this function realization means. Further, the calculation unit 19 may be configured by a CPU common to the control unit 20.

  Next, the configuration on the background measurement side magnetic levitation electrode ionization chamber 2a side will be described with reference to FIG. In FIG. 2, 2c is a transparent glass window for light transmission opened for the control of the floating of the electrode 3a, 4a is a coil wound around a magnetic body constituting the electromagnet 4, 5a is an internal electrode of the Faraday cage 5, 5b Is an external electrode of the Faraday cage 5, 6 is a capacitor provided between the internal electrode 5a and the external electrode 5b, 7a and 7b are insulators that insulate between the internal electrode 5a and the external electrode 5b, and the external electrode 5b is As with the background measurement side magnetic levitation electrode ionization chamber 2, it is grounded. Although not shown, a lid is provided on the front surface of the background measurement side magnetic levitation electrode ionization chamber 2a and opens and closes when the electrode 3a is magnetically levitated. Further, the lower portion of the external electrode 2a and the conductive floor portion on which the external electrode 2a is placed are in close contact with each other, and the ionization volume portion is in a sealed state during measurement.

  The capacitance of the Faraday cage 5 is measured in advance by a tester, and this value and the measurement time interval are input from the input unit 23, whereby the background measurement side magnetic levitation electrode ionization chamber 2a and the resistance measurement side ionization chamber 2b. Using the cage voltage measured at each Faraday cage, the product of the change in cage voltage per hour and the capacitance is calculated. Thereby, the charge and current of the ionization chambers 2a and 2b can be calculated. Details will be described later.

  Next, the structure of the resistance measurement side ionization chamber 2b will be described with reference to FIG. In FIG. 3, 13 is a high-resistance or ultra-high resistance sample, 14 is a sample holder to which the sample 13 can be mounted for measurement, 15 is a thin electrode that suspends the electrode 3b and the sample holder 14 in this order and electrically connects them. It is a conducting wire. Reference numeral 16 denotes a support cap that is connected to the end of the thin conducting wire 15 to suspend the electrode 3b and the sample holder 14 and closes an opening opened on the upper surface of the resistance measurement side ionization chamber 2b. The support cap 16 is grounded. Since the external electrode of the resistance measurement side ionization chamber 2b is also grounded, the support cap 16 is preferably connected to this external electrode. In addition, about the internal electrode 5a of the Faraday cage 5, the external electrode 5b, the capacitor | condenser 6, and the insulators 7a and 7b, it is as having demonstrated in the background measurement side magnetic levitation electrode ionization chamber 2a mentioned above, and description is abbreviate | omitted. Although not shown, a lid is provided on the front surface of the resistance measurement side ionization chamber 2 b and opens and closes when the sample 13 is set on the sample holder 14. Similarly to the background measurement side magnetic levitation electrode ionization chamber, this ionization chamber 2b is in a sealed state during the measurement.

  When the sample 13 is mounted on the sample holder 14 of the resistance measurement side ionization chamber 2b, the sample 13 and the sample holder 14 are electrically connected, and further, between the electrode 3b and the sample holder 14, and between the support cap 16 and the sample holder 14, It is electrically connected by the thin conducting wire 15. When the electrode 3 b is charged by the electrostatic charger 8, the charged charge (positive charge) is charged and then moved through the thin conductive wire 15, the sample holder 14, the high resistance or ultrahigh resistance sample 13, and the support cap 16. At first, a weak leak current starts to flow. At the same time, after charging, the air in the resistance measurement side ionization chamber 2b is ionized by external radiation or the like, and the ionized anions (or cations) are collected by the electrode 3b to reduce the charged charge. When this is measured by the Faraday cage 5, the change in the cage voltage is reduced by the amount of the leaked charge and the charge reduced by the ionization, and the capacitance of the Faraday cage 5 input from the input unit 23 and the measurement time interval are measured. Is used to calculate the product of the cage voltage variation per hour and the capacitance. As a result, in the resistance measurement side ionization chamber 2b, a current obtained by adding the leakage current and the background current is measured. Here, the electrode 3a and the electrode 3b have the same surface area, and the sample holder 14 and the thin wire 15 for setting the sample are attached to the electrode 3b, but the total surface area of the sample holder 14 and the thin wire 15 is the same. Is negligibly small compared to the surface area of the electrode 3b. Therefore, the charge collection characteristics of the ionization chamber 2a and the ionization chamber 2b may be regarded as the same.

  Subsequently, a procedure of resistance measurement by the ultrahigh resistance measurement device will be described. FIG. 4 is a flowchart of resistance measurement according to the present invention. Make the following preparations before starting measurement. First, the front cover of the background measurement side magnetic levitation electrode ionization chamber 2a is opened, and the electrode 3a is magnetically levitated (step 1). Then close the lid and seal. Once the electrode 3a is magnetically levitated, the electrode 3a continues to levitate until the power is turned off by the action of the levitating driver means 18. Next, the front lid in the resistance measurement side ionization chamber 2b is opened, the sample 13 is set in the sample holder 14 (step 2), and the lid is closed and sealed. Then, positive charges are charged to the electrodes 3a and 3b by using the electrostatic charger 8 of the background measurement side magnetic levitation electrode ionization chamber 2a and the resistance measurement side ionization chamber 2b (step 3).

  Next, on the input screen displayed on the display of the display unit 21, the input unit 23 inputs the measurement time interval, the previously measured capacitance of the Faraday cage 5, the measurement end time, and other measurement conditions. Then (step 4), the measurement management means 20a starts control for automatically performing resistance measurement. First, it is checked whether or not a measurement end instruction such as forced end is input (step 5). If there is no measurement end instruction, it is checked whether a predetermined time has elapsed. (Step 6). When a predetermined time elapses, the control unit 20 opens the shutter 10, the elevation control means 20 b operates the actuator 12 to raise the Faraday cage 5, and reads the potentials (cage voltages) of the electrodes 3 a and 3 b with the electrometer 11 ( Step 7) The Faraday cage 5 is lowered and the shutter 10 is closed at the same time. The read data is sent to the calculation unit 19, and the charges on the electrodes 3 a and 3 b are calculated from the read voltage and the capacitance of the Faraday cage 5.

Here, if the cage voltage measured by the electrometer 11 is V _K and the capacitance of the Faraday cage 5 measured in advance is C _K , the charge Q on the electrodes 3a and 3b is Q = C _K × V Calculated as _K. Further, if the time interval to be measured is Δt, the difference in the cage voltage generated during this Δt is ΔV _K , and the amount of charge decrease during this time is ΔQ, then ΔQ = C _K × ΔV _K , and this time interval The current i flowing during Δt is calculated as i = C _K × ΔV _K / Δt using i = ΔQ / Δt, that is, the change amount ΔV _K / Δt per hour of the cage voltage V _K.

Assuming that the current of the electrode 3a is i _A , the current of the electrode 3b is i _B , the respective background currents are i _A ^b and i _B ^b , and the leakage current of the sample 13 is i, the current of the electrode 3a is i _A = i _A ^b , and the current of the electrode 3b is i _B = i _B ^b + i. Arrangement of background measurement side magnetic levitation electrode ionization chamber 2a and the resistance measurement side ionization chamber 2b are close, background current i _A ^b is not substantially different and background current i _B ^b i _A ^b = i _{Since B} ^b , the leakage current i can be calculated as i = i _B −i _A. When the capacitance of the resistance measurement side ionization chamber 2b is C _B and the applied voltage (voltage applied to the sample) applied between the electrode 3b and the grounded external electrode is V _B , Q = Since C _K × V _K = C _B × V _B , V _B = V _K × C _K / C _B is obtained. When the resistance value of the sample 13 is R, the resistance value R is calculated as R = V _B / i. As this V _B, an average value (addition average) of V _B before and after the time interval Δt may be used, or one of the front and rear may be used. However, using V _B at the start of measurement makes the calculation easier.

With such read the cage voltage _{V K} at step7, electrodes 3a, the reduction amount ΔQ of charge on 3b, the electrode 3a to the time interval Delta] t, the current _i A flowing from 3b, calculate a i _B (step8), The leakage current i flowing through the sample 13 is obtained from the difference between the two, and the resistance value R of the sample 13 is calculated using the resistance measurement side ionization chamber 2b and the capacitances C _B and C _K of the Faraday cage 5 (step 9). .

  Thereafter, returning to step 5, the measurement is repeated until an instruction to end the measurement is given. When the instruction to end the measurement is given, the measurement is ended.

  In Example 1, the electrical resistance of a Teflon (registered trademark) material was measured with an ultrahigh resistance measuring device. The measurement is performed by setting a disk-shaped Teflon (registered trademark) plate having a diameter of 10 mm and a thickness of 2 mm on the sample holder shown in FIG. 3, and using the electrostatic charger 8, the background measurement side magnetic levitation electrode ionization chamber 2 a, The resistance measurement side ionization chamber 2b was charged with a positive charge, and the decrease in charge on the electrodes 3a and 3b was examined over a long period of time. Here, the ionization volumes of the two ionization chambers are both 1 liter. FIG. 5 is a change diagram of current in each ionization chamber when the resistance measurement of Example 1 of the present invention is performed. (1) shows the measured value of the background current measured in the background measurement side magnetic levitation electrode ionization chamber 2a, and (2) shows the total of the background current and leakage current measured in the resistance measurement side ionization chamber 2b. It is a measured value. Accordingly, the difference in current value between (2) and (1) at each time is the leakage current through the Teflon (registered trademark) plate. As described above, since the voltage applied to the sample 13 can be converted into a voltage between the electrode 3b and the external electrode (ground electrode) by measuring the cage voltage, the electric resistance can be obtained from the applied voltage and the leakage current. Note that the sample 13 is an insulator, and the resistance values of the thin wire 15 and the sample holder 14 are negligibly small compared to this resistance value. FIG. 6 is a relationship diagram between applied voltage and electrical resistance when resistance measurement is performed in Example 1 of the present invention.

According to FIG. 6, there is a stepwise correlation between the applied voltage and the electrical resistance. In FIG. 6, assuming that each region showing a staircase shape is (a), (b), (c), (d), the region (a) has an electric resistance of 8.0 × centered around an applied voltage of 300V. 10 ¹⁶ Ω is shown. The volume resistivity (specific resistance value) calculated from this value and the sample shape (diameter 10 mm, thickness 2 mm) is 3.1 × 10 ¹⁷ Ω · cm. Similarly, the region (b) has an electric resistance of 1.5 × 10 ¹⁷ Ω and a volume resistivity of 6.0 × 10 ¹⁷ Ω · cm, centering around 250V. In the region (c), the electric resistance is 8 × 10 ¹⁷ Ω and the volume resistivity is 1.1 × 10 ¹⁸ Ω · cm, centering around 210V. On the other hand, in the region (d), the applied voltage decreases and the electrical resistance increases on the order of 10 ¹⁸ Ω.

Since there are surface leakage and volume leakage in the insulator leakage current, it is somewhat early to evaluate this ultra-high resistance measuring device only with the volume resistivity value obtained by measurement. Considering that the volume resistivity of the registered trademark is reported to be a value exceeding 10 ¹⁸ Ω · cm, the result of Example 1 clearly shows the relationship between the electrical resistance and the applied voltage. At the same time, the orders are almost matched, and it is considered that the reliability of the measurement data obtained by the ultrahigh resistance measuring device of the present invention can be sufficiently evaluated.

  In Example 2, the electrical resistance of a sample in which a plurality of Teflon (registered trademark) yarns were bundled was measured. The measurement was performed by replacing the thin wire and the sample holders 13, 14, and 15 shown in FIG. 3 with a bundle of a plurality of Teflon (registered trademark) yarns each having a diameter of approximately 30 μm. Three types of measurement samples are available: (a) 20 mm long, 30 μm in diameter, several tens, (b) 20 mm long, 30 μm in diameter, several eight, (c) 20 mm long, 30 μm in diameter, several six did.

  FIG. 7 is a change diagram of current in each ionization chamber when the resistance measurement of Example 2 of the present invention is performed. (A), (b), and (c) of FIG. 7 are time zones in which the above-described samples (a), (b), and (c) are used over time.

  The measurement was carried out in Higashi-ku, Fukuoka City, Fukuoka Prefecture, from 11:00 on April 7, 2003 to 11:00 on April 8. (1) shown in FIG. 7 shows the background current measured by the background measurement side magnetic levitation electrode ionization chamber 2a of FIG. 3, and (2) shows the time zone of (a), (b) and (c). The sum of the background current and leakage current measured by the resistance measurement side ionization chamber 2b is shown, and the background current in which the sample is not set is shown in the time zone other than (a), (b) and (c). The background measurement side magnetic levitation electrode ionization chamber 2a and the resistance measurement side ionization chamber 2b are both configured to have a volume of 1 liter. The difference between the current values of (1) and (2) is the leakage current due to each Teflon (registered trademark) yarn.

As can be seen from FIG. 7, the variation pattern of the time variation (1) and the variation pattern of the time variation (2) are almost synchronized, and the forms are almost the same. This indicates that a certain amount of leakage current is directly added to the background current in the time periods (a), (b), and (c). In addition, (a), (b), and (c) other than the time zone were measured with the sample not set, but (1) and (2) are almost synchronized, and are approximately 2.2 ×. It is within the allowable range of 10 ⁻¹⁷ A. This minimum measurable ionization current of 2.2 × 10 ⁻¹⁷ A will be described later.

FIG. 8 is a voltage-electric resistance diagram when the resistance measurement of Example 2 of the present invention is performed using the ten Teflon (registered trademark) yarns of FIG. 7A described above. The applied voltage applied to the sample during this measurement time (potential difference between the electrode 3b and the grounded external electrode) was 630V to 615V. The electric resistance measured by the voltage varies, but the average electric resistance is 3.0 × 10 ¹⁸ Ω. Although it cannot be simply evaluated, since there are ten Teflon (registered trademark) yarns, the electrical resistance per Teflon (registered trademark) yarn is 3 × 10 ¹⁹ Ω on average.

Here, the maximum electric resistance measurable with the resistance measuring apparatus of this invention is estimated. Example of previous experiments that the difference between the measured values of two units does not exceed 1.6% of the background current value when two background magnetic side electrode ionization chambers are arranged side by side and parallel measurement of only the background current is performed. It turns out. In other words, the minimum measurable current value that can be determined as a significant difference between the two measured values is 1.6% or more of the background current value. In the ultrahigh resistance measurement device of the present invention, in the resistance measurement side ionization chamber 2b, since the charge collection electrode is connected to the sample holder 14 and the thin wire 15, two background measurement side magnetic levitation electrode ionization chambers 2a are arranged side by side. The minimum measurable current value that can be determined as a significant difference may be larger than 1.6%. Therefore, considering various measurement conditions, the value that is not statistically measurable usually does not exceed twice this, so 3.2%, which is twice 1.6%, can be measured with the ultrahigh resistance measuring device of the present invention. The minimum measurable current value is 2.2 × 10 ⁻¹⁷ A, which is 3.2% of the average background current value of 7 × 10 ⁻¹⁶ A. Accordingly, for example, if the applied voltage is 600 V, the maximum electric resistance that can be measured is 2.7 × 10 ¹⁹ Ω.

Furthermore, it is generally known that the sensitivity of the ionization chamber increases in proportion to the increase in the ionization volume. However, since the ionization volumes of the two ionization chambers used in Examples 1 and 2 are both 1 liter, It can be seen that an electrical resistance of 10 ²⁰ Ω can be measured by making improvements such as increasing the volume by 10 times to 10 liters. Note that the volume of ionization chambers for measuring radioactive gas and the like often exceeds 10 liters, and ionization chambers of this size are more common as ionization chambers, and it is extremely easy to improve such sensitivity. Can be done.

The resistance measuring apparatus and the resistance measuring method of the present invention can be applied to the case of measuring the electrical resistance of an insulator of 10 ¹⁵ Ω to 10 ²⁰ Ω, particularly an insulator of 10 ¹⁸ Ω to 10 ²⁰ Ω.

The block diagram of the ultrahigh resistance measuring apparatus in embodiment of this invention Explanatory drawing of the background measurement side magnetic levitation electrode ionization chamber of the ultrahigh resistance measurement device in the embodiment of the present invention Explanatory drawing of the resistance measurement side ionization chamber of the ultrahigh resistance measurement device in the embodiment of the present invention Flow chart of resistance measurement in the embodiment of the present invention Variation diagram of current in each ionization chamber when performing resistance measurement of Example 1 of the present invention Relationship diagram between applied voltage and electrical resistance when resistance measurement of Example 1 of the present invention is performed FIG. 6 is a diagram showing changes in current in each ionization chamber when resistance measurement is performed in Example 2 of the present invention. Voltage-electric resistance diagram when resistance measurement of Example 2 of the present invention was performed

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Background measurement side magnetic levitation electrode ionization chamber outer case 1b Resistance measurement side ionization chamber outer case 2a Background measurement side magnetic levitation electrode ionization chamber 2b Resistance measurement side ionization chamber 2c Transparent glass window 3a, 3b Electrode 4 Electromagnet 4a Coil 5 Faraday Cage 5a Internal electrode 5b External electrode 6 Capacitors 7a, 7b Insulator 8 Electrostatic charger 9a Light emitting element 9b Light receiving element 10 Shutter 11 Electrometer 12 Actuator 13 Sample 14 Sample holder 15 Thin wire 16 Support cap 18 Floating driver means 19 Calculation unit DESCRIPTION OF SYMBOLS 20 Control part 20a Measurement management means 20b Elevation control means 20c Arithmetic processing means 21 Display part 22 Memory | storage part 23 Input part 24 Time measuring means 25 Count means

Claims (4)

A first internal electrode and a first external electrode, which are provided in a container containing an ionizing gas and are electrically connected by setting a sample, are charged with a predetermined amount of charge during the measurement. And a resistance measurement side ionization chamber for measuring the potential of the first internal electrode, which decreases according to the electrical resistance of the sample, with a first Faraday cage,
A second internal electrode provided in a container containing an ionizing gas and magnetically levitated and a second external electrode provided in the container are provided, and a charge charged by a predetermined amount at the time of measurement depends on a background radiation dose A background measurement side magnetically levitated electrode ionization chamber for measuring the potential of the second electrode that decreases by the second Faraday cage;
Calculating a first current value based on a change amount of the potential of the first internal electrode per time, and calculating a second current value based on a change amount of the potential of the second internal electrode per time; An arithmetic unit for obtaining a difference between the first and second current values;
An ultra-high resistance measuring device including a control unit for magnetically levitating the second internal electrode and controlling each Faraday cage,
The ultrahigh resistance measurement apparatus, wherein the calculation unit obtains an electric resistance of the measurement sample based on a voltage applied to the sample and a difference between the first and second current values. 2. The ultrahigh resistance measuring device according to claim 1, wherein a sample holder is electrically connected to the first internal electrode and the first external electrode, and the sample is set in the sample holder to perform resistance measurement. . The ultrahigh resistance measuring device according to claim 1 or 2, wherein the external electrode is grounded. Each of the resistance measurement side ionization chamber containing the ionizing gas and the background measurement side magnetic levitation electrode ionization chamber are provided close to each other, and in the resistance measurement side ionization chamber, the internal electrode and the external electrode are electrically connected by the sample, In the background measurement side magnetic levitation electrode ionization chamber, internal electrodes are magnetically levitated, each internal electrode is charged by a predetermined amount, ionized gas is ionized by the action of background radiation, and the potential of each internal electrode is set by a Faraday cage. Measure the electrical resistance of the sample by calculating the current value based on the amount of change in potential of each internal electrode per hour, calculating the difference between the two, and dividing the voltage applied to the sample by the difference An ultra-high resistance measurement method characterized by:

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