Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
2000-12-19
2003-02-11
Le, N. (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
C324S548000, C324S659000, C324S658000, C324S677000
Reexamination Certificate
active
06518777
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and a apparatus for measuring the insulation resistance of an electronic component. Particularly, the invention relates to a method for removing the influences of noise due to mechanical vibrations occurring in equipment for checking the characteristics of an electronic component having the piezoelectric effect.
2. Description of the Related Art
Conventionally, a measuring circuit is used to measure the insulation resistance of an electronic component such as a ceramic capacitor.
FIG. 1
shows the conventional measuring circuit using a current voltage conversion system. Reference character Rs denotes an inrush current limit resistance of an electronic component
1
as a tested sample, and reference character Rx denotes the insulation resistance of the electronic component
1
. The value of Rs is much smaller than the value of Rx. A ceramic capacitor is usually shown by a parallel equivalent circuit composed of the insulation resistance Rx and a capacitance. In this figure, however, only the insulation resistance Rx is provided to simplify the illustration. Reference numeral
2
denotes an operational amplifier having a feedback resistance Rf. In the circumstances, a current i flowing to the electronic component
1
from the output Vo of the operational amplifier
2
is obtained. Then, with a power supply voltage E and the current i, the insulation resistance Rx of the electronic component
1
can be obtained by the following equations.
i=Vo/Rf
Rx=E/i
In this method, the leakage current i is extremely small and there is susceptibility to the influences of noise, although control is simple and a quickly response can be obtained.
In addition, as shown in
FIG. 2
, there is an insulation resistance measuring circuit using an electric charge accumulating system. One example is described in Japanese Unexamined Utility Model Publication No. 5-064782. In this measuring circuit, a switch SW and a feedback capacitance Cf are connected in parallel between the inverting input terminal of an operational amplifier
2
as a high input impedance amplifier and the output terminal thereof. The switch SW is turned from ON to OFF to measure an output Vo after t seconds. The value of t is, for example, set to be a desired value of approximately 0.1 to 10 seconds. Then, a current i flowing through an electronic component
1
from the output Vo is obtained-by the following equations. In addition, with a power supply voltage E and the current i, the insulation resistance Rx of the electronic component
1
is obtained.
i=Cf·Vo/t
Rx=E/i
Since the electric charge accumulating circuit serves as an integrator, the circuit can reduce the influences of hums due to a commercial power supply and the like.
When stress is applied to a dielectric member in a situation in which a DC voltage is applied, the piezoelectric effect permits an electric charge according to the stress to be generated from the dielectric member. In general, in apparatuses for checking the characteristics of electronic components, there are used many devices such as a part feeder, a motor, and a hopper, which produce mechanical vibrations due to driving. With the propagation of the vibrations through an electronic component, a noise current due to the piezoelectric effect is generated. However, as mentioned above, a leakage current i, which is measured to obtain the insulation resistance of the electronic component
1
, is extremely small. In addition, a piezoelectric noise current occurring due to mechanical vibrations applied to the electronic component
1
is superimposed on the measured current i to make a measurement error.
As a result, the former measuring circuit using the current voltage transformation system cannot remove the influences of noise. In addition, the latter measuring circuit using the electric charge accumulating system cannot remove the influence of the above-mentioned piezoelectric noise current, either.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an insulation resistance measuring method, which can remove the influences of piezoelectric noise due to mechanical vibrations applied to an electronic component and can measure the insulation resistance of the electronic component with high accuracy.
In order to accomplish the above object, according to a first aspect of the present invention, there is provided an insulation resistance measuring method including the steps of applying a predetermined measurement voltage to an electronic component arranged in a position subjected to periodic mechanical vibrations from the outside, measuring a current flowing through the electronic component, and integrating the value of the measured current flowing through the electronic component over the period of the mechanical vibrations or over a time which is an integral multiple of the period thereof to obtain the insulation resistance of the electronic component.
According to a second aspect of the present invention, there is provided an insulation resistance measuring method including the steps of applying a predetermined measured voltage to an electronic component arranged in a position subjected to periodic mechanical vibrations from the outside, measuring a current flowing through the electronic component, and integrating the value of the measured current flowing through the electronic component over a time which is the least common multiple of the period of the mechanical vibrations and the period of a commercial power supply to obtain the insulation resistance of the electronic component.
According to a third aspect of the invention, there is provided an insulation resistance measuring method including the steps of applying a predetermined measured voltage to an electronic component arranged in a position subjected to periodic mechanical vibrations from the outside, measuring a current flowing through the electronic component, in which the period of the mechanical vibrations is equal to or less than ½ of the period of a commercial power supply, integrating the value of the measured current flowing through the electronic component over the period of the mechanical vibrations, integrating the value of the measured current flowing through the electronic component over the period of the mechanical vibrations after a time which is ½ of the period of the commercial power supply has passed from the onset of the above integration, and obtaining the average of the results from the two integrations.
According to a fourth aspect of the present invention, there is provided an insulation resistance measuring method including the steps of applying a predetermined measurement voltage to an electronic component arranged in a position subjected to periodic mechanical vibrations from the outside, measuring a current flowing through the electronic component, in which the period of a commercial power supply is equal to or less than ½ of the period of the mechanical vibrations, integrating the value of the measured current flowing through the electronic component over the period of the commercial power supply, integrating the value of the measured current flowing through the electronic component over the period of the commercial power supply after a time which is ½ of the period of the mechanical vibrations has passed from the onset of the integration, and obtaining the average of the results from the two integrations.
According to a fifth aspect of the present invention, there is provided an insulation resistance measuring apparatus including a DC measurement power supply, an electronic component arranged in a position subjected to periodic mechanical vibrations from the outside, and an electric charge accumulating circuit for integrating an input current i to obtain a voltage output Vo so as to obtain the insulation resistance of the electronic component. The DC measurement power supply, the electronic component, and the electric charge accumulating
Hayashi Akihiro
Kamitani Gaku
Teramura Koichi
Burns Doane , Swecker, Mathis LLP
Hamdan Wasseem
Le N.
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