DEFECT DETECTION METHOD FOR THERMISTOR ELEMENT

摘要

PROBLEM TO BE SOLVED: To provide a defect detection method for a thermistor element capable of efficiently detecting an internal defect within a thermistor.SOLUTION: The defect detection method includes the steps of: measuring a frequency response property of impedance; creating a Cole-Cole plot with a real number component R as a transverse axis and an imaginary number component X as a vertical axis; defining the real number component R in a low frequency lower limit of a curve obtained in the plot as Rmax and calculating a semicircle of a virtual circle of which the center is (Rmax/2, 0) and which is approximate to the curve; calculating a degree of distortion of the curve obtained in the plot from the semicircle as a distortion rate; setting a minimum distortion rate under the presence of the internal defect as a reference value on the basis of correlation data between the distortion rate that is calculated by measuring a plurality of elements beforehand and the presence/absence of the internal defect in an element assembly; and determining the presence of the internal defect in the element assembly in the case where the calculated distortion rate is greater than the reference value.SELECTED DRAWING: Figure 1