Evaluation of the sharpness of concentric needle electrodes by a penetration test.

This paper deals with a method to evaluate the sharpness of the concentric needle electrode (CNE) and the consistency of sharpness on repeated penetration. An aluminum foil of standard thickness and properties was used as the penetration medium. A load profile was obtained as a function of time, and has been correlated with the shape and quality of grinding of the tip of the CNE. This load profile can be used as a quality evaluation method. This method is utilized for the assessment of the impairment of the needle tip on repeated penetration and hence for comparison of different needle electrode models.