Before revision: 200px| thumbAn electronic apex locator is an electronic device used in endodontics determine the position of the apical constriction and thus determine the length of the root canal space.
After revision: 200px| thumb150px|root canal meter, the world's first electrical root canal length measuring instrument released by Onuki Medical Instruments in 1969An electronic apex locator is an electronic device used in endodontics determine the position of the apical constriction and thus determine the length of the root canal space.