Abstract: Method for testing a balance spring or a balance spring blank arranged to form a balance spring, the balance spring being required to have at least one predetermined expected resonance frequency, the testing method including the following steps: a. applying to the balance spring or balance spring blank, a vibratory excitation that varies over time in order to cover a predetermined frequency range, b. identifying at least one characteristic of a resonance frequency of the balance spring or balance spring blank, such as a resonance peak, during, or in response to, the vibratory excitation over the predetermined frequency range, c. subjecting the resonance frequency characteristic identified in step b. to a prediction machine in order to determine if the balance spring or balance spring blank is affected by a defect.

Abstract: A method for inspecting a spiral or a spiral blank arranged to form a spiral, the spiral having to exhibit at least one predetermined resonant frequency, the inspecting method including the following steps: a. applying to the spiral or to the spiral blank a time-varying vibrational excitation to cover a predetermined frequency range, b. identifying at least one characteristic of a resonant frequency, such as a resonance peak, of the spiral or of the spiral blank during the vibrational excitation over the predetermined frequency range, c. submitting to a predicting machine the resonant frequency characteristic identified in the step b. to determine a stiffness of the spiral or of the spiral blank and/or determine whether or not a dimensional correction of the spiral or of the spiral blank is necessary to obtain the predetermined resonant frequency.