Abstract: In a method and apparatus for determining a variation in criteria, parameters and/or command values of an automatic piecing operation at an automatic piecing apparatus of an automatic spinner, a piecer and/or a length of thread in which the piecer is located is measured in accordance with criteria of diameter or diameter per unit of length and evaluated for improving the piecer, with at least one sensor disposed in a thread travel path, upon resumption of winding after a piecing operation in which a spun yarn is received. A piece of thread containing the piecer is scanned by measuring with the at least one sensor in terms of location of thick and/or thin places with respect to the piecer at defined measurement points, as further criteria of the piecing operation. The measured data are continuously input into event counters connected downstream of the at least one sensor.