Permissible oscillation bandwidth
The permissible oscillation bandwidth is the oscillation amplitude of a sinusoidally varying torque with which the transducer can be stressed for 10⋅106 vibration cycles without causing any significant variations in its metrological properties.
The amplitude is specified as a peak-to-peak value, that is, as the difference between maximum and minimum torque. See also Fig. 7.
As well as the permissible vibration bandwidth it is also necessary to define a permissible upper limit for the torque which occurs. This upper limit usually coincides with the nominal torque (in both the positive and negative direction). Values which differ from this are explicitly declared in the specifications.
The concept has been taken from standard DIN 50100, which deals with continuous vibration testing (fatigue testing) within the context of materials testing, and has been transferred from mechanical stress to torque.
The deciding factor for fatigue strength is the number of vibration cycles alone. The frequency is not significant within the frequency range that is relevant to mechanical processes*). According to DIN 50100, it can be assumed to a close approximation for the case of steel materials that a mechanical component is fatigue proof under a given load if it endures the number of 10⋅106 load cycles under the respective load.
The upper limit for torque in the case of vibrational loading replaces explicit information about the mean vibrational loading. Within the range defined by the positive and negative limits, both pulsating torque and alternating torque are permissible (see Fig. 7).
Fig. 7: Terms used in connection with the oscillation bandwidth
*) see also: H.-J. Bargel, G. Schulze: Werkstoffkunde (Materials Science), VDI-Verlag GmbH, Düsseldorf, Germany 1988