As we discussed in a previous article, there are two types of calibration uncertainties, random and
systemic. Since a calibration lab is responsible for correctly reporting their uncertainty, it is important to understand the differences between these types of contributors and how each can be considered.
As a framework to differentiate the two types, consider that uncertainties caused by random contributors lend themselves to be determined by statistical measurement methods whereas, uncertainties that are systemic in nature need to be surveyed versus more accurate methods. As an example, in accelerometer calibration...
limited stroke length of electro-dynamic (ED) shakers providing limited acceleration levels at declining low frequencies, and the limited resolution of the piezoelectric reference accelerometer in the presence of the sensor's rising electric noise floor. By adopting and applying proven technologies in a novel combination, it is now possible for improved simplicity and reduced measurement uncertainties of dynamic vibration calibration at very low frequencies. The commercially available combination of a high accuracy optical displacement reference and ultra-long stroke (>250 mm stroke) calibration grade linear actuator has created a new standard in ultra-low frequency calibration.
Michael J. Lally