We have a loading frame equipped with 6 LVDTs which are connected to a data logger (DAS). There is a peculiar erractic functioning. Sometimes, LVDTs work just fine and readings are acceptable. However, after one test or at most after two tests, the data logger connected to the LVDTs shows no reading even if the LVDTs are given a full stroke (stroke length is 100mm). What could be the possible reason for this? I have no expertise in the internals of LVDTs or that of the data logger.