Contact gap, measured in microns, is the distance between the mating reed blades of a Reed Switch in open state.
Several factors affect the contact gap of a Reed Switch. Although a Reed Switch having a lower Operate AT should have a smaller gap and a Reed Switch having a higher Operate AT should have a corresponding higher gap, this is not so.
Reed Switches in longer glass tubes, consequently having more flexible blades will have a larger contact gap than a smaller reed switch with a shorter glass tube, even though they may have the same Operate AT.
