In the field of vibration control, detection of absolute displacement signal is being required in order to implement a sky-hook spring. Then, two kinds of absolute displacement sensors have been already proposed without utilizing integrators to avoid a drift problem. At first, it is described how and why the sensors should be developed in this paper. Next, structures and characteristics of the proposed sensors are compared with each other to reveal their differ-ences. When the bandwidths are expanded in order to apply the sensors to industrial scenes, resonant peaks will be appeared in both low and high frequency regions. Whereas the former resonance can be suppressed by inner velocity feedback, the latter resonance called high frequency dynamics is finally discussed and analyzed by a factorial analysis.