The invention disclosed herein provides methods and materials for observing the state of a sensor, for example those used by diabetic patients to monitor blood glucose levels. Typically a voltage such as a voltage pulse is applied to the sensor in order to solicit a current response from which for example, factors such as impedance values can be derived. Such values can then be used as indicators of a sensor's state, for example the state of sensor hydration, sensor noise, sensor offset, sensor drift or the like.