Abstract: A capacitance displacement type measuring probe for measuring the vibration of a dynamoelectric machine including a dynamoelectric machine with helical grooves in its collector ring is disclosed. The probe measures the vibration of the dynamoelectric machine by measuring the change in capacitance of a capacitor established by the probe and the collector ring. The probe has a parallelogram sensing face which includes a sensing electrode having a parallelogrammed sensing surface whose axial length is of a predetermined dimension to coact with the parameters of the collector ring. The axial length of the sensing surface is formed such that the sensing surface scans a constant total high and total low area on the collector as the collector rotates. To measure vibration the probe is deployed at a fixed point in space with its parallelogrammed sensing face in parallel with the longitudinal axis of the rotating member to form a capacitor.