An inertial measurement unit capable of providing information relating to all six degrees of freedom in an orthogonal three axis system is shown having a mechanical oscillator constructed from two counterbalanced platforms which form a single unit for rotation about a single torsional axis. A plurality of accelerometers are mounted upon at least one of the counterbalanced platforms. Each accelerometer has an input axis, an output axis, and a pendulous axis. Each accelerometer is mounted such that the input axis is at a predetermined angle to the single axis of rotation and the counterbalanced platform. The accelerometers are used to measure angular rate along the pendulous axis and linear acceleration along the input axis. These signals may then be electronically separated to produce acceleration and angular rate outputs for a three axis orthogonal system.