A vacuum sensor for sensing vacuum in a sealed enclosure is provided. The sealed enclosure includes active MEMS devices desired to be maintained in vacuum conditions. The vacuum sensor includes a motion beam anchored to an internal surface in the sealed enclosure. A driving electrode is disposed beneath the motion beam and a bias is supplied to cause the motion beam to deflect through electromotive force. A sensing electrode is also provided and detects capacitance between the sensing electrode disposed on the internal surface, and the motion beam. Capacitance changes as the gap between the motion beam and the sensing electrode changes. The amount of deflection is determined by the vacuum level in the sealed enclosure. The vacuum level in the sealed enclosure is thereby sensed by the sensing electrode.