Accelerometer

Abstract

An accelerometer having a plate-like proof mass (), flexible mounting legs () each co-planar with the proof mass (), a ring-like support (), in which the proof mass () is moveably mounted, with each mounting leg () being connected at one end to the proof mass () and connected at another end to the support () and with the mounting legs () extending substantially perpendicularly to the sensing direction, a plurality of interdigitated capacitor fingers mounted, in a gaseous medium, in the ring-like support () for sensing linear movement of, and for providing gaseous medium squeeze damping for the proof mass () in the sensing direction, with the fingers, proof mass (), mounting legs () and support () being co-planar and formed from a single plate of mono-crystalline silicon, which fingers comprise fixed first, second, third and fourth arrays () of laterally spaced fingers extending substantially perpendicularly to the sensing direction and away from the support () towards to the proof mass (), and moveable fifth, sixth, seventh and eighth arrays () of laterally spaced fingers extending substantially perpendicularly to the sensing direction from and attached to the proof mass () towards the support (), with the interdigitation of the first and fifth arrays () and of the third and seventh arrays () being at a first offset in one direction in the sensing direction from a median line between adjacent fingers in the first, second, third and fourth arrays (), and with the interdigitation of the second and sixth arrays () and of the fourth and eighth arrays () being at a second offset equal and in the opposite direction to the first offset and means for providing a first drive voltage to the first offset arrays () of fingers and an equal and opposite second drive voltage to the second offset arrays () of fingers such that the interdigitated fingers provide for the proof mass sensing of displacement in response to acceleration applied to the accelerometer, drive and damping of displacement.