Micromechanical precision silicon
weight sensor
SOLUTION AND ITS BENEFITS
The weight sensor has an elastically suspended upper electrode and a
lower electrode. The upper electrode, or a structure connected to it, acts
as a pan surface. A device keeps the electrodes at a constant spacing,
irrespective of a mass being weighed. The mass can be resolved from a
feedback signal.
COMPETITIVE ADVANTAGE
Has improved stability and small size. Can measure one gram with an
accuracy of one millionth part per gram, or better.
TECHNICAL DESCRIPTION
At least one electrode is divided into at least two areas, to electrically
control the electrode surfaces, so that they remain
parallel, by separately adjusting the force on each partial
electrode surface. The upper electrode is suspended on
three symmetrical radial beams (1). The beams act as
springs, yielding elastically vertically. The other ends of
the beams are connected to a silicon substrate (4). The
lower electrode (15) is circular. The device is formed by
bonding a micromachined substrate on a glass plate (8),
on which the lower electrode is patterned.