Jc. Lotters et al., DESIGN, REALIZATION AND CHARACTERIZATION OF A SYMMETRICAL TRIAXIAL CAPACITIVE ACCELEROMETER FOR MEDICAL APPLICATIONS, Sensors and actuators. A, Physical, 61(1-3), 1997, pp. 303-308
Small triaxial accelerometers are needed in the medical field for the
monitoring of mobility. For this purpose, a new highly symmetrical inh
erently triaxial capacitive accelerometer has been designed. The basic
structure of the device consists of six capacitors surrounding a cent
ral mass which is suspended by springs made of the rubber elastic poly
mer polydimethylsiloxane. The advantages of the design are a low off-a
xis sensitivity, an equal sensitivity in all axes and a reduction of t
he sensor's dimensions. In order to show the practical feasibility of
the design, a number of manually assembled prototypes of the triaxial
accelerometers have been realized with dimensions down to 2 mm X 2 mm
X 2 mm. The prototypes are capable of detecting accelerations in three
directions with unfortunately unequal sensitivities per axis (e.g., f
rom 0.8 to 1.1 V (m s(-2))(-1)) and a maximum off-axis sensitivity of
3% in the well-assembled devices. Clinical measurements have been carr
ied out with the prototypes. The measurement results indicate that the
triaxial accelerometer is sensitive enough to register the kind of mo
vements that occur in healthy persons during normal standing.