A transducer system comprising, a multiple capacitive transducer having a flexible dielectric sheet of elastic nonconductive material, a first plate of flexible conductive material defining a region located adjacent a first surface of the sheet, and a plurality of second plates of flexible conductive material located adjacent a second surface of the sheet, with the second plates defining areas aligned with the region of the first plate. The system separately forms signals responsive to the capacitance between the first and second plates.
A system for monitoring bone union at a bone fracture (13) comprises a fracture cast sleeve (15) to the external surface of which is bonded a transducer (16). Transducer (16) is electrically-conductive and has an electrical resistance which varies with elastic extension and contraction of the transducer. The output of transducer (16) is applied via a resistance-sensitive network (18) to a data evaluating device (20) arranged to normalize signals received from transducer (16) with respect to the time interval during which that signal appears since the signal is of an impulse nature depending upon the rate at which the force is applied to the fracture (13). The normalized signal is further normalized having regard to the mass of the limb concerned and a plurality of such signals are stored in store (30) together with a data log from date data device (32) and these signals are fed to a trend evaluator (34) in order to predict the time interval before bone union occurs.
A pressure transducer (26) is disclosed. A multiplicity of signal plates (Cs, Cr, Csf, Crf) are disposed on a first quartz disc (88). Opposing the signal plates (Cs, Cr, Csf, Crf) across a gap formed by an annular frit (92) is a common plate (94) disposed on a second quartz disc (86). The signal plates (Cs, Cr, Csf, Crf) and common plate (94) form capacitors which are operable to modulate alternating excitation signals applied to the signal plates. The capacitances vary the modulation during deflections of the discs (86, 88) as a result of pressure changes, and the common plate (94) algebraically sums the modulated excitation signals into a single output from the transducer (26).
A device comprising a system of switches and sensors placed inside a person's footgear which send positional information through wireless telemetry from a transmitter to a receiver. This positional information is entered into a computer and processed according to prestored algorithms, yielding a non-dimensional ambulation index. This invention also comprises a method for calculating the non-dimensional ambulation index.
A capacitance elastomeric pressure sensor includes top and bottom mounting plates arranged to support a pair of electrode layers. The first electrode layer is supported on the upper surface of a dielectric disc held by an upper mounting plate. The second electrode layer is located beneath the disc and includes a conductive elastomeric layer overlying an elastomeric support layer. In the preferred embodiment, the elastomer is a silicone elastomer and the conductive layer is formed by admixing a conductive carbon powder with the silicone. The sensor is particularly effective in sensing pressure changes in this low range, e.g. 0-1 inch of water. In the most preferred embodiment the elastomeric layer is prestrained for temperature compensation.
A pressure sensor including a pressure capsule such as a dual diaphragm quartz capacitance pressure capsule and structure for supporting and sealing same within the pressure environment to be measured. The pressure capsule having two parallel quartz plates spaced by a dielectric ring forming a vacuum chamber therein. The structure providing a force balanced support for compressively loading the pressure capsule through the dielectric ring. The structure further having transfer port therein to communicate the pressure environment to both plates.
