Biomechanics Gait Analysis Lab - Biomedical Engineering ...

3. Technical Description
The Biomechanics Gait Analysis Laboratory equipment
consists of Force Sensitive Resistor Insoles, Footswitch
Insoles, insole driver circuits, Telemetry devices, and
National Instruments BNC-2120 and PXI-6040E in the PXI-1031
box. The Force Sensitive Resistor Insoles and Footswitch
Insoles are powered through the drive circuit, which is
part of the transmitter telemetry device. The transmitter
device sends the signal to the receiver telemetry device,
which is connected to the BNC-2120. The BNC-2120 receives
analog or digital signals and relays the signals to the
PXI-6040E, which provides the data to the LabVIEW® software
program in a computer. Since the system begins with input
from the insoles, a detailed description of the insoles
will be given first, followed by the remaining equipment in
order as listed above.
Force Sensitive Resistor (FSR) Insoles
The FSR insoles are comprised of force sensitive resistors,
sandwiched between cut-to-size shoe insoles and taped
together with Gorilla brand duct tape. A diagram of an FSR
insole is shown in Figure 35. Rubber disks are placed on
either side of the sensing area to concentrate the force
directly onto the sensing area to provide a better reading,
which is indicated in Figure 36. The FSR has a three male
square pin connector, also shown in Figure 36 and Figure
35. The middle connector is connected to ground and the
two outer pins are used for the voltage supply input and
the voltage output. The two outer pins can be either used
as the input or the output. The force sensor is an
extremely thin, flexible printed circuit. The force sensor
is made of two layers of a polyester/polyimide substrate
sheet. For each layer, conductive silver is applied, on top
of which a layer of pressure-sensitive ink is applied. An
adhesive joins the two layers of substrate together to
complete the force sensor. The active sensing area is
outlined by the silver circle around the pressure-sensitive
ink, which can be seen in Figure 36. The silver lines
extend from the sensing area to the two outer connector
male square pins to form the leads.
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