Biomechanics Gait Analysis Lab - Biomedical Engineering ...

3. Make sure that the sensor end of the FSR is in the
middle of the grips, for even force application.
4. Set-up two speeds on the Tinius Olsen machine, speed 1
at 0.01 and speed 2 at 0.005 (see manual for Tinius
Olsen machine to set-up speeds)
5. Hook up the insole to the transmitter telemetry
device, attach probes from a digital multimeter to the
output of the receiver box, and turn on both telemetry
boxes.
6. On person starts speed 1, and calls out the force
every 10 lbs starting at 40 lbs, while the other
person writes down the output voltage reading. At 200
lbs select speed 2, and continue until 350 lbs is
reached.
7. Turn all devices off when done
From this data determine the FSR resistance value at each
voltage reading, using the equations in Figure 39, and
divide the resistance by 1 to get conductance. Using the
conductance data and its matching force output, plot
conductance vs. force in Excel and use linear regression to
extrapolate the equation that will relate output force to
conductance.
Footswitch Insoles
The footswitch insoles consist of four compression closing
switches, at the heel, 1 st metatarsal, 5 th metatarsal, and
toe, as shown in Figure 42. These switches act as an open
or closed electric circuit, which requires an input of 5
volts. When pressure is applied to the switches, two
rubber cylinders contact pieces of brass sheets on each
side of the insole, which acts to close the electric
circuit, as shown in Figure 43. The only information that
this will provide is that pressure is being applied and the
length of time that pressure is applied. This will not
show variations in applied pressure. The footswitches can
provide velocity, cadence, stride length, and information
on gait cycle, single limb support, swing, and stance. The
footswitches do not need to be calibrated, which is a
difficult and lengthy process.
The drive circuit for the footswitch insoles is simply a
+9V battery connected to a voltage regulator to reduce the
input voltage to +5V, which is shown in Figure 37. The
footswitches are connected to the transmitter with a pulldown
resistor in between. The pull-down resistor is need
Page 50