Biomedical Engineering Reference
In-Depth Information
Figure 11.5
The conductance of the FSR versus force
V
+
r
Data
acquisition
card
+
_
V
r
R
Figure 11.6
The electric circuit for measuring the resistance '
r
'
In this figure the conductance of the FSR can be calculated from Equation 11.2.
R
1
r
1
r
V
+
⇒
V
V
r
−
1
R
V
r
=
C
=
=
(11.2)
R
+
By combining Equations 11.1 and 11.2 we find a relationship between the force and
voltages and
V
+
.
1
b
a
V
V
r
−
1
R.a
−
F
=
(11.3)
where
a
= 0.079,
b
=
−
0.016, R = 10 k
,and
V
+
=5V.
The voltages and
V
+
are transmitted to the data acquisition card and the force is
calculated by the processing software from Equation 11.3 .
11.4 Shaft Position Sensor
A built-in linear potentiometer was used to find the position of the shaft. The relationship
between resistance of the potentiometer and the length of the shaft is plotted in Figure 11.7.
