Page 72 - Handbook of Biomechatronics

Sensors and Transducers 67

Fig. 7 Example of a cable.

To evaluate the force which Jacob can control, you use a system of cables
and pullies to apply various forces to Jacob’s residual limb. With feedback
from Jacob, you determine an acceptable range of forces.
With your evaluation of Jacob’s physical capabilities and the capabilities
of his current prosthetic system, you decide to design Jacob an electrically
powered prosthetic system.

3 SIMPLE SENSORS
With the invention of the integrated circuit, standard electrical sensors
continue to get smaller, more efficient, cheaper, and easier to use. The ability
to develop electrical-mechanical systems on the microscopic scale, micro-
electrical-mechanical systems (MEMS) have also been a great benefit to
sensor technology (Lamers and Pruitt, 2011).
A standard electrical sensor consists of a minimum of three electrical
lines: a supply voltage, a ground, and the sense voltage. The supply voltage
provides power to the sensor. The ground is the electrical reference, value
zero. The sense voltage is the response of the sensor to the environment. As
the senor responds to external stimuli, generally a resistance value will
change which causes a proportional change in the sense voltage through
Ohm’s law, the current draw of the sensor being constant.
There are many different types of electrical sensors and many different
uses of these sensors in biomedical design applications. What follows is a
review of some of the more common electrical sensors.