Page 69 - Handbook of Biomechatronics

64 Jeff Christenson

section, examples of nonelectrical sensors are discussed. In the standard sen-
sor elements section, some of the basic building blocks of many of the com-
mon sensors are described. In the common sensors section, electrical sensors
which are found in many devices are described. In the biological sensors sec-
tion, systems for sensing various outputs of the human body will be detailed.
These sections are not meant to be complete lists of all possible sensors, but
are designed to be an introduction to possible sensors for biomechatronic
systems.
As each sensor is discussed, examples of biomechatronic devices will be
presented which implement said sensors. To facilitate this discussion, let us
suppose there is a theoretical person, named Jacob, who had his leg ampu-
tated above the knee about 2 years ago. He has been wearing a passive pros-
thetic knee and foot system about a year, but has experienced some
discomfort and hopes you can provide him a better biomechatronic device.

2 PASSIVE SENSORS

Often when designing a biomechanical system, the default inclination
is to implement an electrical sensor. It is important to consider all options in
the design processes, even those that may appear to be less technical. There
are several pure mechanical sensor options which can be successfully
implemented to result in a cheaper and often more reliable device.
However, these devices are often bulkier and may require more attention
by the user.

2.1 Ruler
A ruler (Fig. 3) is used to measure distance (https://en.oxforddictionaries.
com/definition/ruler, Accessed 21 August 2017). Through visual inspection
of the indicators on the ruler, the distance can be determined. For long
distances, tape measures are used. Rulers are readily available in Standard
and Metric gradations, or both.
Before designing Jacob a new prosthetic system, you decide to evaluate his
current device to determine if it might be adjusted better to fit Jacob’s needs.

Fig. 3 Example of a ruler.