KINEMATICS - Biomechanics and Motor Control of Human Movement - page 53

+

Supply
voltage

R 1

+

V

Unbalanced
bridge

R a

12
V

Balance
potentiometer

m

− a +

R b

−

R 1

a

Supply
voltage

−

Figure 3.7 Electrical bridge circuit used in most force transducers and accelerometers.
See text for detailed operation.

Advantages

1. Output signal is available immediately for recording or conversion into
a computer.

Disadvantages
1. Acceleration is relative to its position on the limb segment.
2. Cost of accelerometers can be excessive if a large number are used;
also the cost of the recorder or analog-to-digital converter may be high.
3. If a large number are used, they can encumber movement.
4. Many types of accelerometers are quite sensitive to shock and are easily
broken.
5. The mass of the accelerometer may result in a movement artifact, espe-
cially in rapid movements or movements involving impacts.

3.3 IMAGING MEASUREMENT TECHNIQUES

The Chinese proverb “A picture is worth more than ten thousand words” holds
an important message for any human observer, including the biomechanics
researcher interested in human movement. Because of the complexity of most
movements, the only system that can possibly capture all the data is an imag-
ing system. Given the additional task of describing a dynamic activity, we are
further challenged by having to capture data over an extended period of time.
This necessitates taking many images at regular intervals during the event.
There are many types of imaging systems that could be used. The discus-
sion will be limited to three different types: movie camera, television, and