Citation
Talib, Dayang Nurul Nahar
(2017)
Resistive sensor array readout circuit for foot plantar pressure measurement system.
Masters thesis, Universiti Putra Malaysia.
Abstract
Readout circuit is used for interfacing between sensor and digital signal
processing unit. It is widely implemented in sensory system to obtain variety of
useful information such as pressure and voltage etc. Readout circuit designed
for large scale sensor array is important for improving the effectiveness of data
acquisition system. However to design such system, many additional
components are needed which contributes to complexity and increment of power
consumption. This thesis focuses on the design, development and performance
study of the readout circuit for large scale sensor array in term of low complexity
and high accuracy. The prototype of readout circuit comprises of sensor array,
signal acquisition system and graphical user interface. Sensor array has been
constructed from 64 FlexiForce pressure sensor to sense pressure values on the
foot plantar. Data acquisition system consisting of analogue multiplexer and
microcontroller are responsible for selection and digitization of pressure data
from the sensor array to the computer to be processed. Then, the processed
pressure data is displayed by graphical user interface (GUI) for analysis purpose.
A new mathematical equation is also proposed to identify the resistance value
on each array. The proposed readout circuit has achieved the objective in terms
of low complexity by using microcontroller, multiplexer and standard resistors.
While in terms of accuracy, the result obtained from two different evaluations
showed satisfactory performance. Results from the first evaluation involving a
prototype readout circuit using standard resistors representing resistive type
pressure sensor node has resistance value percentage error between 0.04% to
6.5%. Whereas the result obtained from the second evaluation using FlexiForce
sensors shows that when pressure is applied on one sensor in each column, the
pressure readings of other sensor placed in the same column are also change.
The percentage of changes are within the range of 2.14% to 13.46% of the
pressure applied onto the sensors. In this research, embedded ADC in PIC
microcontroller has been utilised to reduce the complexity, while wireless data
transmission has also been implemented in the system for portability.
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