By examining the curve of Fig.7. it is observed that it is almost linear. This leads to the development of linear
approximation of speed attained with applied input voltage by plotting a linear trend line equation and comparing it
with the curve obtained. Thus linear calculated values or true values of motor speed are obtained. The error
percentage is calculated from the measured value and the true values of speed. From the percentage error curve in
Fig.8. it is observed that the percentage error lies between ±6%.