A Comparison of Four Sensor-based Input Methods for Scanning Keyboards

Four sensor-based methods for computer input were compared. The methods were button, accelerometer, flex sensor, and pressure sensor. The sensors were held in the user's hand in a grip position (button, pressure) or attached via a Velcro band either to the index finger (flex) or on the back of the hand (accelerometer). The methods were used for the select operation with a single-switch scanning keyboard using a Qwerty letter arrangement. The setup used a 700 ms scanning interval, a 200 ms scanning delay (after each selection), and auditory feedback for switch activations. Twelve participants completed five text-entry tasks with each sensor. The text entry rates were slow, but in the expected range for single-switch input. Button selection was the fastest at 2.35 words per minute (wpm) and had the highest efficiency with 82%. The flex sensor followed at 2.26 wpm with 77% efficiency, followed by the pressure sensor at 2.07 wpm with 74% efficiency. The accelerometer was the slowest at 1.89 wpm and had the lowest efficiency at 68%. Statistical tests indicated a significant effect of sensor type on entry speed and efficiency, though post hoc comparisons revealed no pairwise significance, potentially due to the limited sample size. Qualitative results supported the findings: The button sensor received the most favourable user ratings across comfort, fatigue, and preference, with six of twelve participants selecting it as their preferred choice. Four participants selected the flex sensor as their preferred choice