The analog and continuous time signals measured by the sensor and modified by the signal conditioning circuitry must converted into the form a computer can understand. This is what is referred to here as data acquisition. It should be clearly understood that this step is only necessary when interfacing human gestures to a digital computer. If, for example, one wanted to use the direction of eye gaze to control a wheelchair, no data acquisition would be needed. The continuous analog voltages could be directly used to control the analog steering mechanism.
Section 5, however, deals specifically with the sampling and quantization techniques for using the information from the user to control a digital computer. The effects of such a process on the waveform received from the signal conditioning circuitry must be clearly understood in order to design the best possible computer controller for the given application.