Which of the following is not considered an analog sensor?

The correct answer identifies the quadrature encoder as not being considered an analog sensor because it operates using a digital signaling method. Quadrature encoders are designed to provide positional information through the detection of rotational movement using two output signals that indicate direction and speed. These signals are typically in the form of pulses, allowing the system to determine both the position and the direction of rotation.

In contrast, the line tracker, accelerometer, and gyro sensor are all categorized as analog sensors. The line tracker uses analog signals to detect the presence of a line based on light reflection. The accelerometer measures acceleration through analog voltages that correspond to movement along its axes. Similarly, the gyro sensor provides angular velocity in analog form, reflecting the rate of rotation around an axis. Thus, the quadrature encoder stands out as it relies on discrete signaling rather than continuous voltage signals, distinguishing it from the other options.