Answer

Correct Option: (iii) Forward and inverse direction (tachometer with quadrature measures bidirectional speed)

Explanation

Tachometer encoder (incremental / quadrature) measures rotational speed and direction.

• Quadrature (A/B channels) 90° out of phase → via phase lead/lag determines forward vs reverse and counts pulses → speed $\omega = \Delta\text{pulses}/\Delta t$.
• False pulse: Noise, not speed type.
• Single revolution in multiple track: Absolute encoder (Gray code), measures absolute angle, not tachometric speed.
• Exact position: Position encoder, not tachometer.

Tachogenerator gives analog voltage ∝ speed, but quadrature encoder gives digital bidirectional speed.

Final Answer

Forward and inverse direction speed (bidirectional) → Option (iii).