The number of pulses is _________ to the _________ of the vanes.

• A. Inversely proportional, diameter
• B. Proportional, temperature
• C. Fixed, RPM
• D. Proportional, RPM

Answer: (D)

Pulses come from each vane passing the sensor, so how often they occur depends on how fast the vanes are turning. Each revolution produces a fixed number of pulses (equal to the number of vanes), so the pulse rate equals that fixed pulse-per-revolution count times the RPM. In other words, pulses per minute = (pulses per revolution) × RPM, which means the pulse rate is directly proportional to RPM. The other factors, like diameter or temperature, don’t set the cadence of pulses in this setup. If you have more vanes, you’ll get more pulses per revolution, but the relationship to RPM remains proportional.