A pulse input speed indicator operates by measuring the number of pulses received per second, which correlates to speed. In analog systems, the average voltage from these pulses is filtered to provide a steady reading, while digital systems simply count pulses within a defined "gating time" of one second. Calibration can be performed by comparing the indicator's readings with a reliable reference, such as GPS for vehicle speed, and adjusting parameters like pulse width or gating time accordingly. Understanding the relationship between pulse frequency and speed is crucial for accurate measurements. Overall, the discussion highlights the basic principles and calibration methods for both analog and digital pulse input speed indicators.
