In the context of sensors, what does hysteresis refer to?

• A. The dimensional tolerance of a sensor
• B. The difference between sensor output at rising and falling input; affects repeatability and noise immunity.
• C. The physical size of a sensor
• D. The power consumption of a sensor

Answer: (B)

Hysteresis in sensors is the idea that the output depends on the history of the input, not just its current value. It creates a gap between the input level that makes the sensor switch on and the level that makes it switch off, so the sensor doesn’t toggle back and forth with small fluctuations. This deadband between rising and falling input helps with repeatability and noise immunity because minor noise near a threshold won’t cause rapid on/off changes. A common way this shows up is in Schmitt-trigger circuits or magnetic sensors, where the switch-on level is higher than the switch-off level. The other aspects listed—dimensional tolerance, physical size, and power consumption—are not what hysteresis describes; they relate to physical and electrical specifications, not the path-dependent output behavior.