What is hysteresis in sensor readings and how does it affect performance?

• A. The dependency of output on input history; can cause lag and repeatability issues.
• B. A measure of how fast sensors respond to changes.
• C. The average of multiple readings.
• D. The maximum deviation allowed by a sensor.

Answer: (A)

Hysteresis describes a situation where a sensor’s output depends on the history of the input, not just its current value. In practice, as the input increases and then decreases, the readings follow different paths, so the same input level can produce different outputs depending on whether the input is rising or falling. This creates a lag in the sensed signal and reduces repeatability, because repeated measurements at the same input value may differ based on the prior state. For example, a temperature or magnetic sensor might switch on at a higher threshold when warming up and switch off at a different threshold when cooling, producing a noticeable loop or deadband. Hysteresis isn’t about how fast a sensor responds (that’s response time), nor about averaging multiple readings, nor about the maximum deviation allowed (that’s tolerance/accuracy).