Differences

This shows you the differences between two versions of the page.

Link to this comparison view

visan:hysteresis [2023/11/17 03:13] – created optrixvisan:hysteresis [2025/12/18 22:50] (current) – external edit 127.0.0.1
Line 1: Line 1:
 +====Hysteresis====
  
 +In control systems, **hysteresis** is used to prevent digital signals (such as alarms, alerts and relays) from rapidly flicking between their //on/off// or //true/false// states.
 +
 +In these cases, you'll usually have a **switch point** and a certain amount of **hysteresis**.
 +
 +The output will change when you reach the //switch point//. But instead of changing back the moment the value drops below the switch point, it will allow a small amount of additional dropping before it goes back to its original state. The difference between the switch point and the point that the output resets is the hysteresis.
 +
 +===Example===
 +
 +For example, let's look at a temperature control alert, where you're trying to keep the temperature  under 30 degrees.
 +
 +If using a simple 'greater than' comparison, a value might reach exactly 30 degrees. But thanks to subtle variations in measurement, it will drift both above and below that value.
 +
 +==Without Hysteresis==
 +
 +^Input Value^Output Value^
 +|29.9|Off|
 +|30|Off|
 +|30.1|On|
 +|30.2|On|
 +|29.9|Off|
 +|29.7|Off|
 +|30.1|On|
 +|29.9|Off|
 +|25|Off|
 +|23|Off|
 +
 +==With Hysteresis==
 +
 +This time we'll look at the same input data, but we'll add 1 degree of hysteresis
 +
 +^Input Value^Output Value^
 +|29.9|Off|
 +|30|Off|
 +|30.1|On|
 +|30.2|On|
 +|29.9|On|
 +|29.7|On|
 +|30.1|On|
 +|29.9|On|
 +|25|Off|
 +|23|Off|