The Hysteresis setting defines a tolerance band for alarm alerts. This feature prevents multiple alarm alerts if the reading oscillates around the specified threshold. See the graph for an explanation.
Without a hysteresis of 5°C, the alarm raised at point 8 would end at point 9. With the hysteresis function, the alarm continues until the temperature rises above the tolerance band (point 10), that is, 5°C + (-15°C) = -10°C.
- Hysteresis = 5°C (RED):
- The unit sends 3 e-mails (SMS)
- Alarm at points 0..4, 8..10, 12 and beyond
- No hysteresis (0°C) (BLUE):
- The unit sends 8 e-mails (SMS)
- Alarm at points 0..1, 2..3, 8..9, 12..13, 14 and beyond