Hysteresis

The liquid levels in your tanks may sometimes fluctuate during an alarm condition, which causes repeated alarm reports.

For example, in a Connect Tank the liquid level increased to the high alarm threshold and the device sent a high alarm report. Note that during this alarm condition, the liquid level may continue to increase and decrease repeatedly between normal and high thresholds. In this situation, if you do not set a hysteresis range, the Connect Tank device sends an alarm report every time the device measures the liquid level at the high threshold.

Hysteresis works with the high and low alarm thresholds to tell the device when to keep an alarm on without sending additional alarm reports, or when to shut off an alarm. Use this to avoid repeated alarms during common liquid level fluctuations.

For example, if your high alarm threshold is 20 inches and your hysteresis value is 10 inches, then your high alarm hysteresis is 30 inches. The following figure shows how a high alarm and hysteresis work in a tank.

	Alarm state	Description
1	On	The device measures that the water increased above the high threshold. The device sends an alarm report to Remote Manager.
2	On	The device measures that the water decreased below the high threshold, but it is still above the hysteresis so the alarm remains on. If the water increases again above the high threshold, no additional alarm reports are sent.
3	Off	The water decreased below the hysteresis so the alarm turns off. If the water increases again above the high threshold, the alarm turns on and the device sends another alarm report.

For a low alarm hysteresis, if your low alarm threshold is 70 inches and the hysteresis value is 10 inches, then your low alarm hysteresis is 60 inches. The alarm is on and stays on when the liquid level decreases below the low threshold and remains below the hysteresis. The alarm turns off when the water increases above the 60-inch hysteresis.

Setting the hysteresis threshold to 0 (zero) causes Connect Tank to send an alarm report every time the liquid level reaches a high or low alarm threshold.

Note Setting the hysteresis threshold to 0 (zero) may cause excessive data usage and reduce battery life.