Hysteresis

Sensor values may sometimes fluctuate during an alarm condition, which causes Connect Sensor to send multiple alarm reports.

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 sensor input value fluctuations.

For example, a pressure sensor input value increases to the high threshold and the device sends a high alarm report. However, the pressure sensor input value continues to increase and decrease repeatedly between normal and high thresholds during this alarm condition. If you have not set a hysteresis range, the Connect Sensor device sends an alarm report every time the sensor input value reaches the high threshold.

The following are examples of how high and low hysteresis works with a voltage input:

• High hysteresis: If your high threshold is 10 volts and your hysteresis value is 2 volts, then your high alarm hysteresis is 8 volts. This means that the alarm turns on when the sensor input value reaches 10 volts and remains on if the sensor input value stays above 8 volts. No additional alarm reports are sent during this alarm condition. The alarm turns off when the sensor input value falls below 8 volts.
• Low hysteresis: If your low alarm threshold is 2 volts and the hysteresis value is 3 volts, then your low alarm hysteresis is 5 volts. This means that the alarm turns on when the sensor input value reaches 2 volts and remains on if the sensor input value stays below 5 volts. No additional alarm reports are sent during this alarm condition. The alarm turns off when the sensor input value rises above 5 volts.

Setting the hysteresis threshold to 0 (zero) causes Connect Sensor to send an alarm report every time the sensor input value exceeds a high or low alarm threshold.

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