SmartSwarm 300 Series
:
85
When you select the Low Threshold event type on a register, you must enter two fields:
●
The
Threshold
field specifies the value below which the register must decrease in order to trigger an
MQTT publish.
●
The
Hysteresis
field allows you to prevent multiple MQTT publishes due to process noise. Once the
register has crossed the Threshold value in the negative (decreasing) direction it must cross the value
[Thr Hysteresis] in the positive direction before it is considered to have re-crossed.
●
NOTE: This rule is STATEFUL. For example, when the Low Threshold is crossed, in either direction, an
MQTT publish will be triggered. But if the register remains below (or above) the threshold, no further
messages will be published. An MQTT publish will occur only on state transmissions:
The following rules are STATEFUL: High Threshold, Low Threshold, High Rate, Low Rate.
The following example shows the same register as before. The red callouts show when MQTT publishes will be
triggered, assuming that a “Low Threshold” rule is applied, with Threshold = 15 and Hysteresis = 5: