When a sensor goes quiet
Silence is the real danger
A sensor giving a wrong value can be spotted. A sensor giving nothing at all cannot, and that is far worse, because you carry on believing you are being watched over.
A silent sensor is flagged as such: silence is not good news.
How you notice
Three signs, in this order. On the estate, the time of the last reading that stops moving. On the curve, a blank spreading in from the right. And above all: a dedicated alarm, because a silent sensor deserves to be reported just as much as a crossed threshold.
That is a rule in its own right, and Cybelia Cloud sets it up at installation: "when this sensor has sent nothing for three hours, then raise an alarm". The delay depends on the sensor's normal rhythm, an electricity meter reporting every minute and a humidity probe reporting every quarter of an hour do not have the same patience.
Check that every important sensor has a silence rule. If you only ask Cybelia Cloud one question, ask that one. Without it, a flat battery leaves you blind without a single message.
The causes, from most to least common
The battery, in the vast majority of cases. Then the sensor having been moved: somebody took it down to paint, or a trolley knocked it, and it now sits behind a lump of metal that blocks the radio. Then the gateway: if all the sensors on a site go quiet at once, it is not them, it is the gateway, check it is powered and that the network is working. Finally, rarely, the sensor itself, and it gets replaced.
What you have to do
Nothing technical. Report it, saying whether it is one sensor or several, that is the detail that saves support the most time. Meanwhile the history already recorded is untouched: a silent sensor does not lose the earlier readings.
In closing
A silent sensor is more dangerous than one that is wrong, because you carry on believing you are monitored. That is why silence raises an alarm just as a threshold breach does.
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