Telemetry is the flow of readings from devices to wherever they are stored and analyzed. The word predates IoT, coming from spacecraft and remote weather stations, but the pattern is the same: a device measures, packages the values with a timestamp and identity, and sends them without anyone asking. The result on the receiving side is time-series data, one row per device per interval.
Telemetry design is mostly about deciding how much to send and how often. A device reporting every second produces a large and expensive dataset that may be mostly identical values; reporting only on change saves bandwidth but hides whether a silent device is healthy or dead, which is why many systems add a heartbeat. The IoT data pipeline guide follows telemetry from ingestion to action.
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