RAIN RFID Sensors — and how CoolTag implements one

RAIN RFID Sensors — and how CoolTag implements one

RAIN RFID has long been the backbone of item-level identification in retail, logistics, and manufacturing. A new generation of sensor-enabled RAIN RFID tags is now extending the technology from identification to condition awareness — and CoolTag is QDat.io's working implementation of that shift, built around the Axzon AZN5201-AFR IC.

What a RAIN RFID sensor is

A traditional RAIN RFID tag stores a unique identifier (EPC) and responds to reader queries. A sensor-enabled tag adds an onboard measurement capability — most commonly temperature — that can be read alongside the EPC, in the same RFID exchange, without any line of sight or physical connection.

The key shift is autonomy. The tag is not just queried for its identity; it logs measurements on its own, stores them locally, and surrenders that history wirelessly when a reader passes by.

CoolTag, built on the Axzon AZN5201

CoolTag is the autonomous peel-and-stick UHF RFID temperature logger inside Cooldat®. It is built around the Axzon AZN5201-AFR — a flexible 33 × 100 mm label with a thin printed battery, no separate enclosure, no return logistics.

The headline properties:

How CoolTag records

Once armed by a QDatFX or QDatDroid reader session, the tag samples temperature autonomously at a user-defined interval and writes each sample to encrypted flash:

Duration vs interval

A logging session has two ceilings: the printed battery supports up to ~3 months of active logging, and the flash holds exactly 4096 samples. Whichever runs out first ends the session.

Below ~32-minute intervals, the memory is the bottleneck:

Above that, the battery is the bottleneck — at 1 h or longer intervals, you get ~3 months of logging regardless of how much flash is left.

Rule of thumb: flash time = 4096 × interval. Pick the longest interval your application can tolerate so the battery, not the memory, ends the session.

Tamper-evident by design

Samples are encrypted at the moment of measurement, before being written to flash:

Energy management — printed battery, multi-week life

CoolTag is powered by a thin, flexible, printed battery — REACH/SVHC, RoHS, and EU battery-directive compliant. No coin cells, no reverse logistics.

A dedicated ADC verifies battery voltage at every logging event so out-of-range samples are flagged.

The five states of a CoolTag

A CoolTag passes through five lifecycle states:

1. No-Battery. Reader has passive RF access to MTP memory — EPC, user, and configuration can be staged before battery insertion.

2. Sleep. Battery installed but isolated. ≤1 nA drain. This is the shelf-life state.

3. Standby. Reader command wakes the RTC; battery drain rises to ~100 nA. Defines operating life.

4. Ready. Once the RTC is set, configuration is locked from MTP into the real-time controller. Cannot be altered without removing the battery.

5. Logging. Periodic logging events (≈80 ms each) write encrypted samples to flash. Stops when full, when battery falls below threshold, or at the programmed count.

How a sample reaches QDat.io

The full path from a CoolTag in the field to the QDat.io cloud:

1. CoolTag records. Autonomous sampling to encrypted on-chip flash. No connectivity required during transit.

2. Reader meets tag. A fixed portal or handheld interrogates the tag over RAIN UHF and pulls the log — or just the alarm flag — wirelessly.

3. Reader client publishes. QDatFX (on Zebra FX7500/FX9600 fixed readers) or QDatDroid (on RE40-based handhelds and the EM45 phone) wraps the raw RFID exchange into structured CoolTag stream messages.

4. WSS MQTT to QDat.io. The client publishes those messages over an MQTT connection carried on secure WebSockets — TLS-encrypted, NAT-friendly, low-latency, resilient to intermittent links.

5. QDat.io ingests. The broker writes into time-series storage, fires alarm and exception workflows, and exposes the history through REST and MCP APIs for dashboards, integrations, and AI agents.

The 4096-sample encrypted log on the tag remains the canonical record. QDat.io replicates and reasons over those logs — but the cryptographic proof of each sample lives on the CoolTag itself.

Why this matters for cold chain

Cold-chain compliance has traditionally relied on data loggers placed at the shipment level — one logger per pallet or truck. Sensor RAIN RFID enables item-level evidence: every package in a shipment can carry its own temperature history.

Standards and compliance

Read the full specs

This post is the narrative version of the CoolTag product page. For the full specification tables — RFID performance, data logging, temperature sensor, security, energy, memory, physical, lifecycle, and architecture — see the CoolTag page.

The underlying Opus IC is covered by the Axzon U.S. patent portfolio.