DALI · Concepts
How data flows
What happens to a reading from the moment a sensor sends it until it reaches a file, a Modbus register or your cloud.
A station does four things with every reading: it collects it, turns it into a parameter, stores it, and hands it on. Each step is set up on a different page of the console.
1. Collect
The station reads its sensors through its inputs:
| Input | Set up on |
|---|---|
| Modbus devices over RS-485, RS-232 or TCP (the station acts as the Modbus master) | Modbus |
| SDI-12 sensors | SDI-12 |
| Analog channels and digital inputs | Analog and digital |
| GPS and the station's own health (signal, supply, temperature) | Built in |
2. Turn readings into parameters
A parameter is one named value with a unit and a number of decimals, such as "GHI (W/m2)". Most parameters take a reading from an input and apply scaling and an offset. A calculated parameter is worked out from other parameters. Parameters are set up on the Parameters page; see also Calculated parameters.
The order of parameters on the Parameters page matters. It is the column order in downloaded files and the register order on the station's Modbus slave.
3. Store
The station keeps two kinds of data:
| Kind | What it is | Set on Device, Storage |
|---|---|---|
| Logged data (also called processed or minute data) | One record per logging interval, for example every minute. What most people want. | Update Interval from 1 to 60 minutes |
| Raw data (also called 1-second or instantaneous data) | Readings at a short fixed interval, with a flag per value saying whether it was fresh. | Turned on with Enable Raw Data Logging; Update Interval from 1 to 30 seconds |
Records are grouped into files. Create Interval decides how much time one file covers: 1, 3, 6 or 12 hours, or 1 day (logged data can also use 1 month).
Data is written to the station's internal storage. If the station has an SD card fitted and turned on, it also keeps an archive there, and the files on the card are encrypted. See Data downloads.
When a sensor stops answering
If a sensor goes quiet, the station does not keep repeating its last value as if it were new. The value is marked stale and is written as NaN (not a number) in files, cloud uploads and Modbus registers, so a real reading of zero is never confused with "no data". You can switch this back to the older behaviour of writing 0 under Device, Storage, Stale Value Representation. See Device.
4. Hand it on
| Way out | What it does | Read more |
|---|---|---|
| Download from the console | ZIP files of CSV data for any date range | Data downloads, Download data |
| Modbus slave | A SCADA system or PLC reads the latest values from the station over Modbus TCP, RS-485 or RS-232 | Modbus slave register map |
| Aeron Cloud (Live3) | The station uploads to Live3, where you see charts, alerts and reports | Cloud upload |
| Cloud destinations (firmware 4.1 and later) | The station sends data to your own service: HTTPS, Azure IoT Hub, Azure Event Hubs, AWS IoT Core, MQTT, SFTP or a TCP socket | Cloud destinations |
| USB drive | When turned on under Device, Storage, plain CSV files are copied to a USB drive plugged into the station | Device |
A dropped network does not lose uploads. Each destination remembers how far it has got and, once the connection is back, sends everything it missed that is still stored on the station.
Time stamps
Every record carries the station's local date and time. If you change the station's time zone later, records already written keep the offset that was in effect when they were recorded. Keep the station's clock right with NTP or GPS; see Set the time.