SunSpec Model 307 — Base Met

Installation

1. 1Enable Modbus TCP on the weather station or connected data logger under the communication or Modbus section of its configuration interface, noting the assigned IP address and TCP port (default 502).
2. 2Connect the weather station or logger to the same LAN segment as the ModbusCloud Gateway, ensuring no firewall blocks TCP port 502 between the two devices.
3. 3In the ModbusCloud portal, add a new device, import the SunSpec Model 307 — Base Met template with one click, and assign the correct unit ID matching the station's Modbus slave address.
4. 4Verify the connection by checking live values for tmpamb and wndspd in the portal register view; confirm readings match the station's local display or manufacturer diagnostic tool.

Things to watch for

01

All registers return the SunSpec NaN value. What is wrong?

Many weather stations and loggers only populate registers that their hardware sensor suite actually supports. A NaN in rh, pres, elecfld, surwet, or soilwet is normal if the physical sensor for that point is not installed. Confirm which sensors are fitted by consulting the station datasheet and cross-check against the PICS document for your specific device.

02

The gateway connects but the model ID register reads an unexpected value.

SunSpec devices expose multiple models in a chain starting at a base address, typically 40001. If you poll the Model 307 block at the wrong offset, the id register will not return 307. Use SunSpec auto-discovery or manually confirm the absolute Modbus address of the Model 307 block by reading the chain from the base address forward past the Common Model block.

03

Wind direction reads zero continuously even when wind is present.

A persistent zero on wnddir can indicate that the sensor is not connected, the vane is physically stuck, or the station firmware maps north as zero and genuinely reports zero during calm conditions. Check the physical wind vane for obstruction, verify sensor wiring at the station terminal block, and test with a known wind direction by rotating the vane manually.

04

The ppt register returns an integer I cannot interpret. What do the values mean?

The ppt field is an enumerated type with no physical unit. The SunSpec Model 307 specification defines discrete integer codes for precipitation type, such as none, rain, snow, or mixed. The exact code table depends on the implementing device's firmware. Consult the device manufacturer's PICS or application note to map the integer to the correct precipitation category.

Registers (13)

13 read / 0 write

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