Hukseflux SR05-D1A3
Digital second class pyranometer that measures global solar irradiance and its own body temperature.
The Hukseflux SR05-D1A3 is a digital second class pyranometer that measures global solar irradiance on a flat surface, at weather stations, greenhouse sites and PV systems. This Modbus RTU template reads irradiance in W/m², sensor body temperature, calibration data and identification, and lets you change the Modbus address and serial settings and restart the sensor from ModbusCloud.
- Protocol
- Modbus RTU
- Connection
- RS485, 19200 baud
- Registers
- 30, read and write
- Brand
- Hukseflux
- Key readings
- Global solar irradiance · Sensor body temperature · Uncompensated irradiance · Thermopile voltage · Sensor sensitivity · Calibration date · Serial number
- Available commands
- Modbus address · Serial settings · Restart · Resistance check
- Compatible models
- SR05-D1A3 · SR05-D2A2 · SR05-DA1 · SR05-DA2
- Last updated
Registers (30)
28 read, 4 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| Irradiance (Temperature Compensated) | W/m² | Read | |||
| Sensor Body Temperature | °C | Read | |||
| Irradiance (Uncompensated) | W/m² | Read | |||
| Sensor Voltage Output | mV | Read | |||
| Sensor Electrical Resistance | Ω | Read | |||
| Scaling Factor Irradiance | Read | ||||
| Scaling Factor Temperature | Read | ||||
| Modbus Address | Read and write | ||||
| Serial Communication Settings | Read and write | ||||
| Restart | Write | ||||
| Resistance Check | Write | ||||
| Sensor Model Part 1 | Read | ||||
| Sensor Model Part 2 | Read | ||||
| Sensor Serial Number | Read | ||||
| Sensor Sensitivity | Read | ||||
| Response Time | s | Read | |||
| Sensor Resistance (Calibration) | Ω | Read | |||
| Sensor Calibration Date | Read | ||||
| Firmware Version | Read | ||||
| Hardware Version | Read | ||||
| Sensor Sensitivity History 1 | Read | ||||
| Calibration Date History 1 | Read | ||||
| Sensor Sensitivity History 2 | Read | ||||
| Calibration Date History 2 | Read | ||||
| Sensor Sensitivity History 3 | Read | ||||
| Calibration Date History 3 | Read | ||||
| Sensor Sensitivity History 4 | Read | ||||
| Calibration Date History 4 | Read | ||||
| Sensor Sensitivity History 5 | Read | ||||
| Calibration Date History 5 | Read |
Loading registers…
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If a device is not in the library yet, we build the template for free as soon as we have the register data.
Use cases
- Show outside radiation next to the greenhouse climate values on one dashboard and keep 365 days of history.
- Download the irradiance history as CSV to work out daily radiation sums for irrigation or crop records.
- Use an automation on irradiance to send a webhook or email to your climate or screen control when it passes a set level.
- Put irradiance next to the yield of a PV system on one dashboard to see whether the array performs as expected.
- Get an alert when the pyranometer stops sending values, or let automatic monitoring flag a frozen reading.
- Read the calibration date and sensitivity remotely to plan the recalibration every two years.
Installation
Power the sensor with 5 to 30 VDC, 12 V recommended: brown to plus, black to minus. Connect black also to the common of the RS-485 bus and leave blue unconnected.
Wire white (RS-485 B, data plus) to the RS-485 plus terminal and gray (RS-485 A, data minus) to the minus terminal of the ModbusCloud Gateway. Terminate both bus ends with 120 Ω.
Mount the sensor level and free of shade, with the cable exit pointing north in the northern hemisphere. On a grounded mount, leave the shield unconnected at the cable end.
Every sensor ships with address 1. For several sensors on one bus, give each a unique address with the Hukx Sensor Manager on a PC, or write Modbus Address and then Restart, one sensor at a time.
In ModbusCloud, add a Modbus device with protocol RTU, address 1, 19200 baud, 8 data bits, even parity and 1 stop bit, and import this template.
Check that Irradiance (Temperature Compensated) follows the daylight and that Sensor Serial Number matches the label on the sensor.
Things to watch for
The pyranometer does not answer. What should I check?
Check the supply first: 5 to 30 VDC on brown and black, with black also on the bus common. Then check 19200 baud, even parity, 1 stop bit and address 1 in ModbusCloud, and swap white and gray if nothing comes back. Leave blue unconnected: digital and analog output cannot run at the same time. An SR05-D2A2 talks TTL, not RS-485.
Why does irradiance go slightly below zero at night?
That is the zero offset of a thermopile pyranometer. On clear, windless nights the SR05 can read down to about -5 W/m². Values that are clearly too high or too low in daylight point to a dirty dome, shade, poor leveling or a cable fault. Clean the dome with a soft cloth about every two weeks.
Why are irradiance or temperature 100 times off?
The sensor sends irradiance and body temperature in hundredths, and the template divides by 100. Check that Scaling Factor Irradiance and Scaling Factor Temperature both read 100, the factory value. If one shows another value, that reading is off by the same ratio; contact Hukx before you rely on it.
How do I change the address or write to the sensor?
Writing is off per gateway by default; request it for the gateway in the portal. Write an address from 1 to 247 to Modbus Address, or a setting number to Serial Communication Settings, then write Restart: only then does the change take effect. Match the Modbus device in ModbusCloud. Write Resistance Check only for diagnostics, never on a schedule. Sensitivity and calibration data are read-only.
Why does the sensor model name show odd characters?
The model name sits in two blocks of four registers. An SR05-D1A3 from serial number 3819 and an SR05-D2A2 from 3524 store two characters per register. Older sensors, mostly sold as SR05-DA1 and SR05-DA2, store one character per register, so the text shows gaps. Sensor Serial Number is the quickest check.
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