RS485 solar irradiance sensor 3S-IS

Modbus RTUIEC 61724-1

Product overview
The 3S-IS is an irradiance sensor for solar PV monitoring that provides temperature-compensated irradiance measurements and Modbus RTU communication over RS485. It integrates a monocrystalline reference cell and a PT1000 cell-temperature sensor. Supplied with mounting bracket and 3 m UV-resistant LIYYC11Y cable; aluminum UV-protected housing; IP54 standard (IP65/IP68 options). Designed for plug-and-play integration with PLC, SCADA and datalogger systems.

How it works

• A monocrystalline solar cell generates a short-circuit current proportional to incident irradiance.
• A precision shunt resistor converts the cell current into a measurable voltage signal.
• An integrated PT1000 temperature sensor on the cell back compensates temperature effects.
• A microcontroller processes signals and computes temperature-compensated irradiance in W/m².
• Processed data are transmitted via RS485 using Modbus RTU.

Key features

• Standards: IEC 61724-1 Class A and IEC 60904 calibration series.
• Uncertainty: ≤1% (IEC61724-1 Class A); resolution 0.1 W/m².
• Response time: 1 s (configurable to 500 ms on request).
• Communication: RS485 up to 38400 Baud, Modbus RTU; galvanic isolation 1000 V between power and RS485 bus.
• Power: 12–30 V DC; consumption ≤30 mA @24 VDC.
• Environment: operating −40 °C to +85 °C; humidity 0–100%.
• Mechanical: aluminum housing, dimensions 140 × 110 × 42 mm, weight ~0.3 kg; IP54 (IP65/IP68 options).

Available models (summary)

• 3S-IS — RS485 Modbus RTU — ≤1% — no external sensor inputs
• 3S-IS-1 — RS485 Modbus RTU — ≤1% — ambient OR module temperature sensor input
• 3S-IS-2 — RS485 Modbus RTU — ≤1% — ambient OR module temperature input; wind speed input
• 3S-IS-2T — RS485 Modbus RTU — ≤1% — ambient AND module temperature inputs
• 3S-IS-3 — RS485 Modbus RTU — ≤1% — ambient, module temperature and wind speed inputs
• 3S-IS-4 — RS485 Modbus RTU — ≤1% — ambient, module, wind speed; wind direction OR relative humidity
• 3S-IS-5 — RS485 Modbus RTU — ≤1% — module temperature, wind speed, wind direction, relative humidity and ambient temperature

Calibration and testing
Each sensor is calibrated on a Class AAA sun simulator according to IEC 60904-2 and IEC 60904-4 using a reference cell calibrated by ISFH (Germany). Devices are validated outdoors against a calibrated reference cell from Fraunhofer ISE.

Technical specifications

• Item codes: 3S-IS, 3S-IS-1, 3S-IS-2, 3S-IS-2T, 3S-IS-3, 3S-IS-4, 3S-IS-5
• Reference cell: monocrystalline silicon (31 × 31 mm)
• Irradiance range: 0–1600 W/m²
• Uncertainty: ≤1% (IEC61724-1 Class A)
• Resolution: 0.1 W/m²
• Response time: 1 s (500 ms on request)
• Drift: <0.3%/year
• Field of view: >160°
• Tilt-azimuthal angle: 0°–0°, ≤1°
• Output rate: 1 Hz
• Data output: RS485 up to 38400 Baud; Modbus RTU
• Power supply: 12–30 V DC; consumption 30 mA max @24 VDC
• Electrical connection: 3 m LIYYC11Y PUR cable, UV and weather resistant (6 conductors twisted including ground)
• Galvanic isolation: 1000 V between supply and RS485 bus
• Cell temperature sensor: PT1000 Class A (EN 60751)
• Operating temperature: −40 °C to +85 °C
• Operating humidity: 0–100%
• Dimensions: 140 × 110 × 42 mm
• Weight: ~0.3 kg
• IP rating: IP54 (IP65, IP68 options)
• Housing material: aluminum
• Compliance: IEC 61724-1:2021 and IEC 60904 series

Modbus specification

• Baud rates: 1200, 2400, 9600, 19200, 38400
• Parity: None, Even, Odd
• Stop bits: 1 or 2 (2 only when parity = None)
• Default configuration: 9600, 8N1, address 1

Applications
Monitoring and performance assessment of solar PV plants, integration with PLC/SCADA and dataloggers, meteorological stations and PV testing sites.

Components

• UV-resistant aluminum sensor housing
• Monocrystalline PV reference cell laminated with EVA and Tedlar
• Electronic board with microcontroller for signal conditioning and Modbus RTU communication