Class A pyranometer 3S-IS+

RS-485Modbus RTUfor solar energy test applications

Product Overview
3S-IS+ is an Advanced Class A irradiance sensor designed for photovoltaic power plants. It measures solar irradiance on PV modules in W/m² and supports plant performance monitoring. Its modular architecture accepts additional module/ambient temperature, wind speed/direction, relative humidity and pressure sensors. Measured data is transmitted via Modbus RTU over RS485.

How it works
The 3S-IS+ incorporates a monocrystalline silicon reference cell that responds to light like a PV module. The cell current is converted to a measurable signal through a precision shunt resistor. A PT1000 temperature sensor mounted behind the cell provides temperature compensation so the electronics output a temperature‑compensated irradiance value in W/m². Data is available over Modbus RTU (RS485).

Diagnostic LEDs

• Power LED — indicates correct supply when voltage is within operating range (typically 12–24 V DC).
• Tx LED — Transmit — blinks when the sensor sends data via Modbus RTU.
• Rx LED — Receive — blinks when the sensor receives a valid Modbus request (useful to verify polling and communication).

Key benefits

• Class A accuracy. Complies with IEC 61724-1 with uncertainty ≤ 1%; each unit is calibrated under Class AAA sun simulator using an ISFH-calibrated reference cell.
• Modular design. Add module/ambient temperature, wind, humidity and pressure sensors to create a compact field weather station.
• Representative response. Reference cell structure and spectral response mirror PV modules for meaningful comparisons.
• Fast response. Standard response time is 1 second (optionally 500 ms).
• Easy daisy-chain. Termination resistor can be enabled/disabled via GUI to simplify RS485 networks.
• Field-ready construction. Glass-fiber reinforced UV-resistant ASA housing and UV-resistant PUR cable.
• Long-term reliability. SunSpec compliance, galvanic isolation, free software updates and 5-year warranty.

Available Models (summary)
3S-IS+ — Communication: RS485 Modbus RTU; Uncertainty: ≤1% (Class A); External sensors: none allowed
3S-IS-1+ — Communication: RS485 Modbus RTU; Uncertainty: ≤1% (Class A); External sensor: Ambient OR Module Temperature Sensor
3S-IS-2+ — Communication: RS485 Modbus RTU; Uncertainty: ≤1% (Class A); External sensors: Ambient OR Module Temperature Sensor, Wind Speed Sensor
3S-IS-2T+ — Communication: RS485 Modbus RTU; Uncertainty: ≤1% (Class A); External sensors: Ambient Temperature Sensor, Module Temperature Sensor
3S-IS-3+ — Communication: RS485 Modbus RTU; Uncertainty: ≤1% (Class A); External sensors: Ambient Temperature, Module Temperature, Wind Speed
3S-IS-4+ — Communication: RS485 Modbus RTU; Uncertainty: ≤1% (Class A); External sensors: Ambient Temperature, Module Temperature, Wind Speed, Wind Direction OR Relative Humidity Sensor
3S-IS-5+ — Communication: RS485 Modbus RTU; Uncertainty: ≤1% (Class A); External sensors: Module Temperature, Wind Speed, Wind Direction, Relative Humidity & Ambient Temperature Sensor
3S-IS-6+ — Communication: RS485 Modbus RTU; Uncertainty: ≤1% (Class A); External sensors: Module Temperature, Wind Speed, Wind Direction, Relative Humidity, Ambient Temperature and Pressure Sensor

Difference vs 3S-IS
3S-IS+ adds diagnostic LEDs (Power, Tx, Rx), changes in enclosure dimensions and typically lower power consumption. The earlier 3S-IS uses an aluminum housing and has different enclosure dimensions and power characteristics.

Additional information
The irradiance measurement range is 0–1600 W/m². The sensor reproduces module conditions to compare expected vs actual production and calculate performance ratio (PR). Each unit is factory-calibrated under a Class AAA sun simulator with an ISFH-calibrated reference cell.

Technical specifications

• Product Code: 3S-IS+, 3S-IS-1+, 3S-IS-2+, 3S-IS-2T+, 3S-IS-3+, 3S-IS-4+, 3S-IS-5+, 3S-IS-6+
• Sensor Type: Monocrystalline silicon reference cell (31 mm x 31 mm)
• Measured Data: Irradiance and internal cell temperature; module/ambient temperature, wind speed/direction and relative humidity/pressure via external sensors
• Irradiance Range: 0 – 1600 W/m²
• Uncertainty: ≤ 1% (Class A as per IEC 61724-1)
• Resolution: 0.1 W/m² (Class A)
• Response Time: 1 second (Class A), option 500 ms
• Drift: < 0.3% / year
• Field of View: 170°
• Data Output: RS485 up to 38400 Baud
• Communication Protocol: Modbus RTU
• Power Supply: 12 – 30 V DC (24 VDC recommended)
• Power Consumption: Typical 21 mA, maximum 30 mA @ 24 V DC @ 25°C
• Galvanic Insulation: 1000 V between power supply and RS485 line
• Cell Temperature Sensor: PT1000 Class A (EN 60751)
• Cable: 3 m 3x2x0.22 mm², 24 AWG LI2YC11Y-TP PUR cable, UV and weather resistant
• Operating Temperature Range: -40°C to +85°C
• Operating Humidity Range: 0% – 100% RH
• Dimensions: 135 x 105 x 50 mm (W x D x H)
• IP Rating: IP54 (optional IP68)
• Housing Material: ASA (glass fiber reinforced, UV-resistant)
• Calibration: Each sensor calibrated under Class AAA sun simulator per IEC 60904-2 and IEC 60904-4 using an ISFH-calibrated reference cell
• Compliant Standard: IEC 61724-1:2021 and IEC 60904
• Origin: Türkiye