TECHNICAL SPECIFICATIONS OF ADVANCED IRRADIANCE SENSOR

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 IEC61724-1 standard)
Resolution	0,1 W/m² (Class A as per IEC61724-1 standard)
Response Time	1 second (Class A as per IEC61724-1 standard)
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 the power supply and the RS485 line.
Cell Temperature Sensor	PT1000 Class A according to 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
Calibration	Each sensor is calibrated under Class AAA Sun Simulator as per IEC 60904-2 and IEC 60904-4 by using a reference cell calibrated by ISFH-Germany
Compliant Standard	IEC 61724-1:2021 and IEC 60904
Origin	Türkiye

What is the purpose of an irradiance sensor?

To understand how efficiently a photovoltaic power plant actually operates, you need to know how much solar irradiance falls on the panels. The irradiance sensor measures exactly this. The value it provides in W/m² allows you to compare expected production with actual production and calculate the performance ratio (PR).

When output drops, it’s difficult to distinguish whether the problem is due to the environment or the system. Irradiance data clarifies this distinction. That’s why irradiance sensors are a fundamental part of professional PV monitoring systems.

How does 3S-IS+ work?

The 3S-IS+ contains a monocrystalline cell. The cell reacts to light just like a solar panel. The current produced by the cell is converted into a measurable signal via a precision shunt resistor.

Temperature is one of the most important factors affecting the measurement. The PT1000 temperature sensor at the back of the cell corrects this effect. The electronic board calculates the temperature-compensated irradiance value in W/m² and transmits it to the data loggers via Modbus RTU over the RS485 line.

It is important that the reference cell behaves in the same way as a solar panel, because the sensor mirrors the conditions that the panels actually experience.

The box features diagnostic LEDs.

Power LED

Indicates that the sensor is powered correctly. When the supply voltage is within the required operating range, typically 12–24 VDC, the LED turns on, allowing quick confirmation that the power connection is correct.

Tx LED — Transmit

Blinks when the sensor is sending data via Modbus RTU. This indicator helps verify that the sensor is actively transmitting information to the connected master device, such as a data logger, PLC, or SCADA system.

Rx LED — Receive

Blinks when the sensor receives a valid Modbus request. This is useful for checking whether the master device is polling the sensor and whether communication settings such as baud rate, slave address, and protocol configuration are correct.

Why Choose 3S-IS+ Advanced Irradiance Sensor?

• Class A accuracy. Compliant with IEC 61724-1, with an uncertainty of less than 1%. Each sensor is calibrated with a reference cell calibrated by the ISFH Institute in Germany and under a Class AAA solar simulator.
• Modular design. By adding module temperature, ambient temperature, wind, humidity, and pressure sensors to a single main unit, you can build a complete weather station in the field.
• Speaks the same language as the panel. The reference cell has a similar structure to a PV panel and responds to light in the same way as the panels.
• Fast data. Response time is one second and can be reduced to 500 ms on demand.
• Easy multi-connection. Thanks to the termination resistor that you can turn on and off via the GUI, you can quickly establish daisy chain connections without additional hardware.
• Designed for field use. The glass fiber reinforced, UV-resistant ASA housing and UV-resistant PUR cable withstand harsh outdoor conditions.
• Long-lasting reliability. Comes with SunSpec compliance, galvanic isolation, free software updates, and a 5-year warranty.

Available Models of the 3S-IS+ Advanced Irradiance Sensor

All models below are IEC 61724-1:2021 Class A compliant, factory-calibrated, and built with the same durable construction. The only difference is the number and type of external sensors that can be connected via RS485 Modbus RTU.

Note: IP54 protection class may pose a risk in terms of sealing in tracker systems and rear-side irradiance measurement. IP68 is recommended for systems moving at high angles. Evaluate the protection class selection according to your field conditions.

Model	Communication	Uncertainty	External Sensor Options
3S-IS+	RS485 Modbus RTU	≤1%, as per IEC61724-1 standard Class A	No external sensor can be connected
3S-IS-1+	RS485 Modbus RTU	≤1%, as per IEC61724-1 standard Class A	Ambient Temperature Sensor OR Module Temperature Sensor
3S-IS-2+	RS485 Modbus RTU	≤1%, as per IEC61724-1 standard Class A	Ambient Temperature Sensor OR Module Temperature SensorWind Speed Sensor
3S-IS-2T+	RS485 Modbus RTU	≤1%, as per IEC61724-1 standard Class A	Ambient Temperature SensorModule Temperature Sensor
3S-IS-3+	RS485 Modbus RTU	≤1%, as per IEC61724-1 standard Class A	Ambient Temperature SensorModule Temperature SensorWind Speed Sensor
3S-IS-4+	RS485 Modbus RTU	≤1%, as per IEC61724-1 standard Class A	Ambient Temperature SensorModule Temperature SensorWind Speed SensorWind Direction Sensor OR Relative Humidity Sensor
3S-IS-5+	RS485 Modbus RTU	≤1%, as per IEC61724-1 standard Class A	Module Temperature SensorWind Speed SensorWind Direction SensorRelative Humidity and Ambient Temperature Sensor
3S-IS-6+	RS485 Modbus RTU	≤1%, as per IEC61724-1 standard Class A	Module Temperature SensorWind Speed SensorWind Direction SensorRelative Humidity, Ambient Temperature, and Pressure Sensor

What is the difference between 3S-IS+ and 3S-IS?

Both models share the same measurement motor. Both are IEC 61724-1 Class A, have uncertainties below 1%, and use the same Modbus RTU communication. Therefore, you can choose between the two without compromising accuracy. The difference lies in the few details.

Features	3S-IS+	3S-IS
Diagnostic LEDs	Yes (Power, Tx, Tr)	No
Enclosure dimensions	135 x 105 x 50 mm	140 x 110 x 42 mm
Power Consumption	Typical 21 mA, maximum 30 mA @ 24 V DC @ 25°C	30 mA – 60 mA max. @24 V DC
Housing material	ASA	Aluminum