Technical Specifications of Self Cleaning Irradiance Sensor

Item Code	3S-SCIS
Measured Data	Irradiance and Cell Temp.
Irradiance Range	0…1600 W/m²
Uncertainty	≤1% (Less than 2%; as per IEC 61724-1 standard Class A)
Resolution	0,1 W/m² (Less than 1 W/m²; as per IEC 61724-1 standard Class A)
Response Time	1 sec. (Less than 3 sec; as per IEC 61724-1 standard Class A)
Drift	<0,3% / year
Field of View	170° (Larger than 160° as per IEC 61724-1 standard Class A)
Tilt-Azimuthal Angle	0°- 0° (≤1°; as per IEC 61724-1 standard Class A)
Output Rate	1/s
Data Output	RS485 up to 38400 Baud
Communication Protocol	Modbus RTU
Power Supply	110-240V AC or 24V 5A DC
Power Consumption	Pump Passive: Max. 20 mA @ 24V DC; Pump Active: Max. 3 A @ 24V DC
Cabel Length and Features	3 m LI2Y(st)C11Y PUR Cable, UV and Weather Resistant
Galvanic Isolation	1000 V between power supply and RS485 bus
Cell Temperature Sensor Type	PT1000 Class A as per EN 60751
Operating Temperature Range	-20°C…85°C
Operating Humidity Range	0%…100% RH
Water Tank Capacity	18 Liters
Water Consumption	36 Liters/year (Refilling required twice a year for daily cleaning)
Washing Liquid	Pure Water: 100% (Should be used when the ambient temperature is above 0°C); Pure Water: 65% + Antifreeze: 35% (Should be used when the ambient temperature is below 0°C)
Water Hose Length	5 m (up to 20m on request)
Max. Water Line Height	5 m
Weight	10 kg
IP Rating	IP54 (Optional IP 65, IP 68)
Sensor Housing Material	Aluminium
Standard	IEC 61724-1:2021 and IEC 60904
Calibration	Each sensor is calibrated under a Class AAA Sun Simulator according to IEC 60904-2 and IEC 60904-4 standards using a reference cell calibrated by the ISFH Institute in Germany.
Origin	Türkiye

Why is Sensor Cleaning Important for Accurate Readings?

The surface of the irradiance sensor becomes dusty and dirty over time. A dirty sensor will read lower irradiance levels, which can falsify calculations such as the performance ratio. Therefore, keeping the sensor clean is essential in Class A monitoring.

The IEC 61724-1:2021 standard (clause 8.2.5 and Table 7) mandates the reduction of contamination effects on irradiance sensors within the scope of Class A monitoring and requires at least weekly cleaning in typical installations. Technologies that provide contamination reduction equivalent to weekly cleaning are also accepted. 3S-SCIS is designed precisely to meet this requirement.

Automatic cleaning eliminates the need for regular field visits to manually clean the sensor. This reduces labour costs and ensures the sensor remains clean and provides consistently accurate measurements.

How Does the 3S-SCIS Cleaning System Work?

A cleaning system consisting of a water tank, pump, and hose line is connected to the sensor. The system washes the sensor surface at a time determined via a user interface (GUI).

• Scheduling: By default, cleaning runs once a day at a time specified by the user. If desired, the number of daily cleanings can be increased to three by defining three different times via the GUI.
• Water consumption: An 18-liter tank is typically refilled twice a year, with an annual water consumption of approximately 36 litres for daily cleaned sensors.
• Water hose: The standard hose length is 5 meters and can be extended up to 20 meters upon request. The maximum height of the water line is 5 meters.

Washing fluid is selected according to the air temperature. When the temperature drops below 0°C, antifreeze is added to prevent freezing.

Washing Liquid	Terms of Use
100% pure water	When the air temperature is above 0°C
Pure water 65% + antifreeze 35%	When the air temperature is below 0°C

How Does 3S-SCIS Irradiance Measurement Work?

The 3S-SCIS incorporates a real photovoltaic reference cell. This cell reacts to light just like a solar panel, so the sensor mirrors the conditions that the panels actually see. A Class A PT1000 temperature sensor behind the cell corrects for the effect of temperature on the measurement.

The device calculates the temperature-compensated irradiance value in W/m² and transmits it to data loggers via Modbus RTU over an RS485 line. Each sensor is calibrated under a Class AAA Sun Simulator according to IEC 60904-2 and IEC 60904-4 standards using a reference cell calibrated by the ISFH Institute in Germany.

What Are the Advantages of Self Cleaning Irradiance Sensor?

The self-cleaning irradiance sensor offers several advantages for reliable and low-maintenance solar monitoring as outlined below.

• Automatic cleaning: It cleans the sensor automatically at regular intervals, reducing labour costs by eliminating the need for manual cleaning and field visits.
• Class A compliant: Meets IEC 61724-1:2021 Class A monitoring requirements with an uncertainty of <1%.
• Similar behaviour to with panels: The PV reference cell has a similar structure to the panels and responds to light in the same way.
• Easy integration: Connects to data loggers via Modbus RTU output over RS485 and SunSpec compatibility.
• Flexible power supply: Operates with 110-240 V AC or 24 V DC.
• Backed by SEVEN: Comes with remote installation service, free software updates and a 2-year warranty.

How to Install the Self Cleaning Irradiance Sensor?

Pay attention to the following points when installing the system.

• Mount the irradiance sensor next to the solar panels, ensuring it is aligned at the same angle and orientation as the solar panels.
• Place the water tank under the solar panel or in another suitable area to protect it from sunlight and reduce evaporation.
• If the air temperature drops below 0°C, add antifreeze to the washer fluid (65% distilled water + 35% antifreeze).
• Mount the electronic panel under the solar panel or in another protected area using appropriate equipment and the mounting brackets on the back of the panel.
• Set cleaning times and the number of daily cleanings (maximum three) via the user interface.
• Fill the tank periodically, depending on the number of daily cleaning.