Solar Radiation Sensor Box for Solar Irradiance 3S-SR-2T-WS-MB


Irradiance sensor is an affordable solution for measurement of solar irradiance. The powder-coated aluminum case in conjunction with the solar cell laminated between glass and Tedlar foil builds a very reliable and rugged sensor.


A silicon solar cell can be used as an irradiance sensor, because the short-circuit current is proportional to irradiance. Our sensors are built out of a monocrystalline solar cell connected to a shunt. Due to the low resistance of the shunt the cell operates next to short circuit.
The temperature coefficient of the short-circuit current creates a small error. Therefore, all of our silicon sensors with the extension TC have an active temperature compensation, which reduces this error by factor 20.

The compensation is realized by using a specific temperature sensor laminated to the rear side of the solar cell. The measuring signals of short-circuit current of the cell and the resistance value of the temperature sensors is measured by a microcontroller.

The calculated values of irradiance and temperature given onto a RS485 port with customer specification protocol. The electronic circuit is optimized for low power consumption.


The solar cell is embedded in Ethylene- Vinyl- Acetate (EVA) between glass and Tedlar. Plain integration into the top cover of the box Advanced weatherproof junction box made of UV resistant material with cable gland and screw-less terminal for the connection of the measuring cable, therefore, the sensor construction is comparable to that of a standard PV module. The electrical connection is realized by a 3m cable.

All sensors are calibrated in simulated sunlight against a reference cell of the same type. The reference cell is periodically calibrated against A reference cell calibrated by fraunhofer ise, freiburg.


General Information
Solar Cell Monocrystalline Silicon (50 mm x 33 mm)
Current shunt 0.1 W (TK = 30 ppm / K)
Operating temperature -20°C to +70°C
Electrical connection via 3 m cable, UV and weatherproof
Power supply 12 to 28 VDC (40 mA typically at 20 VDC)
Interface RS485 up to 19200 Baud
Protocol The sensor is connected via a 2-wire RS485 bus with open vendor-independent Modbus RTU protocol
Galvanic isolation 1000 V between power supply and RS485 bus
Case, protection mode Powder-coated aluminum, IP 65
Dimensions, weight 155 mm x 85 mm x 40 mm, approx. 360 g  
Irradiance 0…1500W/m2, Error with temperature compensation compared to pyranometer within the operating range of -20°C to +70°C and vertically beam of irradiance. ± 5 %
Temperature Error at minimum and maximum temperature. ± 1.0°C  
Electrical Connection
Color mapping of cable Red (wire) Power (plus),Black (wire) Power (minus),Brown (wire) Data + / A ,Orange (wire) Data – / B ,Black (large profile) Shielding
Input, Wind Speed 3S-WS-PLS-CON, Wind speed sensor, reed contact, pulse with Binder 712 M9 2 pins connector
Input, Ambient Temperature or Module Temperature 3S-AT-PT1000-CON or 3S-MT-PT1000-CON, Ambient or module temperature sensor, PT1000, with Binder 712 M9 3 pins connector
Integrated Module Temp. Integrated module temperature sensor, PT1000  
Calibration All sensors are calibrated in artificial sunlight against a reference cell calibrated at the Physikalisch-Technische Bundesanstalt (PTB, National Metrology Institute of Germany).
Modbus Specification
Baud Rate 1200, 2400, 9600, 19200, 38400
Parity No, even, odd
Stop Bit 1, 2 (only at no parity)
Factory Default 9600 Baud, 8N1, address: 1



3S-WS-PLS-CON Wind speed sensor, reed contact, pulse with Binder 712 M9 2 pins connector
3S-AT-PT1000-CON Ambient temperature sensor, PT1000, with Binder 712 M9 3 pins connector
3S-MT-PT1000-CON Module temperature sensor, PT1000, with Binder 712 M9 3 pins connector
3S-MTG-01 Mounting bracket for Solar Radiation sensor 3S-SR-2T-WS-MB
3S-PS-12VDC Power supply, 220VAC, 50/60Hz, 12VDC, 300mA
3S-Shield-A Solar Radiation Shield for Ambient Temperature Sensor PT100, PT1000, DS18B20 etc.