SEVEN soil monitoring system calculates the soiling ratio of the PV system by comparing the irradiation values received from two irradiance sensors, which are the clean sensor and the dirty sensor. The cleaning of the irradiance sensor is done automatically with pure water.

According to IEC 61724-1 standard, the soiling ratio should be calculated once a day. The measurement has to be made within ±2 hours of local noon time. The user decides the cleaning of the module by checking the soiling ratio to prevent production loss and increase the efficiency of the PV system.

Equipment Specifications

Irradiance Sensor

Irradiance Sensors:
A solar cell in a UV-protected aluminium housing with connectors and a ventilation plug measures the irradiance value. One of the irradiance sensors is left in the same conditions as the PV panels (dirty sensor) and the other is cleaned once a day (clean sensor). The number of cleaning times can be increased depending on the site conditions, to measure the soiling ratio.

Electronic Box & HMI Display

Electronic Box & PLC Display:

It includes a, PLC – HMI Display for monitoring and recording the Soiling Ratio as per IEC61724-1. The displayed value is the daily average soiling ratio. This device must be mounted in a way that it won’t be affected by precipitation and sun.

Mounting Plate:

Stainless steel plates painted in black. See page 6 for technical drawing. These plates should be mounted in parallel and at the same angle as the solar panels.

Spray nozzle for injecting water on the sensor surface to clean it.

Water Tank:
The cleaning tank has a capacity of 40 liters and is filled with pure water. A full tank provides 1 year of cleaning sprinkles. The tank should be filled once a year. It will be sufficient if the pump runs once a day.


General Information
Clean Reference Cell Monocrystalline silicon (52 x 52 mm)
Soiled Reference Cell Monocrystalline silicon (52 x 52 mm)
Operating Temperature 40°C / +85°C
Soiling Ratio %0 – %100
Resolution %1
Uncertainty ≤%1
Followed Standard IEC61724-1 (Annex C)
Water Consumption 40 lt./year
Antifreeze Ratio %80 Pur Water + %20 Antifreeze
Max. Water Line Length 2,5 Meters
Communication Protocol Communication via Modbus RTU protocol and 2-wire RS485 Bus
Water Tank Capacity 40 Liter
Soiling Sensor Wiring Information
Green RS485 A / Data (+)
Yellow RS485 B / Data (-)
Electrical Box Wiring Information
RS485 2 pin connector
220 V AC 3 pin connector
Water Pump 4 pin connector
Irradiance Sensor 6 pin connector

The system consumes approx. 100 mililiter water for single run for 2,5 meters water hose length. The water tank is able to serve 400 days (13.3 months). Consult SEVEN if the water hose longer than 2,5 meters.