Soiling Measurement System

The effect of dust, dirt, pollen, and other contaminant accumulation on PV modules, commonly referred to as soiling, is an important environmental factor that causes reduced PV power plant energy generation. Average annual energy losses due to soiling are typically in the range 1-6% but strongly depend on conditions at the site, with higher annual, short term, or monthly losses found in some cases. Therefore, accurate monitoring of soiling losses has become increasingly important, especially for utility-scale PV power plants, which might be subject to performance guarantees that mandate a limit on loss generation due to soiling.

The SMS systems use a simple and reliable method for measuring soiling losses. It uses the side-by-side comparison of the measured output of two co-planar, normalized PV reference modules, the first of which is kept clean as a control and the second of which naturally accumulates soiling at the same rate as the power-producing modules of the plant. The control module is kept clean through manual washing. The comparison is made on the basis of the measured currents, which serve as a proxy for the effective irradiance received by the soiled versus the clean module, and also on the basis of the measured maximum powers, which represent actual power production of soiled versus clean modules. In both cases, the measurements are temperature-corrected and normalized. The soiling ratio SR is the instantaneously measured ratio of dirty-to-clean (test- to-control) module outputs at any given point in time.

SR measurements can be performed with uncertainties on the order of ±4% or better on an absolute basis, depending on calibration conditions, operating temperatures, angular alignments, and other factors.


  • IP Protection : IP-65
  • Weight: Approx. 2kgs
  • Warranty : 2 years against manufacturing defect
  • Recommended Recalibration: 1 year
  • Applications: Indigenous Soil Monitoring System specially designed for monitoring Soiling Percentage for Solar PV plant
  • Certifications: NABL Accredited lab – at an additional price on request


  • Soil Measurement System (0-5Amp): STPL-SMS-5A
  • Soil Measurement System (0-10Amp): STPL-SMS-10A
  • Soil Measurement System (0-15Amp): STPL-SMS-15A
  • Soil Measurement System (0-20Amp): STPL-SMS-20A
  • Soil Measurement System along with 10Watts Solar Panel: STPL-SMS-2SP


  1. Two Separate Solar Panels should be provided and installed by the customer.
  2. One Solar Panel should be manually cleaned
  • 32GB inbuilt data storage
  • MODBUS TCP output to communicate with SCADA
  • Inbuilt FTP push for uploading data on server
  • Inbuilt Wi-Fi communication for uploading data on cloud
  • Simultaneously saves data in SD card in multiple .CSV files at user defined time Interval.
  • Simple and easy configuration using PC based utility.
  • Does not require any kind of on-site programming.
  • Operational in extreme environment with standard operating range of 0oC to +60oC
  • Highly accurate and precise soil monitoring system specifically designed for Solar Power plants
  • Simple and user-friendly to install
  • Time synchronization with SCADA
  • No. of Channels : 4 Nos (2 Nos for Solar Panels and 2 Nos for Module Temperature Sensor)
  • Module Temperature Measurements : 
    • Range : -40o to 150oC
    • Accuracy : ± 0.2oC
    • Resolution : 0.01oC
  • Short Circuit Current Range : 0-5Amp, 0-10Amp, 0-15Amp and 0-20Amp
  • Voltage Measurement Range : 0-80V
  • Shunt Accuracy : ± 0.5%
  • Resolution : 400µA/1mV
  • Response Time : 100ms
  • Solar Module Range : Upto 330Watts
  • Processor : Broadcom BCM 2387 chipset 1.2 GHz Quad-core 64-bit ARM Processor
  • Protocols Supported : MODBUS, Ethernet, FTP, and HTTP
  • Storage : Internal Flash Memory (RAM): 1GB External Memory: 32GB expandable upto 256GB
  • Data Logging Time Interval : 1min to 24 hours in multiple time stamp
  • RTC : Inbuilt with battery back-up Accuracy: ± 2 minutes per year
  • Time Synchronization : Server PC, SCADA Server and Internet Server
  • Communication : 
    • Wired: MODBUS TCP/485
    • Wireless: Wi-Fi
  • Peripheral Ports : 4 USB Ports
  • System Power Requirement : 
    • Voltage: 9 to 16V DC
    • Current: <500mA
  • Power Consumption : <10Watts
  • Environmental Conditions : 
    • Operating Conditions: 0o C to 60o C non condensing Environment
    • Storage Conditions: 0o C to 80o C non condensing environment
  • Battery Back-up : Optional 12AH battery for back-up in case of power failure
  • Physical Dimensions : 400 x 300 x 180 mm3

Soiling Measurement System