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Dual-RC18 Soiling & Irradiance Measurement Kit

Make: Atonometrics                                      Model: Dual RC18.
Multipurpose dual RC18 PV reference cell kit – a simple and compact solution for measuring both soiling and irradiance.
✅ Measurand: Soiling and irradiance
✅ Sensor Type: Silicon cell
✅ Signal Output: Digital (Modbus RS485) and Analog (0-1.5 V, 0-10 V, 4-20 mA)
✅ Supplied With:  10 m Standard Cable, Factory test/ Calibration Certificates.

Dual-RC18 Soiling & Irradiance Measurement Kit:

The Dual-RC18 Soiling & Irradiance Measurement Kit is a device used to measure both the amount of sunlight that reaches a solar panel (irradiance) and the amount of dirt or other material that has accumulated on the surface of the panel (soiling). The kit includes a sensor that measures the amount of light that passes through a small portion of the panel, which can then be used to calculate the amount of soiling on the entire panel. The kit also includes a pyranometer, which is a sensor used to measure the amount of sunlight (or irradiance) that reaches the panel. The data collected by the sensors can be used to optimize the performance of a solar power system by helping to identify when and where cleaning is needed, and by allowing for adjustments to be made to the system’s tracking and orientation to maximize the amount of sunlight that reaches the panels.

Multipurpose dual RC18 PV reference cell kit—a simple and compact solution for measuring both soiling and irradiance. Your on-site personnel manually wash the labeled “clean” cell on a regular schedule. Use the clean cell for accurate irradiance measurement and compare the dirty cell to the clean one to calculate the soiling ratio.

Soiling Ratio Calculation

  • Program your data logger to ratio the daily average dirty cell irradiance to the clean one
  • Sample datalogger code available

Reference Cells

  • Uses Atonometrics RC18 Series PV Reference Cells: crystalline silicon PV cells with an internal precision shunt resistor and RTD, temperature correction, temperature output, and digital control
  • Digital (Modbus RS485) and analog (0-1.5 V, 0-10 V, 4-20 mA) output options
  • See the RC18 datasheet and user manual.


  • The included cable hub box allows powering and communicating using a single cable when using the Modbus RS485 option. For analog options, use two cables, one for each reference cell.
  • Various cable length options are available.


  • IP67-rated cast aluminium enclosures
  • Aluminium mounting plate

Application and features of Dual-RC18 Soiling & Irradiance Measurement Kit:



✅ Solar PV Plant
✅ Solar Research
✅ Weather Monitoring
✅ Small, light, low-power, and easy to install.
✅ Easily adapt to fixed-tilt or tracker installations.
✅ Single connection cable for digital option.
✅ No on-site calibration needed and no calibration data to manage – internally calibrated to W/m2



Dual RC18.

Irradiance measurement range

0 to 1500 W/m²

Irradiance resolution

0.1 W/m²

Soiling ratio measurement range

0.00 – 1.00

Soiling ratio precision


Operating temperature

-35 to +80 °C

Input power

8-28 VDC (12-28 VDC for 0-10V analog output)

PV cell

Crystalline Si, 20 mm x 20 mm

PV cell windows

Low-iron solar glass

Calibration data

Internally calibrated; no calibration data to manage


Optional configuration kit allows PC-based setup

Communication protocol

Modbus over RS485, user-settable Modbus addresses

Baud rate

Up to 57.6k

Analog output options

0-1.5V, 0-10V, or 4-20mA

Analog output signals (each cell)

Choose 2: Irradiance, Cell temperature, Short-Circuit Current

Current consumption

0-1.5V or 0-10V mode: both cells together, typ. 16-30 mA, 4-20mA mode, both cells together: 30-110 mA

Output impedance

0-1.5V or 0-10V mode: 2 kohm

Internal voltage drop

4-20mA mode: Allow 3.5 V minimum


Powder-coated cast aluminum housing

Outdoor rating



Mounting plate: 7.00 in. x 8.50 in. / 177.8 mm x 215.9 mm


2.0 lb / 0.9 kg


Mounting holes dia. 0.406 in. / 10.3 mm, see diagram

Cable Type

Shielded, weather resistant, UV-rated, 24 awg / 0.2 mm²

Cable length options

4 m, 10 m, 25 m, 50 m, 100 m, custom


M12 circular connector, IP67

Pinout (each cell)

Power, Ground (3x), Analog 1 & 2, RS485 A & B, Shield

Single cable option

Included cable hub box for digital options, use a single cable for both cells

Response time

0.15 s

Electronics non-linearity

± 0.03% of range


± 0.02% of range

Temperature drift, -35 °C to 80 °C

± 0.4% at 1000 W/m²

Cell temperature measurement

± 1 °C

Irradiance calibration

± 1.2%, calibrated to NREL-traceable reference standard

Overall irradiance uncertainty

± 2.0% @ 1500 W/m², ± 2.9% @ 100 W/m²


0.5% / year


IEC 61724-1 Class A, IEC 60904-2, IEC 60904-3, IEC 60904-10

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