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RC18 PV Reference Cell

Make:  Atonometrics       Model: RC18.
✅ Specifically designed for low-cost, high-accuracy solar irradiance measurements for outdoor monitoring of PV systems
✅ Measurand: Solar Irradiance
✅ Sensor Type: Silicon cell
✅ Signal Output: Digital and Analog Outputs
✅ Supplies With: 10 m Cable, Factory test/ Calibration Certificates.

Designed for PV System Monitoring

Specifically designed for low-cost, high-accuracy solar irradiance measurements for outdoor monitoring of PV systems

Digital and Analog Outputs
Both digital and analog outputs in a single, flexible product
Digital communication uses Modbus over RS485.
Two analog outputs, user-configurable to 0-1.5V, 0-10V, or 4-20mA
Analog output options include irradiance, shortcircuit current, and temperature.

No Need to Track Calibration Data
You never have to track calibration data or reprogram data loggers or SCADA systems when you install or change out the reference cell
Measurements are performed by a precision micro-controller circuit
Both digital and analog outputs are internally calibrated

Cell Design
Crystalline silicon PV cell
Short-circuit current measured with precision shunt resistor.
Cell temperature measured with RTD
Automatic temperature compensation as well as optional temperature output.

Robust Mechanical Construction
IP67-rated cast aluminum enclosure provides for protection from the elements and solid mounting Optional Spectral Matching Filter.
Standard window is solar low-iron glass
Optional CdTe-matching window material Connectorized for Easy Installation
M12 circular connector allows for easy installation, user-selectable cable lengths, and simple change out for recalibration.






Main Data


Measurement range

0 to 1500 W/m²


0.1 W/m²

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


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

Current consumption

typ. 8-15 mA



Analog output options

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

Analog output signals

Irradiance, Cell Temperature, Short-Circuit Current

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



4.53 x 2.56 x 1.18 in. / 115.1 x 65.0 x 30.0 mm


0.6 lb / 0.3 kg


4 mounting holes, dia. 0.217 in. / 5.50 mm




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

Measurement Specifications


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