Radiometers (PAR, rad)

RBR offers PAR radiometers (RBRcoda PAR) and narrow-band radiometers (RBRcoda rad) with a fixed channel width. Additionally, we support PAR sensors from LI-COR.

Overview

PAR sensors measure intensity of visible light at frequencies associated with photosynthesis. Narrow-band radiometers are available in a variety of wavebands.

The RBRconcerto3 and RBRmaestro3 can integrate the RBRquadrante four-channel radiometer, which supports multiple radiation measurements (combinations of PAR and rad sensors) within the same sensor package.

RBR radiometers

The RBRcoda PAR and RBRcoda rad integrated sensors are cosine sensors which can measure light within one hemisphere. Fig. 25 shows an RBRcoda PAR sensor connected to an RBRconcerto3.
The maximum depth rating of RBR radiometers is 2000m.

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Fig. 25.    An RBRconcerto3 C.T.D.PAR with a cosine PAR sensor (RBRcoda PAR)

Specifications

Optical radiometry

Parameter Value

Dynamic range

>5.5 decades (nominal)

Initial accuracy1

±2%

Linearity

±1%

Operating temperature range

-5°C to 35°C

Cosine response error (water)

±5% at 0-60°, ±10% at 61-82°

Azimuth error (water)

±1.5% at 45°

Out-of-band rejection2

>25dB (typical), OD 2.5

1 RBR calibrates radiometers with NIST traceable references.
2 Out-of-band rejection is wavelength-dependent for narrow-band radiometers.

PAR

Parameter Value

Wavelength range

400nm to 700nm

Full scale range

0 to 5000µmol/m²/s (minimum)

Resolution

±0.010µmol/m²/s

Narrow-band channels

Parameter Value

Centre wavelengths (CWL)1

380 / 413 / 445 / 475 / 488 / 508 / 532 / 560nm

Full width at half-maximum (FWHM)

10nm (25nm for CWL 475nm)

Full scale range

0 to 400µW/cm²/nm (minimum)

Resolution2

±0.001µW/cm²/nm

1 Other CWL options within the 300-1100nm range are available upon request. Contact RBR for more information.

2 Resolution is wavelength-dependent for narrow-band radiometers.

Dark offset is internally temperature-compensated.

LI-COR

PAR sensors options from LI-COR (Fig. 26) include cosine (one hemisphere, depth rating 560m) or spherical (omnidirectional, depth rating 350m) PAR sensors.

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Fig. 26.    An RBRconcerto3 C.T.D.DO.PAR with a spherical LI-COR PAR sensor.

Specifications (LI-COR)

Parameter Value

Wavelength range

400 to 700nm

Calibrated range

0 to 10000µmol/m2/s

Initial accuracy

±2%

Calibration equation

PAR

\[\text{PPF}_c=C_0+C_1*C_2*(V+X_0+X_1*(T-X_3)+X_2*(T-X_3)^2)\]

Irradiance

\[Irr_c=C_0+C_1*C_2*(V+X_0+X_1*(T-X_3)+X_2*(T-X_3)^2)\]