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Enabling better global research outcomes in soil, plant & environmental monitoring.

EQ08-S Secondary Pyranometer


The Middleton EQ08-S is a precision pyranometer for the measurement of global solar irradiance on a plane surface. It exceeds the international accepted specifications for a high quality pyranometer. The EQ08-S incorporates a second generation precision thermoelectric sensor that has exceptionally low directional error without compromise to signal strength or response time. The EQ08-SE version has an in-built amplifier to give a millivolt output for easy signal measurement.


  • Marine grade aluminium, hard anodised for corrosion resistance.
  • Bubble level on top of instrument for easy viewing.
  • Fully sealed construction for low-maintenance.
  • Strong output signal.

Solar radiation at Earth’s surface is typically defined as total radiation across a wavelength range of 280 to 4000 nm (shortwave radiation). Total solar radiation, direct beam and diffuse, incident on a horizontal surface is defined as global shortwave radiation, or shortwave irradiance (incident radiant flux), and is expressed in Watts per square meter.

The EQ08-S Pyranometer is for measuring total global solar irradiance on a plane surface. It exceeds the requirement s for both an ISO9060 Secondary Standard Pyranometer and a WMO High Quality Pyranometer. The EQ08-SE version has an in-built signal amplifier.


The EQ08-S series is machined from marine-grade aluminium and is hard anodised to provide a durable, corrosion-resistant finish. It has a blackened thermal sensor shielded by two glass domes. The sensor incorporates a precision thermoelectric element that generates a passive microvolt output proportional to the intensity of the incident radiation. It is equally receptive to all radiation wavelengths and therefore its response to solar radiation is non-selective spectrally. The sensor has been designed to give exceptionally low directional error without compromise to signal strength or response time.

Performance Specification ISO9060 Secondary Standard EQ08-S, SE (typical)
Response time (to 95%) < 15s 14s
Zero off-set: a) 200 W.m-2 + 7 W.m-2 < + 3 W.m-2
b) 5K.h-1 ± 2 W.m-2 < ± 1 W.m-2
Non-stability (per year) ± 0.8% < -0.5%
Non-linearity (100-1000W.m-2) ± 0.5% < ± 0.5%
Directional response (w.r.t. 1000 W.m-2) ± 10 W.m-2 (30-80°) ± 5 W.m-2 (30-80°)
Spectral selectivity (0.35 to 1.5µm) ± 3% < ± 2%
Temperature response (for 50K interval) ± 2% < ± 0.5%
Tilt response (0-90°) ± 0.5% < ± 0.2%

Exceeds every ISO 9060 parameter for a Secondary Standard Pyranometer. Temperature compensated thermopile sensor has black receiver & flat spectral response. The EQ08-S has a passive microvolt output, and the EQ08-SE version has an in-built signal amplifier to give a millivolt output for easy measurement. Metal shade disc is thermally insulated from the body. Stainless steel feet thermally insulate instrument from mounting structure. Dual glass domes protect the sensor from air temperature fluctuations. Supplied with simple mounting kit. User’s Guide and Calibration Certificate included.

Viewing Angle 2 pi steradians
Irradiance – 4000W/m2
Spectral Range 300 – 3000nm (nominal); 305 – 2850nm (50% points)
Sensitivity (Typical) Q08-S: 13-15μV/W.m-2 ; EQ08-SE: 1.0mV/W.m-2
Initial Calibration Uncertainty (k=2) < ± 1.5% (traceable to WRR)
Impedance EQ08-S: 40Ω ; EQ08-SE: 100Ω
Power Requirement (EQ08-SE only) 5.5-14.5 VDC; 6mA
Operating Temperature -35 to +60°C
Operating Humidity 0-100% RH
Bubble Level Resolution 0.1°
Level Adjustment one fixed foot, two adjustable feet
Desiccant orange silica gel (non-toxic)
IP Rating Sealed to IP66
Mounting Method Central M10 hole in base, plus pair M4 holes on 65mm P.C.D.
Output Lead 6m
Shipping size & weight; net weight 30 x 230 x 180mm, 2Kg; 0.8Kg