Delta-T Devices - Model SPN1 - Sunshine Pyranometer for Solar Radiation Measurement System

• Global (Total) and Diffuse irradiance in W.m^-2
• WMO sunshine threshold: 120 W.m^-2 direct beam
• DNI (Direct Normal Irradiance) calculations
• Sunshine status
• No moving parts, shade rings or motorised tracking

The SPN1 Pyranometer is exceptionally easy to use; it needs no routine adjustment or polar alignment and works at any latitude.

An internal heater keeps the pyranometer dome clear of dew, ice and snow down to -20°C (in still air conditions), ensuring reliable readings in difficult climatic conditions. The pyranometer design is protected by patents EP 1012633 and US 6417500.

SPN1 Pyranometer Resource Centre

The Resource Centre contains a wide range of application and technical information for the SPN1 Pyranometer  – covering DNI calculation, tilt correction, performance validation, and much more. Visit the SPN1 Resource Centre.

Direct and Diffuse Radiation

The SPN1 Pyranometer uses an array of seven miniature thermopile sensors and a computer-generated shading pattern to measure the direct and diffuse components of incident solar radiation. It computes direct radiation by subtracting the diffuse from the global (total) radiation.

Sunshine Duration

The WMO threshold for bright sunshine is 120 W.m^-2 in a plane perpendicular to the direct solar beam. The Pyranometer uses an algorithm based on the ratio of direct to diffuse radiation, combined with their absolute values, to estimate sunshine duration to within a few percent of the WMO standard.

The SPN1 Pyranometer does not need to be adjusted or repositioned to track the sun – a distinct advantage over devices with shadow rings. There are no complex electro-mechanical assemblies and no burnt paper tracks to interpret.

Outputs and logging

The SPN1 Pyranometer provides 2 analogue voltage outputs for global and diffuse radiation, and a digital output for sunshine duration, which can be connected to data loggers, such as the Delta-T Devices GP2 and the compact GP1.

Readings can also be obtained directly from the RS232 port and viewed/logged using the SunData software supplied.

The GP1 Data Logger from Delta-T Devices is a powerful general purpose data logger that provides a low cost logging solution for the SPN1 Pyranometer.

The SPN1 Pyranometer is ideally suited to multiple solar radiation measurement application areas, including PV (photovoltaic) efficiency monitoring, air pollution studies, cloud cover research, ET and heat flux studies, canopy analysis, and building energy management systems.

Evaluation of the SPN1 Pyranometer for measuring Total Optical Depth

Over the last 2 years Prof Victor Estelle’s Solar Radiation Research group at the University of Valencia has been running an SPN1 Pyranometer alongside Cimel and Prede sun photometers to see how it compares with these higher precision but more complex instruments.  Preliminary findings indicate a relatively good correspondence – scientific posters were presented at Skynet Rome 2016 and EGU Vienna 2016.

Direct-Normal Irradiance (DNI) is the amount of solar radiation arriving in unit time at the Earth’s surface on a unit area perpendicular to the direction to the Sun. It is a common practice to compare solar panel efficiency to DNI, particularly in field trials. Output from an SPN1 Pyranometer allows calculation of DNI in sun tracking, horizontal and tilted installations.

• Overall accuracy: Total (Global) and Diffuse radiation:
• ±5% Daily integrals
• ±5% ±10 W.m-2 Hourly averages
• ±8% ±10 W.m-2 Individual readings
• Resolution: 0.6 W.m-2 =0.6 mV
• Range: 0 to >2000 W.m-2
• Analogue output sensitivity: 1 mV=1 W.m-2
• Analogue output range: 0 – 2500 mV
• Sunshine status threshold: 120 W.m-2 in the direct beam
• Accuracy: Sunshine status: ±10% sun hours with respect to the threshold
• Accuracy: Cosine correction: ±2% of incoming radiation over 0-90° Zenith angle
• Accuracy: Azimuth angle: ±5% over 360° rotation
• Temperature coefficient: 0.02% per °C (typical)
• Temperature range: -40 to + 70°C
• Stability: Recalibration recommended every 2 years
• Response time: 100 ms (typical)
• Spectral response: 400 – 2700 nm
• Spectral sensitivity variation: 10% (typical)
• Non-linearity: < 1%
• Tilt response: Negligible
• Zero offsets:
• < 3 W.m-2 for a change of 5°C/hr in ambient temperature
• < 3 W.m-2 dark reading
• Latitude capability: -90° to + 90°
• Environmental sealing: IP67
• Sunshine status output:
• No sun=open circuit
• Sun=short circuit to ground
• Power requirement: 2 mA (awake ), <30 µA (asleep)
• 5 V – 15 V DC
• Heater power: 12 V – 15 VDC, up to 1.5 A
• RS232 connector: 5-pin M12
• Signal output & power-in connector: 8 pin M12
• Mounting options: 3 x M5 tapped holes in base at 108 mm dia, 120° spacing
• Size & Weight: 126 mm dia. x 94 mm high, 786g