• Measures global (total) and diffuse irradiance in W/m²
• WMO sunshine threshold: 120 W/m² direct beam
• No routine adjustment or polar alignment
• No moving parts, shade rings or motorised tracking
• Works at any latitude
• Unique ground glass dome
• Wideband thermopile sensors
• Near ideal spectral and cosine response
• Standard output sensitivity
• Matches or exceeds the ISO First Class standard and the
WMO Good Quality standard for a solar pyranometer in
all respects apart from the spectral response - which is
accurate to ±10% over 0.4 to 2.7 μm
Pyranometer Delta-T Sunshine SPN1
Description
The Sunshine Pyranometer is a patented, meteorological class instrument, with built-in heating, designed for long-
term outdoor exposure. It is an affordable alternative to shade-ring pyranometers, pyrheliometers and traditional sun-
shine recorders. The SPN1 is exceptionally easy to use; it needs no routine adjustment or polar alignment and works
at any latitude.
Unique Design
The Sunshine Pyranometer uses an array of seven, miniature thermopile sensors and a computer generate shading
pattern to measure the direct and diffuse components of incident solar radiation. The shading pattern and thermo-
piles are arranged so that at least one thermopile is always fully exposed to the solar beam, and at least one is fully
shaded from it, regardless of the position of the sun in the sky. All seven thermopiles receive an equal amount of diffuse
light. From the individual thermopile readings, a microprocessor calculates the global and diffuse horizontal irradiance
and from these values an estimate of sunshine state is made. The Sunshine Pyranometer is protected by patents EP
1012633 & US 6417500.
SPN1 Design Principles
The principles used in the Sunshine Pyranometer have been tried and tested in the Delta-T BF3 Sunshine Sensor. The
original design has been enhanced, using miniature thermopile sensors, a high quality ground glass dome and alu-
minium housing. The electronics have also been redesigned for higher accuracy and lower power consumption. The
SPN1 computes direct radiation by subtracting the diffuse from the global (total) radiation.
Outputs
The Sunshine 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. Readings can be obtained directly from the RS232 port.
Heating
An internal heating keeps the dome clear of dew, ice and snow down to -20°C (in still air conditions), ensuring reliable
readings in difcult climatic conditions.
page 1/5
Specications
Characteristic Description / Value
Spectral range 0 to > 2000 W/m²
Resolution 0.6 W/m² = 0.6mV
Analog output sensitivity 1mV = 1 W/m²
Analog output range 0 ... 2500 mV
Sunshine status threshold 120 W/m²
Sunshine status output No sun = open circuit
Sun = short circuit to ground
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
Quality Standard SPN1 matches or exceeds ISO First Class standard and WMO Good
Quality standard for solar pyranometers in all respects apart from
spectral response - which is accurate to ±10% over 0.4 to 2.7 μm
Overall Acuracy ± 5% daily integrals
Global (Total) ± 5% ± 10 W/m
2
hourly averages
Diffuse Radiation ± 8% ± 10 W/m² individual readings
Accuracy gures give 95% condence limits, i.e. 95% of individual
readings will be within stated limits under normal climactic condi-
tions.
Power requirements 2 mA (excluding heating power)
5 ... 15 VDC
Heating power 12 ... 15 VDC, up to 1.5 A
Heating control Continuously variable up to 20 W output for external temperatures
below 0°C
Lowest snow & ice-free temperatures
(with heating in use)
-20°C at 0 m/s wind speed
-10°C at 2 m/s wind speed
Temp coefcient ± 0.02% per °C typical
(-20 ... +70°C)
Temperature range -40 ... +70°C
Recalibration / stability Factory calibration recommended every 2 years
Spectral response 400 ... 2700 nm
Spectral sensitivity variation 10% typical
Latitude capability -90 ... +90°C
Connection 8-pole plug (M12)
Cable 8-wire cable, length: 5 m
Environmental IP67 sealing
Mounting options 3 x M5 tapped holes in base; 108 mm pcd, 120° spacing
Size / weight 140 mm (diameter) x 100 mm (height), 940g
Manufacturer Delta-T Devices Ltd.
Pyranometer Delta-T Sunshine SPN1
page 2/5
Pyranometer Delta-T Sunshine SPN1
page 3/5
Sensor Connection to Ammonit Meteo-40 Data Logger
Function
Plug
Pin No.
Sensor Cable
Wire Colour
Meteo-40
Analog Voltage / Digital
Supply Sensor
Gobal irradiance 1 white
Ax A
Diffuse irradiance 2 brown Ax+1 A
Signal ground 3 green Ax b, Ax+1 b
Sun status 4 yellow Dx
Ground 5 grey GND
Supply 6 pink 4 ... 15 VDC
Heating 7 blue 12 VDC
Heating 8 red GND
Sensor Connection Diagram to Ammonit Meteo-40 Data Logger
SPN1 validation and testing - direct and diffuse
SPN1 Design Principles
The principles used in the Sunshine Pyranometer
have been tried and tested in the
Delta-T BF3
Sunshine
Sensor. The original design has be
en
enhanced, using miniature thermopile sensors, a
h
igh quality ground glass dome and aluminium
housing. The electronics have also been
redesigned for higher accuracy and lower pow
er
consumption.
The SPN1 computes direct radiation by subtract-
ing the diffuse from the global (total) radiation.
Comparison Results
Prototype versions of the Sunshine Pyranometer
have been tested over several months against
Kipp & Zonen CM6B sensors, one shaded by a
solar tracking disk. Sample results are shown on
this page.
y = 0.9945x
R
2
0.9967 =
y = 1.0006x
R
2
0.9994 =
-4
-2
0
2
4
6
8
10
12
14
16
0 5 10 15 20
CM6B Global & Diffuse MJ.m-2
SPN1 Diffuse MJ.m-2
0
2
4
6
8
10
12
14
16
18
20
SPN1 Global MJ.m-2
SPN1 Daily Integrals Global & diffuse
compared with Kipp CM6B & tracking disk
Sept – Dec 2004, daily integrals. (Note use of
offset axes to make traces visible).
0
20
40
60
80
100
120
0 500 1000 1500 2000 2500 3000
W avelength nm
relat ive contri bution
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
SPN1 Spectral Response Graph shows
the spectral response of the SPN1 (thermopile,
diffusers and dome combined) and the solar
spectrum at ground level.
0
1
2
3
4
5
6
7
8
9
1
1
2
0 10 20 30 40 50 60 70 80 90
Zenith angle (degrees)
SPN1 Cosine Response Graph shows the
typical cosine response of the SPN1 compared
to the ideal cosine curve. The upper curve
shows the relative accuracy.
_____
ideal cosine
__
z
__
absolute limit
__
z
__
relative error
……
2% limits
0
100
200
300
400
500
600
700
800
900
1000
0
5
:0
0
06:
0
0
0
7
:0
0
0
8
:0
0
0
9
:0
0
10:
0
0
1
1
:0
0
1
2
:0
0
1
3
:0
0
14:
0
0
1
5
:0
0
16:00
1
7
:0
0
1
8:
0
0
1
9
:0
0
27 April 2006
W. m- 2
SPN1 Direct and Diffuse Outputs (solid
traces) compared with a pair of Kipp CM6B
pyranometers with solar tracking and shading
disk
(
broken traces
)
.
y = 1.0032x - 0.6309
R
2
0.9942 =
y = 1.006x - 1.2429
R
2
0.9986 =
-200
-100
0
100
200
300
400
500
600
700
800
0 100 200 300 400 500 600 700 800 900 1000
CM6B Global & Diffuse W.m-2
SPN1 Diffuse W.m-2
0
100
200
300
400
500
600
700
800
900
1000
SPN1 Global W.m-2
SPN1 Hourly Averages Global & diffuse
compared with Kipp CM6B & tracking disk
Sept – Dec 2004, hourly averages. (Note use
of offset axes to make traces visible
)
.
___
Solar
___
SPN1
Applications
Meteorology
• Solar radiation
• Climate change
• Air pollution
• Sunshine duration
• Cloud cover research
Agronomy & plant science
• ET and heat ux studies
• Canopy analysis and modelling
Architecture and building design
• Building Management Systems
• PV efciency and energy balance
Pyranometer Delta-T Sunshine SPN1
page 4/5
Pyranometer Delta-T Sunshine SPN1
Sunshine Duration
The WMO threshold for bright sunshine is 120 W/m² in a
plane perpendicular to the direct solar beam. This cannot
be measured directly using horizontal cosine-corrected
sensors, and so the SPN1 uses an algorithm based on the
ratio of direct to diffuse radiation, combined with their ab-
solute values, to estimate this to within a few percent of the
WMO standard.
The graph compares the performance of the BF3* and a
Campbell-Stokes sunshine recorder over a trial period
of several months. Against the WMO standard, the BF3’s
typical daily error was 20 minutes. In contrast, the Camp-
bell-Stokes was less precise, giving a typical daily error of
nearly an hour.
* The SPN1 is an advanced version of the current BF3 Sunshine Sensor. Both
instruments use the same sunshine hours algorithm.
Comparison of SPN 1 with WMO and ISO pyranometer standards
ISO:
Secondary
Standard
ISO:
First Class
WMO:
High Quality
WMO:
Good Quality
SPN1 Notes
Response time: ISO & WMO < 15 s < 30 s 0.1 s To 95% of nal value (Actual
response time is 100ms)
Zero off-set response: ISO & WMO 7 W/m² 15 W/m² < 3 W/m² To 200 W/m² net radiant loss to sky
(ventilation)
Zero off-set response: ISO & WMO ±2 W/m² ±4 W/m² < 3 W/m² For 5°C/hr change in ambient
temperature
Resolution: WMO ±1 W/m² ±5 W/m² 0.6 W/m² Smallest detectable change
Non-stability: ISO & WMO ±0.8% ±1.5% < 1.0% Change in sensitivity per year
Non-linearity: ISO & WMO ±0.5% ±1% < 1% Deviation from sensitivity at 500
W/m² over 100 to 1000 W/m² range
Directional response: ISO & WMO ±10 W/m² ±20 W/m² ±20 W/m² Error due to assuming that the
normal incidence response at 1000
W/m² is valid for all directions
Spectral selectivity: ISO (0.35...1.5
μm)
WMO (0.30...3.0 μm)
±3%
±2%
±5%
±5%
± 10%
(0.4...2.7 μm)
Deviation to the mathematical
product of spectral absorptance
and transmittance from the mean
Temperature response: ISO & WMO ±2% ±4% ± 1% Error due to 50°C ambient tem-
perature change
Tilt response: ISO & WMO ±0.5% ±2% See note* Deviation from the horizontal
responsitivity due to tilt from hori-
zontal to vertical at 1000 W/m²
Achievable uncertainty:
WMO hourly total
WMO daily total
3%
2%
8%
5%
5% ±10 W/m²
5%
95% condence level
page 5/5
