The Model TSR-1 Thermopile Shadowband
Radiometer is a scientific field instrument that
simultaneously measures total, direct-normal,
and diffuse irradiance across the entire solar
spectrum from 300 nm to 2800 nm. The
thermopile rotating shadowband instrument
represents a major breakthrough in solarradiation
instrumentation, combining YES
rotating shadowband radiometer technology with
a true thermopile pyranometer to provide all
components of solar irradiance with one
instrument. With its advanced design, accuracy,
high reliability, and automated remote operation,
the TSR is the ideal solution for applications
such as solar resource assessment.
The TSR is based on the field-proven YES
multifilter rotating shadowband (MFR)
technology, which was initially developed by
scientists at the US Department of Energy’s
Pacific Northwest Laboratory for renewable
energy research, and licensed to YES, Inc.
Scientists and engineers at YES have made
significant advances in the instrument
technology to produce rugged and highly
accurate instruments for atmospheric radiation
measurements. These systems have been
operating many years in the USDA’s UVB
monitoring network
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The TSR offers the following key features:
- Thermopile pyranometer detector
- Angle-corrected direct-normal data
- Thermally stabilized detector
- Smart rotating shadowband
- Multichannel data acquisition and control
- (DAC) system for PV/thermal monitoring
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| The TSR’s thermopile detector is sensitive to
solar radiation across the full spectral range of
the sun, from 300 to 2800 nm, while silicon
photodiode-based detectors are sensitive from
only 400 nm to 1100 nm. This means that a
thermopile's sensitivity captures a range about
four times wider than a silicon detector, and
therefore provides a much more accurate
measurement of available solar resources. Because the solar spectrum varies greatly
throughout the day, so-called spectral “correction
algorithms” cannot accurately compensate for the
quite limited spectral range of a photodiode.
In addition to the thermopile’s broadband response,
another advantage of the design is that using a
single detector to measure all three solar radiation
components eliminates calibration errors introduced
into the measurement by the use of multiple
instruments, which require separate calibrations and
have higher operating costs. |
| An ideal Lambertian surface has a perfect cosine
response: the light received is directly proportional
to the cosine of the angle of incidence. Because
no surface has a perfect Lambertian response, the
angular error of the surface must be measured
and then corrected in order to achieve 1%
measurement accuracy. Each TSR is individually
characterized in an optical facility to measure its
angular (cosine) response. The data processing
software then applies these cosine coefficients to
the collected raw data to angle correct the directnormal
irradiance (DNI), to compensate for unique
imperfections in the detector. A generic angular
correction would provide inaccurate DNI results. |
| All detectors experience shifts in sensitivity with
changes in ambient temperature. To eliminate
temperature dependence, the TSR uses a
heater and precision thermal control circuit to
maintain the thermopile detector at a stable
constant temperature, which is slightly above the
maximum anticipated ambient air temperature.
The heater also helps to dry any dew and
precipitation from the radiometer and keep water
vapor out of the radiometer head, which helps
maintain calibration stability. A humidity indicator
on the side of the radiometer lets you know at a
glance if the O-ring seals have been
compromised. |
When you install the TSR, you align and level
the instrument and then initialize the system
based on your site location. The system uses
GMT time, site location parameters, and a
precision solar ephemeris calculation to ensure
the shadowband is aligned when making its
shaded measurement. This provides the diffusehorizontal
irradiance. To compensate for the
excess sky blocked during this shaded
measurement, the system actually makes three
shaded measurements when blocking the sun:
one completely blocking the diffuser and then
two to either side of the diffuser. The algorithms
used by the TSR to perform a predictive,
calculated block of the sun result in data that are
significantly more accurate than data from
systems that simply sweep the band and
estimate the location of the sun. Such estimating
(non-predictive block) rotating-shadowband
sweep approaches are prone to measurement
error due to the high variability in the diffuse
component under partly cloudy conditions.
The smart rotating shadowband of the TSR
system enables you to measure all three solar
irradiance components with one instrument.
Without the TSR, you need a normal incidence
pyrheliometer (NIP) mounted on a 2-D
altitude/azimuth sun tracker and two ventilated
thermopile pyranometers mounted on the sun
tracker with a shading disk. The NIP provides
the direct-normal irradiance while the shaded
pyranometer provides the diffuse irradiance; the
other pyranometer provides the total irradiance.
In contrast, a TSR contains just one moving part,
the shadowband, and a single detector to
maintain and calibrate, thus achieving the
accuracy of the NIP/pyranometer/tracker
configuration at a fraction of the cost. While
sweeping-band systems employing photodiode
detectors provide the advantages of a single
detector approach, they lack the broadband
performance and accuracy of the TSR. |
In addition to controlling the shadowband, the
embedded automatic control and data acquisition
system can monitor up to 30 other analog signals
for inputs such as PV or thermocouples, and/or a
Model PTU-2000 pressure, temperature, and
relative humidity met sensor. Up to six tower
mounted anemometers can be configured at sites
where wind resource assessment is desired.
The automated control system also enables
remote operation via standard RS-232 serial data
communications at unattended sites. It can be run
from AC line with standby battery power, or via PV. |
| ISO Classification |
ISO Classification |
| Spectral Response |
300 nm to 2800 nm
MFR-7 includes thermopile
channel and six additional
channels: 415, 500, 615, 673,
870, and 940, each 10 nm
FWHM for optical depth, column
aerosol, and water vapor |
| Cosine Response |
Better than 1% over 0-80° zenith
angle for angle corrected DNI
data; better than 5% for raw data |
| Response Time |
< 1 second |
| Effective Field of View |
5 degrees |
| Sensitivity Range |
0-1500 W/m2 |
| Operating Range |
-50°C to +50°C (+80°C storage) |
| Power Requirement |
110/250 Vac, 50/60 Hz 50 Watts
(max) or 12 Vdc 1A(typ),3A(max) |
| Sampling Rate |
Up to 4 samples/minute |
| Communication |
RS-232 port; 802.3 Ethernet
option, GSM cell modem option,
or user-supplied telco modem |
| System Memory |
1 week standard, up to 6 months
with memory expansion option |
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