PMO6-CC
An absolute cavity radiometer system for measuring the direct solar irradiance.
General Specifications
The PMO6-CC is a self-contained system designed to measure the direct
solar irradiance. It consists of a radiometer head (absolute cavity pyrheliometer)
and a control unit.
The heart of the radiometer head is a blackened cavity in which the solar radiation
is absorbed. It was developed at PMOD/WRC and is of the same type as the earlier PMO6
instrument series.
The PMO6-CC control unit (“CC” stands for “Computer Controlled”)
is a development of the Davos Observatory aimed at providing the largest possible
freedom and convenience to operate the system either manually or remotely controlled
from an external computer. It contains an internal PC and voltmeters to conduct
measurements and to communicate with the user using its display and touch-panel
or its RS232 port.
Principle of operation
Absolute radiometers are based on an electrically calibrated heat flux transducer
and a cavity as receiver. The cavity ensures high absorption over the spectral
range of interest. The principle of the measurement relies on the substitution
of the radiant power by electric power. During operation of the instrument, an
electronic circuit maintains a constant heat flux from the cavity heater by adjusting
the input power. The heat flux is measured differentially between two cavities
in order to compensate for the rate of change of the heat sink’s temperature.
Traceability to WRR
Each unit is compared to the World Standard Group to provide direct traceability
to the World Radiometric Reference.
Operation
The standard mode of operation of the radiometer consists of alternate measurements
with the shutter closed and open. The duration of each phase (closed and open)
may be chosen (default: 60 seconds). The number of cycles and the integration
time are also free parameters. The start time of the measurements can be set to
a predefined time. After every open/closed cycle, the irradiance is shown on the
display and sent out to the RS232 port.
After completion of a measurement series, all the irradiances of the series can
be read on the display or downloaded using the RS232 port.
Functionality check, configuration, …
Various dialog modes are provided to check the functionality of the H/W as shutter,
A/D, housekeeping, to set the date and time and to implement the instrument parameters
Contact address
Dr. Wolfgang Finsterle, e-mail:
w.finsterle(at)pmodwrc.ch
, phone: +41 81 417 51 53
Specifications
PMO6-CC Radiometer
| Dimension: |
80 x 80 x 230 mm |
| Mass: |
2.15 kg |
| Field of view (full angle): |
5° |
| Slope angle: |
1° |
| Range: |
up to 1400 W/m2 (Or custom design available) |
| Traceability to WRR: |
< 0.1% |
| Operating temperature range: |
-25 °C … +50 °C |
PMO6-CC Control Unit
| Dimension: |
280 x 270 x 85 mm |
| Mass: |
3 kg (approx.) |
| Power requirement |
8.5 W |
| Accuracy: |
Absolute measurement uncertainty is less then 50ppm of radiometer full-scale
range; |
| Outputs: |
Analog: ± 10 V
Digital: RS232, 9600Bd, 8 Bit, non Parity, 1 Stop |
| Operating temperature range: |
10 °C … +40 °C |
