Pyranometer is a device that measures global or stray radiation. Pyranometer consists of black metal that is consisting 2-layered glass, located under the semisphere and includes copper-conglutinative thermal pairs. How junctions of the thermal pairs are located under the black metal surface. The cold junctions are located in a manner which they will not receive any radiation.
The main logic of the pyranometer is; the black surface reaches a higher temperature than the cold junction thanks to the absorption of the light with the generated electric power. The integral of the electricity movement power, which is between 10 mV and 20 mV is calculated for a certain period. And the result of this calculation is the global radiation measurement value.
The output of a single thermal pair is about 22 microVolts/C (Celsius). This is why more than one thermal pair can be attached to each other in serial to achieve a voltage value. Also, the serial connection of thermal pairs can increase the sensitivity.
Pyranometer is horizontally placed to measure the total radiation on any horizontal surface.
Another name of pyranometer on the market is solarimeter.
What Are Pyranometer Types?
1. Kipp and Zonen CM11 Pyranometer Type
Kipp-Zonen CM11 Pyranometer consists of 100 pairs of thermal sensors placed on a thick film tablet and located under a glass surface. Heating of pyranometer body is prevented with a white screen. CM11 Pyranometer is fed with a special level and rotated for the full level setting. The inner side of the dryer film box is protected against moisture.
Kipp and Zonen CM11 Pyranometer has 305-2800 nanometer range operation which runs with 4 to 6 microvolts/Watt/square meter. This pyranometer type can measure the radiation up to 4000 watts/square meter.
Kipp-Zonen has a display part called SOLRAD. There is the RS232 serial interface in order to connect the pyranometer to the computer. Thus both measured values and integral sums can be transmitted from the serial port to the computer and many analyzes can be performed with the collected data.
2. TSP-1 Pyranometer Type (Yankee Environmental Systems)
The TSP-1 pyranometer type is based on thin film platinum resistance instead of usual thermal pair technology. TSP-1 pyranometer has 300-3000 nm (nanometer) range operation which runs with 3 mV/W/square meter.
The YESDAS-2 system of Yankee environmental systems is a system which operates remotely and without a person in front of the system. This system is an information collection system that ensures the various solar radiation sensors to function with 32 analog and 6 digital inputs. YESDAS also includes software that enables the information analysis on platforms such as a computer, Unix, and Macintosh.
3. International Light Model IL1700
IL1700 is a research-purpose radiometer which has sensors, advanced processes and display unit. IL1700 is designed to measure the currents of light sensors. This solar pyranometer can measure photo-diodes currents up to 0,2×10 – 12 amperage. IL1700 automatically sets the range with decimal places during the merge of the released. This merging process is carried out in a range that can be divided into 40 groups of ten in a period which can last up to 18 years.
IL1700 can be controlled remotely with a computer system. 1 multiplexer and 8 detectors can be controlled, selected and information can be read with a computer.
IL1400A model is the portable, battery-powered and 32-character LCD display version of IL1700. Dynamically, IL1400A can automatically provide the range of 7 steps of 10 digits between 35 million and 1. The merging process can be carried out with 20 units of 10 digits and it can take up to 24 hours. IL1400A also provides analog record output, standard TTL output and optionally, RS232 to connect to the computer’s serial port.
4. Photovoltaic Pyranometer
Another pyranometer type is photovoltaic battery-powered one. When the output current of the photovoltaic battery operated with a current close to the short-circuits current, it is proportional to the multiplier solar radiation. This current is measured and displayed as solar radiation.
The Yellot Solarimeter and the HD9021 radiometer are the examples of photovoltaic pyranometers. This pyranometer has some advantages. The most important advantage is the fact that it is cheap, it does not being affected too much by the heat and does not need any external power supply.
The disadvantage of the photovoltaic pyranometers is the fact that they have cosine reaction failure and operates in a narrow-selective band. Photovoltaic solar cells are more sensitive to infrared wavelengths. Fails that occur as a result of spectral response is around +- 3% in normal daylight conditions.
It is important to measure solar radiation falling on a sloped surface for the calculating the amount of radiation falling into solar collectors. Pyranometer devices can be used in calculating solar radiation falling on sloped surfaces. The calibration of pyranometers varies depending on the angle of the device with the horizontal surface. This is why pyranometer manufacturers publish calibration tables for the measurement of radiation falling on sloped surfaces.