CNR 4 Net Radiometer Instruction Manual
IMPORTANT USER INFORMATION Reading this entire manual is recommended for full understanding of the use of this product. The exclamation mark within an equilateral triangle is intended to alert the user to the presence of important operating and maintenance instructions in the literature accompanying the instrument. Should you have any comments on this manual we will be pleased to receive them at: Kipp & Zonen B.V. Delftechpark 36 2628 XH Delft P.O.
DECLARATION OF CONFORMITY According to EC guideline 89/336/EEC 73/23/EEC We: Kipp & Zonen B.V.
CONTENTS IMPORTANT USER INFORMATION ................................................................................................................................... 1 DECLARATION OF CONFORMITY ..................................................................................................................................... 2 CONTENTS ..................................................................................................................................................................
1 GENERAL INFORMATION The CNR 4 is a 4 component net radiometer that measures the energy balance between incoming short-wave and long-wave Far Infrared (FIR) radiation versus surface-reflected short-wave and outgoing long-wave radiation. The CNR 4 net radiometer consists of a pyranometer pair, one facing upward, the other facing downward, and a pyrgeometer pair in a similar configuration. The pyranometer pair measures the short-wave radiation. And the pyrgeometer pair measures long-wave radiation.
1.1 Connecting the CNR 4 1.1.1 The difference between temperature and sensor connection CNR 4 has several output signals: two voltages for the pyranometers, two voltages for the pyrgeometers, and two temperature sensors as standard: a 4 wire Pt-100 connection and a 2 wire connection for the 10k thermistor. Depending on the used data logger one of the temperature sensors can be used.
CNR 4 NET RADIOMETER • SENSOR 8 WIRE CABLE • 8-ADRIGES KABEL • CÂBLE 8 FILS • CABLE DE 8 CONDUCTORES Wire Function Connect with 4 3 5 2 8 6 1 7 1 2 7 8 5 4 6 3 Kabel Fil Cable Funktion Fonction Función Red Rot • Rouge • Rojo + Blau • Bleu • Azul Blue - White Weiss • Blanc • Blanco + Black Schwarz • Noir • Negro - Grey Grau • Gris • Gris + Yellow Gelb • Jaune • Amarillo - Brown Braun • Brun • Marrón + Green - Grün • Vert • Verde Pyranometer Upper Oben • Supérieur • Superior Pyr
1.1.3 The radiometer Temperature connector (T) The temperature connector of the CNR 4 carries the signals for the PT-100 and Thermistor. The PT-100 and Thermistor have identical accuracy, the reason for selecting one or the other is mainly the data logger involved. The Pt-100 temperature sensor has 4 wires, two for the measuring current and two for measuring the voltage over the resistor (100 Ohm @ 0 °C) . In this way the measurement accuracy is minimally affected by the cable length.
1.1.4 The (optional) CNF 4 connector The optional ventilator CNF 4 for the CNR 1 has separate wires for heating and ventilation. In case the heater is used also the ventilator should be active. The other way around the ventilator can be used without heating. When the ventilation unit is mounted later on the CNR 4, the extra bottom plate mounts to the bottom of the CNR 4. The (S) and (T) cables run on both sides of the ventilator to the back of the CNF 4 housing.
1.1.6 Using the CNR 4 measuring Net Radiation In the CNR 4 all components are measured separately. This implies that you should connect all individual radiometers and one of the temperature sensors. The two pyranometers will measure the solar radiation, both incoming and reflected, the two pyrgeometers will measure the Far Infrared radiation. For proper analysis of the pyrgeometer measurement results, they must be temperature corrected using the temperature measurement.
Temperature [EC] Resistance [Ω] Temperature [EC] Resistance [Ω] Temperature [EC] Resistance [Ω] -30 -29 -28 -27 -26 -25 -24 -23 -22 -21 -20 -19 -18 -17 -16 -15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 88.22 88.62 89.01 89.40 89.80 90.19 90.59 90.98 91.37 91.77 92.16 92.55 92.95 93.34 93.73 94.12 94.52 94.91 95.30 95.69 96.09 96.48 96.87 97.26 97.65 98.04 98.44 98.83 99.22 99.61 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 100.00 100.39 100.78 101.17 101.
Temperature [EC] Resistance [Ω] Temperature [EC] Resistance [Ω] Temperature [EC] Resistance [Ω] -30 -29 -28 -27 -26 -25 -24 -23 -22 -21 -20 -19 -18 -17 -16 -15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 135200 127900 121100 114600 108600 102900 97490 92430 87660 83160 78910 74910 71130 67570 64200 61020 58010 55170 52480 49940 47540 45270 43110 41070 39140 37310 35570 33930 32370 30890 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 29490 28150 26890 25690 24550
1.1.6.4 Calculation of the albedo for solar radiation The albedo is the ratio of incoming and reflected Solar radiation. It is a figure somewhere between 0 and 1. Typical values are 0.9 for snow, and 0.3 for grassland. To determine albedo, the measured values of the two pyranometers can be used. The pyrgeometers are not involved, as they do not measure Solar radiation. Do not use measured values when solar elevation is lower than 10 degrees above the horizon.
1.1.6.6 Calculation of the Net (total) radiation The Net radiation, NR, can be calculated using all 4 sensor measurement results: NR = (E upper pyranometer) + (E upper pyrgeometer) - (E lower pyranometer) - (E lower pyrgeometer) (1.8) Where E is the irradiance that is calculated for the pyranometer according to equation 1.1, for the pyrgeometer according to equation 1.2. the terms with T cancel from this equation. 1.2 CNR 4 Performance under different conditions Below, table 1.
Typical graphs for the pyrgeometers Upper pyrgeometer, day with alterna3ng cloud fields pyrgeometer: U_emf / Sensi3vity [W/m²] Temp YSI 44031 [°C] Figure 1.2.2 partly clouded day for the upper pyrgeometer Upwelling signal (downward facing) pyrgeometer Pyrgeometer: U-‐emf / sensi3vity [W/m²] Figure 1.2.
It is assumed that when ambient temperature varies, the Net Far Infrared radiation remains roughly the same, independent of ambient temperature. The resulting measured values of the pyrgeometer's and pyranometer's are stated in columns 4 to 7. These are indicative figures only, they depend strongly on other circumstances; the pyrgeometer results, of course, change with the sensor temperature. This is indicated in column 8.
2 CNR 4 PROPERTIES The CNR 4 consists of two pyranometers, for measuring solar radiation, and of two pyrgeometers for measuring Far Infrared radiation. Two temperature sensors are available as standard, a Pt-100 and thermistor. The optional ventilation unit CNF 4 is described in chapter 2.5 2.1 Properties of the CNR 4 Net-Radiometer The properties of CNR 4 are mainly determined by the properties of the individual sensors.
2.1.1 Specifications of the CNR 4 General specifications Environmental 0 - 100% RH (Relative Humidity) Definition Intended for continuous outdoor use Bubble level sensitivity < 0.
2.2.1 Specifications of the pyranometer Pyranometers Specification Unit Value (All indicated values are absolute values) Spectral range nm 300 - 2800 (50% points) Definition Sensitivity Instrument sensitivity within a specific spectral range µV/ W/m² Definition Impedance Calibration factor Ω Definition Response time s % % % W/m² Definition Zero offset B W/m² < 15 (0 to -200 W/m² / IR net irradiance) < 3 (at 5 K/h temp.
Irradiance: W/m² Definition Non-stability Measurement range % Definition Spectral selectivity Definition <1 Maximum change of sensitivity per year, percentage of full scale % < 3% (350 – 1500 nm spectral interval) Deviation of the product of spectral absorption and spectral transmittance from the corresponding mean within the indicated spectral range Definition Uncertainty in daily total 0 to 2000 % < 5 (95 % confidence level) Achievable uncertainty International standards WMO ISO Good quality
2.2.2 Spectral properties of the pyranometer The spectral properties of the pyranometer are mainly determined by the properties of the absorber paint and the glass dome. These are depicted in figure 2.3 Figure 2.3 The spectral sensitivity of the pyranometer in combination with the spectrum of the sun, under a clear sky. 2.2.
Figure 2.4 The directional response, or cosine response, of the pyranometer: On the horizontal axis, the zenith angle is shown (0E zenith angle equals 90E angle of incidence). The vertical axis shows the deviation from the ideal cosine behaviour expressed in percents.
2.3 Properties of the pyrgeometer The pyrgeometer consists of a thermopile sensor and a silicon window integrated in the CNR 4 body. The thermopile is coated with a black absorbent coating. The paint absorbs the radiation and converts it to heat. The resulting heat flow is converted to a voltage by the thermopile. Most electrical specifications are determined by the thermopile and the resistor. Spectral specifications are determined by the absorber paint and the window.
Definition Sensitivity Instrument sensitivity within a specific spectral range µV/W/m² Definition Impedance Calibration factor 20 to 200, typically 50 Ω Definition Response time Typical resistance measured at the output < 18 (95% response) s Definition Non-linearity Sensor response time % < 1 (from -250 to +250 W/m2 irradiance) % Maximum deviation from the responsivity at -100 W/m2 due to any change of irradiance within the indicated range.
2.3.4 Spectral properties of the pyrgeometer The spectral properties of the pyrgeometer are mainly determined by the properties of the absorber paint and the silicon window. The silicon window is coated on the inside with an interference filter, which blocks the solar radiation. The spectral characteristics of the pyrgeometer are depicted in figure 2.5 Transmittance [%] FIR WINDOW TRANSMITTANCE 100 50 0 1 10 100 Wavelength [µm] Figure 2.
2.4 Properties of the CNF 4 (optional) ventilation unit The ventilator and heaters purpose is to prevent dew deposition on the pyrgeometer and pyrgeometer window, and thus increase measurement accuracy and reliability. Using the ventilator and heater will have negligible effect on the pyranometer reading. Generally these errors are small relative to the errors that would have been caused by water deposition. More information for the pyrgeometer on this can be found in chapter 2.3.2 2.4.
2.5 Properties of the Pt-100 and thermistor The Pt-100 is a common temperature sensor. Essentially it is a resistor that is temperature dependent. The Pt-100 complies with the specifications of DIN, class A. A table stating the resistance values can be found in chapter 1.1.6.3 Alternatively the thermistor, (nominal value is 10k Ohms at 25 degrees Celsius) can be used. A table stating the resistance values can be found in table 1.
3 3.1 CALIBRATION Calibration of the pyranometers The primary standard for pyranometers is the World Radiometric Reference. Reference pyranometers that are used at Kipp & Zonen are calibrated using the primary standard. The Kipp & Zonen pyranometer calibration is traceable to the World Radiometric Reference. Further reference conditions are as follows: temperature 20 degrees Celsius, irradiance 500 Watts per metre square, in the horizontal position. Each pyranometer has an individual calibration factor.
4 INSTALLATION AND MAINTENANCE For measurement of the Net Radiation, it is most important that the instrument is located in a place that is representative of the entire region that you wish to study. When installed permanently, the net radiometer should be attached to its mounting platform with the rod that is attached to its body. When installed on a mast, the preferred orientation should be such that no shadow is cast on the Net Radiometer at any time during the day.
4.2 Replacing the Ventilator Filter The CNF 4 ventilation unit has a filter that can be checked and if required cleaned or replaced. The cover of the ventilator cover (black part in picture below) can be removed by just pulling it down from the CNR 4. The filter needs to be checked for dust and particles every 6 – 12 months. It can be cleaned by simply washing it in clean water or it can be replaced by a new one. To remount the cover and filter just click it back on the ventilator. Fig 4.
5 TROUBLE SHOOTING This chapter describes what to do if there appears to be a problem. The following chapters give individual information for checking the pyranometer, pyrgeometer, the temperature sensors and the ventilation unit with heater. All connections to the CNR 4 are made with connectors and cables that can be separated from the main instrument. Check at all times that these connectors are properly attached and screwed to the body of the CNR 4.
The CNR 4 body and ambient air should be at the same temperature as much as possible. Let the pyrgeometer rest for at least five minutes to regain its thermal equilibrium. Set the voltmeter to its most sensitive range. To test if the pyrgeometer is working properly, we suggest putting your hand in front of the pyrgeometer. The thermal radiation will cause pyrgeometer to generate a positive voltage when the hand's surface temperature is higher than the pyrgeometer temperature.
6 CMB 1 OPTIONAL MOUNTING BRACKET The CMB 1 mounting bracket is ideal for mounting the CNR 4 to a pole or wall. The stainless steel construction ensures a durable fixation to almost any object. The top U bolts allow rotation of the CNR 4 rod, while the extra screw under the front U bolt allows the rod to tilt. All mounting material for fixation to a horizontal or vertical pole is included. The 2 different sized pairs of U bolts allow for pole sizes between 22 mm and 60 mm.
Fig 7.
7 DELIVERY Check the contents of the shipment for completeness (see below) and note whether any damage has occurred during transport. If there is damage, a claim should be filed with the carrier immediately. In this case, or if the contents are not complete, your dealer should be notified in order to facilitate the repair or replacement of the instrument.
8 RECALIBRATION SERVICE Pyranometers, UV-meters, pyrgeometers, Net radiometers & Sunshine duration meters Kipp & Zonen solar radiation measurement instruments comply with the most demanding international standards. In order to maintain the specified performance of these instruments, Kipp & Zonen recommends calibration of their instruments at least every two years. This can be done at the Kipp & Zonen factory. Here, recalibration to the highest standards can be performed at low cost.
Our customer support remains at your disposal for any maintenance or repair, calibration, supplies and spares. Für Servicearbeiten und Kalibrierung, Verbrauchsmaterial und Ersatzteile steht Ihnen unsere Customer Support Abteilung zur Verfügung. Notre service ‘Support Clientèle’ reste à votre entière disposition pour tout problème de maintenance, réparation ou d’étalonnage ainsi que pour les accessoires et pièces de rechange.
