CNR4 Net Radiometer
19
Alternatively, you can use the Pt-100 to make the temperature measurement. The
Pt-100 requires one current excitation terminal, and one differential analog
ue
terminal. The CR6, CR3000, and CR5000 have current excitation terminals.
shows the Pt-100 resistance values as a function of temperature.
TABLE 8–2. Resistance values versus CNR4 Pt–100 temperature in °C
Temperature
[°C]
Resistance
[
Ω
]
Temperature
[°C]
Resistance
[
Ω
]
Temperature
[°C]
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
101.56
101.95
102.34
102.73
103.12
103.51
103.90
104.29
104.68
105.07
105.46
105.85
106.24
106.63
107.02
107.40
107.79
108.18
108.57
108.96
109.35
109.73
110.12
110.51
110.90
111.28
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
111.67
112.06
112.45
112.83
113.22
113.61
113.99
114.38
114.77
115.15
115.54
115.93
116.31
116.70
117.08
117.47
117.85
118.24
118.62
119.01
119.40
119.78
120.16
120.55
120.93
121.32
121.70
122.09
122.47
122.86
8.4 Calculation of Albedo
Albedo is the ratio of reflected short-wave radiation to incoming short-wave
radiation. This unitless value ranges between 0 and 1. Typical values are 0.9
for snow, and 0.3 for grassland. To determine the albedo, the measured values
of the two pyranometers are used. Do not use the measured values when the
solar elevation is lower than 10 degrees above the horizon. Errors in the
measurements at these elevations are likely and yield unreliable results. This is
due to deviations in the directional response of the pyranometers.
Albedo = (E lower Pyranometer) / (E upper Pyranometer)
(8-3)
