Subject: | NSA/SKYRAD/C1 - Reprocess: Incorrect datalogger program affecting PIR1 and PIR2 downwelling longwave |
DataStreams: | nsaskyrad60sC1.b1, nsaskyrad20sC1.a0
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Description: | The excitation delays using in measuring the PIR1 case thermistor commonly named "Case1"
and the PIR2 dome thermistor called "Dome2" were discovered to have been incorrectly set
to 0 in the Skyrad datalogger program when the new CR23X based Skyrad loggers were
installed. The result of no delay in these measurements results in an error in the measured
resistance of the thermistors, Case1 and Dome2 and thus the calculated PIR1 and PIR2
irradiances. The errors are inversely proportial to temperature.
Users can apply the temperature dependent irradiance corrections shown in the table below.
Recall that the reported uncertainty of PIRs is typically +-.25% to +-.5% or 1 to 2
W/m2. The error corrections become the same order of magnitude or larger than the
instrument uncertainties at or below 260K or 9F.
Correction Table for Skyrad (TWP and NSA) DIR1 and DIR2 Irradiance
DIR1 DIR1 DIR2 DIR2
T[F] Tcase[K] Correction[W/m2] Tdome[K] Correction[W/m2]
109.4 316.13 0.00 316.13 0.00
100.5 311.20 -0.15 311.20 0.12
93.2 307.14 -0.12 307.14 0.10
87.0 303.70 -0.10 303.70 0.08
81.6 300.70 -0.17 300.70 0.14
77.0 298.15 -0.22 298.15 0.18
59.4 288.35 -0.34 288.35 0.27
47.4 281.72 -0.23 281.72 0.18
38.5 276.74 -0.42 276.74 0.34
31.3 272.77 -0.48 272.77 0.38
25.4 269.48 -0.61 269.48 0.49
20.3 266.67 -0.67 266.67 0.54
16.0 264.25 -0.82 264.25 0.66
12.1 262.11 -0.98 262.11 0.79
8.7 260.19 -0.97 260.19 0.78
5.6 258.46 -1.07 258.46 0.86
2.7 256.89 -1.17 256.89 0.94
0.1 255.44 -1.33 255.44 1.07
-2.3 254.11 -1.41 254.11 1.13
-4.5 252.87 -1.43 252.87 1.15
-6.6 251.71 -1.52 251.71 1.22
-8.5 250.63 -1.63 250.63 1.31
-10.4 249.62 -1.73 249.62 1.39
-12.2 248.58 -1.79 248.58 1.44
-15.4 246.82 -1.93 246.82 1.55
-18.3 245.23 -2.05 245.23 1.65
-20.9 243.78 -2.22 243.78 1.78
-23.3 242.44 -2.36 242.44 1.89
-25.5 241.21 -2.58 241.21 2.07
-27.5 240.07 -2.65 240.07 2.13
-29.5 239.01 -2.75 239.01 2.21
-31.3 238.00 -3.02 238.00 2.42 |
Suggestions: | Apply suggested corrections. |
Measurements: | nsaskyrad20sC1.a0: - inst_down_long_hemisp_shaded1_tp
- inst_down_long_hemisp_shaded2_tp
- inst_down_long_shaded2_case_resist
- inst_down_long_shaded2_dome_resist
- inst_down_long_shaded1_case_resist
- inst_down_long_shaded1_dome_resist
more
nsaskyrad60sC1.b1: - down_long_hemisp_shaded1_max
- down_long_hemisp_shaded2
- down_long_hemisp_shaded2_min
- down_long_hemisp_shaded1
- down_long_hemisp_shaded1_std
- down_long_hemisp_shaded2_std
- down_long_hemisp_shaded1_min
- down_long_hemisp_shaded2_max
more
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