NIM/SKYRAD/M1 - Instrument ventilator problem

Data quality office first reported that PIR1 and PIR2 appear to be deviating more than 
typical during the daylight hours.  It was found that the Skyrad PIR ventilator fans were 
building up debris on the intake air filter.  Obstructed air flow results in solar heating 
of the PIR ventilator housing in the later part of the day and biasing the incomming IR 
irradiance values. The slow buildup was insidious and wasn't discovered and corrected 
(i.e. ventilator fans cleaned on a regular and frequent basis) until Feb 23rd. On or around 
December 23rd was when this problem may have first started.  We are unable to quantify the 
extent of the problem in W/m2.  Normal deviation between PIRs is typically 3-5 W/m2.

There is no quantitative way to determine how far from truth the PIRs deviated due to 

enclosure heating.  Avoid using PIR1,PIR2 data after midday to sunset or only when the 
difference between PIR1 and PIR2  is less than the specified uncertainty - typically 2-5W/m2

• 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

• down_long_hemisp_shaded2_max
• down_long_hemisp_shaded2_std
• down_long_hemisp_shaded1_min
• down_long_hemisp_shaded2
• down_long_hemisp_shaded1
• inst_down_long_shaded1_dome_temp
• inst_down_long_hemisp_shaded1_tp
• inst_down_long_hemisp_shaded2_tp
• inst_down_long_shaded2_case_temp
• inst_down_long_shaded1_case_temp
• down_long_hemisp_shaded2_min
• inst_down_long_shaded2_dome_temp
• down_long_hemisp_shaded1_std
• down_long_hemisp_shaded1_max

• Raw data stream - documentation not supported