SGP/ACSM/C1 - Instrument inlet pressure low

The pressure at the inlet to the instrument was at least 100 torr below ambient after work 
was performed on the vacuum line serving the ACSM. The inlet pressure also dropped from 
1.3 torr to approximately 1 torr.  Examination of the data during reprocessing shows that 
aerosol loadings during the period specified are unreasonably low and suggest that the 
instrument was not sampling ambient air.  The data for the specified period are unreliable 
and should not be used.

I visited SPG to perform ACSM tuning and calibration on 2015-10-06. While there I measured 
the flow in the line bringing sample to the ACSM. The flow was > 45 lpm. This high rate 
was pulling a vacuum on the ACSM sampling line. The vacuum was high when the cyclone was 
in line upstream of the ACSM and was the cause of the low pressure seen after the changes 
to the system were made in August. The flow past the ACSM inlet should be 3 lpm. The 
inlet pressure was ~700 torr when it should be ambient. I disconnected the sampling line 
from the Gast vacuum pump and reconnected and connected it to the Aerodyne pump which is 
part of the dryer system. The flow rate is now 3 lpm, the ambient pressure 740 torr, and the 
inlet pressure 1.3 torr. The instrument was calibrated and is now performing properly.

Do not use the data during the specified period.

• Raw data stream - documentation not supported

• ammonium
• amus
• sulfate
• nitrate
• total_organics
• chloride
• org_mx
• org_mx_err

• total_organics
• inlet_closed
• chloride
• inlet_open
• emission_current
• sulfate
• vaporizer
• nitrate
• flow_rate
• ammonium

• Raw data stream - documentation not supported

• org_mx
• ammonium
• sulfate
• nitrate
• total_organics
• amus
• chloride
• org_mx_err