DQRID : D141017.4
Start DateStart TimeEnd DateEnd Time Data Quality Metric
02/04/2014170003/25/20141800Incorrect
09/12/2014122310/01/20141600Incorrect
10/30/2014163011/04/20141600Incorrect
08/25/2014020008/25/20142330Incorrect
08/14/2014230008/19/20142200Incorrect
08/20/2014100008/22/20141915Incorrect
05/18/2014180007/22/20141800Incorrect
01/24/2014113002/03/20140100Incorrect
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Subject:
MAO/CPC/S1 - CPCU under-counting
DataStreams:maoaoscpcuS1.a1, maoaoscpcuS1.b1
Description:
Under normal operating conditions, the CPCU measured number concentration should be equal 
to or greater than the CPCF measured number concentration. The fact that the CPCU is 
under-counting with respect to the CPCF during this time period strongly suggests that there 
is a clog in the sampling capillary, resulting in a lower than expected sample flow rate 
and therefore a lower than expected measured number concentration.
Suggestions: 
One approach to correcting for this lower sample flow rate in the CPCU is to identify 

sampling periods where it is likely that no sub 10 nm aerosol are being sampled. During 
those time periods, the CPCF and CPCU measured number concentrations should, under 
normal operating conditions, be the same, and the CPCF measurements can then be used to 
calibrate the CPCU sampling flow rate. Over time, the decrease in CPCU sample flow rate can be 
tracked and used to correct the CPCU reported number concentration.
Measurements:maoaoscpcuS1.a1:
  • concentration
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maoaoscpcuS1.b1:
  • concentration
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