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Aerodynamic Particle Sizer (APS)

The APS is an instrument used for measuring aerodynamic particle size distributions in the micrometer range.

AeroViz.rawDataReader.script.APS.Reader 

Reader(*args, **kwargs)

Bases: AbstractReader

APS (Aerodynamic Particle Sizer) Data Reader

A specialized reader for APS data files, which measure particle size distributions in the range of 542-1981 nm (aerodynamic diameter).

See full documentation at docs/source/instruments/APS.md for detailed information on supported formats and QC procedures.

Attributes

nam class-attribute instance-attribute 

nam = 'APS'

MIN_HOURLY_COUNT class-attribute instance-attribute 

MIN_HOURLY_COUNT = 5

MIN_TOTAL_CONC class-attribute instance-attribute 

MIN_TOTAL_CONC = 1

MAX_TOTAL_CONC class-attribute instance-attribute 

MAX_TOTAL_CONC = 700

STATUS_COLUMN class-attribute instance-attribute 

STATUS_COLUMN = 'Status Flags'

STATUS_OK class-attribute instance-attribute 

STATUS_OK = '0000 0000 0000 0000'

ERROR_STATES class-attribute instance-attribute 

ERROR_STATES = {0: 'Laser fault', 1: 'Total Flow out of range', 2: 'Sheath Flow out of range', 3: 'Excessive sample concentration', 4: 'Accumulator clipped', 5: 'Autocal failed', 6: 'Internal temperature < 10°C', 7: 'Internal temperature > 40°C', 8: 'Detector voltage out of range'}

_status_data instance-attribute 

_status_data = None

_distributions instance-attribute 

_distributions = None

Functions

__call__ 

__call__(start, end, mean_freq='1h')

Process APS data and save size distributions to separate files.

Overrides AbstractReader.call to add distribution file saving and filter out size bins from main output.

Parameters:

Name Type Description Default
start datetime

Start time for data processing

 required
end datetime

End time for data processing

 required
mean_freq str

Frequency for resampling the data

 '1h'

Returns:

Type Description
DataFrame

Processed and resampled data (statistics only, no size bins)

_parse_status_flags staticmethod 

_parse_status_flags(status_str)

Parse APS binary status flags string to integer.

Parameters:

Name Type Description Default
status_str str

Status flags in binary format, e.g., "0000 0000 0000 0000"

 required

Returns:

Type Description
int

Integer value of the status flags (0 if normal)

_raw_reader 

_raw_reader(file)

Read and parse raw APS data files.

_QC 

_QC(_df)

Perform quality control on APS data.

QC Rules Applied
  1. Status Error : Non-zero status flags indicate instrument error
  2. Insufficient : Less than 5 measurements per hour
  3. Invalid Number Conc : Total number concentration outside valid range (1-700 #/cm³)

_process 

_process(_df)

Calculate size distribution statistics from QC'd APS data.

Processing Steps
  1. Calculate dlogDp from bin diameters
  2. Calculate number, surface, volume distributions (all in dX/dlogDp)
  3. Calculate total, GMD, GSD, mode for each weighting
  4. Calculate totals for size cutoffs: 1μm, 2.5μm, all
  5. Store distributions for separate file output
Size Cutoffs (APS range: 0.542-19.81 μm)
  • 1μm: particles smaller than 1 μm
  • 2.5μm: particles smaller than 2.5 μm
  • all: full size range

Parameters:

Name Type Description Default
_df DataFrame

Quality-controlled DataFrame with size bin columns and QC_Flag

 required

Returns:

Type Description
DataFrame

Original size bins (dN/dlogDp) + calculated statistics + QC_Flag

_save_distributions 

_save_distributions(mean_freq: str = '1h') -> None

Save size distributions to separate CSV files.

Output Files
  • output_aps_dNdlogDp.csv : Number distribution (dN/dlogDp)
  • output_aps_dSdlogDp.csv : Surface distribution (dS/dlogDp)
  • output_aps_dVdlogDp.csv : Volume distribution (dV/dlogDp)

Parameters:

Name Type Description Default
mean_freq str

Frequency for resampling the data

 '1h'

Data Format

  • File format: Tab-delimited text file
  • Sampling frequency: 6 minutes (typical)
  • File naming pattern: *.txt
  • Data structure:
    • Header: 6 rows of metadata
    • Time columns: Date and Start Time
    • Size distribution data: Columns 3-54

Measurement Parameters

The APS provides aerodynamic particle size distribution measurements:

Parameter Value Description
Size range 542-1981 nm Aerodynamic diameter range
Output dN/dlogDp Number concentration per size bin
Unit #/cm³ Particle number concentration

Data Processing

Data Reading

  • Automatically skips 6 rows of header metadata
  • Parses date and time into datetime index
  • Extracts particle size distribution data (columns 3-54)
  • Rounds size bin values to 4 decimal places
  • Handles transposed data formats
  • Validates datetime values

Quality Control

The APS reader uses the declarative QCFlagBuilder system with the following rules:

+-----------------------------------------------------------------------+
|                         QC Thresholds                                 |
+-----------------------------------------------------------------------+
| MIN_HOURLY_COUNT = 5      measurements per hour                       |
| MIN_TOTAL_CONC   = 1      #/cm³                                       |
| MAX_TOTAL_CONC   = 700    #/cm³                                       |
| STATUS_OK        = "0000 0000 0000 0000" (16-bit binary, all zeros)   |
+-----------------------------------------------------------------------+

+-----------------------------------------------------------------------+
|                            _QC() Pipeline                             |
+-----------------------------------------------------------------------+
|                                                                       |
|  [Pre-process] Calculate dlogDp and total concentration               |
|       |                                                               |
|       v                                                               |
|  +-------------------------+                                          |
|  | Rule: Status Error      |                                          |
|  +-------------------------+                                          |
|  | Status Flags != all     |                                          |
|  | zeros (16-bit binary)   |                                          |
|  +-------------------------+                                          |
|           |                                                           |
|           v                                                           |
|  +-------------------------+                                          |
|  | Rule: Insufficient      |                                          |
|  +-------------------------+                                          |
|  | < 5 measurements        |                                          |
|  | per hour                |                                          |
|  +-------------------------+                                          |
|           |                                                           |
|           v                                                           |
|  +-------------------------+                                          |
|  | Rule: Invalid Number    |                                          |
|  |       Conc              |                                          |
|  +-------------------------+                                          |
|  | Total number conc.      |                                          |
|  | outside range (1-700)   |                                          |
|  +-------------------------+                                          |
|                                                                       |
+-----------------------------------------------------------------------+

QC Rules Applied

Rule Condition Description
Status Error Status Flags ≠ 0 Non-zero status flags indicate instrument error
Insufficient < 5 measurements/hour Less than 5 measurements per hour
Invalid Number Conc Total < 1 OR > 700 #/cm³ Total number concentration outside valid range

Error Status Codes (from TSI RF command)

Bit Binary Value Description
0 0000 0000 0000 0001 Laser fault
1 0000 0000 0000 0010 Total Flow out of range
2 0000 0000 0000 0100 Sheath Flow out of range
3 0000 0000 0000 1000 Excessive sample concentration
4 0000 0000 0001 0000 Accumulator clipped (> 65535)
5 0000 0000 0010 0000 Autocal failed
6 0000 0000 0100 0000 Internal temperature < 10°C
7 0000 0000 1000 0000 Internal temperature > 40°C
8 0000 0001 0000 0000 Detector voltage out of range (±10% Vb)
9 0000 0010 0000 0000 Reserved (unused)

Valid Concentration Range

    Total Conc (#/cm³)
       ^
   700 +-------------------------------- MAX_TOTAL_CONC
       |   +-----------------------+    (reject if exceeded)
       |   |    VALID RANGE        |
       |   +-----------------------+
     1 +-------------------------------- MIN_TOTAL_CONC
     0 +-------------------------------- (reject if below)
       +----------------------------> Time

Output Data

The processed data contains:

Column Unit Description
Size bins (542-1981 nm) dN/dlogDp Number concentration for each size

QC_Flag Handling

  • The intermediate file (_read_aps_qc.pkl/csv) contains the QC_Flag column
  • The final output has invalid data set to NaN and QC_Flag column removed

Notes

  • Measures aerodynamic particle diameter directly
  • Complementary to SMPS for larger particle sizes
  • Size range approximately 0.5-2 μm
  • Logarithmic bin spacing in size distribution