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Nephelometer (NEPH)

The Nephelometer is an instrument used for measuring light scattering properties of aerosols at multiple wavelengths.

AeroViz.rawDataReader.script.NEPH.Reader 

Reader(*args, **kwargs)

Bases: AbstractReader

Nephelometer (NEPH) Data Reader

A specialized reader for integrating nephelometer data files, which measure light scattering properties of aerosols at multiple wavelengths.

See docs/api/instruments/nephelometers/NEPH.md for usage and docs/guide/reader-reference.md for the file layout, status codes and QC rules.

Attributes

nam class-attribute instance-attribute 

nam = 'NEPH'

SCAT_COLUMNS class-attribute instance-attribute 

SCAT_COLUMNS = ['B', 'G', 'R', 'BB', 'BG', 'BR']

CAL_COLUMNS class-attribute instance-attribute 

CAL_COLUMNS = ['sca_550', 'SAE']

MIN_SCAT_VALUE class-attribute instance-attribute 

MIN_SCAT_VALUE = 0

MAX_SCAT_VALUE class-attribute instance-attribute 

MAX_SCAT_VALUE = 2000

STATUS_COLUMN class-attribute instance-attribute 

STATUS_COLUMN = 'status'

STATUS_OK class-attribute instance-attribute 

STATUS_OK = 0

Methods:

_raw_reader 

_raw_reader(file)

Read and parse raw Nephelometer data files.

Parameters:

Name Type Description Default
file Path or str

Path to the Nephelometer data file.

 required

Returns:

Type Description
DataFrame

Processed Nephelometer data with datetime index and scattering coefficient columns.

_QC 

_QC(_df)

Perform quality control on Nephelometer raw data.

QC Rules Applied (raw data only)
  1. Status Error : Non-zero status code indicates instrument error
  2. No Data : All scattering columns are NaN
  3. Invalid Scat Value: Scattering coefficient outside 0-2000 Mm^-1
  4. Invalid Scat Rel. : Wavelength dependence violation (B < G < R)
  5. Insufficient : Less than 50% hourly data completeness

Note: SAE calculation is done in _process() after QC.

_process 

_process(_df)

Calculate scattering coefficients and SAE.

Processing Steps
  1. Calculate scattering coefficient at 550nm
  2. Calculate SAE (Scattering Ångström Exponent)

Parameters:

Name Type Description Default
_df DataFrame

Quality-controlled DataFrame with scattering columns and QC_Flag

 required

Returns:

Type Description
DataFrame

DataFrame with sca_550, SAE, and updated QC_Flag

Raw format

Time Record Format T YYYY MM DD HH NN SS
Example T 2022 05 08 13 29 22
Data Record Format D mode time B G R BB GB RB
Example D NBXX 2258 7.527e-5 6.984e-5 4.275e-5 6.821e-6 1.070e-5 5.130e-6
Auxiliary Record Format Y x pressure Sample Temp Inlet Temp RH lamp voltage lamp current BNC voltage Status
Example Y 348 973 302.8 300 91.2 12.5 5.7 2 0000
  • File pattern: *.dat (raw data file, record-oriented, no header)
  • Native frequency: 5min (config fallback; the grid actually used is detected per file and reported as df.attrs['raw_freq'])
  • Record types, identified by column 0:
    • T records: Timestamp information
    • D records: Scattering measurements
    • Y records: Status and RH information

Parse recipe

  • read_csv(header=None, names=range(11)), then grouped by the record type in column 0
  • T = timestamp: YYYY MM DD HH MM SS across columns 1–6, zero-padded and concatenated, parsed as %Y%m%d%H%M%S
  • D = data: the NBXX (normal scattering) sub-group is used, falling back to NTXX (total scattering); columns 3–8 × 1e6 → B, G, R, BB, BG, BR in Mm⁻¹
  • Y = state: column 2 pressure, 3 temp1 (sample temperature), 4 temp2 (inlet temperature), 5 RH, 9 status (e.g. 0000, coerced to a nullable integer). Column 1 (total counts) and column 8 (status hex) are present in the file but not read.
  • A file containing a record type outside {B, G, R, D, T, Y, Z} is skipped with a warning naming the offending rows

Quirk: Y-row fields are attached to the data frame positionally (.values), so a file with unequal D and Y counts misaligns or raises.

Measurement parameters

The Nephelometer provides measurements at three wavelengths (TSI 3563 bands):

Column Wavelength Description
B 450 nm Total scattering (blue)
G 550 nm Total scattering (green)
R 700 nm Total scattering (red)
BB 450 nm Backscattering (blue)
BG 550 nm Backscattering (green)
BR 700 nm Backscattering (red)

Status & error codes

Column status (from Y record field 9), mode numeric with ok_value=0 (see status modes): a row is an error when the status is not 0 and not NaN. Only 0 (normal operation) is defined; there is no register table, so df.attrs['status_conditions'] is not produced. A missing status column is logged by check_status_columns and leaves the rule inert.

To treat a code as OK, whitelist its numeric value:

RawDataReader('NEPH', path, ignored_status_errors=[4])

QC rules

Rule Condition Severity
Status Error status ≠ 0 and not NaN (see above) error
No Data all six scattering columns (B, G, R, BB, BG, BR) are NaN error
Invalid Scat Value any scattering column ≤ 0 or > 2 000 Mm⁻¹ (MIN_SCAT_VALUE / MAX_SCAT_VALUE) error
Invalid Scat Rel B < G and G < R — inverted wavelength dependence (expected Blue > Green > Red at 450 / 550 / 700 nm) error
Insufficient an hour holds < 50 % of the points it could have held at the detected frequency (edge hours scaled by coverage) advisory (WARNING) — recorded, data kept

SAE and sca_550 are computed in _process after QC, not checked by a rule.

Output

_process runs _scaCoe on B, G, R (using the 450/550/700 nm bands) to add sca_550 and SAE, then re-attaches every non-scattering column.

Column Unit Description
B, G, R Mm⁻¹ Total scattering coefficients
BB, BG, BR Mm⁻¹ Backscattering coefficients
sca_550 Mm⁻¹ Scattering at 550nm
SAE - Scattering Angstrom Exponent (positive by convention)
RH % Relative humidity from the Y record
pressure as exported Pressure from the Y record
temp1, temp2 as exported Sample and inlet temperature from the Y record
status - Raw status code from the Y record, carried through unchanged

Files written per read are listed in RawDataReader Reference §1.

Notes

  • Provides information about aerosol optical properties and size distribution
  • Supports both normal and total scattering modes
  • Wavelength dependence follows Rayleigh scattering principle