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GRIMM Aerosol Spectrometer

The GRIMM is an optical particle counter that measures particle size distributions across multiple size channels.

AeroViz.rawDataReader.script.GRIMM.Reader 

Reader(path: Path | str, reset: bool | str = False, qc: bool | str = True, **kwargs)

Bases: AbstractReader

GRIMM Aerosol Spectrometer Data Reader

A specialized reader for GRIMM data files, which measure particle size distributions in the range of 0.25-32 μm.

See docs/api/instruments/particle-sizers/GRIMM.md and docs/guide/reader-reference.md for the file layout and QC procedure.

Attributes

nam class-attribute instance-attribute 

nam = 'GRIMM'

Methods:

_raw_reader 

_raw_reader(file)

Read and parse raw GRIMM data files.

Parameters:

Name Type Description Default
file Path or str

Path to the GRIMM data file.

 required

Returns:

Type Description
DataFrame or None

Processed GRIMM data with datetime index and size channels as columns. Returns None if the file is empty.

_QC 

_QC(_df)

Perform quality control on GRIMM size-distribution data.

QC Rules Applied
  1. No Data : every size channel is NaN
  2. Negative Conc : any size channel is negative (physically impossible)
  3. Insufficient : less than 50% hourly data completeness
Notes

Deliberately conservative. Concentration range limits (the equivalent of SMPS's MIN_TOTAL_CONC / APS's MAX_TOTAL_CONC) are not applied: this reader has no sample corpus to calibrate a plausible range against, and a wrong threshold silently deletes good data. The three rules here need no site-specific tuning — a negative count is invalid under any configuration.

Producing a QC_Flag at all is required by the pipeline contract (see docs/guide/data-levels.md, rule R2): rates are computed by comparing the raw frame against the flag, so a reader without one leaves the report rate-less.

Raw format

  • File pattern: *.dat (the config glob; the content is tab-delimited text)
    • A407ST*.dat files use a wider channel layout (see below)
    • Other GRIMM formats
  • Native frequency: 6min is the config fallback; the grid actually used is detected per file and reported as df.attrs['raw_freq']
  • Encoding: ISO-8859-1
  • Header layout: 233 rows of metadata, then the header row at the hard-coded line index 233
  • European date format (DD/MM/YYYY HH:MM:SS, dayfirst=True) in the first column, which becomes the Time index

Parse recipe

  • read_csv(header=233, delimiter='\t', index_col=0, parse_dates=[0], encoding='ISO-8859-1', dayfirst=True)
  • Size distribution channels: columns 0–10 are dropped, and so are the trailing 5 columns — or every column from index 128 onwards for files named A407ST* (channels 11–127)
  • All values are divided by 0.035 (the scaling factor to particles/cm³)
  • Empty files are warned about by name and skipped

Measurement parameters

The GRIMM provides:

  • Size range: 0.25 to 32 μm
  • Resolution: Multiple size channels
  • Output: Number concentration for each size bin
  • Units: particles/cm³ (after scaling)

Status & error codes

None — the GRIMM export carries no status column, so there is no Status Error rule and no status mode applies. ignored_status_errors has no effect on this reader.

QC rules

The size channels are the numeric-valued columns left after the metadata columns were dropped in _raw_reader.

Rule Condition Severity
No Data every size channel is NaN (also fires on every row when the file has no numeric channel at all) error
Negative Conc any size channel < 0 — impossible for a counter under any configuration 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

Deliberately absent: concentration range limits, the equivalent of SMPS's MIN_TOTAL_CONC / APS's MAX_TOTAL_CONC. There is no GRIMM sample corpus to calibrate a plausible range against, and a wrong threshold silently deletes good data. The three rules above need no site-specific tuning. Producing a QC_Flag at all is required by the pipeline contract (rates are computed by comparing the raw frame against the flag), which is why the reader has a _QC even though it is conservative. Total-concentration consistency and time-based outlier checks remain possible future additions.

Output

Column Unit Description
Time index — Data acquisition time
Size channels particles/cm³ Number concentration for each bin

There is no _process step: L2 hands on the size channels unchanged.

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

Notes

  • High resolution size information
  • Wide size range coverage
  • Multiple size channels
  • Standard scaling factor applied
  • European date format support