CSV data format - Revision history

Bcmwiki: Consistency pass 2: airflow range via Configuration, multi-wavelength as in-development, ESP32/Pi CSV filename split, legacy sensor wording

2026-06-08T18:47:40Z

Consistency pass 2: airflow range via Configuration, multi-wavelength as in-development, ESP32/Pi CSV filename split, legacy sensor wording

← Older revision		Revision as of 18:47, 8 June 2026
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	=== Filename Convention ===		=== Filename Convention ===

	* Active session: <code>YY-MM-DD_HHMMSS.csv</code> (based on session start time)		* Active session: <code>YY-MM-DD_HHMMSS.csv</code> on ESP32 builds, <code>DD-MM-YY_HHMMSS.csv</code> on Raspberry Pi builds (based on session start time)
	* Fallback (no RTC sync): <code>nosync_HHMMSS.csv</code> (based on uptime)		* Fallback (no RTC sync): <code>nosync_HHMMSS.csv</code> (based on uptime)

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	\|}		\|}

	==== Multi-Wavelength Columns (~~optional~~, if hardware ~~installed~~) ====		==== Multi-Wavelength Columns (in development, not in shipped hardware) ====

	Same structure as 880nm, repeated for each wavelength:		Same structure as 880nm, repeated for each wavelength:

Bcmwiki: Fix ATN formula: ATN = -100*ln(Sen/Ref), dimensionless; sigma enters BC not ATN (verified vs firmware measure.cpp)

2026-06-08T16:20:51Z

Fix ATN formula: ATN = -100*ln(Sen/Ref), dimensionless; sigma enters BC not ATN (verified vs firmware measure.cpp)

← Older revision		Revision as of 16:20, 8 June 2026
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	\| <code>bcmSen_880nm</code> \|\| float \|\| V \|\| Sensor channel voltage (880nm LED through sample spot)		\| <code>bcmSen_880nm</code> \|\| float \|\| V \|\| Sensor channel voltage (880nm LED through sample spot)
	\|-		\|-
	\| <code>bcmATN_880nm</code> \|\| float \|\| — \|\| Attenuation at 880nm = ~~−ln~~(Sen/Ref) / σ		\| <code>bcmATN_880nm</code> \|\| float \|\| — \|\| Attenuation at 880nm = −100·ln(Sen/Ref), dimensionless. The absorption cross-section σ enters the BC concentration, not ATN.
	\|-		\|-
	\| <code>BCngm3_unfiltered_880nm</code> \|\| float \|\| ng/m³ \|\| Real-time BC concentration (unsmoothed)		\| <code>BCngm3_unfiltered_880nm</code> \|\| float \|\| ng/m³ \|\| Real-time BC concentration (unsmoothed)

Bcmwiki: Wiki update: sync with manual and dev docs (2026-03)

2026-03-08T13:10:12Z

Wiki update: sync with manual and dev docs (2026-03)

New page

== CSV Data Format ==

bcMeter stores measurement data as CSV files. This page documents the file format and column definitions.

=== File Format ===

{| class="wikitable"
! Property !! Value
|-
| Delimiter || Semicolon (<code>;</code>)
|-
| Encoding || UTF-8
|-
| Decimal separator || Dot (<code>.</code>)
|-
| Line ending || LF (<code>\n</code>)
|-
| First row || Column headers
|}

=== Filename Convention ===

* Active session: <code>YY-MM-DD_HHMMSS.csv</code> (based on session start time)
* Fallback (no RTC sync): <code>nosync_HHMMSS.csv</code> (based on uptime)

=== Column Definitions ===

==== Core Columns (always present) ====

{| class="wikitable"
! Column !! Type !! Unit !! Description
|-
| <code>bcmDate</code> || string || DD-MM-YY || Measurement date
|-
| <code>bcmTime</code> || string || HH:MM:SS || Measurement time
|-
| <code>bcmRef_880nm</code> || float || V || Reference channel voltage (880nm LED through clean filter)
|-
| <code>bcmSen_880nm</code> || float || V || Sensor channel voltage (880nm LED through sample spot)
|-
| <code>bcmATN_880nm</code> || float || — || Attenuation at 880nm = −ln(Sen/Ref) / σ
|-
| <code>BCngm3_unfiltered_880nm</code> || float || ng/m³ || Real-time BC concentration (unsmoothed)
|-
| <code>BCngm3_880nm</code> || float || ng/m³ || BC concentration with rolling average applied
|-
| <code>relativeLoad</code> || float || % || Filter loading (0 = clean, 100 = saturated)
|-
| <code>AAE</code> || float || — || Ångström Absorption Exponent (requires multi-wavelength)
|-
| <code>Temperature</code> || float || °C || Internal device temperature
|-
| <code>airflow</code> || float || L/min || Measured airflow rate
|}

==== Multi-Wavelength Columns (optional, if hardware installed) ====

Same structure as 880nm, repeated for each wavelength:

* <code>bcmRef_520nm</code>, <code>bcmSen_520nm</code>, <code>bcmATN_520nm</code>, <code>BCngm3_unfiltered_520nm</code>, <code>BCngm3_520nm</code>
* <code>bcmRef_370nm</code>, <code>bcmSen_370nm</code>, <code>bcmATN_370nm</code>, <code>BCngm3_unfiltered_370nm</code>, <code>BCngm3_370nm</code>

==== Environmental Columns (optional, sensor-dependent) ====

{| class="wikitable"
! Column !! Type !! Unit !! Description
|-
| <code>humidity</code> || float || % || Relative humidity (BME280/SHT4x)
|-
| <code>hPa</code> || float || hPa || Atmospheric pressure (BME280)
|-
| <code>PM2.5</code> || float || µg/m³ || Particulate matter <2.5µm (SPS30)
|-
| <code>PM10</code> || float || µg/m³ || Particulate matter <10µm (SPS30)
|}

==== GPS Columns (optional, if GPS module connected and has fix) ====

{| class="wikitable"
! Column !! Type !! Unit !! Description
|-
| <code>lat</code> || float || degrees || Latitude (WGS84)
|-
| <code>lon</code> || float || degrees || Longitude (WGS84)
|-
| <code>altitude</code> || float || m || GPS altitude above sea level
|}

==== Metadata Columns ====

{| class="wikitable"
! Column !! Type !! Description
|-
| <code>notice</code> || string || System notices or warnings per data point
|-
| <code>sampleDuration</code> || float || Actual measurement duration for this sample (seconds)
|-
| <code>notes</code> || string || User-added annotations
|}

=== Example Data ===

<pre>
bcmDate;bcmTime;bcmRef_880nm;bcmSen_880nm;bcmATN_880nm;BCngm3_unfiltered_880nm;BCngm3_880nm;relativeLoad;AAE;Temperature;airflow
04-03-26;19:37:09;0.9679;0.9321;3.76;1686;1686;0;0;0;0.4659
04-03-26;19:42:09;0.9745;0.9335;4.3;4028.5;1686;0;0;0;0.3088
04-03-26;19:47:09;0.9752;0.9315;4.59;2371.4;1830.2;0;0;0;0.2832
</pre>

=== Import Notes ===

* '''Excel:''' Use "Text Import Wizard" and set delimiter to semicolon. The date format DD-MM-YY may need manual conversion.
* '''Python/Pandas:''' <code>pd.read_csv('file.csv', sep=';')</code>
* '''R:''' <code>read.csv2('file.csv')</code> (uses semicolon by default)