uThing::VOC sensor data output

Reported datapoints

The following table shows the data outputs from the device:

Output variable Unit Range Description
Temperature °C -40 - +85 ambient temperature estimated outside the device
RelativeHumidity %RH 0 - 100 ambient Relative-Humidity (*) estimated outside the device
Pressure hPa 300-1100 atmospheric (barometric) pressure (1000 hPA = 1 bar)
GasResitance Ω 1K-1M hot-plate raw gas resistance (ohm)
IAQ - 0-500 Air Quality Index (check BSEC classification)
IAC_accuracy - 0-3 0: not-fixed-yet (IAQ invalid), 3: maximum-stability
equivalentCO2 ppm - CO2 equivalent estimate
eqBreathVOC ppm - breath-VOC concentration estimate

(*) relative humidity

Relative humidity refers to the ratio of the amount of moisture in the air at a certain temperature to the maximum amount of moisture that the air can retain at the same temperature. In other words, relative humidity measures how much of the moisture capacity of the air is used.

uThing::VOC™ provides three different reporting formats for the processed BSEC data. Check the configuration section below for instructions on how to change this output format.

JSON

JSON is the default output reporting format due to its ubiquitous use on IoT applications. It’s also human readable. An output example is shown below.

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{
    "temperature": 24.68, 
    "pressure": 1019.38, 
    "humidity": 45.64, 
    "gasResistance": 597617, 
    "IAQ": 28.3, 
    "iaqAccuracy": 3, 
    "eqCO2": 511.21, 
    "eqBreathVOC": 0.52
}

CSV

For applications where a simple mean for data-logging is needed, the board can be configured to output the data in CSV format (comma separated values).

When the board is configured in this mode, the column order is the following:

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[temperature], [pressure], [humitidy], [gasResistance], [IAQ], [accuracy], [eqCO2], [eqBreathVOC]

Output example:

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    24.65, 1019.42, 46.23, 597617, 26.9, 2, 506.7, 0.51
tip: Exporting data to Excel

As a quick way to do some simple dataloging into a file, the sensor data can be sent to a plain text file with the following command: $ cat /dev/ttyACM0 > airQuality.csv

Additionally, if the “&” symbol is added at the end of the command, the process will be forked, and the system will keep storing the data until the user logs out or the dongle is disconnected.

Then the generated file can easily be opened in Excel or any spreadsheet application for evaluation.

Optionally, the column formatting can be pasted into the first line of the generated CSV file, simplifying the analysis on the spreadsheet apps.

Human-readable

The 'human-readable' format reports a more descriptive output that includes the measuring units.

Ouput example:

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Temperature: 24.70 C, 
Humidity: 45.12 rH,
Pressure: 1019.38 hPa, 
Gas resistance: 599759 ohms, 
IAQ: 27.1, 
IAQ Accuracy: 3, 
CO2equivalent: 507.1, 
Breath VOC equivalent: 0.51