particulates_sampler - bruno-beloff/scs_dev GitHub Wiki

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DESCRIPTION

The particulates_sampler utility reads a set of values from the Alphasense optical particle counter (OPC). The reported values are:

per - the period of time between the previous reading and this reading
pm1, pm2p5, pm10 - particulate densities of PM1, PM2.5 and PM10 in ug/m3
bins - the particle count, for particles of increasing size
mtf1, mtf3, mtf5, mtf7 - time taken for particle movement between system points
sht.hmd, sht.tmp - humidity and temperature at point of sampling (OPC-N3 only)

The particulates_sampler utility operates by launching a background process. This OPCMonitor process reads the OPC values at specified intervals (which may be different from the intervals used by the parent process). In addition, the process power cycles the OPC if its laser safety control has tripped.

The scs_mfr/opc_conf utility is used to specify the OPC model, background process sampling time, and OPC control power saving mode.

When the particulates_sampler utility starts, it power cycles the OPC. When the utility stops, it stops operations on the OPC, and stops the OPC fan.

The particulates_sampler writes its output to stdout. As for all sensing utilities, the output format is a JSON document with fields for:

tag - the unique tag of the device (if the system ID is set)
src - a source identifier ("N2" or "N3")
rec - the recording datetime in ISO 8601 format
val - a value field containing the sensed values
exg - data interpretations, as specified by opc_conf.py

Command-line options allow for single-shot reading, multiple readings with specified time intervals, or readings controlled by an independent scheduling process via a Unix semaphore.

If any errors are detected while the OPC is running, these are logged. the log can be interrogated using the scs_mfr/opc_error_log utility.

SYNOPSIS

particulates_sampler.py [-n NAME] [{ -s SEMAPHORE | -i INTERVAL [-c SAMPLES] }] [{ -v | -d }]

Options
--version	show program's version number and exit
-h, --help	show this help message and exit
-n NAME, --name=NAME	the name of the sampler configuration
-s SEMAPHORE, --semaphore=SEMAPHORE	sampling controlled by SEMAPHORE
-i INTERVAL, --interval=INTERVAL	sampling interval in seconds
-n SAMPLES, --samples=SAMPLES	number of samples (1 if interval not specified)
-v, --verbose	report narrative to stderr
-d, --debug	report detailed narrative to stderr

EXAMPLES

./particulates_sampler.py -v -s scs-particulates

FILES

~/SCS/conf/opc_conf.json
~/SCS/conf/schedule.json
~/SCS/conf/system_id.json
~/SCS/log/opc_error_log.csv

DOCUMENT EXAMPLE - v0

{"rec": "2021-10-11T11:06:57Z", "tag": "scs-bgx-431", "src": "N3", "val": {"per": 4.1, "pm1": 1.7, "pm2p5": 6.3, "pm10": 24.1, "bin": [106, 31, 25, 5, 9, 5, 2, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], "mtf1": 34, "mtf3": 34, "mtf5": 43, "mtf7": 48, "sfr": 3.66, "sht": {"hmd": 37.3, "tmp": 23.8}}, "exg": {"rn20": {"pm1": 3.6, "pm2p5": 5.5, "pm10": 27.1}}}

DOCUMENT EXAMPLE - v2

{"rec": "2021-10-11T11:11:14Z", "tag": "scs-be2-3", "ver": 2.0, "src": "N3", "val": {"per": 4.1, "pm1": 0.7, "pm2p5": 3.2, "pm10": 33.3, "bin": [50, 24, 6, 2, 4, 2, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], "mtf1": 29, "mtf3": 32, "mtf5": 19, "mtf7": 54, "sfr": 3.73, "sht": {"hmd": 43.6, "tmp": 25.6}}, "exg": {"src": "rn20", "val": {"pm1": 1.5, "pm2p5": 6.4, "pm10": 58.7}}}

BUGS

The particulates_sampler utility is not process-safe - it should therefore be run by only one process at a time.

RESOURCES

Data formats/Topic: particulates
ISO 8601