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134 lines
4.4 KiB
ReStructuredText
134 lines
4.4 KiB
ReStructuredText
.. include:: ../Plugin/_plugin_substitutions_p05x.repl
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.. _P052_page:
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|P052_typename|
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==================================================
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|P052_shortinfo|
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Plugin details
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--------------
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Type: |P052_type|
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Port Type: |P052_porttype|
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Name: |P052_name|
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Status: |P052_status|
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GitHub: |P052_github|_
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Maintainer: |P052_maintainer|
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Used libraries: |P052_usedlibraries|
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Description
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-----------
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SenseAir is a Swedish manufacturer known for their CO2 sensors.
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Below, in the "Supported Hardware" section, are links to a number of their sensors.
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CO2 is a gas which we humans exhale. It is also formed as a by-product from burning any carbon based substance.
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For example, burning gas or wood.
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It is important to keep CO2 levels low to create a healthy indoor climate.
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Typically one would aim for an indoor CO2 concentration of less than 700 ppm.
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The outdoor global CO2 levels are about 411 ppm and rising quite fast.
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Calibration
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-----------
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As with any sensor, CO2 sensors need calibration.
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That's why CO2 sensors are calibrated at the factory using highly specialized chambers with full control of the air entering those chambers.
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.. warning:: Do NOT!!! try to calibrate using the bCAL pin on the CO2 sensor, unless you know what you're doing.
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Many sensors may already have been destroyed or at least have their factory calibration cleared by improper calibration.
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CO2 sensors have at least two important calibration points:
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* 0 ppm, where the sensor is placed in a gas which contains no CO2.
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* 400 ppm, which is an approximation of the global CO2 levels (sadly already outdated).
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Apparently a number of sites and/or blogs instruct users to pull the bCAL pin to GND for a certain amount of time.
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On SenseAir sensors, this may trigger one of these calibration points to be set:
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* 4 ... 8 seconds: The current CO2 levels will be assumed to be the new "400 ppm" level.
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* 16+ seconds: The current CO2 levels will be assumed to be the new "0 ppm" level.
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As may be clear from the warning above, one should **NOT** try to do this!!
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It is very hard to create a proper 400 ppm CO2 concentration as simply breathing near the sensor will cause a significant rise in CO2 concentration.
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Other factors affecting the CO2 levels:
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* Industrial areas.
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* Busy roads.
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* Being in a city.
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* Near plants while the sun has set. (plants convert CO2 into O2 due to sunlight, but this process reverses while the sun has set)
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* Close to something burning. (e.g. cooking using gas, burning candles, wood fire, etc.)
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* Living creatures, like humans or animals.
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A NDIR CO2 sensor generates IR light of a specific wave length and measures the absorption of this light.
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Thus direct sunlight and/or heat from a stove, heater, etc. may affect CO2 measurements as this is adding extra IR light into the measurement.
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CO2 sensors typically have an Automatic Base Calibration mode (sometimes referred to as ABC mode, but it is unsure whether this is a trademarked name).
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With this mode enabled, the sensor keeps track of the minimal raw sensor value seen in some time period (e.g. 1 week).
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This new value is then considered to be the new 400 ppm value.
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SenseAir sensors will not immediately jump to this value if it differs a lot from the current value.
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So it may take several weeks (sometimes months) for a sensor to correct an incorrect 400 ppm level calibration.
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Therefore, again the warning: **Do NOT perform manual calibration using the bCAL pin**
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It may seem a bit strange to put all those warnings here, but it really happens a lot that people immediately start to damage CO2 sensors by trying to calibrate them while there is nothing wrong with the sensors.
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It is unclear as to why this happens to CO2 sensors over-and-over again.
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Maybe there is some popular blog out there instructing readers to do so.
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But please, **DO NOT CALIBRATE CO2 SENSORS using the bCAL pin**
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Supported hardware
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------------------
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.. .. |P052_usedby|
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:ref:`P052_S8_page`
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:ref:`P052_S11_page`
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:ref:`P052_tSense_K70_page`
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Sensor
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^^^^^^
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See: :ref:`SerialHelper_page`
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Commands available
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^^^^^^^^^^^^^^^^^^
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.. include:: P052_commands.repl
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.. Events
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.. ~~~~~~
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.. .. include:: P052_events.repl
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Change log
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----------
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.. versionchanged:: 2.0
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...
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|added|
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Major overhaul for 2.0 release.
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.. versionadded:: 1.0
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...
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|added|
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Initial release version.
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