3D Upfitters Temp Sensor Instrukcja instalacji - Strona 7

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VOC Sensor Calibration

Warning: Do not place touchscreen in direct sunlight! It is designed to be used indoors.

You can calibrate outdoors as long as its in the shade.

The button in the middle is the air quality reading from the SGP30 air quality sensor board,

which measures TVOC (total volatile organic compound). Typically we see values of up to 500

ppb (parts per billion) inside an enclosure when printing ABS and half that when printing PLA

depending on the particular brand of ﬁlament.

The VOC sensor uses a MOS (Metal Oxide Semiconductor) sensor to track VOC levels. A MOS

sensor is a small metal plate coated in various materials which allow it to attract or repel

speciﬁc types of molecules. A constant charge is applied to one side of the MOS plate, and the

resulting resistance is read on the other side. Resistance temporarily increases as molecules

bounce oﬀ the plate, and this change in resistance is logged and fed into an algorithm to

calculate the VOC parts per million.

When you start the touchscreen for the ﬁrst time, the VOC sensor will go into calibration mode

for 12 hours and assume that the surrounding air is a clean baseline, i.e., no 3D printing, laser

cutting, or other air pollutants. Why is the ﬁrst 12-hour calibration necessary? The ﬁrst time

your device is powered on, it has no preexisting baseline, so it must ﬁnd one. Because each

sensor has atomic-level diﬀerences due to the manufacturing processes, each has a unique

baseline resistance. Running the sensor for 12 hours initially allows it to come into contact with

ordinarily occurring VOCs (and other molecules regularly found in its environment). So it will not

VOC Sensor Recalibration

Why might be recalibration necessary? Over time, as molecules bounce oﬀ the MOS plate, the

coating slowly degrades, and molecules may become 'stuck' to the plate. The molecules

gradually increase the resistance by sticking to the MOS plate, which reduces sensor accuracy.

To counteract this, recalibration is occasionally required. By recalibrating the VOC sensor, a

new baseline will be created, and all future values will be compared to that baseline and

adjusted accordingly. Recalibration should only be run while the air is as VOC-free as possible.

To recalibrate the sensor, go to the Info Page (press the 'i' in the top-right of the screen), and

then press the "Recalibrate" button - it should ﬂash green. For the next 12 hours, the main

page's VOC button will display "Calibrating."