The left digits are the height from the easel to the head and the right digits show the length of the bellows for focus, both are in cm to one decimal place. I prefer to note these two figures rather than take a reading from the column. When not being used it reverts to a 24hr clock. The sensors are ultrasonic with slightly different sampling systems for each one since one only needs to measure a small distance.
The unit uses a dht22 to correct for temperature and humidity in order to account for variations in the speed of sound due to changing conditions in the room.
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