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Kategorie: Diplomové, bakalářské práce |
Tento dokument chci!
Práce popisuje principy a problémy při realizaci ultrazvukového anemometru. Je popsán princip výpočtu rychlosti větru a následné korekce výpočtu. Pro realizaci jsou využity ultrazvukové sensory a microcontrolér ARM Cortex-M3. Práce se zabývá generováním PWM signálu, jeho analogovou filtrací, zesílením a odvysíláním. Na přijímací straně jeto nízkonapěťový zesilovač a komparátor. Vyvíjený kód je popsán pomocí vývojového diagramu.
Illustration 2. Thermistor with resistor
create voltage divider. Analog is
connected microcontroller built converter.
There are two types thermistors [10]:
● PTC Positive temperature coefficient. One side connected the ground and the other ADC
reference, our case 3,3 With the lowest temperatures the impedance thermistor
will near infinite and ADC will measure near the other hand the higher
temperature put impedance near values and will measure 3,3 with ADC.where [-] temperature coefficient and [K] change temperature. The resistance increase with increasing
temperature and temperature coefficient positive. Hence the measurements temperature between stated values can be
enumerated with linear approximation equation calculation stated above. Data-sheet of
this component has complete table impedance for each change within the whole
range. [11]
We can see most simple way how connect thermistor with microcontroller on
image above. It’s from Arduino temperature measurement test application. Its resistance
in 25°C ambient and measurement range -40 125 °C.
For purposes our application, NTC thermistor Vishay was used. Temperature coefficient negative. Thermistor has
± diversity impedance value, degree calibration will necessary.11: Thermistor connection [12]
12
. The resistance decrease with increasing
temperature.
● NTC Negative temperature coefficient
