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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.
Temperature coefficient negative. The resistance decrease with increasing
temperature. Its resistance
in 25°C ambient and measurement range -40 125 °C. Thermistor has
± diversity impedance value, degree calibration will necessary.11: Thermistor connection [12]
12
.
For purposes our application, NTC thermistor Vishay was used.where [-] temperature coefficient and [K] change temperature.
There are two types thermistors [10]:
● PTC Positive temperature coefficient. Thermistor with resistor
create voltage divider. It’s from Arduino temperature measurement test application.
Illustration 2. The resistance increase with increasing
temperature and temperature coefficient positive.
● NTC Negative temperature coefficient. 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. Analog is
connected microcontroller built converter. 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. [11]
We can see most simple way how connect thermistor with microcontroller on
image above
