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