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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.
Used capacitor has nF
and resistor 390 This values shift cutoff frequency 40,8 kHz. Lower frequencies will attenuated. set amplification
with resistor and 80kΩ feedback resistor R2.
Slew rate V/μs and permit amplify frequencies till MHz [6]. For
this purpose was designed second order low pass filter. These values amplify signal by
28.
3.
For amplification used operational amplifier TL071 Texas Instruments. That’s amplification. Instead evaluation board PWM
generator takes place artificial pulse generator.
We can see connection this circuit image below. and volts set low and high
level pulse. Another ones are odd multiple the first one. Cutoff frequency with
capacitor and resistor 470 33,9 kHz. So
we would like eliminate 120 kHz, 200 kHz and higher harmonic components. This was created Pspice
software Orcad for the purposes simulation. PER period the generating signal and its width, both μs. For
elimination component was chosen high pass filter. Results measurements and calculation wind speed are printed the
TI evaluation board built Screen.Temperature sensor used correct airspeed reach better precision calculated
wind speed. First harmonic
component frequency kHz. TR
and are rising and falling edge width.
Square wave signal composed from many harmonic components.2 PWM filter and amplifier
Signal from PWM generator has high level 3,3 and low use whole
potential transmitter have adjust this PWM signal obtain kHz harmonic
signal with amplitude peak peak. will use
symmetrical power supply with non-inverting connection. That’s per octave, the third harmonic component will be
attenuated [7]. It’s
commonly using low noise power amplifier with power supply voltage till ±18 [6].
14
. Used filter has dual
attenuation.
Our PWM signal square wave signal with component 1,65 DC
component not suitable for usage with symmetrical power supplied amplifier
