1. 1D UltraSonic Anemometer Preliminary Design Review by Vanessa Dubé Michael Jao Chethan Srinivasa Robert Vice

2. Outline • Background • Project Specifications • Preliminary Design • Proposed MDR prototype specifications

3. Background • What is a Sonic Anemometer? • Device that measures wind speed • What will be our tasks? • Measure small wind speed • Generate our own frequency • Make it inexpensive and as light as possible

4. Block Diagram Speaker/Receiver Receiver/Speaker Trans 1 Trans 2 Frequency Generator PIC Stop Counter Start

5. Possible Errors • Transducer angular offset • Negligible because change in angular offset has relative effect • Chip Delay • Average of several hundred measurements taken every second • Phase Shift of Wave • Same wave point starts and stops counter

6. Project Specifications • Send and Receive ultrasonic signals across transducers, that are not affected by noise • Accurately measure time it takes to send a signal from one transducer to the other • Measure low wind speeds.

7. Preliminary Design • Familiarize then Test and Implement Send/Receive transducers, minimizing noise • Experiment with air flow generators to simulate wind • Implement counters along with other circuitry to calculate time delay of sine waves • Use simple methods to calculate wind speed, thus verifying our experimental anemometer

8. Prelim. Design (cont’d) • Design amplifier to optimize peak-to-peak voltage of received signals • Try to use minimal voltage to trigger counter

9. Initial Calculations • Assume: vwind = 1 mm/s, d = 1 m Calculate Dt and then take the inverse to find the desired counter frequency V1-V2 = (.001)*2 [m/s] Now, calculate t1 and t2: t1 = 3.030303 [ms] t2 = 3.030284665 [ms]

10. Initial Calculations (cont’d) Dt = t1 - t2 = 1.8365e-8 [s] So, frequency is 1/Dt : 54.45 MHz Nyquist Frequency = 2*54.45 Frequency = 108.9 MHz 27 bit register

11. Proposed MDR Prototype Specifications • Have an experimental anemometer that can measure small wind speeds • Minimize POWER and WEIGHT