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 Trans 1Trans 2 Speaker/Receiver Receiver/Speaker Counter Frequency Generator PIC Start Stop

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: v wind = 1 mm/s, d = 1 m Calculate  t and then take the inverse to find the desired counter frequency V 1 -V 2 = (.001)*2 [m/s] Now, calculate t 1 and t 2 : t 1 = 3.030303 [ms] t 2 = 3.030284665 [ms]

10. Initial Calculations (cont’d)  t = t 1 - t 2 = 1.8365e-8 [s] So, frequency is 1/  t : 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