Analogtodigital Conversion and Digitaltoanalog Conversion with DSP ES3

Analog-to-digital Conversion and Digital-to-analog Conversion (with DSP) ES-3

A very simple (…too simple!) Digital-to-analog converter 8 R V 1 V 2 V 4 V 8 VOUT 4 R 2 R R 8 R

A simple Analog-to-digital converter Analog Input + - scitec. uwichill. edu. bb

A simple Analog-to-digital converter Analog Input 3. 5 v + - high low 0 v 1 v 2 v 4 v 3 v 00000100 000000 11 01 0 Improve accuracy: scale the DAC scitec. uwichill. edu. bb

Nyquist Sampling Rate The sampling of data must be at least twice the rate as the maximum frequency of the analog signal: fs>2 fmax V(t) Time, t Use a low pass filter with fc = fmax to remove harmonics sine

Nyquist Sampling Rate The sampling of data must be at least twice the rate as the maximum frequency of the analog signal : fs>2 fmax V(t) Aliasing Time, t

Digital Signal Processing

Running average of 10 pts

Digital Filtering Removing Noise and Interference from a Digital Signal Find the average of N points

FFT of a noisy sine wave and its digitally filtered signal sine + noise filtered noise

DSP Example

Simple Notch Filter to remove 60 Hz interference Vin(n) f. S = 1440 samples per second 60 Hz sine t (s) 1/60 s Vin(n-12) Vin(n) Vout(n) = Vin(n) + Vin(n - fs / 2 fnotch) = Vin(n)+Vin(n-12) This adds the sample that is 1800 out of phase at 60 Hz

Matlab demo es 3_60 Hz. m