Define analogue to digital conversion

DEFINE ANALOGUE TO DIGITAL CONVERSION?

·         ADC is characterised by its sampling rate and the number of bits output

·         Sampling rate – is the number of times a second that the input analogue signal can be sampled and digitised

·         Number of bits output – is the number of bits used to quantize the input analogue signal

·         Conversion from analogue signal to digital signal causes a loss of information. This loss is due to sampling and quantization. (The minimum sampling limit is the Nyquist limit – ensures accurate representation of signal.)

·         Quantization also causes loss of information. Analogue signals may  take on  any value between minimum and maximum. A digital signal is limited to a finite/discrete number of values (– 2ⁿpossible values).

8 BIT VS. 10 BIT CONVERSION?

                8 Bit                                       10 Bit

                                1V/2⁸=1V/256                              1V/2¹⁰=1V/1024

Loose info           ++                                           +

Speed                   Faster                                   Slower

Accuracy              lower accuracy                  better accuracy

               

Image memory -                                              Increase

Disc space           -                                              Increase

Cost                       -                                              higher cost

Use                        Fluoroscopy                       CT and other….