About ADC and DAC conversions?

[Surender Reddy]

if we convert a analog value into digital value,then again convert it into analog value ,
can we get same analog value? or any data loss?
any data loss! why?

 

[genboo547]

certainly,there is data loss.Because in the a to d conversion we use quantization mechanism(where round off is occurring).

 

[Tahmid]

genboo,547 has said it above. Another important factor is resolution. I'll explain with an example.

Say you're using an 8-bit ADC (for example) and have an input of 2.756V. The ADC reference voltage is 4.096V. So, the ADC reading is 171. Say you're using an 8-bit DAC with reference of 4.096V. So, the DAC output now is 2.747V. Now, it gets worse if you're using a, say, 5-bit DAC. Then, the ADC reading is scaled for 5-bit to 20. Then, you get an output of 2.643V. You just lost 0.113V due to rounding off.

However, this data loss/error can be minimized if you use a high-resolution ADC and DAC. Even 10-bit is good.

Hope this helps.
Tahmid.

 

[Pheetuz]

Another factor that is worth taking into account is the signal to noise ratio of the analogue voltage that you trying to measure, there is no point in having a 16bit A2D converter that can measure a 76uV change of signal over a 5V range if you have a signal with 1mV of noise on it, you would just be quantising noise!
It all depends on the signal that you are trying to measure, A2D and D2A conversion is a very interesting topic in itself with a lot factors having a major effect on the quality of your signal, such as the frequency of the signal you are trying to measure.