| ??? 07/04/06 13:05 Modified: 07/04/06 13:21 Read: times Msg Score: +1 +1 Good Answer/Helpful |
#119615 - 24bit accuracy can never be achieved Responding to: ???'s previous message |
Christoph said:
True, but drift effects might be irrelevant (for example, if the signal is filtered with a highpass filter later on),... Random drift effects cannot be eliminated by any kind of filtering! Drift changes the gain and offset setting and is hidden unless you recalibrate your set up. Assume someone wants to achieve 24bit precision. Then, all his electronics must not produce an additional inaccuracy of more than 0.06ppm!! But if you have a look at analog components you will find for instance, that a high quality metal film resistor shows a temperature drift of up to 50ppm per °C. So, the temperature drift of only one such resistor at only 1°C temperature deviation creates an error, which is about 800 times higher than allowed. Long term drift of such a resistor is about 2ppm per day, which is about 30 times too high. And this is the performance of only one resistor! You can choose some better resistors, of course, showing some less drift than the candidate above. But even with the most precise resistor of the world you will never achieve 24bit accuracy. Even not if you recalibrate your set up every 10 seconds or so. Not even mentioning, that the reference must show an accuracy of even higher than 24bit... Kai |
