| ??? 11/02/11 14:00 Modified: 11/02/11 14:03 Read: times |
#184517 - Good Advice Responding to: ???'s previous message |
Per Westermark said:
Low or high quantity - I would recommend a single ADC with multiplexed inputs.
It will normally give less variance between the multiplexed inputs, that multiple ADC does. Remember that multiple ADC requires you to connect your single voltage reference to all ADC in a noise-free manner. Next thing is that a single ADC means that you have a single set of errors from nonlinearity, and non-uniform step sizes. With multiple ADC, they can have different characteristics. This is good advice. I mentioned it before but it seems to have been lost in the non-linear noise of this discussion. See here http://www.8052.com/forum/read/184455. The single A/D, with a single reference voltage source, is almost a necessity when you decide to do the summations in the MCU firmware. The separate A/D idea for each channel leads back once again to there being multiple paths, each having its own error budget, that make any possible compensation and calibration more complicated. Now of course if each A/D and its attached reference voltage were perfect components you could do almost anything you wanted. But by now most of us know how far from perfect these things actually are!! Michael Karas |
