The "holding cap" is disconnected from the input during the conversion time. After the conversion it is automaticly connected to the input pin again. Now, if the voltage on the input pin has changed conciderably during the conversion, I'd guess that you need a new acquisition time to let the holding cap re-charge to the new input voltage, before starting a new conversion, not ? Jan-Erik. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist