Interestig,
but there is only enob definition and not its pratical menaning; also
there ins't any definition of noise free resolution. For example, what
means:"enob of an adc 12 converter is equal to 11 bit"? and "noise
free resolution of a 12bit adc is 10 bit"?
Thanks
The least significant bits of an A-D converter have some level of
uncertainty because an analog level may fall between two steps of the
digital output - the A-D converter may hunt between the two levels,
thus there is "noise" in the output. When measuring with a 12 bit
ADC, even the circuit layout and the wiring can affect the reading and
the accuracy of the lowest bits of the measurement.
Very simplified examples:
A-D converter measures in 0.1 volt steps.
Analog input varies by 0.05 volt.
Which step does the A-D converter put out?
The 0.1 volt step below the actual value?
The 0.1 volt step above the actual value?
The circuit is exposed to outside interference (RF or AC). How much
does the output change in response to the interference?
The input of the ADC is high impedance and the conductance of the
circuit board is affected by moisture. How much does the output
change when the humidity is 95% ?
John
