A 16-bit data acquisition board input range can be set to various ranges like +/-10V or +/-0.5V ect.
If our input signal’s range is +/-0.3V with a noise floor of 1mV does it make sense to set the range to +/-0.5V instead of +/-10V?
For +/-10V range the ADC resolution becomes 20/(2^16)=0.3mV. And for +/-0.5V range the ADC resolution becomes 0.015mV. But our noise floor is 1mV.
Can we say the DAQ input range here doesn't have any effect on the overall resolution?
Best Answer
Noise would not typically be what determines your input scaling. You should aim to condition your input signal (whatever it is) in a way that fits your application (whatever that is) and, in doing so, match it to the chosen range of your ADC. Looking at signal to noise and ADC resolution is all a part of that, and must be considered from a system point of view.
So long as you keep the "information" part of your signal above whatever noise is present, and your DAC has enough resolution to preserve it, you did what you need. It's often the case that the 12 or 16 bits of a DAC is much more than needed for the app anyway, and system noise is greater than one LSB - but that may not be an issue.
Other factors (such as what system power supplies are available and their quality) also play a part.
For example if you are making a high end audio DAC, you have a totally different set of goals and constraints compared to a designer of a strain gauge amp for mechanical measurements.