I have a dumb question to ask (for a lot of you) but it has been bugging me for a while and I need someone who can give me a clear answer. (I'm a second-year in electrical engineering.)
I am working on a project where I need to measure precisely the induced voltage due to AC magnetic field on a solenoid. The induced voltage is to be measured by DAQ via ADC. Working on the project brought up the question that I always had: Do we really need an analog filter if the signal is to be converted to digital?
Following the blueprint of the project, the signal needs to be amplified (sure) and then filtered (bandstop filter) before it is to be sent to the DAQ card. My question is whether this step is necessary at all. Can we not remove all the noise in the signal or unwanted frequency/time components digitally using Matlab or other software? My inkling is that some elementary analog filter is needed so that the signal is not too noisy for the digital signal processing to reproduce the original signal faithfully. (Let's also say I know what the spectrum should look like ideally.)
I do need to make the filter and I was planning on making a simple active filter with RC components and an op-amp to sort of smooth out the signal.
If my inkling is correct, why do we have lab-grade filters that cost tens of thousands of dollars when it can be done more cheaply using ADC, digital signal processing and perhaps DAC if we want analog in the end?
Any elucidation regarding my confusion would be greatly appreciated. Hopefully people can see where my confusion is coming from.
P.S.: For my project, I'm working at DC - <100 kHz range.