When You configure a Channel in the above mentioned oscilloscope, then you can find one option as "Noise filter" which is further given in terms of bits (1 bit, 1.5 bit, 2 bit et.c). So what is meaning of that bits and purpose of Noise filter in oscilloscope. How it gives more cleaner waveforms ?
Hello Nandan,
It should be noted that the modern digital oscilloscopes now use high speed ADCs (or Flash ADCs to be precise) to sample signals in GSPS ranges. Also FPGAs are used to implement digital filter to remove noise from the signal.
Now coming back to your question, indeed your scope must be sampling the input and applying digital filter to it. Suppose you are using a 10bit ADC, the least significant bits would be dancing to 1s and 0s which in real sense may be noise and not the actual signal components. Therefore in what an ADC is specified in terms of its quality is the ENOB or Effective Number of Bits. That means, after you apply a digital filter, the real "Essence" of the signal is not 10-bits ( as from your ADC) but an effective value of 9bits or 8 bits. Thus the effectiveness of the filter to result into a quality of signal is 1bit (when 9-bit result is available) or 2-bits (when 8-Effective bits of information is useful).
When you refer the datasheets of the high -speed sampling ADCs the manufacturer always state the ENOB parameter which is a very important factor to be considered in Signal Processing Applicaitons.
Also, please do not confuse with the digital filters (FIR or IIR) that we use commonly in our DSP applications. The oscilloscope uses a primary filter to remove any noise fluctuations to give a better or cleaner signal as you are experiencing.
I have tried to put the info in a simpler way that I could, and hope that it is useful to you.
Thanks and best luck!
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