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Yes, unless you know for a fact that the DC voltage does not include any significant signal content above the Nyquist frequency (i.e., half your sampling rate).When we sample a DC voltage using an ADC or microcontroller, do we need to apply an anti-aliasing filter like in the case of AC voltages, please?
At some point in the future measuring the Vpp AC ripple might be useful, if you have an open channel.
If you're making a DC/DC switching converter, you need to be careful with the filter for measuring the output DC voltage. You certainly cannot treat it as DC, because if you don't control it correctly then it won't be DC. Instead, use a fast low-pass filter based on your sampling frequency. Also make sure that your sampling is not coherent with your switching/ripple - if you only measure the peaks of the ripple you will overestimate your voltage, if you only measure the valleys you will underestimate it.
I agree if "sampling rate" is how often you want to take a voltage reading to see a change, and not the intrinsic sample rate of the ADC, which is generally much higher.....................
Since the battery voltage varies slowly, the time constant is chosen based on ADC sampling rate; not necessarily based on the battery voltage rate-of-change.
Such steep filters are only needed if the upper signal frequency is close to 1/2 the sample rate.Typically Nyquist filters are defined by pass.band ripple <1dB and stop band attenuation> 80dB hence steep slope. These are used in telephony 8ksps with brick wall filters to pass below 3KHz , i.e. 7th order or so.
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or an 11 pole Elliptical filter
Sorry for the question: by fast do you mean "steep"?
Good system should sample about 10 times faster than the Nyquist frequency.
His task is opposite. He wants to remove unwanted noise. This pretty much can be done in software by some sort of smoothing, such as FIR filer. However any high frequency components (above the Nyquist frequency, which is the sampling rate divided by two) cannot be filtered out of the signal after the sampling is done (no matter how sophisticated your software is). Thus, it is necessary to have a hardware filter which will remove everything above the Nyquist frequency before the signal is sampled. Using hardware filters to remove components with lower frequencies is not a good idea because even if you want to remove them, you can do it in software without any need for hardware changes, which gives you much more flexibility.