Hello guys I am interfacing around 10 analog sensors with esp32 wroom 32d module and I want to design an ADC filter circuit that can pass 2000 hz approximately. It would be helpful if someone suggests a filter design or anything that can help since I worked mainly with digital design and microcontroller programming and not good at this.
I appreciate your suggestions.
What's the stopband specification - passband DC to 2kHz is clear, but you need to specify a stopband too.
pass 2000 hz approximately
Does that mean that the filter will pass frequencies below 2000Hz, above 2000Hz or a band around 2000Hz? How do you get the 2000Hz value? How fast must the filter "roll off"?
Generally filtering for an ADC is to reduce the effects of aliasing. Aliasing occurs when a frequency above the Nyquist frequency (sample rate / 2) is input to the ADC. So an anti-aliasing filter is a low pass filter with a cut off near the Nyquist frequency. The number of poles determines determines the roll off rate.
An anti alias filter tutorial.
There are lots of tutorials on filters on the net.
The cutoff has to be well below the Nyquist frequency, the stopband must start at/before the Nyquist frequency
which is why I mentioned it.
Yes I mean it should pass below or equal to 2000 hz signals and not above. Yes it is anti aliasing circuit.
So, you want a low-pass filter.
Set R equal to the value of Xc
(the capacitive reactance) at
the cut-off frequency.
Herb
Workaholic:
Yes I mean it should pass below or equal to 2000 hz signals and not above. Yes it is anti aliasing circuit.
Typically for an anti-aliasing filter, one needs to specify both the passband range, and the range in which out of band signals are sufficiently attenuated (stopband). Thus parameters are passband cutoff, passband flatness, and stopband.
From the link provided in post #2:
Typically the middle of the transition region is at least half the sampling rate so that the stopband does not alias back into the passband in the digital domain.
Alternately you might describe what are your sensors and how fast you'd like to get updates and the requirements could reasonably be derived from that information.