The new downsampling performed on the JS220 uses a sinc1 filter, also called a boxcar filter or a simple average filter. This filter implementation is straightforward. An output is computed once every N input samples, and each output is the average of the previous N input samples. The output rate is 1/N of the input rate.
The sinc1 filter is maximally smooth in time. It guarantees no overshoot, even on square waves. For applications where you are attempting to size the power supply current capacity, this filtering is ideal.
While the sinc1 filter is guaranteed to preserve DC accuracy, the sinc1 filter’s frequency response rolls off gently. You can easily encounter aliasing where higher frequency components are represented as lower frequency components.
The existing wideband filter, which is still the default, gives a much better and flatter frequency response while avoiding aliasing. However, the sharp cutoff in frequency results in ringing in the time domain. This behavior is known as the Gibbs phenomenon.
You now have the option to choose whichever filter is best for your measurement.
