Low pass filter

What it does

Low pass filters can be used to reduce measurement noise and clean up your waveforms.

Each of your PicoScope channels can have a low pass filter operating at a different cutoff frequency so the waveform present on each can be filtered differently, or not at all.

The low pass filters are applied to the data in each complete waveform buffer (the part of the oscilloscope's memory that stores a chunk of data) after the measurements have been captured; you will not see the filtering effect until after the buffer is full.

How it can help you

Every measurement contains noise to a greater or lesser extent depending on the part under test and test conditions.

Where the noise is excessive and stops you from being able to determine whether a waveform is good or bad, the Low pass filter feature can clean them up so you can compare them to other reference waveforms and make more sound diagnostic decisions.

Excessive filtering, where the cutoff frequency has been set too low, may remove important measurement characteristics and prevent proper evaluation. So there is a balance to be found between acceptable levels of noise and the degree of filtering.

If your non-PicoScope oscilloscope displays waveforms which are almost always entirely free from noise then it is likely to be filtering them without your knowledge, which could cause you, unknowingly, to make incorrect diagnostic decisions.

How to use it

Open the Channel Options panel for the channel on which the Low pass filter will be applied and select the DSP tab.

Within the Low pass filter section, you can activate or turn off the feature and select the cutoff frequency as required.

An animation showing how to use the Low pass filter feature in PicoScope 7 Automotive