Imagine that you have a sensor, and that the sensor output is corrupted by noise.  An example of a situation like that could be a pressure sensor at the bottom of a tank of liquid.  If there is liquid being pumped into the tank, the pressure signal would have a noisy component due to the turbulent swirling as the liquid enters the tank.  The sensor has an output voltage as shown below.

The voltage from the sensor might look like the one you can generate below by clicking on the "Start" button.

Now, if this is the output of the sensor, it may not be particularly useful.  We need to filter the noise from the signal.  The filter would be added as shown below.

The next simulator shows how the filter reduces the noise.  In the simulator you can set the time constant of the filter.

        The sensor output voltage is 2v corrupted by noise that fluctuates generally within +/- 0.2v of 2.0 v.  You can set the filter time constant before a run.  Click the "Clear" button to clear, then start the simulation again.

        Here the situation is different.

• The sensor output voltage is 2v with a sinusoid added.  The sinusoid has an amplitude of 0.4 v.
• the sensor output is corrupted by noise that fluctuates generally within +/- 0.2v of 2.0 v.
• You can set the filter time constant before a run.  Click the "Clear" button to clear, then start the simulation again.