I'm trying to put together an edge detection unit for a delay measurement unit using the CTMU of a PIC micro-controller.

The edge detection seems to work as shown in the image below, however i see a negative dip after the falling edge. I noticed that the dip is present in the Vcc power line as well. I think this is causing issues with my CTMU since its giving me negative readings for very short periods
Is it possible to remove this dip?

My setup is very simple for the result below. An arduino uno produced a pulse every 1us which is connected to an edge detection setup as shown below

I also noticed that the strange wave produced after the falling edge is visible on my PIC uP whenever a pulse is produced on a pin

 

Hello,

Do you use decoupling capacitors on the power lines of both chips?
Decoupling or Bypass Capacitors, Why?

The ringing that you see might be an artefact of the scope.

Bertus

 

Is the probe ground connected close to the point you are measuring?