Shielded computer keyboard
We have tried to shield the standard PS2 or USB keyboards with MuMetal or with aluminum foil. The MuMetal shield is difficult to make, because a large sheet of MuMetal is needed and it needs to have many holes punched in it, one hole for each key of the keyboard. It is also expensive because of the price of MuMetal. The result is equivalent to the aluminum foil, this is justified also by the fact that the electric currents in the keyboard's printed circuits are very low, so the magnetic field is also very low, so the emissions can be blocked by a conductive sheet like aluminum foil instead of a magnetic shield like MuMetal. The aluminum foil is cheap and quite easy to install, and the results are good.
From the exterior the keyboard is the same as the original, while inside it looks like the following picture.
