disturbed recording of moves DGT Smartboard

[Jonathan003]

I use my DGT Smartboard to record games being played on it face to face with someone. The recording of the games works fine unless there is material on the table that interferes with the electromagnetic signal. Like a metal or brass plate lying on a wooden table. I wonder if there is a material that I could use to shield the disturbance of the magnetic signal? Some material I can bring to put between the board and the metal or brass plate.