# Magnetic field around the printer

I'm using a low voltage active screwdriver that is sensitive to magnetic fields.

It is weird, even I put a metal piece on the glass over the heated bed and check it with the pen, it lights fully. If I hold the pen on air anywhere nearby, it is weak but still lights a bit.

My cards and PSU are not mounted on the case. I also grounded my PSU with a small cable from G to V-. So, what could be the reason? Is that normal for such complicated devices? Just curious.

• What is a "low voltage active control pen"? – Tom van der Zanden Jun 18 '17 at 14:01
• I will replace 'pen' with 'screwdriver'. It is simply a screwdriver with voltage detector for DC, much like the one here – morevitamins Jun 18 '17 at 16:21
• If it's detecting DC voltage, that is not being sensitive to a magnetic field. If it truly detects magnetic fields, I'd suspect the perms in the motors. – Carl Witthoft Jun 19 '17 at 12:17
• It is possible I might be overreacting this as well. Those screwdrivers are too sensitive after all. – morevitamins Jun 19 '17 at 19:05