DC magnetic fields can develop in many steel or iron objects if they have been exposed to magnetic fields, current, or friction.
This App detects residual magnetism in steel parts quickly and accurately. Simply place the device edge near or against the object being tested, to have a reading representing the magnetism in the object at that site as well as polarity. Will also possible to verify thoroughness of de-magnetizing.
Check out your car, bed frame, desk furniture or any other metal objects you spend time with.
Can also be used to check the strength of magnets.