Iwatsu SS-500 Series Instruction Manual page 38

Preparing for Measurement
6
Wait for 30 minutes or more.
Wait at least 30 minutes after starting to supply power to
the SS-530/SS-531 to accurately measure a current before
executing demagnetization and automatic zero-
adjustment. See "Executing demagnetization and
automatic zero-adjustment" (p. 3 3).
32

Do not execute demagnetization and
automatic zero-adjustment or measure current
immediately after starting to supply power to
the SS-530/SS-531.
An offset voltage may increase due to the heat
generation of the SS-530/SS-531.