Nor-Cal CDG 160 OP Lit - Manual (Page 30)

30 CDG160-OP-LIT (2010-06)
4.4 Activating the Factory Setting (Factory Reset)
All user defined parameters (e.g. zero, filter) are restored to their
default values.
Loading of the default parameters is irreversible.
Loading the default parameters:

Put the gauge out of operation.

Keep the <ZERO> button depressed for at least 5 s while
the gauge is being put into operation (Power ON).