The software SDSoft proposes a table with some possibilities:

• choice of pressure min
• choice of pressure max
• pressures read on the reference manometer

The standard EN 13790  recommends a deviation of max  +/- ...

• 0,2 bar between 1 and 2 bar
• 10 % for pressure > 2 bar 
  

The pressure is adjusted on the working manometer to the value indicated in the table, in such a way that the needle is located opposite a graduation. The real pressure is read on the reference pressure gauge (more precise) and is introduced in the table.