When the measured pressure has a large variation range, and the maximum and minimum working pressures may not meet the above requirements at the same time, the maximum working pressure condition should be met first when selecting the instrument range. The standard series of electric oil pressure gauge measuring range are: -0.1-0.06,0.15; 0-1,1.6,2.5,4,6,10X10" MPa (where n is a natural integer. It can be positive or negative).

Generally, when the measured pressure is relatively stable, the maximum working pressure should not exceed 2/3 of the full scale of the instrument;

When the measured pressure fluctuates greatly or when the pulsating pressure is measured, the maximum working pressure should not exceed 1/2 of the full scale of the instrument;

In order to ensure measurement accuracy. The minimum working pressure should not be lower than 1/3 of the full scale;