Why instrument pressure signal measured from 3 psi not from 0psi?

Measuring pressure signals starting from 3 psi instead of 0 psi often indicates a specific application requirement, such as avoiding the effects of atmospheric pressure or ensuring that the pressure sensor operates within its optimal range. This approach can help improve accuracy and sensitivity, as many sensors have a minimum pressure threshold below which they may not function reliably. Additionally, it may be necessary to maintain a certain baseline pressure to prevent cavitation or other issues in fluid systems.