Pressure difference that occurs on a new, clean filter, if a specific flow rate is passed through it. It is dependent on the layout of the filter element and the filtration grade as well as the viscosity and the magnitude of the flow rate flowing through the filter.
The dirt holding capacity of a filter and with it the pressure difference of a filter have upper limits. Both are higher the smaller the initial pressure difference. It is therefore an important parameter for the selection of a filter.
However, on its own the value does not say much. In addition information on the dirt holding capacity of a filter is necessary, as a filter with a low ΔpA can clog quicker than a filter with a higher ΔpA (see filter life).