Why bridles pipe are not accurate when measuring liquid with different density.
A simple calculation to show error in level measurement by bridles.
Pv + ρoil g H1 + ρwater g H2 = Pv + ρoil g H1* (1)
Pv + ρoil g H1 + ρwater g (H2+ Htap) = Pv + ρoil g(H1* + H2*) + ρwater g Hwater (2)
Equalizing the formula:
ρoil H2* = ρwater H2*
Clearly it is a contradiction since both oil and water density could not be the same, under same temperature and pressure.