Pressure P(liq) on any surface and container walls at depth h, by the liquid of desnity d, is:
P(liq) = d × g × h + P(air)
where P(air) is the air pressure and g is the acceleration due to gravity (constant for a given place) at the place of liquid container. Replacing constants the equation becomes:
P(liq) - P(air) = K × h in short: Pressure difference represents liquid level. One convenient unit that clubs pressure with level is mHO (pressure felt at depth inmeters while being immersed in water) Trumen hydrostatic pressure transmitter utilizes pressure exerted by liquid P(liq) and substract it by air pressure P(air) using a single pressure sensitive diaphragm and air-vent in connection cable. As Trumen hydrostaticpressure transducer is immersed deeper in the liquid, the P(liq) becomes higher than P(air) and the diphragm minutely deforms.
This diaphragm deformation can't be seen visibly, but it is caught by piezo-resistive sensors secured on the sensitive diaphragm.
Thus pressure exerted by liquid is sensed by Trumen hydrostatic sensor which is directly denotes the depth from the surface of liquid.
P(liq) - P(air) = K × h