Introduction to Level Measurement with Differential Pressure Transmitters

Most level measurement done is achieved through inference. Inferential level measurement techniques obtain a level indication by monitoring the pressure exerted by the column of liquid.
The pressure exerted at the base of a column of liquid is given by:

Pressure = Height of column of liquid * Density of Liquid * Acceleration due to gravity

               Pressure  =  H*D*g

In terms of weight density(N/m3), S, we can organize the above formula to read:

               Pressure = H*S

Because the specific gravity of a liquid can be expressed as the ratio of the weight of the volume of a liquid to that of an equivalent volume of water, in level measurement applications, we can define level as:

Level = Height * Specific gravity of liquid = H * S.G

Where H = Height of liquid to be measured
S.G = Specific gravity of the liquid

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