# What Effect on Hydrostatic Level Transmitter if Liquid Density Changes?

The lever transmitter (LT) in this level control system is hydrostatic; i.e. it senses liquid level in the vessel based on the hydrostatic pressure exerted by the liquid’s height in the vessel:

## Hydrostatic Level Transmitter

Suppose the density of the liquid within the vessel decreases. What effect will this have on the controlled liquid level?

In other words, what will the liquid level inside the vessel do over time in response to this change in density?

Be sure to explain why the level will be affected (or not affected), not just what will happen to the level.

Credits: Tony R. Kuphaldt

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## 4 thoughts on “What Effect on Hydrostatic Level Transmitter if Liquid Density Changes?”

1. If the density of the fluid changes, so the Level Transmitter will identify the level different that the real measurement of the Vessel. Density has a direct impact on volume by the formula is d = m/V.

2. The transmitter is deriving level form a pressure measurement.

In this case Pressure = ρgh (density x gravity constant x height)

A change in density will increase or decrease the pressure measured.
In effect there is more or less weight on the diaphragm of the transmitter depending on how dense the liquid in the tank is.

3. Hola,

Si la densidad disminuye, el transmisor LT lo interpretará como una disminución del nivel debido a que la presión medida se ve afectada por la densidad según la siguiente ecuación: P=h*g*d = m*m/s^2*kg/m3 = N/m2; debido a está variación en la medida el lazo de control LIC tratara de reducir la salida de la válvula para mantener el SP anterior a la reducción de la presión.