FMX21

A hydrostatic level transmitter detects liquid level by measuring the hydrostatic pressure of the liquid. The core principle is based on the formula P = ρ·g·H + P0. When the liquid density remains constant, atmospheric pressure is introduced into the sensor's negative pressure chamber through a vent tube to compensate for atmospheric pressure (P0). The liquid hydrostatic pressure (P) is then proportional to the liquid level height (H). The process pressure directly acts on the internal sensing element, such as a ceramic process isolation diaphragm. The pressure compensation tube transfers atmospheric pressure changes to the back of the sensing element for compensation. The deformation of the sensing element generates a capacitance change proportional to the applied pressure. The capacitance variation is converted into a pressure-proportional signal, which has a linear relationship with the liquid level. After temperature compensation and linearization, the transmitter outputs a standard 4–20 mA signal.

Fundamental

The Waterpilot FMX21 transmitter uses an oil-free capacitive ceramic measuring cell for hydrostatic level measurement in the process industry and environmental applications. With HART output and adjustable measuring ranges, it features automatic density compensation to improve level measurement accuracy. Certified for drinking water measurement, it also offers an integrated temperature measurement function. Application versions are available for wastewater and sludge measurement.