The Problem:
Rotameter RAMC is often used in critical applications where safety is paramount. RAMC has the option of low flow alarm outputs. A low flow contact is set and an alarm is activated if flow drops below the minimum level. But what happens if the float is mechanically blocked? The meter works wrong and the blocked float cannot be seen through the solid S.S. tube !!

Under normal flow conditions the guided float tumbles round its center of gravity. This generates small movements of the pick up magnet. This fluctuation is measured by the Microprocessor. Below are typical fluctuations

The mechanically blocked float does not generate small movements of the pick up magnet. These Zero -fluctuations are measured by the Microprocessor. If these are under a certain level, the alarm current is set. The level is determined during an Autozero adjustment.

The Zero-fluctuations are recorded under no flow condition when the float is at the rest point (Autozero). A level for minimum fluctuations including a safety factor is generated.