How does a flow monitor for liquid media work?
In order for a flow monitor for water to permanently measure the flow rate of a liquid, it works with functional principles that differ depending on the model.
- Thermal principle - also known as the calorimetric principle
A thermal flow monitor for water uses a heated temperature sensor and another, which is not heated, as a reference. When there is a flow, the heat is carried away from the heated sensor. The difference between the two sensors provides information about the flow rate. If the liquid is not flowing or the flow rate falls below a certain value, the temperature differential changes, triggering an alarm or controlling a system.
Flow monitors for liquids from SEIKOM Electronic rely primarily on this measuring method due to the high accuracy and the fact that no moving parts are used.
- Mechanical principle:
A frequently used functional principle of a flow switch for water is the so-called paddle switch. Here, a paddle is immersed in the flow of liquid. When the liquid flows at a sufficient speed, it pushes the paddle in a certain direction. A switch detects the position of the paddle. If the flow rate falls below a set value, the paddle moves back to its starting position and activates the switch.
Experience has shown that paddle guards are comparatively maintenance-intensive, as the paddles can become stuck due to foreign bodies or increasing corrosion.
- Electronic principle
Flow monitors for water can also use the principle of inductive or capacitive detection. In this case, the flow is monitored by the change in electrical properties, such as inductance or capacitance, which are influenced by the flow velocity.
- Differential pressure principle
In some systems, the flow is routed via a throttle point in the pipe. The resulting pressure difference before and after the throttle point is proportional to the flow rate. A pressure switch that reacts to this difference can be used here as a flow monitor for water.
Where no floats can be installed, electromagnetic flow monitors for water are suitable. However, these can only be used with liquids that are electrically conductive. A magnetic field is introduced into the pipe system. A high electrical voltage is then applied. When the medium flows through the pipe, the magnetic field is activated and the flow rate is measured.