Flow switches are used for the display and monitoring of the flow of liquid and gaseous media. The instruments feature a high switching accuracy and functional safety, low switch hysteresis and continuous switch point setting by the user.
Electronic flow switches offer the operator a local display of the flow values and, at the same time, an output of an electrical signal (PNP, NPN or 4-20 mA) for transmission to a remote control room. Thus, flow switches are used for the display and monitoring of the flow of liquid and gaseous media.
How do flow switches work?
The FSD-4 flow switch is based on the calorimetric measurement principle. The temperature difference that occurs due to the cooling effect of flowing media is measured here. The flow rate can thus be calculated on the basis of the temperature difference.
Furthermore, the design of these flow measuring instruments allows exact monitoring of the temperature without the need to set up an additional measuring location. Calorimetric flow switches are also known as thermal flow monitors and are ideal for monitoring coolant circuits or for controlling filter units. Flow monitors / flow switches do not need any auxiliary power and work on the float measurement principle. A float activates a reed contact as soon as the flow velocity exceeds a preset value.
What are possible areas of application for flow switches?
Corrosion-resistant materials enable applications in areas such as the chemical industry, machine building, the pharmaceutical industry and in medical engineering.
How does a flow switch with the mechanical paddle principle work?
Electromechanical flow switches based on the paddle principle transmit the movement of a fluid to a switching element via a paddle mechanism. This transmits a signal as to whether the medium is flowing or not ("flow/no flow"). Flow switches with mechanical paddle principle are mainly used in wet sprinkler systems to signal the start of flow, or in heating and cooling systems to signal flow interruptions.
How are electronic flow switches different to paddle-controlled flow switches?
Electronic flow switches determine the flow via a calorimetric measurement principle. The cooling of a heated element is proportional to the flow rate of the fluid. With a known pipe cross-section, this yields the flow volume, which is specified in cubic metres per second (m³/s), for example. One advantage is that, with electronic flow switches, there are no moving parts - the measurement is made via a sensor rather than a paddle. This ensures wear-free monitoring of the flow. The model FSD-4 electronic flow switch from WIKA not only measures the flow, but also the temperature of the medium using the calorimetric measurement principle. It can thus be used both as a flow switch and as a temperature measuring instrument.
