Principle of operation
A suspended body is introduced into a cylindrical slotted nozzle. Depending on the model, the installation of the flow monitor is either dependent on its position (only with suspended bodies) or independent of position (suspended bodies with spring). A reed switch is connected, external to the flow circuit and is sealed into a free-adjustable housing (switch housing), thereby protected from external influences. The incoming medium moves the suspended body in the direction of flow. If the suspended body, with its integrated magnets, reaches the position of the reed switch, the contact studs close. If the rate of flow becomes greater, the suspended body will move further in the direction of flow, with the maximum movement limited by a stop, which prevents the suspended body moving beyond the switching area of the reed switch (bistable behaviour).
Areas of application would include the monitoring of liquid and gaseous media, for example, in refrigeration systems and refrigeration circuits of welding machines, laser and piping systems, pumps, compressors, hydraulic systems, etc.
The switching point can be continuously adjusted within the switching range. Corresponding to the flow speed present, the actual flow rate can be much larger than the maximum scale value (ie the maximum value on the scale can be exceeded).
Notes on installation
With units that are dependent on position, the flow monitor must be installed vertically in the system with the flow from the bottom to the top. Units independent of position may be installed in the system in any position, as long as the direction of flow is such that an increase in the flow produces a corresponding positive movement on the scale (ie from a lower to a higher reading).
Viscosity compensated units can be installed in the system in any position, again with the direction of flow such that an increase in the flow produces a corresponding positive movement on the scale.
Switch hysteresis
This refers to the distance travelled by the suspended body between the switch-on and switch-off quantities. The typical hysteresis of the suspended body tube is attained by selecting reed switches with lower differences between the pick-up and drop-off activation levels (dose differential).
Viscosity compensation
This is achieved by installing a spring connected to a perforated plate. As the spring has already been artificially aged, no readjustment is necessary.
Maintenance
Due to its design, the flow unit requires no maintenance. Cleaning at regular intervals should only be carried out in the case of media that contain magnetic particles. These cleaning intervals can be correspondingly extended by the use of a filter with a magnetic separator.
Some considerations to be kept in mind: the medium must not contain any solid particles. The installation of a dirt trap of type SF, SFD or SFM is recommended.
The unit with the contact device must not be located near any strong magnetic field. Always observe the maximum electrical values of the reed switch.
Setting the switching point entails moving the arrow on the switch housing to the desired switch-off point on the scale of the unit housing.
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