The flow meter and switch model DS08 works according to a modified variable area principle. The float is guided in a cylindrical measuring tube by means of a spring. The flowing medium moves the float in the flow direction. An externally mounted pointer indicator is magnetically coupled to the float and thus, following the float position, indicates the flow rate on a scale.
A reed contact is mounted outside the meter in a sealed housing. When the float reaches the position of the reed contact the switch will close. With higher flows the float moves further upward until it reached a built-in float stop, still keeping the switch closed. This ensures a bistable switch function at any time. The reed contact is adjustable over the full measuring range of the meter.
The built in spring and magnetic float are very reliable. As the spring opposes the float and the flow, it is possible to mount the flow meter in any orientation. The strong spring, combined with an orifice in the float, limit the effects of viscosity changes to an absolute minimum compared to regular variable area flow meters.