Reed flow switch DSV-3

variable-areareed switchfor liquids

The proven KOBOLD flow meters and switches model DSV are based on the principle of the well-known float-type flow meters, except for the conventional tapering measuring tube. These patented instruments are provided instead with a cylindrical flow tube with conical slots around the periphery. This eliminates the usual problems of guiding the cylindrical float within a tapering measuring glass. The novel design, including the provision of an appropriately dimensioned annular gap of constant width between the float and the flow tube, has enabled the sensitivity to dirt to be considerably reduced. The float contains a permanent magnet which actuates a bistable reed contact external to the measuring tube, that is, the flowing medium is hermetically separated from the electrical contact. In addition it is embedded in a height-adjustable switch housing, thus ensuring that the contact is protected even in an aggressive atmosphere. As the medium enters the instrument, the float rises. Once its magnetic field reaches the contact tips of the reed switch, the contact connects. As the flow increases the float rises further until it reaches its stop. This prevents the float from going beyond the contact range of the magnetic operating tube, that is, the contact remains connected, thus ensuring bistable switching. The top edge of the float serves to indicate the flow on the measuring glass in l/min.