The Type 790 Flowmeter is based on the variable area principle, with some models using the guided float system.

The flow rate is indicated by the position of the top of the float against the scale on the tube. In addition to the visual readout, this flowmeter may be fitted with minimum and maximum limit switches, or a transmitter.

Accuracy Class :
4 according to VDE/VDI 3513 Sheet 2 e.g. 1 % of end value + 3 % of indicated flow inaccuracy in l/hr resp. m³/hr.

Electrical Accessories :
Insure that the float is the type with a built-in magnet before fitting electrical accessories, otherwise they cannot be actuated. The contact 024.86.06 has a closure with a lowering float (Min. flow) or a closure with a rising float (Max. flow). The contacts are adjustable over the complete range. See also the special data sheet.

Valves :
When measuring liquids, valves may be installed before or after the Flow Sensor. For gases, valves must always be mounted after it. Valves should always be opened slowly to prevent  unnecessarily accelerating the float against the float rest.

Installation :
The Flow Sensor must be mounted with the flow tube axis vertical, with the media flowing upwards. Insure there are no undue stresses acting upon it.

Pipe size reductions or enlargements before or after the flowmeter do not normally cause serious errors, it is preferable, however, to install the Flow Sensor in a straight length of pipe.