The VHS flow transmitter measures the flow using the volumetric
principle, and is suitable for fluid, viscous, lubricant media (e.g.
lubricating oil). If the material for the VHS is selected appropriately,
aqueous fluids such as soaps, pastes, and emulsions with nonabrasive
characteristics can also be measured, as long as they
have sufficient lubricity. Because of the volumetric functioning
principle, the device is almost completely independent of viscosity.
The VHS system consists of two interlacing screws which run in
opposite directions, driven by the flowing medium. A magnetically
pre-tensioned Hall sensor positioned outside the flow space detects
the screw flanks, and creates a frequency signal proportional to the
flow. Here, two pulses correspond to one revolution of the screws,
and therefore to a specific measured volume (see data table) There
are no magnets in the flow space. A push-pull transistor output, an
A / B output or a two wire output are available as signal output. The
push-pull output can as desired be switched as a PNP or an NPN
output, and emits a frequency proportional to the flow rate.

The A / B output consists of two push-pull outputs, whose signals
are phase-shifted by 90 °. This makes it possible to determine the
direction of flow using the bidirectionally driven sensor.

The 2 wire model represents the pulse as two different currents,
and has the advantage of reduced wiring effort. Alternatively, it is
possible to use add-on electronics with signal processing, in the
series OMNI, FLEX and LABO.
The device bodies are made of aluminium, and the connections
either of aluminium (achieves PN 160 bar) or steel (achieves PN
350 bar). Optionally, both process connections can be fitted with
SAE flanges, which simplify the installation in the pipework, and in
both cases achieve a pressure resistance of PN 350.