Important Basic Information; Function Description Of The Fhg Flow Meters - Omega FHG Series User Manual

Important basic information

These installation and operating instructions should provide you with the information you need to properly install and commission
the flow meter. Installation, commissioning and testing are to be performed by trained and qualified personnel only. These operating
instructions must be read and applied carefully to ensure proper, trouble-free and safe operation of the flow meter. Omega is not
liable for any damage incurred resulting from not complying with the instructions in this operating instruction. It is not permitted in
any case to open the device.

1. Function Description of the FHG Flow Meters

FHG flow meters measure the flow rate based on the screw pump principle.
A pair of rotors fitted precisely into the housing constitutes the measuring
element. An integrated gear and non-contact signal pick-up system detects
the rotations of the measuring element and converts them to digital pulses.
Together with the housing walls, the rotor edges form closed measuring
chambers in which the fluid is transported from the inlet to the outlet side.
The fluid volume put through within one main rotor rotation is the rotation
volume, which is divided by the sensing gear and digitised, processed and
output in the sensor module.
Advantages
• High degree of precision that is mostly independent of viscosity
• Pulsation-free measurement
• Lowest pressure losses
• Short response time due to innovative rotor profile and
• Highest functionality due to intelligent sensor technology
• Gentle fluid measurements
Sensor System Explanation
The non-contact pick-up system consists of two GMR bridges (sin /cos), which
are located in a sensor unit in cartridge design. It detects the movement of
the sensing gear and routes the sin/cos signals to the preamplifier electronics.
The preamplifier electronics digitise and amplify the sensor signals and mul-
tiply them by a high-resolution interpolator using adjustable settings. The
square wave signals are bidirectional and can be utilised by any evaluating
instrument as well as computers and PLC controls.
The resolution is selectable in steps from factor 1 to 128.
In case of a 1-channel evaluation, a separate directional signal is available.
An adjustable pulse filter can offset and suppress negative flows (e.g. gene-
rated by vibrations) while still in the device.
The frequency of the output signals is proportional to the flow (volume flow)
and depends on the respective flow meter size. The frequency range is from
0 to 100 kHz. The preamplifier is protected against reverse polarity and
incorrect connection. It is designed for media temperatures of -30°C to
+120°C and is mounted directly on the FHG flow meter.
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