SIKA Induq VMM Series, Руководство по эксплуатации

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Installation of VMM
i ndu Q
®
- Series VMM
- 10 - © SIKA • Ba_VMM_us • 09/2018
3.2 Measuring principle
The magnetic inductive flow sensor operates on the inductive principle, i.e., a direct current
is generated by the movement of a conductor in a magnetic field:
The measuring pipe of the VMM is in a magnetic
field (B).
An electrically conductive medium (Q) passes through
the pipe. During this, the positive and negative load car-
riers are inversely deflected.
A voltage arises which is perpendicular to the magnetic
field, which is tapped through both electrodes.
The voltage induced during this is proportional to the
average flow velocity of the fluid.
The electronics of the VMM converts the induced voltage into a flow-proportional frequency
signal.
3.3 Functions
Empty pipe detection:
The electronic display unit has the ability for an empty pipe detection, which can be activated
and deactivated.
The operating reliability depends on the conductivity of the liquid medium and the cleanliness
of the electrodes.
As higher the conductivity is, as more reliable operates the empty pipe detection.
Insulation coatings on the electrodes surface worse the empty pipe detection.
Safety of operation:
A comprehensive self-monitoring system ensures maximum safety of operation.
•
Potential errors can be reported immediately via the configurable status output. The
corresponding error messages will also be displayed on the display of the display elec-
tronics. A failure of the auxiliary power can also be detected via the status output.
• All outputs are electrically isolated from the auxiliary power, the sensor circuit and from
each other.
4 Installation of VMM
Before installing, check that

the wetted materials of the device are suitable for the liquid being used
(

§ 11.2 "Materials table").

the equipment is switched off and is in a safe and de-energized state.

the equipment is depressurized and has cooled down.

Please observe in particular "Instructions on potential equalization and cathode protec-
tion" (

§ 4.2).
Suitable tools:

Use only suitable tools of the correct size.