KROHNE IFC 300 Converter Quickstart EN - Manual (Page 52)

3
ELECTRICAL CONNECTIONS
52
IFC 300
www.krohne.com 08/2010 - 4000070303 - QS IFC 300 R06 en
3.7.2 Virtual reference (not valid for TIDALFLUX 4000 & OPTIFLUX 7300 C)
For pipelines which are electrically insulated on the inside (e.g. have an inner liner or are made
completely out of plastic), it is also possible to measure without additional grounding rings or
electrodes.
The signal converter's input amplifier records the potentials of both measuring electrodes and a
patented method is used to create a voltage which corresponds to the potential of the
ungrounded medium. This voltage is then the reference potential for signal processing. That
means there are no interfering potential differences between the reference potential and the
measuring electrodes during signal processing.
Ungrounded use is also possible for systems with voltages and currents in the pipelines, e. g.
electrolysis and galvanic systems.
Thresholds for measuring operation with the virtual reference
3.8 Power supply connection
• The protection category depends on the housing versions (IP65...67 to IEC 529 / EN 60529 or
NEMA4/4X/6).
• The housings of the devices, which are designed to protect the electronic equipment from
dust and moisture, should be kept well closed at all times. Creepage distances and
clearances are dimensioned to VDE 0110 and IEC 664 for pollution severity 2. Supply circuits
are designed for overvoltage category III and the output circuits for overvoltage category II.
• Fuse protection (I
N
≤ 16 A) for the infeed power circuit, as well as a separator (switch, circuit
breaker) to isolate the signal converter must be provided close to the device.
The separator must conform to IEC 60947-1 and IEC 60947-3 and must be marked as the
separator for this device.
INFORMATION!
If there is a virtual reference with wall housing, voltage is permitted between PE/FE of the
converter and the measuring sensor!
Size ≥ DN10 / ≥ 3/8"
Electrical conductivity ≥200 µS/cm
Signal cable use only A (type DS 300)
Signal cable length ≤ 50 m / ≤ 150 ft
DANGER!
The device must be grounded in accordance with regulations in order to protect personnel
against electric shocks.
DANGER!
For devices used in hazardous areas, additional safety notes apply; please refer to the Ex
documentation.