Signal And Reference Voltage Cable Connections - ABB MAG-SM Instruction Bulletin

Electromagnetic Flowmeter Converter
2.4.4 Signal and Reference Voltage Cable
Connections
!
Warning:
The signal cable connections are a function of
the flowmeter primary size! The appropriate
Interconnection Diagram is to be used!
The signal cable should be routed using the shortest path
because the ac signal voltage in the cable is only a few
millivolts. The cable should not be routed in close proximity to
large electrical machinery and switch gear equipment which
could induce stray fields, pulses and voltages.The signal cable
should not be fed through junction boxes or terminal strips.
The maximum allowable signal cable length for the flowmeter
primary designs without a preamplifier is 50 m. If a preamplifier
is installed in the flowmeter primary for metering low
conductivity fluids, the maximum signal cable length is 200 m.
A shielded reference voltage lead is located in the cable parallel
to the signal leads. The signal cable construction includes a
copper shield which encloses the individually shielded signal
leads and the shielded reference leads. The outer shield is
connected to the terminal
shields of the signal leads act as "Driven Shields" for the signal
transmission. The signal-/reference voltage cable is connected
in accordance with the Inerconnection Diagrams to the
flowmeter primary and the converter.
The supply voltage for the MAG-SM with a preamplifier is
connected to terminals -U and +U, instead of 1S and 2S. If the
actual flow direction does not agree with the direction indicated
by the arrow on the flowmeter primary, the connections to
terminals 1 and 1S must be interchanged with those to 2 and
2S. For flowmeter primaries with preamplifiers only the
connections to terminals 1 and 2 must be interchanged to
reverse the direction indicators.
4
in the converter housing. The
1 PVC jacket, white
2 Woven steel wire shield,
∅
0.15 mm
2 Woven copper wire shield,
0.13 mm
4 Electrode flow signal
∅
0.75 mm
Fig.2 Signal Cable Construction D173D018U02
!
Note:
The flowmeter system complies with the NAMUR-
Recommendations 5/93 "Electromagnetic Compatibility
of Equipment in Process and Laboratory Applications".
A new signal cable was developed and introduced to
meet these requirements which utilizes two separate
outer shields. The outer shield is connected to terminal
SE in the flowmeter primary and to terminal
converter.
If the flowmeter primary does not include a SE terminal
then only one end of the outer shield is to be connected
at the converter.
1
2
3
4
5
6
7
5 Reference voltage jacket, white
6 1 each shielded, woven copper
∅
wires, 0.1 mm
7 Polyethylene, natural
in the