London Electronics IL2-L, Детали подключения, масштабирование и общая информация

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12
Clean Earth
Installation hints for best performance
This section offers several suggestions which will help you get the best performance from
your weighing system.
Loadcells create very small signals which can easily be corrupted by electrical noise. These
steps will ensure you get the best possible performance from your meter.
1. Use good quality screened signal cable, with 3 twisted pairs. Belden 8777NH,
Belden 9503 and AlphaWire 6010C are good choices, available from many
electrical distributors.
2. Even if your loadcell is only a 4 wire device, we recommend you use 6 core cable
between the display and the loadcell, and wire as shown in the diagram opposite.
This will ensure that any resistance changes in your cabling, caused by changes
in temperature, will be cancelled.
3. Each pair should be dedicated to a signal function as shown opposite, for maximum
noise immunity. (One twisted pair for Excitation, one twisted pair for Sense, one
twisted pair for Signal) This will ensure that any electrical noise induced in the
cable is properly cancelled. Mixing functions carelessly amongst the twisted pairs
can actually worsen noise performance.
4. The cable should be routed away from noisy wiring and devices such as power
feeds from inverters, discharge-lighting cables, welder cabling etc, and should
preferrably be routed in a dedicated low voltage signalling/instrumentation conduit
or cable tray.
5. Screened cable should be earthed at the display end only.
6. All wires and screens coming out of the screened cable should be kept as short
as possible to minimise pickup of noise.
7. If you are using barriers, you should earth your screen as shown below, paying
particular care that you do not earth both ends of any run of of cable.
NB If using
galvanic isolation barriers, connect 10K from terminal 2 to terminal 3 and 10K
from terminal 3 to terminal 5 on the display’s Sig. Input connector to maintain the
input signal within the common mode range of the excitation sense circuit.
Barriers
E
A
R
T
H
Connect screen
to earth ONLY
at this end. Connect screen
to earth ONLY
at this end.
Do not
connect
screen at
this end.
Do not
connect
screen at
this end.
Length of screened cable Length of screened cable
Loadcell
Hazardous Area Safe Area
Terminal 7
on logic
input
connector
S
ig
. I
n
p
u
t
L
o
g
i
c
I
n
P
o
w
e
r
Display connections
Loadcell connections
Barrier connections
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