Siemens SIWAREX R Operating Instructions Manual - Page 10
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2
Installation/Assembly
2.1
Installation
SIWAREX R load cells may only be assembled and connected by qualified
personnel.
If a scales is equipped with a single load cell, this can be connected directly to the
weighing module if space allows. To bridge greater distances the connecting cable
can be extended through a junction box.
Several load cells are connected in parallel in a junction box.
Load cells can be fitted with 4 or 6-wire connecting cables.
Four-wire connecting cables should not be shortened or lengthened because the
line resistance is temperature-compensated. If the length of the connecting cable is
altered, the input and output resistance also changes. This change can be
corrected by adjusting the scales but this does not compensate temperature-
related changes in resistance of the missing or lengthened piece of cable. The
value of the remaining temperature error is shown in the table below. The
SIWAREX measuring cable 7MH4702-8AA / -8AB is used as the basis for these
observations. The feed lines are connected in parallel (double).
Table 2-1 Remaining temperature error of a cell per 10 K in %:
Change in
length
3 m
5 m
10 m
If 3 or 4 cells are operated in parallel and the cable of a cell is lengthened, the
additional error is about a third or a quarter. Prerequisite is an even load
distribution on the cells.
ATTENTION
On 6-wire connecting cables, the feed voltage is fed back as a reference voltage to
the weighing module. Shortening or lengthening has no effect on the measuring
result.
Figures 2-1 and 2-2 show the parallel connections of load cells in 4 and 6-wire
technology.
SIWAREX R Load Cells Operating Manual
A5E00159640
K
RN
0.0012
0.0003
0.0020
0.0005
0.0040
0.0009
Only EMC-safe housings (e.g. SIWAREX JB) may be used to
extend connecting cables.
Series
BB
CC
0.0007
0.0007
0.0012
0.0011
0.0024
0.0022
SB
0.0009
0.0014
0.0029
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