Rice Lake EL304A Signal Trim Junction Box - Manual (Page 3)

2
The terminal strips are labeled “Cell 1” through “Cell 4” and are used to connect
the individual load cells. Determine the number of load cells to be connected to
the junction box. The EL-304A has been designed to connect and trim four load
cells. However, it is possible to use this box with other combinations. On a track
scale or other system where load cells may be connected together in section
“pairs”, even numbers of cells (four or eight) may be used with the EL-304A. This
is done by paralleling the excitation and signal leads of a load cell pair, and
connecting them to the same input on the J-Box. However, it is recommended
practice when using more than four load cells to “daisy-chain” EL-304A J-Boxes
together using the expansion connectors.
After determining the wiring pattern, route the load cell cables through the nylon
cord grip assemblies. Leave the grips loose until final closure. Before connecting
load cell cables to the terminals, check that all wire ends have been properly
stripped and tinned. Connect the load cell and indicator cables to the appropriate
connectors. DIP switches 3 and 4 must be ON for any cells which you will be
trimming. If using less than four load cells, remove any unused channels from the
circuit by turning dip switches 3 and 4 to OFF on those channels.
The INDICATOR terminal strip is used to connect the main cable to the indicator.
Determine the indicator’s load cell input connections from the operating manual.
Run a cable from the indicator to the junction box through the larger cord grip and
make the connections on the INDICATOR terminal.
Wiring
RICE L
A
KE W
EIGH
ING SYS
TE
M
S
CELL #1
CELL #2 CELL #3
INDICATOR
+EXC
–EXC
+SEN
–SEN
+EXC
–EXC
+SEN
+SIG +SIG
–SEN
–SIG –SIG
SHLD SHLD
+EXC –EXC +SIG –SIG
SHLD
EL 304A
REVISION 1
1-90
+EXC –EXC +SIG –SIG
SHLD
+EXC –EXC +SIG –SIG
SHLD +EXC –EXC +SIG –SIG
SHLD
CELL #4
SECTION #1
TRIM
SECTION #2
TRIM
1 2 3 4
OFF
1 2 3 4
OFF
1 2 3 4
OFF
1 2 3 4
OFF
ON
OFF OFF
ON
EXPANSION
EL304A
COMPONENTS REV
. 1.0 (1-90)
FIGURE 2: EL-304A MAIN BOARD
CABLE DRIP LOOPS
If cables will be exposed to water
or other liquids, bend a short
downward loop in all cables near
the cord grips so any fluids
draining down the cables will drip
off before reaching the junction
box.
SENSE LEADS
Use sense leads to correct small
errors which can cause inaccu-
rate readings and drifting
problems, especially if the
indicator is located far from the
junction box.
1 2 3 4
OFF
DIP switches 3 & 4 must
be ON to enable trimming.
WIRING PATTERN
See back cover of Rice Lake
Weighing Systems Load Cell
Product Selection Guide for
wiring color codes.