Caution, Trimming procedure – Rice Lake EL304A Signal Trim Junction Box User Manual
Page 4
3
To prevent water and other
contaminants from entering the
J-Box, fill any unused cable grips
with post screw plugs (part
number 19538). One plug is
provided.
Trimming Procedure
The EL-304A J-Box is a signal trimming device. Each cell can be set for coarse,
medium, or fine trim with its own 4-pole dip switch. Switches 1 and 2 work in various
combinations to alter the sensitivity of the trimming potentiometers as shown in the
table below. Switches 3 and 4 must be ON for each active cell to enable trimming.
Approximate Trim Ranges - EL-304A Summing Board
For example, to enable trimming using the fine adjustment range, set DIP switches
2, 3 and 4 on active channels to ON, and switch 1 to OFF.
1.
Turn the four individual cell potentiometers fully
counterclockwise
to give
maximum signal output from each cell.
To trim cells individually, be sure the Section Trim jumpers
are in the OFF position as shown at right.
2.
To trim cells in pairs, set the Section Trim jumpers to the
ON position. If section trimming is chosen, turn the two
section potentiometers fully
counterclockwise
so both
sections are at maximum signal output.
3.
Remove all weight from the scale and zero the indicator. Place calibrated test
weights over each load cell or section in turn. The amount of test weights to
be used will depend on the scale configuration; for specific recommendations,
refer to
Handbook 44, published by the National Institute of Standards and
Technology (NIST). For a four-cell platform, we recommend using 25% of
scale capacity.
4.
Record the value displayed on the indicator after the test weight is placed in
turn on each corner, directly over the load cell, or over each section. Allow the
scale to return to zero each time to check for friction or other mechanical
problems. Select the load cell or section that has the lowest value as your
reference point. This cell or section will not be trimmed.
5.
Place the same test load over each cell or section in turn. Using the
corresponding potentiometer, trim each cell or section down to equal the
reference point. As corner corrections are somewhat interactive, check all
cells or sections again for repeatability. If necessary, repeat steps 4 and 5.
6.
Tighten the cord grip assemblies with a wrench. To be watertight, each cord
grip must be tightened so the rubber sleeve begins to protrude from the hub.
7.
Unused hubs must be plugged to prevent moisture entry. See the
Electronic
Replacement Parts and Components catalog to order extra hole plugs.
8.
Insert the enclosed desiccant bag and replace the cover, tightening the cover
screws in an alternating pattern to be certain the gasket is compressed equally
in all locations. If the enclosure is located in a damp or wet area, change the
desiccant (part number 16038) every four to six months.
Whenever a large amount of trim
seems necessary to equalize
output (more than 7% of normal
output), check for other possible
problems. Always strive for the
least amount of trim.
!
Caution
!
Caution
When loading the corners with
test weights, do not exceed the
concentrated load capacity
(CLC) specified by the scale
manufacturer.
SECTION #1
TRIM
ON
OFF
1
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2
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5
3
Ω
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7
Ω
s
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F
F
O
F
F
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e
n
o
N
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N
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N
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F
%
8
.
6
–
%
5
3
.
%
8
.
2
1
–
%
7
.
N
O
F
F
O
m
u
i
d
e
M
%
5
.
2
1
–
%
5
3
.
%
3
.
2
2
–
%
7
.
N
O
N
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e
s
r
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o
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%
6
.
7
1
–
%
5
3
.
%
9
.
9
2
–
%
7
.
NOTE: On older models of the
EL-304A Junction Box, the
Section Trim pots work in the
opposite direction as the
Individual Cell Trim pots.
To decrease resistance for
maximum signal on these
units, turn Individual pots
counterclockwise and Section
pots clockwise.