Replacing The Weighing Cell - KERN FTB Service Manual

5.8

Replacing the weighing cell

5.8.1 Replacing a strain gauge weighing cell
Disassembly
• Remove the weighing pan.
• Scales without IP65 protection: Undo the pan support plate retaining screws and remove the pan support plate.
• Scales with IP65 protection (see exploded view drawings in Chapters 2 and 3):
• Undo the 4 M3 x 8 screws fastening the membrane to the load plate support.
• Undo the two M6 x 30 retaining screws of the load plate support and carefully lift the load plate support off.
Caution: If the load plate support remains attached to the membrane, the membrane must be released with a thin pin.
(Insert the pin through the drilled holes in the load plate and carefully press the membrane down.)
• Undo the 3 M3 x 10 screws fastening the small flange to the membrane. Remove the small flange, the membrane, and
the large flange.
• Undo the 2 M3 x 8 fastening screws of the cover plate. Carefully lift off the cover plate together with the rubber seal.
• Turn the scale upside down, unscrew the adjustable feet and remove them.
• Undo the bottom plate retaining screws, removing them and the plate itself.
Replacing the load cell
• Remove the weighing cell cable connector from the analog PCB.
• Undo the 4 retaining screws for the overload plate. Remove the screws, washers and springs.
• Remove the overload plate with the weighing cell screwed to it.
• Remove the weighing cell retaining screws.
• Screw the new weighing cell to the overload plate. Caution: Before tightening the screws, verify that the weighing cell is
aligned exactly parallel with the edges of the overload plate! Screw torque: 10 Nm!
• There is an adjustment screw for the overload stop with scales from specific production series. The overload stop must then
first be readjusted after replacing the load cell. If the adjustment screw has been removed, a drop of superglue should be
applied to the thread to keep the screw firmly in place after adjustment. A feeler gauge should be used to adjust the overload
stop. The adjustment screw is to be tightened until there is a gap between the screw and weighing cell according to the table
below. Caution: Turning the screw too tightly can damage the weighing cell!
Scale
FTB/FTC 3 kg
FTB/FTC 6 kg
FTB/FTC 15 kg
FTB/FTC 35 kg
FTB/FTC 60 kg
• Place the overload plate with the weighing cell screwed to it in the scale. Fit the springs and washers, then tighten the
screws.
• Fit the weighing cell cable connector onto the analog PCB pins.
FTx/ITx-SH-e-0720
Color of overload spring
red
red
white
brown
black
Gap between adjustment screw and weighing cell
0.45 mm
0.45 mm
0.25 mm
0.25 mm
0.40 mm
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