METTLER TOLEDO 2888 Deckmate Floor Scales Installation and Service Manual
(10/96)
Check Wiring
Remove power from the system. Remove the Junction box cover plate
from the platform and check the interior of the junction for moisture or
any foreign material.
Ensure that all wiring connections are tight and that no insulation
material is touching the terminal contacts. Check all cable connections
for correct wiring, the wiring color code are as follows:
Load Cells Instrument Cable
+Excitation Green +Excitation White
+Sense Yellow
+Signal White +Signal Green
Shield Yellow Shield Orange
-Signal Red -Signal Black
-Sense Red
-Excitation Black -Excitation Blue
(Instrument cable color code based upon Mettler Toledo cable no.
510620370)
Check all cable connectors on the junction box. Tighten any connectors
found to be loose.
Check Load Cells
Check each load cell for proper bridge resistances.
Measuring Points Resistance
Any lead to shield or ground Infinity
+Exc (Green) to -Exc (Black) 350 Ohm minimum
+Sig (White) to -Sig (Red) 348 to 352 Ohms
If bridge resistances are within specification, perform a “shorted signal”
symmetry check. Short the signal leads together and place one multimeter
lead on the shorted signals and one lead on the +excitation wire. Note the
resistance value indicated. Next, remove the lead from the +excitation
wire and place it on the -excitation wire. Both resistance values should be
approximately within 1 Ohm.
If the cells pass the above test, reapply power to the scale platform.
Confirm that proper excitation voltage is reaching the load cells by
placing multimeter leads on the excitation positions of each load cell
terminal (excitation voltage can vary from 5 VDC to 15 VDC depending
upon the application and digital indicator used).
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