Fairbanks 2000 SERIES Rocker Column Railroad Scale - Manual (Page 10)

03/10 10 50614 Rev. 5
Power Source The power source of the electronic instrumentation and load cell circuitry
shall conform to the following:
Voltage - 115 v AC +/- 10 v
Frequency - 60 Hz, +/- 0.25 Hz
The power source must be reasonably free from harmonics and electrical transients.
Fusing shall be provided at 15 amp unless otherwise specified by the manufacturer.
The power source shall be a separate circuit back to the distribution transformer.
One side of the 115 v power source shall be at a ground potential.
Power surge protection shall be provided for load cells and instrumentation circuit.
Adequate protection of shielding should be provided to eliminate radio frequency and electro-
magnetic interference. The scale must satisfy the tolerance requirements when the scale
equipment is subjected to RFI and EMI influences.
Cabling: All cabling between loadcells, junction boxes, and electronic instrumentation shall
conform to the following:
All cable shields shall be interconnected and carried to a single ground. This should be a
separate ground from the power source ground and be provided for the loadcells and instru-
mentation circuits only. It should be a copper rod which, when possible, is driven to the
depth of the water table.
The connection between the ground rod and the common ground point of the loadcell and
instrumentation circuits shall be made with copper wire, or the equivelant, of No. 10 gauge or
larger.
All cable shields in the loadcell circuits shall be grounded at one end only.
Loadcell cables shall be physically separate from power cables and never run in the same
conduit system.
(NOTE: A 24 inch to 36 inch separation is required by Fairbanks Scales)
All cable connections, junction boxes, etc., in the loadcell circuits shall be properly protected
against the effects of moisture.
All multi - conductor cabling shall be color - coded, or provided with other means of identifica-
tion of the individual conductors.
Cables from the loadcells to the first junction box shall be in one unspliced length. Junction
boxes shall be located near the top of the pit but not on the weighbridge. Cabling from the
first junction box to a common master junction box shall be in one length unspliced.
This concludes excerpts from the Association of American Railroads Scale Handbook