Junction Box

A junction box sits between the load cells and the indicator. On a floor scale, hopper, tank or silo that is carried by three or four cells, each cell cable lands on a terminal inside the box, and the box passes the combined signal down one cable to the indicator. Many boxes also carry trimming, so the output of each cell can be adjusted until the vessel reads the same wherever the load is placed.

Three details decide fit. First, the number of channels: how many cells connect now, and whether more are planned later. Second, the wiring itself: four-wire or six-wire, open ends or connectors, the colour code the existing indicator expects, and the length of the run from the box to the indicator, since a very long run or a run laid beside power cables is where readings start to drift. Third, the entry and gland sizes for the incoming cell cables and the outgoing cable, so the box closes up properly after wiring.

The housing has to survive the area it is installed in: a dry indoor enclosure on a protected frame, a sealed stainless housing where the area is washed down or dusty, or a box rated for outdoor mounting. Where it is fixed matters too — under the platform, on the frame, or on a nearby wall — and the lid should stay reachable for trimming after the scale is in service. Keep the cable route away from drives and power lines.

When a box is replaced or extended, the field wiring is the specification: how many cells, which terminals, the trim settings that were in use, the cable lengths, and how the reading behaved before the change. Writing those down makes a later cell swap or fault-finding straightforward.