HJB Series
Junction Box
Stainless-steel junction boxes for 4 to 10 load cells, IP65-rated with digital trim and inbuilt surge protection per channel.
Manufacturing
Built, installed & supported by HMT
Compliance support
Calibration & Legal Metrology guidance
System ready
Automation, ticketing & ERP integration
01Overview
Every model shares the same build quality — IP65 grade, stainless steel construction, a digital trim port and inbuilt surge arrestor per load cell — the only difference across the range is load cell capacity.
02How it works
Summing several load cells into one clean signal
A weighbridge or platform scale rarely relies on a single load cell — the deck's weight is shared across 4, 6, or more cells at different mounting points. A junction box takes each cell's individual signal wire and sums them electrically into one combined output that goes to the indicator, so the indicator only ever has to read one signal representing the whole deck's total load, not manage each cell separately.
Digital trim corrects for what manufacturing tolerance can't
Even with precision-machined mounting pads, no deck distributes load perfectly evenly across every cell — small differences in geometry, deck stiffness, or mounting height mean each cell sees a slightly different share of the total load for a given weight. A digital trim port for each load cell lets a technician individually adjust that cell's contribution to the combined signal during calibration, so the corner load differences cancel out and the summed reading matches the true total weight, wherever the load sits on the deck.
Surge protection sits at the box, not the cell
Load cells are precision instruments and among the most expensive individual components in a weighing system, and they're also the components most exposed to lightning-induced surges, since their cabling often runs outdoors between the deck and the control room. An inbuilt surge arrestor per load cell channel in the junction box gives each cell's signal path a protection point close to where it enters the shared wiring, rather than relying on protection only at the indicator end of a long outdoor cable run.
03Manufacturing & build quality
The enclosure is built from stainless steel and sealed to IP65 grade, so dust and directed water jets — the kind a weighbridge junction box mounted outdoors under a deck will realistically face — don't reach the internal wiring and summing circuitry. Inside, each load cell channel gets its own set of terminals, a digital trim potentiometer or equivalent digital adjustment, and a surge arrestor, wired to a common summing bus that feeds the single combined output to the indicator cable. Every unit is assembled and then bench-tested with simulated load cell inputs to confirm each channel trims correctly and that the combined output sums as expected, before the enclosure is sealed and the cable glands fitted for field wiring.
04Problems it solves
Uneven readings across the deck
Without individual trim adjustment per cell, a weighbridge can read slightly differently depending on where along the deck a vehicle's axles happen to sit — the trim function is specifically what corrects that.
Lightning and surge damage to load cells
Outdoor load cell cabling is exposed to induced surges from nearby lightning strikes; a junction box without per-channel surge protection puts the full risk of that event on the load cells themselves, which are far more expensive to replace than a surge arrestor.
Moisture ingress corroding connections
An unsealed or poorly rated junction box lets moisture reach the summing terminals over time, causing corrosion that shows up as drift or intermittent faults — IP65 sealing is specifically there to prevent that failure mode.
Difficulty balancing a multi-cell system without the right tools
Trimming a multi-cell scale without individual digital trim per channel means physically shimming load cells or accepting a less accurate calibration — a proper junction box makes that adjustment an electronic one done from inside the box.
05Why it matters
The junction box is easy to overlook because it doesn't display a number or do anything visible — but it's the point where the accuracy of every individual load cell either comes together correctly or doesn't, and it's the first line of defence protecting those load cells from the electrical surges that outdoor cabling inevitably sees over years of service. A well-built junction box is cheap insurance against replacing load cells after a storm, and it's the reason a multi-cell weighbridge reads consistently no matter where a vehicle sits on the deck.
06Salient features
- IP65 grade enclosure
- Digital trim port for each load cell
- Inbuilt surge arrestor per load cell
- Stainless steel construction
07Specifications
| Model | Capacity (T) | Least Count | Platform Size (m) | Notes |
|---|---|---|---|---|
| HJB-04 | — | — | — | Supports up to 4 load cells |
| HJB-06 | — | — | — | Supports up to 6 load cells |
| HJB-08 | — | — | — | Supports up to 8 load cells |
| HJB-10 | — | — | — | Supports up to 10 load cells |
08Technical file
Need the full technical sheet?
Request drawings, model-specific details and project documentation from the HMT team. A downloadable product file will appear here once approved.
09Complete system
Plan beyond the deck.
A vehicle weighing point can combine the weighbridge with indicator, load cells, traffic management and H-Weigh software for an accountable end-to-end workflow.
08In the field
09Frequently asked
How many load cells can one junction box handle?
Models are available across a 4 to 10 load cell range — match the box to the number of cells your deck or platform actually uses, with most standard weighbridge and floor-scale installations falling comfortably within that range.
Is it rated for outdoor mounting under a weighbridge deck?
Yes — the IP65 enclosure rating is specifically intended for that kind of exposed, outdoor, under-deck mounting position where dust and water spray are a given.
How does the trimming process actually work at calibration time?
A technician places calibrated test loads on the deck at different positions and adjusts each channel's digital trim until the combined reading is consistent regardless of load position — this is normally done once at commissioning and re-checked at periodic recalibration.
Does the surge protection cover the indicator too, or just the load cells?
The inbuilt arrestors protect each load cell's signal path at the point it enters the junction box — separate surge protection at the indicator and power supply ends is a good idea as part of a complete lightning-protection strategy, not a substitute for it.
What maintenance does a junction box need over time?
Periodic inspection for moisture ingress, corrosion at the terminals, and cable gland integrity, plus re-checking trim balance at the same interval the rest of the scale is recalibrated.
10Industries this serves
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