Vehicle Scales

What is a vehicle scale?

A vehicle scale is a large weighing system that takes a vehicle onto a platform and measures it together with its load. It also goes by the names truck scale and weighbridge. Load cells under the platform do the measuring, and the weighing indicator brings the figure up on screen, ready for the records.

When a load is accepted on an estimate or on the number written on the paperwork, small discrepancies grow into a real loss over time. A business with its own scale weighs each vehicle twice, loaded and empty, and documents the difference with its own measurement. Buying, selling and dispatch then all refer to one figure. Meram vehicle scales fall into two sub-groups: Truck Scales for heavy vehicles, and Pickup and Tractor Scales for light ones.

Which group of vehicle scales suits you?

The mix of vehicles using your site decides the group. The first question is: what is the heaviest and longest vehicle the scale will have to weigh? In short:

• Lorries, articulated vehicles and HGVs arrive: Truck Scales
• Only pickups, vans, tractors and trailers arrive: Pickup and Tractor Scales
• Both arrive: the scale is chosen for the heaviest vehicle, and light vehicles are weighed on the same platform
• Produce is bought in small, closely checked lots: a shorter, lower-capacity model reads more finely

Sub-groups at a glance

Truck Scales

These are for sites with heavy goods traffic. The range includes concrete-deck and full steel models, and either type can be installed on the surface or in a pit. Platform length runs from 6 to 22 m and capacity from 40 to 100 t, depending on the model. Beam types, installation differences, foundations and site layout are covered in depth on the Truck Scales page.

Pickup and Tractor Scales

WB-X200, the model in this group, serves light vehicles with a platform that is shorter and lower in capacity than a heavy-vehicle scale. It fits into a small space and lets you weigh crops, feed or goods arriving by pickup on your own premises.

How does a vehicle scale work?

From the outside a vehicle scale is just a large steel or concrete deck. The measuring is done beneath it and in the weighbridge office, by a chain of four linked parts. Knowing what each one does makes it easier to choose the right system and, later, to know where to look if something goes wrong.

Load cells: turning weight into a signal

The platform rests on load cells at its corners and, on longer decks, at intermediate points. When a vehicle drives on, each load cell deforms very slightly in proportion to its share of the load, and the sensing elements inside turn that deformation into a small electrical signal. The total weight is the sum of all the load cell signals. Getting the right result wherever the vehicle stands on the deck therefore depends on the load cells working in balance with one another.

Junction box: combining and balancing the signals

Cables from the load cells meet in a junction box near the platform. Here the signals are combined into one line and carried to the indicator. The junction box is also where corner adjustment is done, so that the same weight shows the same value on every corner of the platform. Keeping the box free of moisture is critical for stable weighing.

Weighing indicator: making the measurement readable

The indicator converts the incoming signal into kilograms, manages zero and tare, and separates gross from net. It is also the indicator that works out the difference between two weighings, prepares the ticket and sends the result to a computer. Placing the display where the operator can see it easily, with a second display the driver can read, heads off disputes from the start.

Weighbridge software: keeping the records

Software connected to the indicator stores each weighing with vehicle, company, product and date. Information that would otherwise be scattered over paper tickets is gathered into one database, and period reports, totals per customer and the data needed for invoicing are drawn from it.

Two-pass weighing and stored tare

The most reliable method is two-pass weighing: the vehicle is weighed loaded on arrival and empty on departure, and the net load is the difference. Where the same vehicles call again and again, the empty weight can be measured once and stored, so only the loaded weighing is needed on later trips. This saves time, but because fuel level, on-board equipment or a change of driver can shift the empty weight, stored tares need to be re-measured at regular intervals.

Choosing by vehicle type

What decides the sub-group is the mix of vehicles the scale sees every day. Two businesses handling the same tonnage may need very different scales because their vehicles differ.

Sites with mostly pickups and tractors

Farms, milk and grain collection points, cooperatives and small stores mostly work with light vehicles. Here a short platform saves space and gives a finer reading on lots of a few tonnes. Where a tractor is weighed with its trailer, the platform must be long enough for the combination; details are on the Pickup and Tractor Scales page.

Sites with mostly lorries

Factory gates, quarries, scrap yards and bulk handling plants work with heavy vehicles. On these sites the length, capacity, deck construction and installation type of the scale are chosen together, and each of those decisions is dealt with on the Truck Scales page.

Mixed fleets

Where both light and heavy vehicles arrive, a single scale is usually chosen for the heaviest and longest vehicle. Light loads can be weighed on it too, accepting a coarser reading step. If light-vehicle weighings are very frequent and small differences matter commercially, a second, shorter scale on its own lane can be considered.

Capacity margin and your future fleet

A vehicle scale is an investment that stays in place for many years, while the vehicles coming to your site may change within a few. Capacity and length are therefore set not only for today’s fleet but for a reasonable view of the future.

A capacity margin is left for two reasons. First, vehicles loaded more heavily than declared turn up from time to time, and the scale should weigh them comfortably rather than at its limit. Second, a growing business may start working with larger vehicles. On the other hand, an excessive margin enlarges the reading step and light loads are weighed coarsely; the right point leaves a sensible gap between the heaviest realistic vehicle and the scale’s upper limit.

Length is a clearer case: extending a platform later usually means a new platform and a new foundation. If longer vehicle combinations are likely in the coming years, choosing the next length up at the outset is usually the most economical route. A plant that works only with rigid trucks today but plans to move its dispatch to articulated lorries within a few years, for example, should size the platform for that plan rather than for today’s vehicles. Telling us about both current and expected vehicle types at the quotation stage lets us strike that balance correctly.