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Truck Scales 101

If you are considering the purchase of a truck scale, then understanding the termainlogy that you will hear is vital.  Truck scales are complex industrial equipment but knowing the basics is a great place to start.  In this guide we will walk you through the main compoents of a truck scale.  

Load Cell:

A load cell is a force transducer. It converts a force such as tension, compression, pressure, or torque into an electrical signal that can be measured and standardized. As the force applied to the load cell increases, the electrical signal changes proportionally. Most standard 70’ truck scales have (8) load cells. There are many different designs of load cells but the most accurate scales in the world typically utilize a rocker column or cannister design.

Junction Box:

Electrical boxes, also known as junction boxes, enclose wire connections. Most commonly, it’s where all load cells are terminated before the “home-run” cable sends a signal back to the scale house. Junction boxes help protect against short circuits, which can cause fires. Most junction boxes are made of a heavy-duty plastic but in wet applications we recommend stainless steel junction boxes.

Home- Run Cable:

This, along with ground cable, is run back from the junction box to the indicator which is commonly positioned in a scale house, or office. This type of cabling typically carries a digital signal and is a 7 conductor, shielded wire. All home-run cable should be ran in a PVC or stainless steel conduit of no less than 1” in diameter.

Indicator:

As a load cell analyzes the pressure being applied to it, the cells are summed together and then converted to a usable number, or “weight,” which is then displayed on an indicator. The indicator usually is inside but if often interfaced with a “scoreboard” or other outdoor type display.

Weighbridge:

This is used to define the steel structure of the scale without any electronics or components. The best truck scales weighbridges use an I-beam structure with nothing “boxing in” these beams or preventing them from receiving air flow under the scale.

Base Plates:

Typically the thickest steel associated with the truck scale, base plates absorb much of the load passed down through the load cell and often sit in very corrosive, or wet environments under the scale. Each load cell sits on a base plate and has a receiver cup that sits between the base plate and the load cell. The least amount of hardware and moving parts that are part of the base plate, the less that can go wrong.

Checking:

The most accurate and repeatable scales are made to move, or oscillate, with truck traffic. This embraces the i-beam design combined with a rocker column load cell. Checking ensures that the scale does not move too much as the trucks drive across them.

Foundation:

Today, most truck scales are installed with above-ground or concrete pit foundations. Depending on state or regional requirements, scales can also be installed in a shallow pit, as opposed to the deep pit required by older mechanical scales. A pit installation requires less space than an above-ground scale since longer approaches are generally required for above-ground configurations. However, pit-styles require sump pumps and drains, and are generally more vulnerable to corrosion due to potential standing water.

Bob Scott

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