Truck Scale Buying Guide - Mettler-Toledo

Project Management Site Validation Design Considerations Scale Performance

Guide Book

Your Next Truck Scale Project Components and Execution

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The purpose of this guide is to provide educational information to both new and sea- soned truck scale buyers. It is intended to provide more and different information than you find in sales brochures. While brochures typically discuss “who” and “what,” this guide answers “how” and “why.” Most content in this guide is intended to be unbiased and universal in nature. However, there are occasional notes that reflect information about METTLER TOLEDO products. Most often, this is to explain how our systems and components work. You should have no trouble distinguishing the universal information from the information that is specific to METTLER TOLEDO. METTLER TOLEDO is not the only company that makes good truck scales. However, we believe that our products provide exceptional quality and meaningful innovations. Our hope is that this guide will help you judge for yourself.

Truck scale systems, including the weighbridge, load cells, software, and accessories, should be hand-picked to suit your business and its needs. With some fairly basic con- siderations, you can establish your requirements for a weighbridge that should last many years.


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Introduction and Terms to Know

Section 1

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How a Truck Scale Works

Section 2

p. 11

Truck Scale Applications and Solutions

Section 3

p. 19

Site Planning

Section 4

p. 29

Truck Scale Selection Basics

Find all the information you need for your next truck scale project.

Section 5

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Load Cells

Section 6

p. 47

Weighbridge Specifications

Section 7

p. 55

Initial Scale Costs and Ongoing Performance

Section 8

p. 65

Installation and Certification

Section 9

p. 71

Maintenance, Service and Warranty

Section 10

p. 79

Scale and Weight Regulations



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Terms to Know

Truck scales are used all over the world. Businesses large and small, as well as transportation agencies, weigh trucks carrying everything from corn and coal to durable goods and solid waste.

Beam slab foundation

A scale foundation using concrete beams poured into an excavation Concentrated Load Capacity, a rating used by NTEP in the United States to define the maximum capacity for a single group of axles Typically a digital system that is designed to monitor and control for one or more variables that can affect weighing accuracy The weight of the loaded truck, meaning the truck and the load combined Set of weighing equipment regulations used by NTEP/NIST in the United States One or more boxes, typically located at the scale, which join the cable connections of the load cells with the scale terminal A term used to describe a scale used for business transactions, which must meet certain performance guidelines


The most common use of a truck scale is to determine the weight of bulk goods being bought and sold in truckload-sized quantities. In those cases, information from the scale is a crucial part of the business transaction. The scale functions much like a cash register. Enforcement agencies use truck scales to check for a truck’s compliance with road-going vehicle weight limits. They are also used to monitor intake and output volumes at facilities, such as solid waste processing and recycling centers, construction sites and more. Most truck scales are located outdoors. That means they must be able to withstand all environmental challenges while working reliably and accurately. Depending on the environment and application, most truck scale owners expect a scale to last 10 to 20 years. Truck scales are important to the daily operations of many of the facilities that use them. They also have a relatively long useful life. That means that selecting a truck scale is an important decision – one that can benefit (or burden) its owner for decades.

Compensation (also digital compensation)

Gross weight Handbook 44 Junction box

Legal-for-trade (or LFT)

Load cells Metrology Net weight

The sensory devices used to measure the weight on the scale

The scientific study of measurement

The weight of the load by itself, minus the weight of the truck. Net weight is often calculated as: gross – tare = net




Weights and Measures authority recognized by the United States and others Weights and Measures authority recognized by many European and Asian countries A scale foundation that uses variable depth concrete piers under each of the scale’s load bearing points A scale foundation that is excavated so that the driving surface is flush with the surrounding ground level


Pier foundation

Pit foundation

Above-ground (or open-sided) foundation

A scale foundation designed to have one or both sides open

Tare weight

The weight of the unloaded truck The scale interface, or control unit


Tread plate

On steel deck scales, the driving surface is often a steel plate with a dia- mond-tread pattern to benefit traction The structure of the scale that the truck drives onto in order to be weighed. Sometimes used to refer to the entire scale.




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Section 1 Anatomy of a Truck Scale

Becoming familiar with basic components

Nearly all truck scales have some common components that work together to measure weight. Scale buyers should be familiar with these components to determine the scale that is best equipped for their needs.


1 - Main Components of a Truck Scale

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1 - Main Components of a Truck Scale

8. Weighbridge Also known as the scale deck, this is the structure that creates the driving surface for the trucks. The weighbridge is typically composed of modular sections that are linked together. 9. Junction Box Many scales require numerous junction boxes as connection points for the load cell cables. However, some newer systems no longer require junction boxes. 10. Load Cells These are the sensors that measure the weight on the scale. Modern scales use load cells as integral structural components. 11. Load Cell Cable The signal from the load cells must be transmitted to the terminal. In most cases, this is done with cables.

12. Unattended Station Unattended weighing offers an effective strategy for increasing productivity, decreasing operating costs, and decreasing in-person contact. It enables drivers to process their own weighing transactions without the need for a scale operator. 13. Traffic Control Light Traffic lights indicate to the driver whether to stop or drive forward during the weighing process. 14. Remote Weight Display A large, digital weight reading is helpful to display a truck’s weight to the driver.

1. Ramp Ramps are used to bring the truck to the same level as an above-ground scale. 2. Gate Gates can be programmed to open and close at specific points during the weighing process to guide drivers. 3. Approach The approach allows trucks to enter the scale from a level surface to ensure accuracy. 4. Scale House The scale terminal and operator are normally located in the scale house.

5. Terminal Also referred to as an indicator, the terminal is the control panel for the scale. It serves as the connection point for other scale peripherals. 6. Computer Scale software on a computer plays an increased role for sites large and small, automating data capture, speeding up weighing times and reducing opportunities for errors. 7. Printer Used for printing transaction tickets, a printer can be located in the scale house or within an unattended station.



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Section 2 Truck Scale Applications and Solutions

Finding the right fit for your weighing application

Truck scales are used for a variety of applications, from verification of inventory to trade of high-end chemicals. The addition of truck scale software can further customize and automate your operation.


1 - Common Truck Scale Applications

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2 - Types of Scale Terminals

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3 - Types of Truck Scales

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4 - Types of Scale Software

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5 - Automate the Scale House

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1 - Common Truck Scale Applications A truck scale can accomplish a variety of applications within your industry, from veri- fying inventory of goods to being the cash register that sells those goods. Below are the common uses of a truck scale. Find the right solution to fit your weighing demands.

2 - Types of Scale Terminals

The design of truck scale terminals varies to suit your needs. Choosing the right terminal can help streamline your business operations.

Scale House Truck Scale Terminal

Unattended Terminal


Verification / Check

Trade / Transaction


A standalone scale terminal is often stored in the scale house and serves as the control panel for the scale. It displays the weight value to the oper- ator, and often serves as the connec- tion point for other scale peripherals such as scoreboards and printers. Manual processing speed due to the required interface between driver and scale operator

Unattended terminals allow you to weigh vehicles and capture informa- tion, 24 hours a day, 7 days a week, without the need for a scale operator. These highly configurable systems can be set up to match the needs of your operation. Fastest processing speed due to the truck driver not having to get out of the truck cab

Application Overview

When a customer wants to use the truck scale to either buy or sell their commodity

When a customer is transporting their goods by truck and wants to ensure that they are compliant with local roadway loading requirements

When a customer is using the truck scale to track and trace the ma- terial they supply and/ or receive

Processing Speed

Desired Outcomes

• Reduce fines • Minimize delays • Optimize loads

• Track supply and inventory • Reconcile billing/in- voices • Reduce fraud and errors

• Accurate and compli- ant billing/ payment • Reduce fraud and errors • Provide exceptional customer service

$ $ $

$ $ $

Typical Project Cost

Additional Information

• Performs simple transactions with gross, tare, and net weights • Can control basic traffic systems

• Performs advanced transactions • Saves yard space and cost by not having to build and staff a scale house Unattended terminals are most often used at sites with heavy truck volume that require a higher level of efficiency and security

Typical Application

Scale house terminals are typically used at sites with 1 to 2 scales and lower daily truck traffic



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3 - Types of Truck Scales Different truck scales are better suited for certain applications. The table below can help match your application to the right truck scale for you, taking into consideration cost, volume, and truck type.

Single-Axle Truck Scale

Full-Length Truck Scale

Multi-Axle Truck Scale

Weigh-In-Motion (WIM) Truck Scale


Similar to a full-length scale but same profile as a full-length scale but with one key difference: instead of intercon- nected modules and shared load cells, each module has its own cells. This allows for the scale to capture both full truck weight and individual axle weights.

In-ground single platform WIM scales capture axle weights while the vehicle is in motion and calculate a vehicles gross weight. WIM scales provide an efficient way to ensure that vehi- cles comply with local highway weight limits.

Composed of a single platform, large enough for a single set of truck axles. These cost-effective scales allow you to weigh each axle separately. In or- der to determine full truck weight, you then add all of the weights together.

Composed of multiple platforms that are connected together to accommo- date an entire truck. This is the most common type of truck scale set-up because most legal-for-trade rules specify that the entire truck be weighed at once.

Processing Speed

Lowest processing speed due to multi- ple stops by the truck

Medium processing speed due to only a single stop by the truck

Medium processing speed due to only a single stop by the truck

Fastest processing speed due to no stops by the truck

$ $ $

$ $ $

$ $ $

$ $ $

Typical Project Cost

Additional Information

• Profile is ideal for sites with space restraints • Solution is not accurate enough for legal-for-trade weighing Single-axle scales are most often used to check compliance against lo- cal roadway limits

• Can be used bi-directionally for legal-for-trade weighing • Cannot capture individual axle weights Full-length truck scales are often used in applications that require a le- gal for trade transactions

• High performance due to more load cells being used in the system • Not designed for bidirectional weigh- ing Multi-axle scales are most often used to in legal-for-trade applications that also want to check for compliance against local roadway limits

• Profile is ideal for sites with space restraints • Solution is not accurate enough for legal-for-trade weighing WIM scales are most often used in applications with heavy truck traffic that require a compliance check against local roadway limits

Typical Application

Consideration for the Future Weigh-in-motion (WIM) solutions have traditionally been utilized by industries such as law-enforcement and logistics, but this technolo- gy is quickly advancing. For operations wanting to boost productivi- ty and throughput, certain WIM solutions could be a good fit. As regulations in legal-for-trade weighing progress, you can be pre- pared for the future by exploring WIM today.



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4 - Types of Scale Software Every business uses software to perform daily tasks. Truck scale software can comple- ment your weighing needs by keeping digital records or performing transactions.

5 - Automate the Scale House Automating your business processes increases productivity and accuracy while decreasing human error. This increase in efficiency results in a timely return on your investment.


Check / Verification

Trade / Transaction

Basic Scale House Software

Advanced TruckScale Software


Basic truck scale transaction soft- ware is used at a single site with 1 to 2 truck scales. It interfaces directly with the scale terminal and can sup- port the pretransaction process by storing customer, vehicle, and prod- uct information in a secure database.

Advanced truck scale software is highly customizable and is best suit- ed for sites with multiple scales that want a greater level of visibility into their truck scale process. It offers ad- vanced reporting that can be deliv- ered quickly to back office operations for review. Fastest processing speed due to customized set up and advanced transaction features

• Scale Type:

• Scale Type:

• Scale Type: Full-length • Terminal Type:

Weigh-in-motion • Terminal Type: In-motion weighing terminal • Software: WIM application software

Weigh-in-motion • Terminal Type: In-motion weighing terminal • Software: WIM application software

Unattended terminal

• Software: DataBridge transaction software

Processing Speed

Medium processing speed due to storing presets of vehicle, product, and customer data

• Scale Type: Multi-axle • Terminal Type:

• Scale Type: Full-length • Terminal Type:

• Scale Type: Full-length • Terminal Type:

$ $ $

$ $ $

Typical Project Cost

Unattended terminal

Unattended terminal

Unattended terminal

• Software: Transaction management software

• Software: Transaction management software

• Software: Transaction management software

Additional Informa- tion

• Typically a single-user network • Electronically stores standard re- ports and transaction tickets

• Can be networked across multiple sites • Remotely calculates transactions via web browser, providing you with pricing flexibility Advanced software is used at sites that are focused on improving both the accuracy and speed of their transaction process

• Scale Type: Single-axle • Terminal Type:

• Scale Type: Full-length • Terminal Type:

• Scale Type: Full-length • Terminal Type:

Typical Application

Basic software is used at sites that want to improve the accuracy of their scale data by eliminating manual data entry

Standalone indicator

Standalone indicator

Standalone indicator

• Software: Transaction management software

• Software: Transaction management software

• Software: Transaction management software

Solution Accuracy



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Section 3 Site Planning

Ensuring operational efficiency

Most buyers expect their truck scale to last 10 to 20 years, depending on their application. That means that when it comes time to develop a plan for the scale site, it is important to consider your future needs. The layout should be adequate, efficient and able to accommodate growth in your operation.


1 - Site Conditions

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2 - Foundation

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3 - Approaches and Ramps

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4 - Scale Site Layout

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5 - Locating the Scale House

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6 - Peripherals and Traffic Control

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7 - Hazardous Areas and Materials

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1 - Site Conditions

Pier Foundation The least expensive foundations use variable depth piers. Concrete piers are poured under each of the scale’s load-bearing points. The total capacity of the scale determines the footprint of the piers, which are then dug to undisturbed soil below the frost line. The soil must have a minimum bearing capacity of 12,200 kg/m 2 (2,500 psf). It can be helpful to include a thin washout slab poured around the piers to aid in periodic cleaning.

There are a few site condition considerations that must be accounted for: subsurface obstructions, drainage, and soil bearing pressure.

Obstructions Subsurface obstructions include human-fabricated obstacles, such as water lines, gas lines, power lines, sewers, drains, and old landfills. They must be moved or avoided. Natural obstacles that must be considered include high water tables, boulders, bedrock and sinkholes. If you have any doubt about what’s under your site, consider ordering test borings before you start excavation. Drainage Every scale located outdoors needs adequate drainage. You do not want excessive storm water or snow-melt flowing over, through, or into your scale. Open-sided scales usually allow water to flow off the foundation naturally. Pit scales, on the other hand, need sufficient drain piping and/or sump pumps. If your area experiences freezing temperatures, also consider frost heave. Damage to the scale foundation can result from the subsurface around the scale expanding and contracting. Adequate subsurface drainage reduces that risk. Soil Bearing The soil at the site needs to be strong enough to support the foundation, the scale and the loads the scale will weigh. That is determined by establishing the soil bearing pressure at the site. Many facilities will have this information on file from construction records when the site was developed. If not, and depending on your area, a civil engineering agency can assess the soil. The soil’s strength may have an impact on the design of the foundation to be used. Specific requirements will be noted on your scale company’s foundation drawings. These typically range from 7,300 kg/m 2 to 12,200 kg/m 2 (1,500 psf to 2,500 psf). If the soil bearing capaci- ty is too low, the foundation design may need to be modified to compensate. 2 - The Foundation A stable foundation is critical. Any movement or settling may throw your scale out of adjustment and neces- sitate recalibration, or worse. Continued movement would mean a continuing need for recalibration. Over time, an unstable foundation could move enough to exceed the scale’s corrective capacity, in which case you must start all over again and build a new one. The foundation must be designed and installed properly. Work closely with your scale supplier. They can advise you on acceptable foundation designs for your locale and they probably have the names of several contractors who have done good foundation work in the past – those who can get the foundation in straight, plumb and level. There are several types of foundation designs. Here, we discuss the two most common ones.

Beam Slab The beam slab foundation has extra excavations beneath the slab into which additional concrete is poured for added support. It will typically include beams running the length of the scale along each side, as well as beams running the width of the slab. In combination, those beams make a ladder-bar formation below the visible slab. Minimum bearing capacity is approximately 7,300 kg/m 2 (1,500 psf). A beam slab foundation is stronger than a pier-style foundation.

Pit Foundation Pit foundations may be designed to allow service technicians adequate space to access components be- neath the weighbridge. The recommended soil bearing capacities are similar to the beam-slab foundation.



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3 - Approaches and Ramps The approach is the part of the scale foundation that the truck drives over just before driving onto the weighbridge or scale deck. In addition to the approach, the scale may need a ramp where the road transitions to the scale foundation. Guidelines for the ap- proach are defined by the Weights and Measures authority in some areas. For example, in the United States, a general recommendation is to make the length of the approach twice the width of the weighbridge. However, specific requirements for approaches often are defined by local authorities depending on the types of trucks you are weighing and the materials they are carrying. There may be a max- imum grade (slope) for approaches and ramps – for example, ½ inch per foot in the United States. Be sure to check the standards for your location. Approach requirements like these are minimums and do not guarantee that every truck can maneuver onto the scale without difficulty. You may need longer approaches if the trucks are coming off a turn and you are installing your scale above ground. Your scale supplier can give you advice on approaches. A popular recommendation is to have an approach on each end of each scale (required in some areas). That minimizes the lateral forces generated by trucks driving off. It also gives you the option of two-way traffic over the scale, which is an added measure of flexibility in your traffic pattern.

4 - Scale Site Layout

Let’s consider the number of trucks you will be weighing each day. In most cases, each truck will be weighed twice: Once loaded and once unloaded. Small commercial Small commercial operations typically make 50 to 100 weighments per day. Unless all trucks arrive at the same time, the requirements for parking and maneuvering will be minimal. One scale should accommodate this volume well, so plan on two-way traffic over it. Make sure there is a bypass around the scale as well. Moderate-volume Moderate-volume operations typically make 100 to 200 weighments per day. These sites should determine when trucks will be arriving and departing because a parking/staging area may be required. The scale queue should not extend onto public streets or highways. These sites may be able to operate with a single scale and bypass if the traffic flow at peak times is manageable. However, two scales can offer advantages. High-volume High-volume operations typically make more than 200 weighments per day. Planners at these sites should be thinking in terms of traffic patterns (control lights and gates, marked roadways, etc.) not just a parking area. These sites require two or more scales. If you expect to handle a significantly higher volume of traffic, you should consider more than two scales. For maximum flexibility, the scales should be able to handle loaded or empty trucks from either direction. There should also be a sufficient bypass around the scales.



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Layout Drawing Draw a complete plan of the area and think about an average day. • Where do the trucks go when they arrive? • Will there be a queue (either or both ways) to use the scale? • Where do trucks go after being weighed? • Is there enough maneuvering room between the scale and the loading docks, considering the turning radius of your largest vehicles? • Do you need a trailer storage area?

Filling Applications Some sites use their scale as a filling tool, where exact amounts of product need to be dispensed into the truck. These locations may have overhead filling equipment that can limit the vertical space the scale can occupy. Share intentions to use your scale in filling operations with your scale supplier. They may be helpful in suggesting the best configuration and additional scale accessories for these operations. When estimating the amount of traffic, consider how your operation will use a scale. Consider whether traffic flow is constant, or if it is significantly greater at certain times of day, month, or year. How long will a truck remain on the scale? Plan your installation to handle the peak periods. 5 - Locating the Scale House The scale house is typically near the scale and may contain indicators, printers and other control devices. Data from the scale can be transferred online or in batches as needed to other locations.

Then consider the what-ifs. • What if a scale is down for maintenance or repair during the day? • What if you get a heavy snowfall, or a heavy rainfall? • What if the capacity of the plant is increased? • What if drivers are forced to wait before they can load or unload? • What happens during the busy season?

Testing the Location It can be worthwhile to perform a test of your selected site before breaking ground. That can be done with the help of traffic cones or other markers to signify the intended location of the scale and accessories. If possible, drive a truck through the configuration to check for issues. Ask experienced drivers if you are unsure of the space they need to maneuver. Housekeeping The buildup of spilled material, packed debris, frozen snow/ice, road mud, etc., under or around the scale can have a significant impact on its life and performance. That is why many suppliers and customers advocate for an open-sided design that can be regularly cleared of stray material. Locating a water hydrant near the scale can aid in regular cleaning operations, so long as pressurized water spray does not present a problem to the load cells, cables, and/or junction boxes at the scale. Mining and aggregates facilities in particular have had success installing wheel/truck wash lanes before the scale. With an automatic wash lane for cleaning the trucks before they approach the scale, the amount of dirt, mud and gravel falling off the trucks is greatly reduced. It limits the chances for the debris to interfere with the operation of the scale. It also allows for a more accurate weight reading.

With the scale house adjacent to the scale, the scale operator can: • Monitor traffic • Communicate with drivers • Transfer paperwork to drivers • Make sure the truck is on the scale properly • Identify the truck and inspect cargo

Ideally, the scale house should be situated so that the operator inside can see the truck to ensure that it is com- pletely and properly on the scale. The driver may not notice if the rearmost axle is not entirely on the scale. Or, some sites with pit scales have had issues with the placement of a truck’s tires along the side of the scale. If the tires are not 100% on the scale, the weight reading will be inaccurate. To ensure proper placement of the truck on the scale, some have even used optical sensors. Video monitoring and voice intercoms can also work well if you are unable to put the scale house near the scale. Many scale companies now offer unattended terminals for driver self-service. These terminals often take the form of a drive-up kiosk that allows a driver to complete a transaction and log data without assistance from a scale operator. Unattended terminals can be advantageous in situations in which 24/7 access is required or when an organization processes repeated similar transactions.



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6 - Peripherals and Traffic Control

• Scale-mounted guard rails are attached to the weighbridge, by either bolting them to a bracket or welding them to the side of the weighbridge modules. They often can be supplied and installed by the scale supplier. • Standalone guard rails are built alongside the scale, but are not attached to the weighbridge. In most cas- es, guardrails will offer superior protection from driving off the side of the scale. They are not always avail- able directly from the scale supplier. Instead, they may need to be sourced and installed by the contractor preparing the foundation. 7 - Hazardous Areas and Materials If you will operate the scale in hazardous areas (flammable or explosive atmospheric concentrations of gases, vapors, mists, dust, or fibers), you will need a scale that has approval (generally from FM, UL, or ATEX) for use in your environment based on its classification. Hazardous area approvals typically are noted on the specifications data for load cells and terminals. For example, some hazardous area classifications place a limit on the amount of voltage that can be used in equipment. Some regulations require the use of energy-limiting barrier boxes to isolate signals. A good scale supplier should be familiar with these requirements and the types of peripherals that may be used in various areas.

Terminals Your scale will have a control unit, often called a terminal or indicator. It can range from simple to elaborate. Below are some of the advanced features you may consider when choosing a terminal: • Control more than one scale with a single terminal • Connect with USB/Ethernet to computers and networks to interact with scale software, transfer data across company networks, and take advantage of remote diagnostics

• Benefit from wireless connectivity with the scale and other accessories • Automate other scale accessories, such as gates and lights for traffic control • View data on graphic displays with varying levels of detail • Store tare/net weights with various memory capacities for transaction logging • Connect to various compatible ticket printers

The terminal also may serve as the power supply to some or all the load cells. Some will specify how many load cells they are able to support. If the power supply to the terminal is subject to fluctuation in your area, consider using an aftermarket power conditioner.

Please note: Hazardous area classification is not the responsibility of the scale supplier. A qualified safety officer at a customer site or local industry regulator must make that determination.

Gates Some sites place gates at one or both ends of the scale. Whether controlled manually or automated, these gates can indicate when a vehicle should drive on or off the scale. This can also be accomplished with traffic lights. Lights Often a green and red traffic light is placed alongside the scale to control the flow of traffic. These lights can be controlled manually or automated. Remote Displays A remote display is a numerical display unit that indicates the weight on the scale. They are often placed at the front of the scale so the drivers and/or filling operators can see the weight of their truck when it is on the scale. Guide Rails Also called guard rails or rub rails, guide rails are an option for most truck scales, although some industries and safety regulations require them. They can be used with pit-style scales to provide guidance to the truck driver approaching the scale. They are more frequently used with above-ground (pitless) scales as a safety device to prevent trucks from driving off the edge of the scale. There are two styles of guide rails.



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Section 4 Truck Scale Selection Basics

Decisions every scale buyer must make and what to know before talking to suppliers

The size, style and configuration of a truck scale can depend on the needs of the purchaser. However, there are also choices that are more subjective. This section discusses some of the fundamental aspects that differentiate one scale from another.


1 - Truck Types, Loading and Usage

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2 - Configuring and Sizing the Weighbridge

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3 - Site Conditions, Construction, and Foundation

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4 - Weighbridge Selection and Options

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5 - Scale Terminal Selection and Operator Tools

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6 - Transaction Management and Automation

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1 - Truck Types and Volume The truck scale is mechanically and structurally designed to support the volume, gross vehicle weight (GVW), and axle group weight of the trucks that will be weighed. Two truck types often weighed by truck scales are over-the-road trucks and off-road trucks. Trucks that are designated to travel over roads must adhere to federal transportation weight and load restrictions. For example, the U.S. Federal Highway Administration (FHWA) of the Department of Transportation sets GVW and axle load limits based on the length of the vehicle. Bridge formula weight calculations set truck weight limits to protect roads and bridges from premature wear and failure.

Important Operational Considerations

• Scale traffic flow: Whether traffic is unidirectional or bidirectional, both will affect truck queuing, traffic control systems, and scoreboards. • One-pass or two-pass weighing: Capturing empty and full truck weights versus using stored tare weights can double scale house weighments per truck but provides a more accurate net weight per truckload. • Scale house and after-hours operation: Processing trucks after normal operational hours may require duplicating scale house systems. • Target truck processing time: Typical manual scale house processing can take up to 5 minutes per truckload. This can create a bottleneck with inbound and outbound trucks causing inefficiency and lines. Automating scale house operations can reduce truck processing to <1 minute. 2 - Configuring and Sizing the Weighbridge The most common truck scale configuration is a full-length scale which provides a single, legal-for-trade weight per truckload. Multi-axle truck scales provide legal-for-trade gross truck weight, as well as separate legal-for-trade sectional axle group weights to ensure proper distribution of loads. Axle scales check axle group loads as a non-legal-for-trade load compliance check. Axle scales can be used as static weighments or in-motion at lower speeds, typically <5 to 8 mph (8 to 12 kph). The deck of your weighbridge needs to physically accommodate the footprint of the largest truck you plan to weigh. It is recommended to size the truck scale by adding 10 feet to the length of the largest truck you plan to weigh. This allows faster and easier positioning on the scale for each driver. Many scale manufacturers will offer standard-sized weighbridges, but will also accept custom dimensions. If you are replacing a pre-existing scale and utilizing an existing foundation, you will need your new scale to fit those dimensions.

Truck Traffic Type

A fundamental determination for selecting the correct truck scale is determining traffic type: • Over-the-road vehicles • Off-road vehicles • Combination over-the-road and off-road vehicles Truck scales for off-road vehicles are designed to the specifications of the vehicle. For example, a CAT 797B off-road vehicle has a gross vehicle weight of 1.375M pounds or 687 tons on a 23.5-ft wheelbase, requiring a highly specialized weighing structure.

Single-Axle Truck Scale

Full-Length Truck Scale

Truck Volume

Scale weighbridge structures are designed for the average loads that will be applied over the life of the structure, which is typically 20 years. High volume loads can prematurely wear out the mechanical structure.

The typical truck scale processes <100 trucks per day on average and is considered low volume (<25,000 per year). High volume operations processing 200 to 500 trucks per day (50,000 to 125,000 trucks per year) may require heavier duty weighbridge structural designs. Seasonal operations may see high truck volumes during harvest or construction seasons, but on average may have lower annual truck volumes.

Multi-Axle Truck Scale



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3 - Site Conditions, Construction, and Foundation A truck scale is a large construction site requiring up to 200 ft (60m) in length and 20 ft (6m) in width of yard space, not including the scale house. Positioning and placement of the truck scale for each site is critical to the efficiency and safety of the operation. Below are the site specific considerations for new truck scale installations.

4 - Weighbridge Selection and Options

A truck scale is a long-term capital asset purchase. Consider trade-offs in asset life, durability, performance, and price.

Design Requirements and Considerations

Site-Specific Considerations

Scale Capacity / Scale Accuracy All truck scales are certified by the local Weights and Measures authority. This authority defines the capacity and accuracy limitations for legal-for-trade applications. Scale division size is based on load cell weighing sensor performance and W&M certification testing. Typical truck scales have a standard division size of 20 lb (10 kg). Higher performance systems can be certified to 10 lb (5 kg) divisions for improved accuracies on smaller vehicles and higher value material. Durability / Scale Life Factors • Structural design life (typically 20+ years) • Estimated load cycles per year (# of truck loads per year) • Safety factor of designed loads (axle group loading, typically 1.5X to 2.5X legal over-the-road) • Verified life cycle testing of designs (typically 2M load cycles at design load)

Truck scales can be installed either flush to the drive surface (in-ground) or raised above ground. There are advantages and trade-offs to both types.

A pit-style scale is placed in an excavated foundation In-ground considerations: • Requires less yard space • Allows cross traffic • More expensive foundation • Susceptible to material build- up in the pit • Requires active drainage system • Maintenance in the pit re- quires confined space safety considerations

Some sites find an open-sid- ed scale easy to clean Above-ground considerations: • Requires more yard space • Less expensive foundation • Less susceptible to material build-up • Raised driving surface can create driving and driver safety issues • Better maintenance and service access

Suitable scale placement can increase the efficiency of a site

Concentrated Load Capacity (CLC) Sectional load test during W&M certification. This is not a measure of design durability.

Other site considerations: • Turning radius for truck alignment

Load Cell / Weighing System Selecting the right load cell system is critical for the truck scale buying process. Typically, the load cell system is the truck scale component that is most susceptible to environmental damage and critical for accurate weighing.

• Hazardous area classification • Truck traffic flow and queuing • Driver and scale house oper- ator safety

Design requirements to consider: • No junction box or load cell termination enclosure at the weighbridge • No legacy strain-gauge analog load cells (50+ year old sensor technology) • Digital, smart sensor network only

Environmental Protection The truck scale is typically positioned outside in the environment and thus can be affected by water, flooding, extreme temperature changes, lightning strikes, rodents, and material build-up.

Critical environmental criteria to consider: • IP68 (high pressure washdown) / IP69K (submersible) rated load cells • Stainless steel hermetically sealed load cells

• 3rd party lightning tested and certified electrical system • Stainless steel shrouded cables to protect against rodents



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Concrete Deck vs. Steel Deck Drive Surface

Scale Options

Truck scales are designed with either steel tread-plate or poured concrete drive surfaces. The customer should select their driving surface based on these differentiating factors.

Guide Rails: Scale mounted guides provide a visual aid to ensure drivers keep the truck on the scale.

Manholes: Pit foundation access may be provided through manhole access in the weighbridge.

Concrete Deck • Weighbridge mass is heavier and more stable to withstand the dynamic loading of over-the- road trucks, 1.5X the weight of a typical over- the-road tractor trailer • Reduced slip hazard in wet or icy conditions

Steel Deck • 2 to 3 week faster installation time

• Portability options available for easy transport from one location to another with simple as- sembly

Scoreboards / Driver Displays: Provides drivers with a large visual display of active weight reading.

Dump-Through Scales: Trucks are emptied through the center of the scale to lower conveyer systems.

Scale Risers: Risers raise the weighbridge to prevent material build-up and to allow easier cleaning.

Custom Finishes: Weighbridges are protected against corrosion with special paint and steel finishes.

Portability Frames: Steel outer structure that allows the weighbridge to be moved for short-term use.

Traffic Control: Automated lights, loops, and photo eyes manage traffic near the scale.



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5 - Scale Terminal Selection and Operator Tools The scale terminal is the primary weight display of the scale. It is typically mounted in the scale house and is an integral element of a Weights and Measures certified system.

6 - Transaction Management and Automation The scale house and truck scale system often operates as the cash register for bulk mate- rial operations. Effectively managing truck scale transactions is critical to the business.

Typical Scale Terminal Functions • Displays weight value • Performs simple transactions with gross, tare and net weights • Stores tare weights to calculate net weights • Calculates simple accumulations, for example, daily tonnage per truck or commodity • Outputs data to a printer, remote display, and other peripheral devices • Stores limited data and transaction information • Offers self-diagnostics

Typical information captured at the scale house includes: • Material type • Price • Truck weight (tare) • Net weight • Customer/account number • Purchase contract • Third-party hauler information • Driver identification number

• Truck identification number • Surcharges, fees, taxes

• Material grade • Material origin

Transaction management software manages the inbound and outbound truck process and also controls: • Interfaces with scale terminal for control of scale, traffic lights, loops and gates/barriers • Provides one-pass, two-pass and multi-pass weighing transactions • Offers a database with tables to store information about vehicles, products, accounts, etc.

Optional Scale Terminal Capabilities • Ethernet / TCP/IP network connectivity • Serial interfaces to common peripherals – printers, remote displays

• Configures reports and tickets • Calculates advanced pricing • Speeds up transactions with presets and group information • Imports and exports data

• PLC / process control connectivity • Manage basic traffic control system • Operates multiple scales with a single unit

Automated Scale House / Unattended Systems

Processing trucks while keeping the driver in the truck cab has many benefits and efficiencies for the bulk material operation. It allows faster processing time, it improves driver safety, and allows contactless processing to reduce health risks. Unattended systems are available and operate similarly to a banking ATM system. Unattended systems can be configured with the following automation tools: • Card/RFID reader for quickly identifying drivers and vehicles • Display for prompting drivers to enter data • Keypad/keyboard or touchscreen for entering data • Ticket printer • Wireless networking • Voice intercom capability (standard or voice-over-IP) • Camera systems for remote monitoring



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Section 5 Load Cells

Understanding the most important components in your scale

Load cells are the heart of any truck scale. They are the sensors that measure the weight of objects on the scale deck. Most truck scales require 6 to 12 load cells. They must work together flawlessly to provide accurate weight readings. There are a few popular types of load cells currently being sold for use in truck scales. Understanding the differences in their operation and features can help you choose a system that will be accurate and reliable, providing the most value from your investment.


1 - Evaluating Load Cells

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2 - Types of Load Cells

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3 - Load Cell Technology Comparison

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4 - Load Cell Geometry

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1 - Evaluating Load Cells You have a number of choices when it comes to load cells. Because load cells are the components that most closely affect scale performance, it is worthwhile to understand how they work and the guidelines they must meet. Do regulations require that they all perform similarly? Most scales are built to comply with the legal-for-trade requirements of Handbook 44, OIML R76, and/or other Weights and Measures regulations. Does that mean that different types of load cells perform the same because they meet the same guidelines? No. Load cell performance guidelines in Handbook 44 and OIML R76 include accuracy tolerances, or error thresholds, used for calibrations. However, the performance standards included in Handbook 44 and OIML R76 still reflect the capabilities of mechanical scales, which are largely antiquated. Mechanical scales have limited capabilities compared to more modern load-cell technologies. In other words, some load cells are capable of performing significantly better than the minimum required. So, what benefits do newer systems offer the scale buyer? • Accuracy A system that is designed to establish and maintain a high level of accuracy means that a business can avoid product or profit loss due to weighing errors. • Reliability A stable and resilient load-cell system means a more reliable scale with less downtime, fewer repair ex- penses and a lower cost of ownership.

2 - Types of Load Cells There are five predominant types of load cell systems used in vehicle weighing applica- tions: analog load cells, hydraulic load cells, hybrid analog/digital systems, digital load cells and POWERCELL load cells.

Analog Analog load cells have been used in truck scales since the 1960s. Each cell con- tains a precision-shaped piece of metal, often steel or stainless steel, that chang- es its shape slightly as a force (weight) is applied. The change is monitored by elec- trical strain gauges and is sent as an analog voltage signal to one or more junction boxes. The combined signal is then transmitted to the scale house where it is mea- sured and converted to a digital signal that indicates the weight. Hydraulic Hydraulic load cells are hydraulic pistons that compress a reservoir of fluid. The compressed fluid flows through individual hydraulic lines to a mechanism, some- times called a “totalizer,” that is located in or near the scale house. This mecha- nism then exerts the accumulated force of the combined fluid pressures onto an analog load cell. This load cell generates an electrical signal that indicates the to- tal weight on the scale. Analog/digital hybrid Here, analog load cells are connected to a junction box that converts the analog signal to digital. A digital signal is stronger and less susceptible to the weighing errors that can occur due to interference from external influences. Digital This is a load cell that generates an analog voltage, which is converted into a dig- ital signal within the load cell enclosure. The data from the cells is processed to determine the total weight. Utilizing a digital signal at the load cell and beyond pro- vides advantages because the signal is not susceptible to interference as analog load cell signals are. POWERCELL ® These load cells utilize digital electronics and are equipped with signal-processing capabilities at each load cell. The load cell can eliminate errors by monitoring and adjusting the weight measurement based on a number of criteria. This process is called digital compensation. POWERCELL load cells have also introduced features such as predictive diagnostics, self-monitoring, breach detection and remote diag- nostic that help ensure accuracy and eliminate downtime.

Now, let’s briefly discuss the various scale technologies in terms of their accuracy and reliability.

Special note: Before the introduction of electronic components, all vehicle scales were mechanical, supported by nu- merous levers and pivot components. Today’s designs require less steel, are more easily installed, and are more accurate and reliable than their mechanical predecessors. Some surviving mechanical scales can be upgraded to full load cell systems.

Keep in mind that METTLER TOLEDO has designed, built and/or serviced scales with each of these technologies.



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