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Choosing the Right Scale

A scale is an instrument for measuring mass. Scales have been around since ancient times when they worked by comparing objects with weights whose masses were known. This measuring principle has been modernized throughout history. While mechanical scales are still used today, electronic scales have become the norm. Scales are used in a wide range of applications, in industry, commerce, research, the medical field, and more.

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  • How to choose a scale

    There are a large number of scale models to meet the specific needs of different weighing applications, but regardless of the type of scale, you will choose a model based mainly on the following criteria:

    Range

    The range of a scale is defined as the maximum mass that the scale can measure, or more simply, the maximum mass value that the scale can display.

    When choosing a scale, define the required range by considering the maximum mass you will be required to measure with it and add a safety margin sufficient to avoid problems if you have to weigh a slightly larger mass than usual.

    Therefore, if you’re planning to weigh goods up to 20 kg, it’s recommended that you choose a scale with a capacity of 30 or 40 kg.

    You should also be careful not to overestimate the safety margin to avoid buying an unnecessarily high-performance scale at a higher price.

    Precision

    A scale’s precision corresponds to the smallest variation in mass and therefore also to the smallest mass that the scale is capable of displaying; for a digital scale, this corresponds to the last digit of the display.

    When choosing a scale, it’s also recommended that you choose a precision higher than the expected accuracy of the measurement. For example, if you want to measure masses to the nearest gram, you should select a scale with an accuracy of 0.1 g.

    Europe recognizes 4 classes of precision, as shown in the table below. The accuracy class is defined by the ratio between the scale capacity and the verification scale interval (Directive 2009/23/EC, Annex I, paragraph 2.1).

    Class Applications Number of Divisions

    (n=range/divisions)

    Verification Scale Division (e)
    I Special Analytical Scales

    R&D in the food industry, hospitals, etc.

    n > 50,000 e ≥ 0.001 g
    II High Laboratory Scales

    Pharmacies, medical analysis laboratories, etc.

    100 ≤ n ≤ 100,000

    5,000 ≤ n ≤ 100,000

    0.001 g ≤ e ≤ 0.05 g

    e ≥ 0.1 g

    III Medium Industrial and Medical Scales

    Industrial production, logistics, etc.

    Medical scales

    Weight/Price Scales

    Bakeries, butcheries, market sales, etc.

    100 ≤ n ≤ 10,000

    500 ≤ n ≤ 10,000

    0.1 g ≤ e ≤ 2 g

    e ≥ 5 g

    IV Ordinary Ordinary Scales 100 ≤ n ≤ 1,000 e ≥ 5 g

    Tray dimensions

    The size of the scale tray must be consistent with the dimensions of the objects to be weighed.

    Minimum weight

    The minimum weight corresponds to the smallest load below which the uncertainty of measurement is considered too great in relation to the measured load.

    Calibration

    To check the accuracy and precision of a scale, there are two types of calibration:

    • Internal calibration: The scale is self-calibrating thanks to a built-in test weight.
    • External calibration: Requires the use of test weights.

    Protection rating

    The working environment will determine the material and protection rating of your scale.

    The materials commonly used to make scales are:

    • ABS: For standard applications
    • Steel: For intensive use
    • Stainless steel: More hygienic and resistant to corrosion and chemicals, widely used in the food, cosmetics, and pharmaceutical industries

    The necessary protection ratings can be classified according to the scale’s working environment:

    • IP 40: Office use
    • IP 54: For use in lightly dusty industrial environments
    • IP 65: Brief contact with liquids, dustproof
    • IP 67: Brief use in damp areas, dustproof
    • IP 68: Extended use in damp areas, dustproof

    Options

    For certain applications, you will need to pay close attention to the scale’s communication capabilities (Ethernet, USB, RS232, etc.), which allow you to connect the scale to a computer, printer, etc.

  • What are the different types of scales?

    In this guide, we’ll be focusing on electronic scales, because although mechanical scales are still available, electronic scales have become the norm.

    There are many different types of scales, and they can be classified according to their configuration or the applications for which they have been designed.

    KERN & SOHN pocket scale

    KERN & SOHN pocket scale

    Pocket scales

    • Small, portable, and lightweight, these electronic scales are ideal for weighing small items (up to 500 g depending on the model)
    • They are highly accurate (down to 0.001 g)
    • Applications: Jewelry, pharmacy, cooking
    METTLER TOLEDO benchtop scale

    METTLER TOLEDO benchtop scale

    Benchtop scales

    • This category includes all scales designed to be placed on a desk, counter, lab bench, etc.
    • These scales can weigh masses from 200 g to 50 kg.
    • These electronic scales are available in a range of materials (plastic, steel, stainless steel, etc.) to suit the working environment.
    • Applications: Industry, food processing, laboratories
    Gram platform scale

    Gram platform scale

    Platform scales

    • The main feature of platform scales is that the weighing platform is separate from the display, allowing great freedom in setting up the weighing station, and guaranteeing good visibility of the display even when weighing large loads. The platform can be placed on the floor or a table, with the display mounted on the wall, on a column, on the floor next to the platform, and so on.
    • These scales cover a wide range of capacities, from 3 kg to several tonnes.
    • They offer a range of platform sizes and configurations (wide, low to the ground, etc.).
    • Platform scales are sturdily built primarily from steel and stainless steel, and offer a high IP 67 or IP 68 waterproof rating.
    • Applications: Logistics (pallet and parcel weighing), industrial production, veterinary medicine, etc.
    Baykon floor scale

    Baykon floor scale

    Floor scales

    • These are platform scales for weighing very heavy goods (from 600 kg to several tonnes).
    • These scales are extremely sturdy, made of stainless steel or steel, and are waterproof for use in harsh environments. The weighing platforms are low to the ground for easy handling of heavy loads.
    • Applications: Industry, logistics
    A&D COMPANY analytical scale

    A&D COMPANY analytical scale

    Analytical scales

    • Also known as laboratory scales, these are used for high-precision weighing (with accuracy in the submilligram range).
    • Because of this level of accuracy, these scales can be fitted with an enclosure to isolate the weighing tray from air movements that could interfere with weighing.
    • Applications: Laboratory applications
    Mettler Toledo counting scale

    Mettler Toledo counting scale

    Counting scales

    • These scales are designed for counting small, identical parts in bulk. The scale must first be set up by weighing a sample to determine the reference mass of a single part. The scale then calculates the number of pieces in a batch by comparing the batch weight with the reference weight.
    • Applications: Screw counting
    KERN & SOHN commercial scale

    KERN & SOHN commercial scale

    Commercial scales

    • These scales are used for commercial transactions based on price by weight.
    • They display the item’s reference price, weight, and total price, often with a dual display for seller and buyer.
    • These scales have stainless steel trays, as these transactions usually involve food; the scales must therefore be hygienic and easy to clean.
    • Applications: Food sales

    Regulated scales

    • For certain applications, standards require scales to be approved (calibration control, periodic verification) to guarantee their legal use. This is particularly the case for commercial scales, scales used in legal or regulatory settings, scales used in pharmacies, and so on.
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