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GLOSSARY OF TERMS When selecting a scale, there are certain things you should keep in mind in order to find the weighing device that best suits your needs. There are certain terms that are used in the weighing industry to describe scale specifications. Here are a few terms to help you decipher the industry jargon.
Accuracy - The scale's accuracy is the smallest increment of weight that the scale displays (display accuracy). Accuracy and capacity are the two most important specifications for selecting your scale. These are also factors in determining the cost, therefore you should select a scale based on the measurements you require. Accuracy is also referred to as Resolution or Readability. Calibration - The process of adjusting a scale's precision using known weights (calibration weights). Calibration should only be performed if your scale is not weighing properly. After calibration, the scale should display the exact weight that is placed on the tray (within a certain tolerance), and also go to Zero when removing any weight. Calibration Weights - These are known masses such as a 25 lb or 50 lb weight. It is important to use the correct calibration weight when calibrating a scale, otherwise, you scale could become highly inaccurate. For instance, if during calibration, the scale asked you to place a 50 lb weight on the platform, and you placed a 100 lb weight instead, your weight readouts on the display would show twice what their actual weight was. Calibration Certificate - A certified document provided by American Scale which provides proof of calibration along with information about when/where the calibration was performed, and with what weights. This service must be performed within the state that you will be using your scale. Calibration certificates are required for scales which are used to sell goods based on weight. If you are selling goods with your scale, it must be Legal-for-Trade and have calibration performed regularly. Capacitance Load Cell - In a capacitance cell, two thin metal wafers are set a small distance apart. As weight is added to the scale, the pressure pushes the two plates closer together. the signal is sent to a microprocessor which then converts it into a weight readout. Capacitance cells are designed to be more durable than strain gauge load cells, but may not be as accurate. Capacity - This is the maximum weight that the scale can accommodate at one time. The heaviest item that you place on the scale determines what capacity you need. Legal for Trade / NTEP Approved - If you are selling goods based on weight, the scale must be certified as Legal-for-Trade. This status is given to scales that meet certain guidelines and restrictions mandated by the Department of Weights and Measures. This ensures that consumers are protected against overcharges. Linearity - A scale's ability to produce the same accurate readout throughout the entire span. Linearity is mostly listed on specification sheets for the high-end precision/industrial scales and not for scales such as pocket scales. Repeatability - Like linearity, this is a specification most seen on precision/industrial scales specification sheets. It refers to the scale's ability to display the same weight consistently for an object and return to zero each weighing cycle. Strain Gauge Load Cell - Most digital scales use a load cell to convert weight to a digital signal. Load cells typically consist of a block of metal with a strain gauge attached that can detect the slight variations in stress on the metal. The strain gauge detects the change in electrical resistance and converts this to a digital signal. The scale's microprocessor converts this signal to a weight and displays it on the LCD. Tare - Tare is used to reset the scale to zero. This can be used to weigh items using a container that you set on the scale. To use the Tare function, place the container or tray (tare item) on the scale and press the Tare button. Your scale should go to zero allowing you to add items to the container and only see the weight of those items within it (net weight). Weighing Platform - The size of the scales weighing platform (also referred to as the Weighing Tray) is something else to consider when purchasing your scale. You want to have a large enough platform area to hold most of your sample. It is permissible for a portion of your product to hang over the side as long as it is balanced and centered on the platform. Your sample should never rest against anything other than the scale's weighing platform, otherwise you will receive an inaccurate reading.
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