Scale Information Database

 

SCALE TERMS EXPLAINED

 

When selecting a scale, there are certain things you should keep in mind in order to find the weighing device that best suites you. There are certain terms that are used in the weighing industry to describe a scales specifications. Here are some useful scale terms to know:


Capacity - This is the maximum weight that the scale can accommodate at one time. Your heaviest item that you place on the scale should determine what capacity you need. For instance, the Micro NHB balance has a 6000g capacity. This scale would be suitable for weighing small items that weigh less than 6000g.

 

Accuracy - The scales accuracy is the smallest increment of weight that the scale displays (display accuracy). For the Micro NHB 6000, the accuracy is 0.1g. This means that the scale counts up in increments of 0.1g (0.1, 0.2, 0.3, 0.4g......and so on). Another scale may have an accuracy of 0.5g, meaning it would count up by 0.5g like: 0.5, 1.0, 1.5.... Therefore, you would never see the display show: 1.4 or something. Accuracy and capacity, are the two most important specs for selecting your scale. They will also play a big role in how much the scale will cost. A scale that is 1000g x 1g is going to be cheaper than a scale that weighs 1000g x 0.1g. Therefore, you should select a scale based on the accuracy and capacity you require. Accuracy is also written as Resolution or Readability.

 

Weighing Platform - The size of the scales weighing platform (also written Weighing Tray) is another thing to consider when purchasing your scale. You want to have a large enough tray area to hold most of your sample, but it is ok if some of it hangs over the side as long as it is balanced and centered on the platform. Also your sample should never rest against anything other than the scales weighing tray, otherwise your readout will be inaccurate.

 

Tare - 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 now add items to the container and only see the weight of those items within it (net weight).

 

Calibration - Calibration is the process of adjusting a scales 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. Typically, a scale calibrates at two points: zero and at the end of its span (span calibration).

 

Calibration Weights - Calibration weights are known masses such as a 100g or 500g weight. It is important to use the correct calibration weight when calibrating a scale. Otherwise, your scale could become highly inaccurate. For instance, if during calibration, the scale asked for you to place 200g weight on the tray, and you placed 100g instead, your weight readouts on the display would show at twice what their actual weight was. For instance, if you placed 1g on the scale it would say 2g, 4g would say 8g, and so on. Obviously, this is not how you would want your scale to perform. Check availability of weights with your scale supplier. Calibration weights do not come with a scale.

 

Calibration Certificate - A Calibration Certificate is a certified document provided by us that provides proof of calibration along with information about when/where the calibration was performed, and with what weights. Cal Certs. are required for scales that 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.

 

Legal for Trade - If you will be selling goods based on weight, with a scale, it must be Legal for Trade. This status is given to scales that meet certain guidelines and restrictions mandated by the SABS (South African Bureau of Standards). This helps insure that consumer is protected against overcharge.

 

Linearity - Linearity is a scales 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. To test linearity of a scale, you would use multiple weights, each of which are a fraction of the scales total capacity. When placed on the scale together, the weight should equal the sum of each individual weight.

 

Repeatability - Repeatability, like Linearity, is a specification most seen on precision/industrial scale spec. sheets. It refers to the scales 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 scales microprocessor converts this signal to a weight and displays it on the LCD.

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