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March 9, 2009

Digital scales

Filed under: digital scales,scales — Tags: ,

What is a Digital Scale?
A digital scale is a weighing apparatus that measures the mass of an object and displays the results in a digital format. Digital scales offer greater precision using complex systems, such as load cell technology which translate the weight of an object into an electronic signal which is displayed to the user in a digital format. Prior to the existence of digital scales, older mechanical weighing technologies were prone to error as they were harder to read. They were also becoming increasingly expensive to maintain, and since so much of the equipment was obsolete, repairs were costly.

How Digital Scales Work
A digital scale typically uses a strain-gauge load cell. A digital floor scale, for instance, uses a platform supported by a column, with a strain gauge fused to the column. The strain gauge is a thin wire whose electrical resistance changes when the wire is stretched or compressed. When a load is placed on the platform, the column and strain gauge are compressed. The corresponding change in resistance of the strain gauge is used used to determine the object’s weight.

digital scalesApplications
As the digital scale slowly replaces mechanical scales, the number of its potential applications continue to grow. Digital scales are highly favored in applications or industries where precision is a necessity. Precision balances are extremely important in scientific laboratories where it is necessary to measure the weight of small amounts of material down to the nearest 1 millionth of a gram (3.53 hundred millionths of an ounce). These weighing devices are usually enclosed in glass or plastic to prevent wind drafts and temperature variations from affecting the measurements. Being able to read the results in a digital format reduced human error and added more reliability and consistency to the weighing process.

Digital scales are faster, more accurate, can achieve higher GMP standards which are easier to read. These scales are also smaller in size allowing for more efficient use of space. Electronic floor and counting scales are usually low profile in structure and come with ramps, reducing lifting and handling problems. Another distinct advantage is that electronic scales can be tied into existing computer and accounting systems, which for most applications makes electronic scales more useful and efficient than mechanical scales.

Important Features
Of course, the most imporant feature in a digial scale is the digital display. There is nothing more impressive than a display that is extremely easy to read. Readability depends on four things: the quality of the LCD, the kind of backlight, display size and the number of digital readouts. A high quality LCD with a true luminescent blue backlight is fairly standard. The size of the display is also important. Sizes go as high as a large 6″ display. The larger the display, the easier it will be to read. Four-digit readouts in 1lb or gram increments are popular depending on the accuracy you require. Besides these standard features, most problems with digital scales fall into two areas: accuracy (or repeatability) and calibration.

Whenever an object is weighed multiple times and displays a different weight every time, the scale is most likely defective or damaged. Variations of weight in the same direction are usually normal. A good scale should show 80 to 90 percent repeatability, i.e, identical or variations in the same direction. For best repeatability testing use a calibration weight or object of known weight.

Digital scales work the best when their internal temperature has stabilized to operating temperature. Temperature changes may produce either a failure to rezero when an object is removed or drift in weight readings. When a scale is moved to a different location always allow time for it’s temperature to adjust to the surrounding environment. It is best to turn the scale on and let it warm up for at least 20 minutes before use. Once the scale has warmed up, then run the calibration routine and the scale should not need to be rezeroed or calibrated again.

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