Most scientific researches and laboratory tests require weighing, which is a critical task. However there is a degree of uncertainty in the measurements. In fact, all weighing – be it the very large or the very small – is subject to a degree of uncertainty. This can be neglected when it comes to large quantities but takes on a great deal of importance when considering minute quantities of substances that require precision weighing of 0.1 mg.
Does your work often involve weighing and measuring test samples? How critical is the accuracy of the data for your research or business? Do you realize the factors that can influence the results obtained from your analytical balance?
An Analytical Balance is a precision appliance that can provide you with the most exact weighing results. In spite of this you can still say there is a wide difference between ‘exact’ and ‘most exact’. Simply put, measurements are finally tentative. The scientific studies of measurements are based on ideal conditions of set parameters. Needless to say, any weighing activity also has its uncertainties. To understand the working of an analytical balance, we also need to be aware of the factors involved in the uncertainty.
Comparison of data from different instruments is also hard to compare because field operation methods vary from specifications by the manufacturer that are conducted under ‘ideal’ circumstances.
Several other factors can affect the accuracy of weighing results obtained. They can be collectively classified into three groups. The first group of deviation in weighing results can originate from the analytical balance itself. Different models of analytical balances have a varying degree of susceptibility in repeatability, non-linearity, sensitivity accuracy and temperature gradient.
The second group causing a deviation comes from actual environmental influences like temperature, humidity, air pressure, heat radiation or exposure to direct sunlight. Analytical Balances, especially the high-end ones are sensitive instruments. Even a slight draft can get you pneumonic results!
The third and final group that might create anomaly in the results occurs from accounting for human error. The way the sample is loaded; technical errors during the weighing process etc. can all alter the weighed results. Even the accuracy of the calibration of the balance should be adjusted according to user-specific actual weighing capacity of the analytical balance so as to obtain the most precise results. Improved models normally support the option of calibrating the scale of an analytical balance at several predetermined capacities.
How is uncertainty accounted for in weighing results?
Does the result obtained by measurement actually represent the value measured? While ‘uncertainty’ stands for a broad, general concept – the error in deviation of results is generally minimized as ‘standard uncertainty’. ‘Standard Uncertainty’ gives an estimate of standard deviation in results obtained from an analytical balance from a combination of various factors. However, even the combined internal and external factors in ‘standard uncertainty’ holds true only when certain basic ‘ideal’ conditions are preserved. For example, the analytical balance is positioned on a level surface and there are no unnatural variations in STP (Standard Temperature and Pressure).
This article was written by Anindita Biswas, a marketing professional with a streak of geek that just refuses to go away! At Tovatech she indulges in her passion for high precision engineering and scientific equipment. Tovatech is a leading North American supplier of analytical balances. For more information on this article visit the Tovatech site from any of the above links.
