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What To Look For In An Analytical Balance

University and industrial laboratory researchers who require extremely accurate measurements of extremely small quantities rely on a precision instrument called an analytical balance. Recent advances in technology have yielded highly accurate analytical balances for use in a broad range of applications.

Shopping for an analytical balance requires more than looking through a catalog.  It is important to be familiar with some of the advanced features available today as well as the proper use of these precision instruments.

One feature in particular is called single cell weighing technology. The weighing cell is constructed of a single block of material, which results in stable temperature behavior, shorter stabilization times, shock-proof construction and accuracy even when the material being weighed is positioned at the edge of the weighing pan. The latter point is important because operators on occasion may initiate an eccentric loading error or corner load error that changes the readout when the same object is placed in various positions on the weighing pan of other types of balances.

Because of the high accuracy of these newer analytical balances, it is critical that they are automatically recalibrated under a programmed schedule.  This can occur every four hours, when there is a temperature fluctuation of 0.5oC (0.9oF), when the balance is switched from a standby to a weighing mode and the two above conditions are met, or if the balance was disconnected from its power source.

Recognizing that technicians may be in the midst of a critical weighing operation, these analytical balances signal an impending recalibration, which can be postponed by the technician until the weighing operation is completed.

There are several special applications that can be satisfied by an analytical balance.  One example is regular pipette calibration – the control of measuring equipment in accordance with ISO 9001 and GLP directives.  This is accomplished by pairing the analytical balance with a PC-based pipette calibration procedure that carries out calculations and compares these with well defined tolerances.  Test records can be printed for archiving or stored on the PC.

A useful accessory for an analytical balance is an electrostatic discharge ionizer, especially when weighing grams and milligrams of non-conductive materials such as plastic, china and glass. Because these and other products may carry an electrostatic charge an electromagnetic field can be generated between the materials being weighed and the analytical balance itself.  This can dramatically impact accuracy. The ionizers can be mounted next to the balance or be manually directed from all sides toward the sample being weighed. A simple precaution such as this can greatly improve the accuracy of your operations.

Some analytical balance models store the tare weight and the weights of samples in separate memories.  This feature enables the balance to add the weights of all the components of a mixture without the weight of the tare cup.  This recipe weighing feature combined with a print function automatically numbers all the ingredients in a formulation and prints out the corresponding number and weight of each component.

Additional features and functions offered in today's precision analytical balances include piece counting, determination of percent deviation of a sample from a reference weight, underside suspended weighing capabilities, GLP/ISO record-keeping capability, large LCD displays and metric/non-metric operation.

However you use an analytical balance remember that it is a critical tool for your operations and must be properly cared for.

About the Author

Tovatech is a distributor of laboratory equipment to the US, Canada, and Mexico. The company specializes in digital scales, pharmaceutical laboratory equipment and ultrasonic cleaners. Tovatech is staffed by chemists and engineers dedicated to providing the right equipment for the food, drug, chemical, healthcare, and equipment manufacturing and maintenance sectors.

You have measured out 10.0123576 grams of NaCl. What amount should you report if the precision of the balance ?

You have measured out 10.0123576 grams of NaCl. What amount should you report if the precision of the balance you used was
(a) + or - 0.01 g?
(b) + or - 0.001 g?
(c) + or - 0.0001 g ?

When determining which figures are significant, the last significant figure is the first uncertain one. The +/- values indicate in which decimal place the uncertainty lies. From this information:

(a) 10.01 g
(b) 10.012 g
(c) 10.0124 g <--round up because following digit is 5 or greater.

Hope this helps

FX-i Precision Balance by A&D Receives Legal for Trade Approval in the US and Canada
SAN JOSE, CA--(Marketwire - March 30, 2010) -

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