An analytical balance allows you to measure the mass of a substance down to 0.0001 gm. Such sensitive balances are primarily used in chemical laboratories. Analytical balances need to be acclimatized to the environment they are being used in. Switching it on at least an hour before use will allow for it adjust to the gravity, the atmosphere and its immediate environment. This process allows the balance to give you the accuracy that is required when measuring powder or substance of minute quantities.

Understanding the basic terms associated with the functioning of analytical balances allows you to fully understand its capabilities. Accuracy of measurement is the ability of the machine to measure a substance to the closest accepted standard value. For example, if the accepted standard weight of a particular substance is 100.000 grams and the analytical balances measures a substance at 100.001 gms, then the accuracy is of the machine is set at 1 mg.

Calibration is the process of bringing the analytical balance to the level of accuracy it needs. A comparison is made between the output figures of the machine against the standard value of the substance to be measured. Calibration is the means of adjusting the machine to attain perfect accuracy. While internal calibration is available, external calibrations are considered more accurate.

Calibration error is the difference of measurements of a substance near the capacity of the balance and its true mass.

The capacity of an analytical balance can be understood as the maximum load it can handle while performing optimally. There are two concepts to be understood in relation to accurate measurement by an analytical balance. The first is readability, which can be understood as the ability of the machine to measure the same substance with the same accuracy, repeatedly. There are test weights available for this purpose. You will have to use the same weight test object as the substance to be measured on the machine repeatedly to test this.

The other concept is that sensitivity drift. This is where the accuracy of the machine changes along with temperature fluctuations. These fluctuations can be external temperature changes around the machine or within the glass chamber. Ideally, the temperature of the environs around the machine should be within 2 to 3 degrees day or night. The machine will also need to be left on the entire day. Once you have eliminated the possibilities of these two concepts, then you can attempt a cornerload on your machine. This means that no matter where you place the substance to be measured on the pan, it will give you an accurate reading. As a test, you can repeatedly change the position of the substance and check that the measurement is the same.

Linearity is the ability of an analytical balance to provide the same level of sensitivity for the complete capacity that it can handle. The best way to test this is to weigh two weights of the same substance separately. The sum of their individual weights should be the same as their collective weight. Linearity calibration uses three main point of calibration – zero, center span and full span. This reduces the level of difference between the actual and displayed weights.

Author Bio: Dr. Bob Sandor is a Director at Tovatech, a leading North American supplier of analytical balances. When not busy running his company, he explores his fascination with the many aspects of various scientific & industrial devices. For more details on the above you can reach him through the analytical balance section of his website.

Category: Education
Keywords: analytical balance definition,accuracy in analytical balance,calibration in analytical balance