30) Lab Essentials : Analytical Weighing Balance

Microbiology Lab Essentials :

30) Analytical Weighing Balance :

Analytical balances are highly sensitive lab instruments designed to accurately measure mass. Their readability has a range between 0.1mg - 0.01mg. Analytical balances have a draft shield or weighing chamber to prevent the very small samples from being affected by air currents.

An analytical balance will measure the accuracy of 0.0001 to 0.00001g. If extream accuracy is not important a top-loading balance will work just fine in measuring the accuracy of 0.001g.

               Parts Of Weighing Balance

The very basic principle that makes a balance

counteracting force is created to be compared to the unknown mass. The weighing pan is attached to an electromagnetic coil, through which electric current is flowing. The coil floats in a magnetic field created by an amplifier.

   

Analytical Balance Parts and Function 

The Beam :

This is generally made of brass or aluminium, and varies in shape and length. ... 

The Pans :

The Standard, the Beam, and Pan Arrestments. ... 

The Case :

Checking the Balance. ... 

1. Place the weighing container on the balance pan and close the doors.
   
   
2. Tare the container by briefly pressing the control bar. The readout will read zero with the container sitting on the pan. This allows the mass of your sample to be read directly.
   
   
3. Add the substance to be weighed. Be careful not to spill chemicals on the balance. If need be, you can remove the container from the weighing chamber while you add the sample provided that noone presses the control bar before you weigh your sample.
   
   
4. With the sample and its container sitting on the pan, close the chamber doors and read the display to find the mass of your sample.

Determination of the Apparent Weight.