An analytical balance or laboratory balance is one kind of important sensitive apparatus designed to calculate an object’s mass properly. The samples could be solid, granular substances, or powders and liquids.
It can be possible to measure up to 0.00001 grams (0.01 mg) by using this apparatus. It has the ability to detect the weight of an object of 100g to within ± 0.01 mg.
Definition of Analytical Balance
An analytical balance or lab balance is a modern class of balance designed to calculate the small mass in the sub-milligram range precisely. The readability range of an analytical balance is 0.1mg – 0.01mg. It comprises a draft shield or weighing chamber to prevent the very small samples from being affected by air currents to produce precise results.
Principle of Analytical Balance
The mass of a sample can be calculated based on the force required to balance the mass of a sample rather than utilizing actual masses. An electromagnet is used to produce a force to balance the sample, then produce the result by measuring the force required.
This balance surrounds transparent material and consists of a door, blocking external influences. Air currents and dust do not affect the weighing performance for this reason.
Parts of Analytical Balance
Balance plate (Pan)- It is one type of container that holds the object for mass measurement.
Weights- This part helps to calibrate analytical scales.
Power button (on/off button)- This part is used to start or deactivate the balance.
‘Tare’ button- This part is used to rebalance the objects and bring them back to a neutral level.
‘Mode’ button– This part helps to set the measurement conversion system such that the conversion system can be changed as necessary.
Draft shields- This help to protect the analytical balances protection from outside factors such as air flows and dust that could compromise precision.
Level adjustment feet- These movable legs enable the balance to be brought to the reference position.
Level indicator- This part helps to indicate the various level in balance.
Display panel- The produced results, errors, information for function settings, and function in progress are shown in this panel.
Weighing Procedure of an Analytical Balance
Firstly, the analytical weigh machine should be set in a suitable location for the measurement to protect it from various environmental problems.It must be free from direct sunlight and make sure there are no extreme temperature changes. Then the analytical balance should be leveled for precise findings. It should be calibrated after keeping a good position.
Press the “tare” button for setting the balance to zero in the no-load condition. Then it can place the object in the center of the weighing pan and then shut the glass door of the weighing chamber. Then it can calculate the value that was displayed after it was stabilized. The ‘TARE’ button is pressed to reset the mass to zero after excluding the sample from the measurement point.
Types of Analytical Balance
1. Equal arm analytical balance
This type of analytical balance works on the principle of a first-class lever. The fulcrum of this balance acts as a beam over a centered pivot connect to which two pans are attached to each other. Two pans of this balance can be balanced against each other in which the sample to be weighed is placed on one pan while the known weight is placed on the other.
2. Single-pan analytical balance
It consists of two knife edges with unequal balance arms. The pan of this balance is supported by the shorter arm, and the longer arm contains a constant counterweight built into the balance beam.
3. Electronic single pan balance
This electromagnetic force type balance generates a magnetic force that balances the load placed on the balance pan after passing the electric current. The current required for the calculation of the mass of the sample is directly proportional to the object’s mass on the pan.
4. Microbalance
This balance measures samples to a resolution of at least 1 million parts per gram. It can be possible to quantify small amounts of a sample, microbalances are employed.
Uses of Analytical Balance
It is widely used for analysis and determination of sample density. It is very much needed for the preparation of various samples. This balance needs calibration of the pipette, differential weighing, piece counting, and interval weighing of the objects.
Factors affecting the performance of an analytical balance or lab balance
The measurement value can be changed for changing temperature. A definite temperature should be kept to get the best measurement value. The precise value from this balance cannot be shown for the disturbances from refrigerators, ventilation systems, or other equipment.
It should not be weighed with highly reactive chemicals to get a precise result. Should use this analytical instrument in a well-ventilated room to ensure precise measurement? It must be calibrated properly before using this instrument for measuring the samples. The magnetic or magnetized sample should be avoided because it creates a magnetic field that influences the sensor coil of the balance.
References
1.Clark, J. W. (1947). An electronic analytical balance. Review of Scientific Instruments, 18(12), 915-918.
