Calibration technique for balances
Depending on the degree of accuracy of precision, the balance can be influenced by many external
factors including, the surface, draughts, ambient temperature, vibration, ‘warming up’ time,
magnetism and static electricity. In general, you need to guard against most of these influences for
the more sensitive balances and you should consider re-calibration if you think any of these
influences may have affected the balances.
Re-calibrating is quick and easy. Standard weights are used to calibrate balances. By following the
manufacturer’s table of tolerances. Put a test weight on the balance. If the reading is within
tolerance limits, you do not need to take further action. If the reading is outside these limits, then
the balance needs to be adjusted.
Using a balance
1. Switch on the balance and allow sufficient time for the device to achieve a thermal
equilibrium.
2. Check for the correct levelling, many are fitted with a liquid ‘spirit level’. Place a calibration
weight on the pan. If the reading is within the manufacturer’s tolerance levels, then no
adjustment is needed. If it is not, then adjust the reading.
3. Never weigh the material directly onto the balance. Use a suitable container or weighing
boat. Weigh the container itself and press ‘tare’ or ‘zero’ to estimate the mass of the
container.
4. Remove the container and then fill it with the substance to be weighed carefully and in the
middle of the container. If an instruction states ‘measure accurately approximately 10g, this
means as close to 10g as possible but not necessarily exact.
5. To maintain the balance, keep it switched on during long activities, keep it clean and
regularly check for drifting of the measurements by using calibration weights.
Drifting in measurements shows when a measurements show when a measurement of a
constant quantity such as a mass is repeated several times and the measurements drift one
way during the experiment. Keep the balance in a clean environment at room temperature.
Balance identifier We use two decimal place balances but it could be a three or four decimal place
balance depending on where you study or work. For our 2-decimal place analytical balances the
required standard is:
The 1 g mass should read between 0.99 g and 1.01 g.
The 10 g mass should read between 9.98 g and 10.02 g.
The 100g mass should read between 99.98g and 100.02g.
Date
Mass of 1
g/g
BTEC Level 3 Applied Science
Within
tolerance?
Mass of 10 g/g
Within
tolerance?
Signature
Date
Mass of 1
g/g
BTEC Level 3 Applied Science
Within
tolerance?
Mass of 10 g/g
Within
tolerance?
Signature