What Can Affect Analytical Balance Accuracy?
Analytical balances are high accuracy instruments. They’re designed to weigh very small amounts of liquid or solids, often in the sub-milligram range - so it’s imperative they’re not only accurate, but are used in environments where their accuracy cannot be affected.
But what can affect analytical balance accuracy?
Due to the extremely sensitive nature of an analytical balance, there are many different factors that can affect their accuracy, moreso than with a standard weighing scale, and even more than with what we would regard as a ‘precision balance’ - a balance that tends to have a higher capacity and therefore readability that’s not quite as fine.
Inaccuracy can present itself in two ways - either an incorrect reading on the balance, or with ‘drift’ - when the weight reading fluctuates, not settling on a single, stable reading.
If you’re using an analytical balance for the first time - or, if you’re looking to improve the accuracy of your analytical balance, read these seven tips for better results.
1. Make sure your balance is in the right environment
Believe it or not, some analytical balances can be so accurate that room temperature will affect their readings. Therefore, it’s essential that you’re strict with temperature control in the room that the balance will be used in. Temperature can affect a material’s density, which can lead to changes in mass.
This is particularly important if you’re weighing liquids. If the temperature is too high, the sample could lose some weight through evaporation. If the temperature is too low, condensation could form in the sample’s container. In both cases, the accuracy of the measurement could be affected.
2. Is there a breeze in the room?
Just like temperature, even the slightest breeze could make a difference to weight readings. We’re not just talking open windows, either: air conditioners, ceiling fans and even someone walking past can cause enough breeze to send the readings on your analytical balance askew.
As with temperature, you should ensure that you’re in a controlled environment when using these devices. Additionally, if your balance has a wind chamber, this will help here.
3. Try to minimise contact with the balance
Touching the balance whilst weighing can affect the balance - whether that’s by causing vibrations, or by putting pressure on the weighing area. Therefore, avoid leaning on the work surface, and always use gloves or tongs when handling samples. Even fingerprints can affect the weight reading!
4. Ensure the balance is on an even surface
Many balances will have adjustable feet, and for good reason - an uneven surface can affect readings, too.
It’s also worth mentioning that, again, vibrations through your work surface and affect readings - and that’s why most analytical balance users opt for an anti-vibration table. Anti-vibration tables greatly improve the accuracy of your balance by negating movement caused by everything from a colleague walking by to passing traffic.
5. Keep your balance clean
Inaccuracies can be caused by debris on the balance, so keeping it as clean as possible is vital. Debris can collect under the removable pan, too, and maybe on the surface of the weighing area. Remember - the tiniest spec of anything can affect the weight reading!
Always remove dust, debris and particles from the weighing area beach time you use the balance. The best way to do this is with a soft brush and a suitable cleaning solution.
6. Protect your balance against electrostatic charge
Electromagnetic fields between the sample and the balance can also alter the result on the screen. This can be of particular concern when you’re working with samples that feature dry non-conductive materials, and weighing in milligrams or smaller.
A discharge ionizer, placed next to the balance, will help here. And it’s also worth noting that fluctuations in power supply can have the same effect, so ensure you’re working from a stable power supply.
7. Does your balance need calibrating?
We left this until last… But it can often be overlooked. Analytical balance accuracy can be affected by the balance being out of calibration. Many balances will have an internal calibration feature; however, it is also worth carrying out your own calibration tests using certified calibration weights.
We recommend you perform your own calibration checks every three months at the least to ensure your balance is providing optimum weighing results.
Choose the best analytical balance for your needs
Analytical balance accuracy is one thing - making sure you have the right balance for your needs is another. There are many on the market and choosing the best balance is not always easy.
Luckily, we have a guide to analytical balances here.
And here’s a handy troubleshooting guide from Adam Equipment, for when you’re having issues with using a balance.