Tips to Get More Accurate Results with Analytical Balances
A common instrument you'll find in labs is an analytical balance. Out of all weighing machines, analytical balances are the most precise instruments. They offer higher readability and accurate measurements, the closest being up to 0.0001g. Analytical balances often have draught-proof weighing chambers for precise mass measurement and are frequently used in conjunction with anti-vibration tables to improve accuracy. When using analytical balances for essential lab measurements, any errors can cost both time and money.
For these reasons, accurate results from analytical balances are crucial. Factors like temperature, vibrations, air drafts, chemical reactions, uncalibrated scales, magnets, improper grounding, slope, and inappropriate handling of samples can all affect the balance readings. While there are several factors that can affect your readings, here are a few tips to get precise results using analytical balances:
1. Pick the Right Environment
Different environmental factors can affect the results of an analytical balance. Factors like air pressure, humidity, temperature, and other operating conditions can lead to inaccurate results. One way to handle this would be to place the balance on a stable surface with minimal environmental exposure. Some balances can determine external factors to estimate the uncertainty of the data, but several balances don't.
Here are four points to keep in mind when placing your analytical balance:
- Ensure that the place is quiet and temperature controlled.
- Place it on a sturdy table with a rubber layer to absorb vibrations.
- Keep the analytical balance near an outside wall if the floor isn't leveled.
- Choose an analytical balance with a self-correct feature for more accurate results.
2. Perform Regular Scale Calibration
Calibration of analytical balances is important for better reliability of the results. Calibration generally needs to be performed at the site where the balance is placed or can be done by sending it to an accredited lab.
Calibration can be performed in two ways:
- Internal Calibration: Some balances offer an internal calibration feature. It does not require any manual effort and can be performed in simple steps using the manufacturer's instructions. This allows your laboratory scales to calibrate some time to time with minimal user inputs.
- External Calibration: External Calibration requires the user to calibrate the analytical balance manually by placing certain approved weights on balance and setting them to standard.
Remember that your analytical balance is placed on a level surface with a suitable environment for accurate results.
Calibration for balance should be performed from time to time for accurate results. If the operating conditions of your balance keep changing, it is a good idea to re-calibrate it before use.
3. Minimize Contact with the Balance
Vibrations are another factor that can lead to inaccurate readings on an analytical balance. They affect analytical balance in particular since they introduce g-loads that can interfere with the primary weighing mechanism of the balance. High-resolution balances with 1 to 0.1 micrograms are even more sensitive to vibrations where reducing a single decimal place can affect the accuracy. To avoid this:
- Minimize contact with the balance by avoiding leaning on the table during operation.
- Place a cork or rubber layer under the balance to absorb all vibrations.
- Consider placing the balance as far as possible from any moving or heavy objects.
- Avoid handling the samples with bare hands before weighing. Always wear gloves or tongs since even fingerprints can also add mass to the container leading to incorrect results.
4. Handle Samples Properly
Analytical balance readings can be affected by any changes in the sample or container besides other factors discussed above. A few ways to prevent this are:
- Clean the containers before each use. Clean and dry containers help ensure no fingerprints or debris can add mass to the container.
- Use a container or vessel of the appropriate size to avoid spills or evaporation. Choose a container with the smallest size possible.
- Make sure you are using the correct balance to weigh the samples. Some balances cannot weigh smaller or larger samples. This could lead to incorrect readings.
- Cover the container before operation. If the sample contains water, not covering the container can lead to evaporation. At the same time, using bare fingers could lead to the absorption of water resulting in incorrect readouts.
- To avoid hygroscopic samples from absorbing moisture, place them in the balance's center and close the doors.
5. Protect Against Electrostatic Charge
Electromagnetic fields between the sample and balance also have the capability to affect the readings. Low humidity or electrostatically charged samples/containers can result in up to gram inaccuracy, especially with non-conductive materials samples.
Follow these tips to avoid misreading’s due to this factor:
- Place a discharge ionizer next to the balance when weighing in increments of milligrams or smaller.
- Check your power supply and ensure it is stable.
- Shield the sample with a metal foil and neutralize static electricity.
6. Clean and Maintain Balances
Cleaning and maintaining your balance and containers is crucial.
- Always remove any dirt or dust from the balance before using it. Wipe it with a soft cloth or brush before each use.
- Warm the balance up after plugging it for the first use.
- Create scale maintenance and scale repair schedule and follow it regularly to keep your balance in good condition.
- Cover and place the balance in a location with a balanced temperature to prevent contamination or any other defects.
- Clean any parts that you can remove from the balance too. Reassemble them appropriately on the balance once they are cleaned.
Keeping your balance clean can help avoid any scale repairs
and maintain the durability and accuracy of your laboratory scale. Balances are sensitive instruments and must be maintained, keeping every detail in mind.
The operating conditions matter a lot in the case of analytical balances. Besides following all the above instructions, place your balance in an appropriate location according to your instrument.
If you use the analytical balance regularly, maintaining it in good working order is essential. Maintenance and calibration of the balance after regular intervals ensure accurate weight measurements and extend its life. A well-maintained balance will have low chances of producing incorrect readings.