Getting your weighing results right the first time is crucial, as it saves you time and money and eliminates the need for rework. Errors caused by inaccurate weighing results, or an error in recording the weighing result cause problems because they are often difficult or impossible to trace.
Very often it is small things that can improve the weighing performance of your balance. This checklist highlights the key considerations when choosing and working with laboratory top-load balances and explains how to:
- Select the right balance
- Determine suitable position for installation and use
- Assure accuracy through calibration
- Ensure accurate results every day
- Improve process efficiency and save time
- Keep your balance clean.
The checklist focuses on laboratory precision balances and describes simple rules that will help you to assess weighing accuracy and keep analytical results right.
How to ensure accurate results every day
In-between calibrations, measuring equipment must be checked regularly to ensure ongoing balance performance. The user should perform these routine tests at fixed time intervals.
The following questions will help you determine if your balance is accurate on an ongoing basis:
- Are you routinely testing with external calibrated weights?
- Are you warming up the balance before first use?
- Are you regularly testing for sensitivity?
- Are you regularly testing for repeatability?
If you answered “No” to any of the above questions, you may benefit from reviewing and revising your SOPs to include or improve your ongoing balance testing. To learn more about routine testing and how to implement it, review the following section.
Put Periodic Testing into Practice
Periodic routine testing using external weights helps for two reasons:
Sensitivity assessment should be carried out most frequently of all routine tests, since it is an integral part of the functional control of a measurement device, and it is also quick and simple. Sensitivity is measured by using a calibrated test weight close to 100% of the balance capacity.
The assessment of repeatability is carried out less frequently as sensitivity, however, it is an important property when weighing small samples, and hence, is relevant for the determination of the minimum weight. Repeatability is usually measured by performing 10 replicate weighings under the same conditions using a test weight close to 5% of the balance capacity.