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​How to Calibrate Analytical Balance

Posted by U.S. Solid on Sep 2nd 2021

One of the key benefits of analytical balance calibration is that you will get accurate weighing results. In this article, we will discuss how to calibrate analytical balance.

What is analytical balance calibration?

Calibration is to compare the measured value provided by the analytical balance with a standard test weight of known accuracy. [1]

Why do we need to calibrate analytical balance?

On one hand, even if it may have already been calibrated by manufacturer, the calibration of the balance could be interfered in transportation. [2]

On the other hand, the performance of the analytical balance might be affected by factors such as temperature, humidity, barometric pressure, altitude, gravitational acceleration and etc. [3]

Therefore, it's necessary to calibrate analytical balance before using.

What are the types of analytical balance calibration?

There are two types of analytical balance calibration, internal calibration and external calibration. [4] And derived from internal calibration, there is another calibration type called automatic calibration.[5]

Withinternal calibration, the balances can be calibrated internally through the built-in test weights. Most of such balances can even be calibrated automatically by setting the interval time.

Not every analytical balance has an internal calibration function. The common ones can only be calibrated externally. External calibration maybe divided into span calibration and linear calibration. Span calibration is to use one standard test weight equal to or close to the maximum capacity of the balance.It is also called single-point or one-point calibration. Linear calibration requires a set of test weights to be measured sequentially. Then the balance will use its built-in program to plot with the measured data and calibrate itself. It is generallyagreed that linear calibration works better than single-point calibration as it covers wider ranges. That said, linear calibration do require more test weights and lengthy procedures.

Take our USS-DBS47 analytical balance as an example, the steps for internal calibration are:[6]

1.Read the manual and install the balance as instructed.

2.Turn it on and warm up for an hour.

3.When the balance is in the no-load state, press the "CAL" button and "CAL-INT" will flashing displayed.

4.Then the balance will start automatic internal calibration.

5.The instrument will return to weighing after calibration.

You can also check the operating video.

The steps for external calibration are for our USS-DBS48 analytical balance are[7]:

1.Read the manual and install the balance as instructed.

2.Turn it on and warm up for an hour.

3.Zero the balance in the weighing state.

4.Press the "ON" button several times in succession until the "E-CAL" is displayed.

5.Press the "O/T" button to confirm and "CAL-200" will flashing displayed.

6.Place the 200g calibration weight on the weighing pan.

7.Then "200.0000g" will be displayed. External calibration is completed.

How to verify a successful analytical balance calibration?[8]

1.Drift check

Put a test weight on 10 different positions on the pan, the value of each measurement should be within the given error range.

2.Performance check

Put 10 different test weights within the capacity range on the center of the pan, and the value of each measurement should be within the given error range.

3.Measurement Uncertainty check

Put a test weight within the capacity range on the same position on the pan 10 times, record the value of each measurement and calculate the measurement uncertainty, the uncertaintyshould be within the given error range.

How often do we need to calibrate analytical balance?

Different analytical balances have different requirements for calibration frequency.

You need to follow the instructions in the manual.

Take our USS-DBS83-120 analytical balance asan example, we suggest you calibrate:[9]
· Each time the use location changes, including moving in the same room
· Each time the ambient conditions change
· Before each use.

References
1. https://en.wikipedia.org/wiki/Calibration
2. https://www.philipharris.co.uk/blog/secondary/how-to-calibrate-an-electronic-balance/
3. http://www.balances.com/and/calibration.html
4. https://www.scalesu.com/analytical-balance-scale-calibration/
5. https://ussolid.com/content/USS-DBS/USS-DBS47%2848%29%20Instruction%20Manual.pdf
6. https://ussolid.com/content/USS-DBS/USS-DBS47%2848%29%20Instruction%20Manual.pdf
7. https://ussolid.com/content/USS-DBS/USS-DBS47%2848%29%20Instruction%20Manual.pdf
8. https://www.scalesu.com/analytical-balance-scale-calibration/
9. https://ussolid.com/content/USS-DBS/Instruction%20Manual%20-%20DBS83.pdf