Calibration World Issue 1-2007 - Beamex - #13

must determine all of the external factors which may influence the proper functioning of the weighing instrument. The factors in question may include the effect of the environment where the weighing instrument is used and how often the instrument needs to be cleaned, regular monitoring of the zero point and the indication number with a constant mass.

Today, the function of weighing instruments, as well as many other instruments, is based on microprocessors. They possess several possibilities for adjusting parameters in measuring procedures. Calibration should be carried out using settings based on the parameters for normal use. It is very important that the users of the weighing instruments, as well as calibration personnel, are familiar with these parameters and use them as protocol. Since there are several parameters in use, it is important to always have the manual for using the weighing instrument easily available to the user.

The content of the calibration certificate

Very often the calibration certificate is put on file as evidence of a performed calibration to await the auditing of the quality system. However, a quality system is usually concerned with the traceability of measurements and the known measuring tolerance of the measurements made. The calibration certificate of a single measuring device is used as a tool for evaluating the process of measuring tolerance and for displaying the traceability of the device in question.

Performing calibrations based on the measuring tolerance is better than doing routine measuring. Therefore, the user must evaluate the process of measuring tolerance and compare this value with the required measuring tolerance of the process.

Summary

Calibration (or verification) is a fundamental tool for maintaining a measuring system. It also assists the user in obtaining the required quality of measurements in a process.

The following must be taken into consideration:

• the type of procedure to be applied in confirming measuring tolerance

^ the interpretation of information while abiding by the calibration certificate

• changing procedures based on received information

Q uality calibration methods and data handling systems offer state-of-the-art possibilities to any company

Mr. Aimo Pusa is the Chief of the Force and Mass Laboratory at Lahti Precision, Finland. He is also Chairman of the National Advisory Committee of Metrology in Finland. Lahti Precision is a global technology company supplying accurate weighing and dosing systems and plants, scales and maintenance services to the process industry.

www.beamex.com/calibrationworld CALIBRATION WORLD 01- 2007