Weighing Scale Calibration

Calibrating a scale means measuring and documenting the accuracy of the scale. If you use scales in your business, you know how important it is that the scales give accurate readings. The calibration of a scale defines the deviation from the target value to the normal value.

Scales are subject to thermal, chemical and mechanical changes. Ambient temperature and wear and tear on the scale affect the measurement result. In the course of the life of a scale, inaccuracies in the measuring process occur. It is normal for the differences to be small at the beginning and large at the end. Without regular calibration, this happens unnoticed. Regardless of whether you run a large, medium or small business, it is important and useful to calibrate scales regularly.

The goal of calibrating a scale is a receipt or certificate that provides information about the accuracy of the scale. The process must be recorded on this slip. The calibration process starts with the definition of the measurement process. This includes the device, the environmental conditions, the standards used and the procedure. With the help of a mathematical model, the calibration process is evaluated, taking into account all known influences. The measurement uncertainty analysis is then carried out. The complete result with calibration value and calibration uncertainty completes the documentation.

Different types of calibration

Internal calibrations (factory calibration or ISO calibration) set a standard in your company. This ensures that all scales in your company can be compared with one another and measured correctly. The weights for factory calibrations are regularly checked by the test equipment monitoring.

Traceable calibrations are performed against a reference (standard) that is nationally consistent. As a result, the traceable calibrations are comparable with all scales of this standard. Since the national values are also compared internationally, a global comparison is possible.

SAMM (Skin Akreditation Makmal Malaysia or known as Lab Accreditation Scheme Malaysia) calibrations belong to the traceable types of calibration. They may only be carried out by SAMM-accredited calibration laboratories like Premier Calibration Sdn Bhd. In Premier, our laboratories work according to the standards of the DSM(Department Standard Malaysia). Working method, measurement, test weights and evaluation (including the measurement uncertainty) correspond to the standards of the SAMM. SAMM endorsed test reports and calibration certificates are accepted internationally. The accepted mechanism for recognition is by means of the Mutual Recognition Arrangements framework of the International Laboratory Accreditation Cooperation (ILAC) and Asia Pacific Accreditation Cooperation (APAC).

To calibrate the scales, weights (standard weights / test weights) are placed on the scales and the deviation of the scales is determined using the weight display. The measurement is carried out several times during the calibration and evaluated statistically. Or the randomness is prevented by fixed standard test conditions.

The result of each measurement looks like this: The reference weights add up to the value X, the scale shows the value Y. The deviation between the two is called the error. This is documented in a calibration certificate. The calibration certificate can also indicate the so-called measurement uncertainty. To do this, the deviations of the weights themselves as well as deviations due to air pressure, temperature, mechanical forces, operation and other sources are taken into account. These are summarized as measurement uncertainties. From both values, the error and the measurement uncertainty, a statement is made as to how reliable the error is. This means the probability that the error was measured correctly.

The certificate for the calibration of a scale contains information on the reference weights and the measured values, the measurement uncertainties and, if necessary, information on various tolerances. The tolerances lead to an evaluation of the balance (good or bad). Only traceable weight standards are used here. This traceability, documented by the corresponding calibration certificates for the standards, is also documented in the calibration certificate for the balance.

Have your scales calibrated by an authorized specialist, ensure the quality of your products and your quality management. With the calibration of an authorized specialist company, you are prepared for internal and external audits of your company. The SAMM calibration certificate documents that international guidelines on measurement accuracy are complied with. Calibrated scales are compatible with scales in other locations. This means that measured values can be compared and evaluated accordingly.

Calibrated scales save costs because you have a precise overview of the filling quantities and any material waste. You avoid product recalls, loss of image and rework.

Regular calibration of your scale reveals creeping aging processes. Wear or mechanical stress can cause drift. This means that the weight display changes slowly. You cannot determine this without calibrating the scale.

With the calibration and its result, you can control processes better and make them more effective. This ultimately leads to better performance of your company.

Inaccurate scales result in poor product quality. Problems in quality management, in internal or external checks and in process handling can be the result of uncalibrated scales. If you do not use the calibration of the scales at regular intervals, scales can simply fail. Unplanned downtimes are the result. Your company can suffer damage to its image if you have to recall products. This can even have legal consequences. Rework also significantly disrupts profitability.

Basically, there is no legal requirement to calibrate a scale. The need for comparable and accurate scales increases in times of globalization. A reliable evaluation of weights is a prerequisite for productivity and efficiency. The advantages of a calibrated scale are described above.

If your company works with a quality management system (ISO 9000ff, Halal, HACCP, Mesti, GMP, IATF 16949,DA, GLP, FDA or similar), calibration is mandatory. Through the quality management system, the company undertakes to meet the normative requirements to check measuring devices at regular intervals. This calibration must be documented.

The purpose of calibrating the scale is to support your company’s operations in the best possible way. Deciding how often to calibrate is a balance of benefits and risks. The calibration interval should be tailored to your needs and not a blanket interval. Questions that determine the interval are: What internal quality assurance guidelines do you have? How high is the risk that a scale fails / no longer measures reliably? What impact does this have on your business? What is the relevance of accurate measurements?

The greater the likelihood and the greater the impact on your business, the more sensible it is to calibrate the scale more frequently. On the other hand, if it is unlikely that the scales are not doing their job properly and the effects are small, a large interval is sufficient. Factors affecting the accuracy of the scale include frequency of use, type of use, location, design and age of the scale.

When a scale is calibrated, the accuracy with which it measures is checked. The deviation from a normal value is determined and documented in a note or certificate. The protocol is the conclusion of the calibration. Further actions are not carried out. The calibration of a scale is not required by law. Reasons for calibration are quality assurance or procedural requirements.

When a scale is adjusted, it is corrected. This means that a professional intervention is carried out on the device. This intervention is intended to bring the device into the permissible tolerance range so that it can measure accurately again. With analogue scales, for example, this can be the adjustment of the pointer using adjusting screws. There is no measurement during adjustment. A new calibration is required after each adjustment. Because the old calibrations are no longer up-to-date due to the adjustment of the measuring device.

Calibration is mandatory for certain companies and devices. It serves to protect consumers. The calibration is carried out by recognized test centers and should deliver trustworthy measurement results. Every scale can be calibrated, but not every scale can be verified. An approved authority determines this for calibration. In Malaysia it is the Skim Akreditasi Makmal Malaysia (SAMM). There are equivalent authorities across Asia and internationally. In Malaysia, all commercial scales must be verified.