Calibration: Definition and Importance for measuring instrument

Calibration is the process of checking and adjusting the accuracy of measuring instruments. Essential in a variety of industrial sectors, it ensures that instruments produce reliable data that conforms to international standards, thereby enhancing product quality, safety and regulatory compliance.

According to the VIM (Vocabulaire International de Métrologie) definition, instrument calibration is an operation which, under specified conditions, establishes a relationship between the values indicated by an instrument and the known values provided by reference standards. It is a set of procedures whereby measuring equipment is compared with reference standards to detect and correct any deviation.

This practice ensures that measurement results comply with established standards and legal requirements, resulting in optimum quality control.

Standards play a key role in calibration, as they serve as reference points for the equipment to be calibrated. These standards must themselves be traced to even more precise standards to guarantee an unbroken chain of traceability.

The calibration process generally comprises a series of methodical steps involving instrument adjustment, documentation of measurement results, and often the application of corrections or adjustments to reduce measurement uncertainties.

Adjustment and calibration ensure that measuring instruments operate within an acceptable range and meet the specific standards required.

The importance of benchmarking lies in its ability to directly influence the quality of products and services supplied, which in turn has an impact on consumer confidence and corporate reputation.

The ongoing development of calibration techniques promises to further improve the accuracy and efficiency of measurements, underpinning progress in many sectors.

Key points

• Calibration is essential for measurement accuracy and conformity.
• Reference standards ensure instrument traceability and accuracy.
• The process influences product quality and is constantly evolving with technology.

Definition of calibration

Calibration is the process of checking and adjusting the output of a measuring instrument against a reference standard. You use calibration to ensure that your instruments produce results that reflect reality as closely as possible, thereby improving accuracy. This process usually involves comparison with instruments of known accuracy, which are themselves calibrated against international standards.

The importance of metrology

Metrology, the study of measurements, is fundamental to ensuring consistency across diverse fields such as manufacturing, laboratories and research. Your ability to succeed in these areas relies on reliable and repeatable measurements, which underlines the vital role of metrology. Accurate measurements are essential for maintaining high quality standards and for process validation, hence the importance of integrating rigorous metrological activities into your practices.

Types of standards

There are several types of standards designed for different uses in metrology:

• Primary standards: These are reference standards of the highest metrological quality. Their characteristics are determined in relation to fundamental physical constants.
• Secondary standards: Standards calibrated in comparison with a primary standard. They are less accurate but more practical for everyday use.

In your work, you may need to use regularly calibrated secondary standards to ensure the quality and consistency of your measurements.

To ensure traceability, standards must be calibrated and periodically verified according to the standards defined by the BIPM (Bureau International des Poids et Mesures) or similar organizations. This ensures that measured values are reliable and reproducible.

Calibration steps

1. Instrument identification: Select the tool or device requiring calibration.
2. Comparison with a standard: Use a reference standard that has an accurate reference value and known measurement uncertainties to compare with your instrument's indications.
3. Document the deviation: Note the difference between the value of the quantity to be measured by the instrument and the known reference value of the standard.
4. Decision on need for adjustment: If your instrument is outside specified tolerances due to measurement uncertainties, adjustment is necessary.

By taking these conscientious actions, you ensure that your measuring instruments operate correctly and produce reliable results.

Choice of measuring instrument

Your choice of measuring instrument should be guided by the accuracy required for your application. Take into account its measuring range, its rangeability or measuring dynamics, its uncertainty, and its compatibility with current standards and established specified conditions. Accuracy and reliability must be your top priorities. That's why you should always choose a product from a reputable manufacturer of measuring instruments .

Typical contents of a calibration certificate:

• Device identification
• Calibration conditions (temperature, pressure, humidity)
• Measurement results (indication of measurement values)
• Comparison with standards (reference values and measurement uncertainties)
• Calibration date and validity date

Calibration company for measuring instruments

For calibration, you can turn to a company specializing in the calibration of measuring instruments, which has the expertise and equipment needed to validate and certify your measuring equipment on site or in the laboratory. It must operate according to a quality control system and strict, recognizable standards to guarantee the traceability of its standards.

Understanding accuracy

Accuracy refers to the closeness of measurements to the actual or reference value. You can assess accuracy by considering your uncertainty; a low level of uncertainty indicates high accuracy.

To illustrate, imagine a target: if your shots hit close to the center, your measurements are accurate.

The importance of precision

Precision, on the other hand, indicates the consistency of measurement results with each other. Precise measurements may not be exact, but they will always be grouped together.

This concept can also be illustrated using a target: if your shots cluster closely, even off-center, they are considered accurate. In your measurements, aim to minimize variation to achieve high accuracy.

Relationship between accuracy and precision

In metrology, although accuracy and precision are distinct terms, you need to consider them together to guarantee the reliability of your measurements. Ideally, you should aim to obtain results that are both accurate and precise, for a faithful representation of the measured quantity.

A practical example would be the calibration of a pressure transmitter to measure pressure; you want the measurements to be both precise and accurate for reliable use.

Calibration is essential for maintaining the accuracy and reliability of measuring instruments. By understanding the fundamentals and applying good practice, you can guarantee the quality of results in a wide range of industrial and scientific applications.

For example, scientific papers depend on precise temperature and pressure measurements to validate their hypotheses.

Metrology therefore plays a central role in the development and improvement of quality systems in industry, where every measurement must be both accurate and precise to meet the stringent requirements of inspection and testing.