The accuracy of measurements is of great importance for production, laboratory research, construction, energy, and other industries. The quality of the product, the safety of technological processes, and the correctness of the decisions made depend on the reliability of the instrument readings.
Over time, even properly functioning measuring equipment may change its metrological characteristics. Accuracy is affected by the intensity of use, mechanical wear, temperature, humidity, vibrations, and other external factors. To monitor the actual characteristics, calibration of measuring instruments is used.
What is calibration of measuring instruments?
Calibration is an integral part of metrological control, which involves carrying out work to establish the metrological characteristics of measuring instruments by determining, under specified conditions, the relationship between the value of a quantity obtained using a measuring instrument and the corresponding value reproduced by a reference standard of the unit of quantity.
Simply put, during the calibration process, the readings of the measuring instrument being tested are compared with reference values. This makes it possible to determine the actual deviation of the instrument’s readings.
Based on the results of the procedure, it is possible to determine whether the metrological characteristics of the measuring instruments meet the established requirements and whether they can be used for specific measurement tasks.
What is the calibration for?
The main purpose of calibration is to obtain information about the metrological characteristics of the measuring instrument.
Regular monitoring makes it possible to detect changes in the measurement instrument’s readings in a timely manner and take the necessary measures. If the deviations exceed the permissible values, the equipment may require adjustment, repair, or replacement.
Calibration is especially important for enterprises where measurement results are used to control technological processes, product quality, or laboratory research.
The main objectives of the procedure include:
- determination of actual deviations in readings;
- assessment of metrological characteristics;
- ensuring the reliability of measurement results;
- confirmation of the traceability of measurements.
Which measuring instruments are subject to calibration
Various types of measuring equipment can be subjected to calibration. The possibility of carrying out the work depends on the purpose of the device, its technical characteristics, and the scope of the laboratory’s competence.
Depending on the specialization, the following may be calibrated:
- devices for measuring temperature;
- pressure measurement tools;
- weighing equipment;
- electrical measuring instruments;
- tools for measuring geometric quantities;
- sensors and transducers;
- measuring systems;
- laboratory measuring equipment.
Before carrying out the work, the type of device, the measurement range, and the characteristics that need to be checked are determined.
How is the calibration performed?
Calibration is carried out according to the established methodology using the appropriate standards and equipment.
Preparation of the measuring instrument
At the first stage, the specialist identifies the measuring instrument, checks its technical condition, completeness, and the possibility of carrying out the necessary work.
The measuring instrument must be prepared in accordance with the established requirements. Depending on the type of equipment, the conditions for its preliminary conditioning, installation, and operation may be taken into account.
Selection of standards
To carry out calibration, reference standards and measuring instruments with known metrological characteristics are used.
The choice of equipment depends on the measurement range, the required accuracy, and the specific features of the instrument.
Performing calibration
The measuring instrument is maintained under the required conditions, after which a series of measurements is carried out at the designated points within the range in accordance with the calibration procedure.
The obtained readings are compared with the values reproduced by the reference standard. The number of measurements and their sequence are determined by the applied procedure.
Processing of results
Based on the obtained data, the necessary characteristics are calculated, including the calibration uncertainty.
The results make it possible to assess the actual condition of the measuring instrument and determine its suitability for further use in accordance with the established requirements.
Formatting the results
After the work is completed, a document is issued containing the calibration results — a calibration certificate. It includes information about the measuring instrument, the standards used, the conditions under which the calibration was carried out, and the obtained results.
Calibration and verification: what’s the difference?
Calibration and verification are often considered similar procedures, but they have different purposes.
Verification is related to establishing whether a measuring instrument complies with mandatory metrological requirements in cases where verification is required by law.
Calibration allows you to determine the actual metrological characteristics of a measuring instrument and establish the relationship between its readings and the values reproduced by standards.
Therefore, before carrying out the work, it is necessary to determine which procedure is required for a specific device and the conditions of its use.
Why is laboratory accreditation important?
When selecting an organization to carry out calibration work, it is necessary to take into account its technical competence and the scope of work it performs.
An accredited calibration laboratory must meet the established requirements for competence, impartiality, and stability in carrying out calibration work.
One of the important benchmarks is compliance with the requirements of GOST ISO/IEC 17025. The standard establishes general requirements for the competence of testing and calibration laboratories.
It is important to take into account not only the presence of accreditation but also the scope of accreditation. It defines the list of specific types of measurements and work that the laboratory can perform within the framework of its confirmed competence.
Therefore, before ordering a service, you should check whether the required type of calibration is included in the scope of accreditation of the selected organization.
What affects the accuracy of calibration results?
The reliability of the results is influenced by a whole range of factors. First and foremost, the characteristics of the standards used, the condition of the equipment, and the conditions under which the measurements are carried out are taken into account.
The significant factors include:
- temperature and humidity;
- vibration;
- electromagnetic influences;
- power supply stability;
- technical condition of the equipment;
- accuracy of the standards;
- correct installation of the device;
- compliance with the methodology requirements.
Therefore, the calibration laboratory must ensure that the conditions meet the requirements of the applied methods and technical documentation.
How often should calibration be performed?
There is no single interval that is suitable for all measuring instruments.
The frequency is determined taking into account the purpose of the equipment, the intensity of use, environmental conditions, the manufacturer’s requirements, and the organization’s internal procedures.
For instruments that are constantly used in critical technological processes, more frequent monitoring may be required. In this case, it is advisable to set the frequency based on the accumulated results of previous calibrations and operating conditions.
Organizations are advised to keep records of measuring instruments and plan calibration work in advance.
What needs to be provided for calibration
Before sending the device to the laboratory, it is necessary to prepare the information that will allow you to correctly determine the scope and conditions of the work.
Depending on the specific equipment, the following may be required:
- name and type of the measuring instrument;
- manufacturer’s or inventory number;
- technical documentation;
- measurement range;
- information about the purpose of the device;
- accuracy requirements;
- previous calibration results.
If the customer has any special requirements, they should also be communicated in advance.
Why is it important to calibrate your equipment in a timely manner?
Using a measuring instrument with unknown or changed metrological characteristics can lead to unreliable results.
In production, this can affect the control of technological parameters and the quality of the finished product. In a laboratory, measurement errors can lead to incorrect interpretation of the results.
Regular calibration helps to timely detect changes in equipment characteristics and make decisions about its further use.
How to choose a calibration laboratory
When selecting a service provider, it is necessary to take into account not only the cost of the service and the deadlines for completing the work. First and foremost, you should check the organization’s competence and the availability of the necessary capabilities to work with a specific type of equipment.
It is recommended to pay attention to:
- The presence of accreditation;
- the scope of accreditation;
- the list of calibrations performed;
- the standards and equipment used;
- the qualifications of the specialists;
- the conditions for conducting measurements;
- the procedure for documenting the results;
- the ability to work with the required measurement range.
It is especially important to ensure that the required type of calibration falls within the laboratory’s declared scope of competence.
Calibration services for measuring instruments
Calibration work is carried out taking into account the type of equipment, the measurement range, and the accuracy requirements. Before starting the procedure, the possibility of carrying out the work is determined, and the appropriate methodology is selected.
When contacting a calibration laboratory, it is necessary to provide information about the device and its technical specifications. This allows you to determine in advance the conditions for carrying out the work, the required equipment, and the list of parameters to be tested.
If an organization works with a large number of measuring instruments, it is advisable to create a unified calibration schedule. This approach helps to systematically monitor the condition of the measuring equipment and prevent missing the established deadlines.
Conclusion
Calibration of measuring instruments is an important part of metrological support for production and laboratory activities. It allows determining the actual characteristics of instruments, identifying deviations, and maintaining the required level of measurement reliability.
When selecting a service provider, it is necessary to take into account technical competence, the equipment used, and the scope of accreditation. An accredited calibration laboratory must carry out work within the confirmed scope of accreditation and ensure the necessary conditions for obtaining reliable results.
Regular monitoring of measuring equipment allows for the timely detection of changes in its characteristics and reduces the risks associated with the use of unreliable measurement results.
