Methodology for performing measurements in accordance with GOST

) представляют собой комплекс правил и операций, реализация которых обеспечивает получение показателей с известной погрешностью. Measurement methods (measurement techniques ) are a set of rules and operations, the implementation of which ensures the obtaining of indicators with a known error. According to the provisions of Federal Law No. 102, the measurements should be carried out by means, certified in accordance with the established procedure.

Factors affecting the error

The deviation depends not only on the metrological characteristics of the measuring means. Of no less importance are the operator's mistakes, drawbacks in the selection and preparation of samples, the conditions in which measurements are made, and other factors. (МВИ) создаются применительно к конкретным условиям с использованием конкретных средств. Accordingly, measurement techniques (MWIs) are created in relation to specific conditions using specific means.

This statement, however, does not mean that each laboratory should develop its own methods. Nevertheless, if a type of measuring instrument is used in the laboratory that is aligned with a certified MVI, the influence factors are within the specified range, the operator has the established qualification, then the physical indicators in this situation will be measured with a certain error.

To the influencing factors should be attributed:

• Humidity and temperature of the ambient air and the environment in which the measurement is made;
• Frequency and voltage of the mains;
• a magnetic field;
• Vibration and so on.

GOST GSI

, согласно госстандарту, включают в себя следующие разделы и структурные элементы: The measurement methods , according to the state standard, include the following sections and structural elements:

1. Name.
2. Sphere of application.
3. Normative references.
4. Terms and Definitions.
5. Abbreviations and notation.
6. Error requirements or attributed characteristics of deviations.
7. Methods and conditions of measurements.
8. Requirements for safety, environmental protection measures, operator qualifications.
9. Measures to prepare for measurements.
10. Performing measurements.
11. Processing of results.
12. Precision control.
13. Applications.

Authorized bodies

создаются и аттестуются в порядке, установленном Росстандартом. In accordance with GOST, measurement procedures are created and certified in accordance with the procedure established by Rosstandart. Verification of the MVI is carried out:

• GNMTS (the main scientific metrological center);
• Territorial bodies of HMS (State Metrological Service);
• Other organizations that have accreditation and have the right to conduct certification.

Verification of methods used outside the spheres of operation of state metrological supervision, the enterprises organize and conduct according to the rules established by them.

Creating an MVI

осуществляется в соответствии с исходными параметрами и включает в себя: The development of the measurement methodology is carried out in accordance with the initial parameters and includes:

1. The choice of method, measuring aids, auxiliary substances, the sequence of operations, the algorithm for calculating the final indicators.
2. . Creation of a draft document on the methodology for performing measurements .
3. Metrological attestation.

The initial requirements include:

1. . Purpose of the measurement procedure .
2. Norms of error.
3. Measurement conditions.
4. Characteristics of the measured object.

The appointment should include:

1. The name (if necessary, the expanded name is given) of the quantity and its characteristics.
2. Restrictions on the scope of MVI application for departmental membership, characteristics and types of facilities, etc.

Norms of error should be specified in the form of parameters specified in regulatory documents, with reference to the normative and technical act, in which they are provided (if any).

The measurement conditions are set in the form of a range of indicators of the influencing variables (factors): electrical, mechanical, climatic and so on.

The characteristic of the object is set by the limiting values of those parameters whose deviation from the nominal values affects the error.

осуществляется в соответствии с действующими нормативно-техническими документами. The choice of the means and method of measurement in the measurement procedure is carried out in accordance with the current regulatory and technical documents. If NTDs are not available, the basis for calculating the error characteristics or the results of their experimental investigation.

Classification

разделяются на группы в соответствии с приемами получения результатов: Certified measurement techniques are divided into groups in accordance with the methods for obtaining the results:

• Direct methods. When using them, the desired value is obtained on the basis of experimental data.
• Indirect methods. In this case, the final value is set taking into account direct measurements of quantities having a definite dependence on the measured object. These methods are used when there is no possibility to use direct methods. For example, the calculation of the density of a solid body is based on the results of measuring its volume and mass.

разделяют на: According to the conditions under which measurements are taken, the measurement techniques are divided into:

1. Contact. They are based on the interaction of the sensing element of the measuring device and the object. A simple example is the determination of body temperature using a thermometer.
2. Non-contact. These methods are based, respectively, on the absence of contact between the object and the sensing element of the measuring device. For example, the calculation of the distance using a radar, in a blast furnace - the determination of temperature by a pyrometer, etc.

Depending on the chosen method of comparing the parameter to be measured with the SI unit, the following are distinguished:

1. The direct method. In such cases, the value is determined from the reference device. For example, it could be a voltmeter, an ammeter, a thermometer, etc. A measure that reflects a unit of measurement does not participate in the process. This task is performed in the SI (measurement system) by a scale.
2. Method of comparison. In this case, the measured parameter is compared with the index that is reproduced by the measure. For example, the mass on the balance weights is determined by balancing the weights.

Types of comparison methods

Among the main ways can be identified:

1. Zero method. When using it, the net effect of the effect of the quantities on the comparison device is brought to 0. For example, the electrical resistance force of a bridge is determined by its absolute balancing.
2. Match method. When using it, the difference that arises between the measures of the desired and reproducible measure is measured when the marks coincide on scales (for example, caliper and vernier) or periodic signals.
3. Substitution method. It is based on comparison with the measure. The measured parameter is replaced by a known value. It is reproduced by measure. The conditions remain unchanged. For example, weighing is performed by alternately moving the mass and weights to one cup of the balance.

Analysis of sewage: the procedure for performing measurements (HDPE F 14.1: 2: 4.135-98)

This MVI allows you to determine the content of elements in certain ranges in a sample solution without dilution.

: HDPE F 14.1: 2: 4.135-98 establishes a methodology for performing measurements of mass concentration :

• Silicon;
• Barium;
• Aluminum;
• Beryllium;
• Boron;
• Thallium;
• Sodium;
• Arsenic and other elements.

If necessary, you can determine the content of oxides of different elements in the samples of sewage, drinking, natural water in a calculated way.

веществ основывается на определении интенсивности излучения атомов и ионов соответствующего элемента, возбужденных в аргоновой плазме. The method of performing measurements of the mass concentration of substances is based on determining the radiation intensity of atoms and ions of the corresponding element excited in an argon plasma.

The mechanism of research

To introduce a solution of a sample (sample) into an atomic emission spectrometer, a peristaltic pump and a nebulizer are used. The solution in the form of small drops (in the form of an aerosol) enters the chamber. Through the torch tube in the flow of argon, the aerosol is injected into the inductively-bound plasma.

During the entire time of the sample in it (about 2-3 ms), evaporation and atomization, ionization and excitation cycles pass. The radiation emitted by ions and atoms is focused by a spectrometer at the entrance slit. Then it is divided along the wavelengths by a diffraction grating (dispersing element).

A spectrometer with a polychromator allows simultaneous multielement analysis. In this case, the monochromatic radiation, after diffraction on the lattice, falls on the output slit. A fixed number of photomultipliers (photoelectron multipliers) is installed at the output. Each of them records the radiation of a specific wavelength at its output.

In an atomic emission spectrometer with the Echelle optical system, the separation (decomposition) of the radiation is produced by a diffraction grating and a prism. At the output, the spectral image is obtained as a two-dimensional image.

The functions of the recorder are performed by a CID (semiconductor matrix detector). The number of recording pixels in it exceeds 250 thousand. As a result, in one measurement it is possible to perform multi-element analysis and register the most sensitive lines of each element.

Example of a measurement procedure: mineralization of samples

Analysis of samples of wastewater containing visible suspended particles (sediment) is carried out in two ways.

The first is a study in open vessels. A sample of sewage containing sediment or suspended particles is mixed. After that, 100 cc are taken into a heat-resistant beaker (or flask). Cm of the sample.

If it is necessary to determine the dissolved forms of substances, the samples are pre-filtered. For this, a membrane or paper filter can be used.

Simultaneously, a blank sample is prepared. It uses deionized or bidistilled water instead of sewage.

To the analyzed and blank samples, add a concentrated nitrogen c-tu (2 cc cm) and hydrogen peroxide (1 cc cm).

The tanks are heated for two hours, not allowing boiling. As a result, the solution evaporates to about 25 cc. cm.

After cooling, the samples are deionized or bidistilled water to the original volume (100 cc).

If the suspension remains, it is removed (by filtration) in a dry container.

Microwave Decomposition

As in the previous case, the sample containing suspended particles should be mixed. A measuring cylinder needs to take 50 cm ^{3 of the} sample and put in a fluoroplastic cylinder.

After this, a concentrated nitric acid (2 cm ³ ) is added to the sample. The mixture is placed in a fume hood for 15-30 minutes.

The fluoroplastic cylinder is inserted into the autoclave (microwave oven) of the microwave oven. In this case, follow the operating instructions for the equipment and observe the precautionary measures.

Apparatus for heating placed in the oven; A program for the decomposition of the sample is established.

Chilled autoclaves are gently shaken. This is necessary to ensure that the contents are thoroughly mixed. Then, the lid is opened to balance the pressure.

Qualitatively decomposed mixture after removal of nitrogen oxides is a yellowish or colorless transparent solution. Insoluble particles on the walls of the liner should be absent.

The solution was cooled to room temperature, then transferred to a 50 cm ³ flask. The walls of the fluoroplastic liner are washed with bidistilled or deionized water (small portions).

Certification

It is carried out for those MWIs that are used in the areas of operation of state metrological supervision. осуществляется также для контроля состояния технически-сложных систем (ГОСТ 22.2.04). Certification of measurement techniques is also carried out for monitoring the state of technically complex systems (GOST 22.2.04).

MVIs that are applied outside the areas of state control and supervision are certified according to the rules defined at the enterprise or in the departmental department.

The key objective of the procedure is to confirm the possibility of carrying out measurements in accordance with the procedure and with an error not exceeding the indicators stated in the document for the procedure.

Certification is carried out by metrological services and other structures authorized to perform the functions of ensuring the uniformity of measurements.

The verification is performed on the basis of the results of the examination of materials and documents compiled during the development of the MVI. These include technical / experimental research materials.

Documents for certification

The list of securities includes:

1. The initial requirements for the creation (development) of MVI.
2. Draft document regulating the methodology.
3. The program and the results of the calculated / experimental estimation of the error characteristics.

Positive result

In case of establishing the compliance of the IMI with the provisions of the regulatory document, the latter is approved in accordance with the established procedure. In it (except for the state standard) it is indicated that the MVI is certified. In this case, the organization (enterprise) whose metrological service conducted the audit is designated. A GNMC or a GMA body may be indicated.

Registration of the MVI

Certified methods are subject to accounting. For this purpose, the Federal Register of Measurement Techniques was created. It consists of several sections.

The procedures regulated by the standard and passed the certification, intended for use in the areas of metrological control and supervision, must be registered without fail.

разработчик направляет во ВНИИМС (Всероссийский научно-исследовательский институт метрологической службы) документ на МВИ с приложением копии свидетельства об аттестации. To enter into the register of measurement techniques, the developer sends a document to the VNIIMS (All-Russian Scientific Research Institute of Metrological Service) with a copy of the certificate of attestation.

Registration fee is not charged.

Each method is assigned a code when entering the register. It includes the abbreviation of the Federal Register, the section number (one digit), the measurement type code (two digits), the registration date (year) and the account number (five digits). For example: FR.1.37.1998.00004.