The method of measurements in accordance with GOST

Measurement Methods (methods of measurement) constitute a set of rules and operations, the implementation of which provides indicators with a known error. In accordance with the provisions of the Federal law № 102, measurements shall be provided, certified in the prescribed manner.

Factors that affect accuracy

Deviation depends not only on the metrological characteristics of measuring instruments. Equally important are operator error, deficiencies in the selection and preparation of samples the conditions in which measurements are made, and other factors. Accordingly, Methods perform the measurement (MVI) are created for specific conditions using specific tools.

This statement, however, does not mean that each laboratory should develop their own methods. However, if the laboratory uses a type of measuring tools, aligned with certified applications, influence factors are within a predetermined range, the operator has an established qualification, then the physical parameters in this situation will be measured with a known margin of error.

Influencing factors include:

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

GOST GSI

Methods perform the measurement, according to the state standard includes the following sections and structural elements:

1. The Name.
2. Scope.
3. Normative references.
4. Definitions.
5. Abbreviations and symbols.
6. Requirements for error or assigned characteristics of deviations.
7. The Methods and conditions of measurement.
8. Security Requirements, and measures for the protection of the environment, qualification of operators.
9. Preparations for the measurements.
10. Measurements.
11. Processing of the results.
12. Control accuracy.
13. Applications.

Competent authorities

In accordance with GOST, methods of measurement Are created and certified in the manner prescribed by Rosstandart. Verification of measurement procedures is carried out:

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• Gnmt (Main scientific metrological center);
• Territorial bodies of GMS (the State metrological service);
• Other organizations, accredited and authorised to perform the certification.

The Test methods used outside the scope of state metrological supervision, the enterprises organize and conduct them according to established rules.

Applications

Development of methodology for measurements is in accordance with the initial parameters and includes:

1. The Choice of method, measuring instruments, auxiliary materials, sequence of operations, the algorithm for calculation of totals.
2. The creation of the draft document to Method of measurements.
3. Metrological certification.

The number of reference included:

1. Assignment Methods perform the measurement.
2. The error.
3. Measurements.
4. The Characteristics of the measured object.

The destination must be specified:

1. The Name (in case of need, given the deployed name) and the value of its characteristics.
2. Restrictions on the scope of MVI departmental affiliation, characteristics and types of objects, etc.

The error should be given in the form of parameters specified in regulations, with reference to regulatory act, which they provided (if any).

The measurement Conditions are specified as a range of indicators of the influence quantities (factors): electrical, mechanical, climatic and so on.

Feature object is given by the limiting values of those parameters, the deviation from the nominal indicators of the effect on the error.

Tool and the Method of measurement the method of measurements Is in accordance with the applicable regulatory and technical documents. If NTD are not available, shall be based on the calculation of the characteristics of error or experimental results of their study.

Classification

Certified techniques of measurements are divided into groups in accordance with the methods of obtaining the results:

• Direct methods. When using the obtaining of the desired values is based on experimental data.
• Indirect methods. In this case the final value is based on direct measurements of variables having a certain dependence on the measured object. These methods are used in the absence of the possibility to use direct methods. For example, the calculation of the density of solids is based on the results of measurement of its volume and mass.

According to the conditions in which measurements are made, Methods perform the measurement share on:

1. Contact. They are based on the interaction of the sensitive element of the measuring device and the object. A simple example is the definition of body temperature with a thermometer.
2. Contactless. These methods are based,accordingly, in the absence of contact between the object and the sensor element of the measuring device. For example, the calculation of the distance by radar, the blast furnace-definition of temperature by the thermometer, etc.

Depending on the chosen method of comparison of the parameter to be measured with the SI unit, there are:

1. Direct method. In such cases, the value is determined by the reading device. For example, it can be a voltmeter, ammeter, thermometer and so on a Measure that reflects the unit of measurement in process does not participate. This task, the SI (system of measurement) performs a scale.
2. Comparison Method. In this case, the measured parameter is mapped to an indicator, which is the measure. For example, the mass on the balance is determined by balancing weights.

Types of comparison methods

Among the main ways are:

1. A Zero method. When it is used the resultant effect of the variables on the device comparison is brought to 0. For example, the strength of the electrical resistance of the bridge is determined by its absolute balance.
2. Method matches. If used, the difference that occurs between the performance desired and reproducible measures, measured at the coincidence of marks on scales (e.g. Vernier caliper and Vernier) or periodic signals.
3. The replacement Method. It is based on the comparison measure. The measured parameter is replaced with the known value. She played measure. Conditions for this remain unchanged. For example, the weighting is carried out by alternately moving the masses and weights on the same scales.

Analysis of waste water: methods of measurement (HDPE f 14.1:2:4.135-98)

The MVI allows to determine the content of elements in specific ranges in sample solution without dilution.

PND f 14.1:2:4.135-98 sets the Method of measurement of mass concentratii:

• Kremniya;
• Maria;
• Aluminia;
• Beryllia;
• Bora;
• Tullia;
• Nutria;
• Arsenic and other elements.

Optionally, you can define the content of oxides of different elements in samples of wastewater, drinking, natural water, by means of calculation.

Method of measurements of mass concentration of the substances is based on the determination of the intensity of radiation of atoms and ions of the appropriate element is excited in an argon plasma.

Movement studies

For the introduction of sample solution (sample) in the atomic emission spectrometer used a peristaltic pump and atomizer. The solution in the form of fine droplets (in aerosol form) to enter the camera. Through the tube of the burner in a stream of argon aerosol is injected into the inductive-connected plasma.

During the whole time of sample (approx. 2-3 MS) undergo cycles of evaporation and atomization, ionization and excitation. Radiation that emit ions and atoms, is focused on the spectrometer entrance slit. Further it is divided by wavelength diffraction grating (dispersing element).

The Spectrometer polychromator allows to perform simultaneous multi-element study. In this case, monochromatic radiation, having a diffraction grating, falls on the exit slit. The output is fixed, the number of PMT (photomultiplier tubes). Each detects radiation from a specific wavelength on your way out.

In the atomic emission spectrometer with an echelle optical system the separation (decomposition) radiation is a diffraction grating and a prism. The output spectral image is two-dimensional.

The functions of the Registrar performs a CID (solid state matrix detector). The number of registered pixels in it exceeds 250 thousand In result for one dimension, you can perform multi-element analysis and register the most sensitive lines of each element.

Example of a technique of measurement: salinity samples

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

The First is research in open vessels. A sample of waste water that contains sediment or suspended particles, stirred. After that, a heat-resistant beaker (or flask) take a 100 CC sample.

If you need to determine the dissolved forms of the substances, the sample is pre-filtered. To this may be a membrane or paper filter.

Simultaneously prepared blank sample. It uses dionisievna or bidistilled water instead of sewage.

To analyze the samples and blanks add concentrated nitric-Tu (2 CC) and hydrogen peroxide (1 CC).

The Container was heated for two hours, not allowing to boil. As a result, the solution uvarivaetsja about 25 CC.

After cooling, samples are brought dionisievna or double-distilled water to the original volume (100 CC).

If there is a suspension, it is removed (by filtration) to dry the dishes.

Microwave decomposition

As in the previous case, a sample containing suspended particles, mix well. A graduated cylinder you need to take a 50 cm³ sample and put in a Teflon cylinder.

Afterthis is added to the sample concentrated nitric-TA (2 cm³). The mixture was placed in a fume hood for 15-30 min.

Teflon cylinder inserted in the autoclave (apparatus for heating) microwave oven. It should be guided by the manual of the equipment and to observe safety precautions.

The Apparatus for heating are placed in the oven; set the program of decomposition of the sample.

Autoclaves are Cooled gently shaken. This is necessary to ensure that the contents are thoroughly mixed. Then to balance the pressure to slightly open the cover.

Efficiently decomposed mixture after removal of the nitrogen oxides is a yellowish or colorless, transparent solution. Undissolved particles on the walls of the liner must be absent.

The Solution was cooled to room temperature, then transferred to flask of 50 cm³. Wall PTFE liner is washed with bidistilled or deionized water (in small portions).

Certification

It is for those of MVI, which are used in the scope of state metrological supervision. Certification of measurement techniques Is also carried out to monitor the status of technically complex systems (GOST 22.2.04).

Applications that apply outside of the regions of distribution of state control and supervision, are qualified according to the rules defined at the enterprise or in a branch office.

The Key purpose of the procedure is the confirmation of the possibility of measurements in the manner and with the error not exceeding the figures stated in the document on methodology.

Certification is carried out metrological service and other structures authorized to carry out the functions of ensuring the uniformity of measurements.

Validation is performed on the basis of the results of the examination of materials and documents compiled during the development of MVI. This includes materials for technical/experimental research.

Documents for certification

In the list of securities include:

1. The Initial requirements for creation (development) of MVI.
2. The Project of the document regulating the procedure.
3. Programme and results of computational/experimental performance evaluation of error.

Positive result

In case of establishment of conformity of measurement procedures the provisions of the governing document last approved in the prescribed manner. In it (except for the state standard) indicates that the MWI is certified. Is designated the organization (enterprise), metrological service which conducted the test. You can specify gnmc or on GMR.

Applications

Validated techniques shall be taken into account. This has established a Federal register of measurement techniques. It consists of several sections.

Regulated by the standard and have passed the certification technique intended for use in the areas of dissemination of the metrological state control and supervision shall be registered in obligatory order.

For inclusion in Register of measurement techniques developer guides in VNIIMS (all-Russian research Institute of metrological service) document on the MVI with the copy of certificate of attestation.

Registration Fee not charged.

Each method using the register is assigned a code. It includes the abbreviation FR (Federal register), section number (one digit), code measurements (two digits), the registration date (year) and number of the account (five digits). Example: FR.1.37.1998.00004.