Metrological assurance of measuring instruments for measuring frequency

 

Unified National System of Ukraine (ENSU), as well as its integration into a worldwide communications network standards stipulate particular telecommunications industry, its harmonious adaptation to the interstate, international, regional and national standardization system.

One of the main objectives is to ensure standardization of measurement. This problem is solved by the appropriate metrological provisioning (MP) of measuring instruments (MI) frequency, which is in testing, verification and calibration of the MI.

Design, manufacture and operation of frequency measurement devices require appropriate metrological support. At the same time providing a range of scientific, technical and organizational measures designed to support the unity and the required accuracy of frequency measurements in all sectors of the economy.

Of particular technical measures should be noted verification devices because it requires a large amount of instrumentation and, above all, frequency measurement. Suffice it to say that for the calibration standard crystal frequency needed: rubidium frequency standard, the frequency comparator, EFC, micro voltmeter selective, spectrum analyzer.

In terms of verification of works all kinds of equipment measurement can be divided into two groups: devices that measure the frequency, and instruments that produce highly stable electromagnetic waves.

The first group of devices calibrated by feeding on their input of highly frequency of electromagnetic waves and to determine the measurement error. Error of the standard frequency and its instability must be at least 3 times smaller than the measurement error of the instrument, which confide. Therefore, for the calibration of frequency, the relevant standards of frequency synthesizers, frequency multipliers. Accuracy of measurement frequency is determined by the points of the frequency range, which are regulated by the normative and technical documentation (GOST, regulations, guidelines for the verification of the instruments). Typically, calibration is carried out in the beginning, middle and end of the frequency range of the instrument.

The second group measurement devices calibrated by comparing the frequency of electromagnetic waves produced by a model with a frequency of the instrument, which has a metrological characteristics, 3 times better. For the calibration of such devices are used frequency standards, frequency of model signals transmitted by radio receivers, oscilloscopes.

With the highest accuracy rate and time of reproducing with highly stable molecular generators.

Test. MI tests are conducted by specialized organizations accredited as a national center test sieves. Tests of samples held at MI state standard established order. MI tests for approval of the type carried out by the approved program, which should contain the following sections: review of technical documentation, an experimental study of MI; clearance test results.

Detailed requirements for the programs outlined in the recommendations of the international metrology bodies. During the tests should be monitored compliance documentation and technical characteristics of the MI conditions and regulatory documents (RD), which apply to them, including the calibration procedure.

Compliance with the approved type MI controlled bodies of the State Metrological Service (SMS) at the location of users.

Verification of MI - is the establishment of SMS authority (other authorized organizations) the suitability of SIT for use on the basis of experimentally determined MX and confirm their compliance with mandatory requirements.

Lists of groups of MI to be verification, approved by the State Standard. Calibration is carried out in accordance with the RD, approved the results of the tests.

The result of verification is to confirm the suitability of MI for use. In this case, it and (or) technical documents applied confidential imprint stamps and (or) issued "certificate of verification". Confidential stigma - a sign the prescribed form, applied to the MI, recognized as a result of verification suitable for use. If the MI as unfit to use, in this case, the image confidential stamps and (or) "certificate of verification" void and issued "certificate of unfitness." Form stamp and certificate of verification, the procedure for applying confidential stamp set by State Standard.

SIT are primary, periodic, exceptional, inspection and expert verification.

Initial calibration is made ​​at the MI from the manufacture or after repairs, as well as the importation of MI across the border in batches. This verification is subjected, as a rule, each instance of the MI.

Periodic calibration is performed at set intervals of time (calibration interval). She was subject to the MI, which are in use or in storage. Specific lists of SIT to be checking, set by their owners - individuals and legal entities. Bodies of the SMS in overseeing compliance with metrological norms and rules checking the accuracy of these listings. Periodic calibration must pass each instance the MI. An exception may be the MI, are on long-term storage. The results of this verification is valid for Calibration interval. The first interval is set at MI type approval, the following are determined on the basis of different criteria.

Extraordinary MI calibration is carried out prior to the date of the periodic verification of the following cases: damage to the sign confidential stigma, as well as the loss of the certificate of verification, the commissioning of MI after prolonged storage (more than one Calibration interval) of reconfiguration, and, if known, or There are assumptions about the shock (mechanical) effects on the MI or the poor of his work.

The inspection is carried out verification of the implementation of SMS authorities of state supervision and departmental control over the state and the use of SIT. It is not allowed to conduct the full extent permitted by the method of verification. Inspection results are recorded in the instrument calibration verification.

Expert verification is carried out with any matters of MX, serviceability and suitability of MI for use. Her conduct SMS authorities upon written request of interested persons.

The order of presentation of MI in fact determined by the State Standard. Calibration is carried out in accordance with established procedures and includes the following:

- Establishing the frequency of work (defined calibration interval) in accordance with ISO 10012;

- The development and documentation of methodologies for work according to the instructions of RD 50-660-88;

- Maintaining appropriate protocols, reflecting the results of operations;

- The organization of storage and use of documentation for verification of the MI.

The primary MX, which is determined by calibration, the error is. It is determined on the basis of comparing the MI under verification and more accurate working standard.

Measures can be believed:

- Reconciliation of (or opposition to the methods of substitution) with a more accurate measure using a comparator. Common to these methods of checking the MI is to provide a signal about the presence of difference in size compared quantities. If this signal by adjusting the model measures would be reduced to zero, we realized a zero measurement method;

- Measurement of the reference value of MI, reproducible measure. In this case, verification is often called a grading. Graduation - a drawing on a scale of marks corresponding to the testimony of the working standard, or definition of his testimony refined values ​​of the magnitude of the applied marks on the scale of the MI, which calibrated;

- Way to gauge when a more accurate measure is checked, only one measure of a set or one of the scale marks valued measures and other measures of the true dimensions are defined by their mutual comparison, in various combinations on instruments for comparison and further processing of the measurement results.

Calibration of measuring instruments is made:

- By direct comparison of the measured values ​​and values ​​that play an appropriate level of working standards and accuracy class. The values ​​of the output measures are chosen equal to the corresponding (often digitized) marks the instrument scale. The greatest difference between the measurement and the corresponding size standard is, in this case, the main error of the instrument;

- By direct comparisons of the readings, which calibrated and the reference for the simultaneous measurement of the same magnitude. The difference of their testimony is under verification absolute error of MI Can be used and other methods of verification.

Verification is important in the selection of an optimal ratio between the standard errors under verification and the MI.Typically, this ratio is assumed to be 1:3 (based on the criterion of negligible error), when checking is introduced amendments to the testimony of MI model. If corrections are not introduced, the reference selected from SIT ratio of 1:5. The ratio of errors under verification and reference SIT is established taking into account the method of verification, the nature of the error, admitting the errors of the first and second kind, and can sometimes differ significantly from the previously mentioned figures.

By checking the right decision State Standard MI may be granted by an accredited MS entities whose activities are carried out in accordance with applicable law and RD for the uniformity of measurements, taking into account the recommendations of the ISO and ІEK.

In those areas where the state metrological supervision and control are not required, to ensure proper operation of the metrological calibration of MI is applied.

Calibration (calibrations) - a set of operations performed to identify and confirm the actual values ​​of the metrological characteristics, and (or) fitness for use of MI, which are not subject to state metrological control and supervision.

Organization performing the calibration work must be attorneys and an identified means of calibration - standards, facilities and other MI used for calibration in accordance with established rules. They are designed to ensure the transfer of units of the size of the national standards of measurement instruments that are calibrated, updated documents regulating the organization and conduct of the calibration work. They include documentation on the MI and calibration, regulatory documents for calibration, the calibration procedure and the use of its data professionally trained and qualified personnel, facilities, meet regulatory requirements.

Certify the results of the calibration gauge mark, applied to a MI or a certificate of calibration, and record in operational documents.

Requirements for calibration laboratories are given in the relevant Standard and the ISO / ІEK 17025-2000 /.

 

LABORATORY WORK №7