The verification of the measuring instrument consists in checking the metrological and other characteristics of certain objects and their similarity with the passport data. Such actions are carried out by specially appointed persons in the intended premises, while using specialized equipment. These actions are called calibration of the scales.
Types of Verifications
- Initial calibration is carried out at the time of release of the scales from production or after repair. Also, such a procedure is carried out during import.
- Periodic verification is applied to those verification tools that have already been put into operation. It is carried out once a year.
- Extraordinary verification is applied when any technical damage occurs, also if the balance was stored for a long time, and after that it was put into operation.
- Inspection verification is carried out during metrological supervision.
State verification is entitled to be carried out by specialists of bodies of the Federal agencies that are involved in technical coordination and are considered state witnesses. In the event that the measuring instruments meet all the requirements, it is considered that they have passed verification. If, as a result of verification, some malfunctions were identified, then instead of a passport a certificate is issued that the device is unsuitable for use. Such scales require repair or calibration. If the verification was successful, the owner retains the appropriate certificate, and the stamp remains on the attorney balance.
Stages of verification of table scales
There are three stages in total. The first step is to calibrate without applying a load. At this stage, it is checked how correctly the scales are installed, and how they respond to an attempt to bring them out of balance. At the second stage, verification is carried out using a weight, the mass of which is approximately 1/10 of the load from the largest weighing boundary. The weight is usually placed in the center and on the sides, while the readings should equal the mass of the weight. The third stage determines the accuracy with which the balance works, taking into account the maximum load. In this case, the weight is set only in the center, the sensitivity of the weight is not checked.
Ways of checking weights
Calibration of scales is carried out in two ways. The first is statistical. It provides a measurement of the forces applied to the sensors being tested and the exposed sample. That is, this method applies to both exemplary and verified weights. The disadvantage of this verification method is that the results may be unreliable. Another disadvantage of this method is that the device being verified is not in operation. A dynamic way to verify conveyor or continuous instruments is to weigh a test sample. The disadvantage of this method is that this process is very time-consuming, while the result of verification will be inaccurate. Products to be weighed must be in the bunker, which is physically impossible to do. Samples of the scales should also be present, which is not always possible. With this method, the scales will not be operated according to the staffing table.
Electronic balance
Verification of electronic scales includes several stages of work: research and testing of the device, identification of metrological parameters, measurement of impermanence of scales that are not subjected to loads. This also includes recognition of the error of the readings of the instrument under test, the sensitivity of the balance. If the balance does not pass the appropriate calibration, then they are not allowed for operation.
Calibration of the scales (the frequency of this procedure is once a year) is carried out in accordance with the legislative documents “On metrology and metrological activity”. Periodic verification is subject to all scales in operation.
Calibration Methods
The documents for the operation of the scales spell out the conditions that must be strictly observed. When the calibration is carried out, the temperature, humidity, atmospheric pressure must clearly correspond to the operating indicator. During the external inspection, the absence of cracks and corrosion is usually established, all controls must be in place, according to the operating documents. If this is a crane device, then the passport must have a certificate of its test for the strength of the crane hook. At the time of testing the scales, it is necessary to identify how good they are, whether the control unit is overloaded. During determination of metrological boundaries, the inconsistency of the readings of the scales is checked in the absence of any loads. Metrological boundaries are calculated using an assessment of weights of the 4th category. If the verification results were positive, then this is noted in the passport and a stamp is made on the scales, which indicates the suitability of the scales for operation. If the verification result is negative, then the balance is not applied.