This is the last article from a series of articles where we reveal the secrets of a 0.1% benchmarking fault rate. As mentioned earlier, it is one of the best indices of quality in the measuring equipment industry in the world.
This time we are presenting to you the final stage of smart meters manufacturing, which is called functional quality control, calibration and verification. Earlier we already described that the semi-finished products have their own quality control stages. For example, SMT workshop has 100% optical control for assembled PCBs and selective visual control by the operators. Additional control takes place at the stage of PCB programming. But all this refers to quality control for some specific meter components.
After that, 100% of the assembled meters pass a compulsory functional quality control, where everything is checked comprehensively.
What does this imply? The meters have certain components, such as a PLC or RF modem, a disconnection relay, various interfaces (USB, RS-485 and an optical port), a meter cover opening sensor and a magnetic field sensor, which are NOT directly related to metrology, but which, nevertheless, are very important for the proper operation of the equipment. It is at the stage of functional quality control that the proper operation of all these components is checked.
The production process is built in such a way that the combination of all its stages forms the so-called product route. The technological system administrator determines the route for each type of product, and then the system itself controls its passage by all meters. If for some reason the meter did not pass the functional quality control (for example, errors were found), the system will not allow it to the next stage of calibration and verification.
At the stage of functional control, there is such a notion as the internal defect allowance. If this level is exceeded, then ADD Grup specialists will study at what stage the mistakes were made and how to repair them. This is necessary in order to eliminate the risk of unplanned extra costs and avoid a decrease in the productivity of the enterprise as a whole.
The equipment used at the stage of functional control is ADD Grup’s proprietary solution (both the equipment itself and the software). For each individual type of product, its software is adapted based on the functionality of the smart meter, as well as the country for which it is made.
The Automatic Functional Control Station (CPS-3) is the pride of ADD Grup, which helps to produce absolutely high-quality high-precision measuring equipment.
The next important stage is the area of calibration and verification of manufactured products. At present, ADD Grup uses calibration equipment from Applied Meters (a Slovak company), which includes an ELMA unit. The cooperation between ADD Grup and Applied Meters lasts for more than 20 years, during which the Slovak equipment has proven to be the best and has never failed.
At the calibration and verification stage, metrological verification of manufactured meters is carried out according to preset parameters. The purpose of this stage is to ensure that ADD Grup smart meters comply with the acceptable accuracy class.
The accuracy class is perhaps the main indicator that determines the quality of measuring equipment. For single-phase and three-phase meters for active energy, the accuracy class indicator is equal to the value “1”, for reactive energy – “2”. For transformer meters used for revenue metering, the accuracy class is “0.5”.
According to the company’s specialists, ADD Grup meters are supplied, being even more accurate than required by the metrological standards. To achieve an indicator of “1”, an indicator equal to “0.5-0.6” is set at the intra-production level. Anything that is worse than this index, as a rule, is rejected. The company deliberately complicates the tasks for itself in terms of accuracy class in order to be completely sure of a positive result.
At the same stage, the final step is the installation of software and the configuration of the meter that meets the requirements of a particular customer. The process of configuration of the finished product is automated, and as a result, the customer receives a meter that is already completely ready for installation in their distribution network.
We would like also to note that the verification and calibration equipment used by ADD Grup is itself verified for accuracy at least once every two years. This process is assigned to our Slovak partner, Applied Meters, a representative of which comes to Moldova with their own, even more accurate equipment, and carries out standardization and issues the appropriate certificates.
In addition, in the period between standardization, ADD Grup regularly practices the so-called cross-verification, when a certain number of meters are brought from one calibration rack to another, to make sure that the results obtained on different racks match. ADD Grup also has its own metrological laboratory certified according to ISO 17025, which selectively verifies a part of the batch of manufactured meters on its equipment.
The result of such scrupulous quality control work speaks for itself. One of thousand smart meters only produced by ADD Grup can theoretically be returned to the manufacturer under warranty. And if we are to speak about individual production processes, since 2009, for example, there has not been A SINGLE complaint from customers on the quality of plastic cases of ADDAX electricity meters.