How to determine whether a sound level meter is qualified based on the certificate?
1. The calibration certificate of the sound level meter is useless. Only if a calibration certificate is issued and a qualified conclusion and accuracy level are reached, it can be used normally.
The daily calibration of sound level meters requires a lot of equipment, including calibrators, standard condenser microphones, signal generators, measurement amplifiers, burst signal generators, precision attenuators, voltmeters, sound sources, muffler boxes (free field), etc. It requires at least 30W to be fully equipped, and it occupies a large space and has certain technical requirements; at the same time, there are not many instruments for sound level meter verification, and the standard equipment must be submitted for inspection every year, so establishing a complete set of acoustic verification equipment is not cost-effective, resulting in Many provincial metrology institutes have not established sound level meter calibration equipment and cannot issue sound level meter calibration certificates.
2. Frequently Asked Questions
①Is the calibration certificate of the sound level meter useful?
The calibration certificate of the sound level meter is useless. Only if a calibration certificate is issued and a qualified conclusion and accuracy level are obtained, it can be used normally.
Sound level meters are mandatory calibration measuring instruments. If the calibration agency issues a calibration certificate or test report, it means that the performance indicators of the sound level meter cannot meet the requirements of GB/T 3785-2010 (IEC 61672:2002). According to the calibration regulations JJG 188- It failed the 2002 test and cannot be used. (There is also a situation where the sound level meter itself is qualified, but the metrology institute does not have verification qualifications and can only issue a calibration certificate. This certificate is also invalid. Just send the sound level meter to a metrology institute with verification qualifications for verification.)
② Can the calibration items of the sound level meter be freely selected?
No, there are 10 items in the conventional sound level meter calibration. A calibration certificate can be issued after all the requirements are met. For many sound level meters that have not obtained CMC or CPA, only 2 to 5 items can meet the requirements, and other functions do not or cannot meet the standards. At this time, the Metrology Institute usually only gives out the inspection qualified indicators, and does not give out other indicators. At the same time, it only issues a calibration certificate, passing all the risks to the enterprise, and still collects its own calibration fees. However, when using a sound level meter with only a calibration certificate, all risks are borne by the enterprise. This risk is very high, and there is no need for the enterprise to bear it. It can only require the issuance of a calibration certificate.
③Is it more advanced to use an international standard sound level meter?
Yes, instruments using international standards are more advanced. The national standard for sound level meters is GB/T 3785-2010, which is equivalent to the international standard IEC 61672:2002. Although the national standard for sound level meters is literally a recommended standard, since the sound level meter is a measuring instrument regulated by the state, it must first obtain a manufacturing license CMC for production. To obtain a CMC, the prerequisite is to pass the type annotation CPA. At present, the type approval of sound level meters completely adopts the IEC 61672:2002 standard, so the national standard of sound level meters (equivalent to the national standard) is actually mandatory.
④Can the company itself write down the performance indicators and accuracy levels of the sound level meter at will?
Can't. Sound level meters, vibration meters and other instruments are produced under state supervision, and their important performance indicators and accuracy levels are given by the national type approval certificate. It is not written casually by the company itself. At the same time, the type approval certificate must be given in the company's product manual.
There are many sound level meters that do not meet the standards, pretending to be imported or other instruments, and can only issue calibration certificates without even giving an accuracy grade. They are 100% unqualified. Production and sales are illegal, and there are huge risks for users, so please be careful.
