Examples of this include the condition of the mill's contents and the characteristic tones produced as the steel balls hit the mill lining, or the noise produced by an ore crusher when unwanted objects are introduced.
The NVMS industrial noise monitors are essentially electronic versions of the human ear, but without the inconsistency between operators. The electronics are housed in a sealed IP66 rated stainless steel enclosure and the microphone is protected by an outdoor weather proof assembly.
Power is drawn from a standard 110/240V supply and the measured sound level in decibels is converted to a 4-20mA signal which can be readily accessed by DCS systems such as Scan 3000 and LCN.
At the heart of the system is a Bruel & Kjaer Sound Level Meter. This instrument is available in several versions and these complement perfectly the typical applications plant operators have in mind.
A basic version of the sound level meter will provide a simple overall noise level whereas enhanced versions offer such features as octave and 1/3rd octave band filtering as well as data logging and frequency analysis.
In many instances octave band or 1/3rd octave band filters are indispensable for plant monitoring, since being able to narrow down the instrument's 'hearing' sensitivity to a particular range of frequencies can allow characteristic tones to be monitored which are otherwise obscured by the general back-ground noise surrounding the equipment.
The entire solution is developed and manufactured by NVMS which means that customised solutions based upon noise monitoring can be readily available. This may include such options as a miniature computer to monitor, log, analyse and act upon results, alarm triggering, activating tape recorders... the flexibility is limited only by imagination