User Manual 4 1 Contents Describes the sound level meter and its general operating principles. A familiarization guide which explains, step by step, a typical measurement. How to prepare the sound level meter for measuring. How to calibrate and measure with the sound level meter. What you are able to do with your results. About this Manual BB11 Mediator 1–3 User Manual 1.1.2 About this Volume This volume of the User Manual deals with all the general aspects of handling and setting up the Mediator and includes instructions for the functionality of the Basic version (Basic.
odular Precision Sound Level Meter Type 2231 is a Type 1 precision instrument in accordance with IEC 651 regulations. It can perform a wide range of measurements, and can be used with a variety of modules. The characteristics of the sound Level Meter depend on the module that you most recently loaded into it - the module’s Software, transferred to the sound Level Meter, adapts the instrument to particular needs. The nature of the measurements that you require will determine those needs. In general, when the sound level, meter receives a signal, it performs several measurements simultaneously (for example, Peak and EMS detection). Therefore, you can look at the Peak and RMS values of the same measurement. A very wide frequency range of 1 Hz to 70kHz allows measurements in the infrasound and ultrasound regions. Depending on the module loaded, the sound Level Meter can perform several special functions, including automatic print-out of data at the end of preset time periods. These print-outs can be in any one of six languages. The sound Level Meter can also communicate with, and be controlled from, a computer. The sound Level Meter has three polarization voltages. This means that you can use almost any Bruel & Kjaer Microphone. 'With Microphone Type 4133 plus extension cable AO 0027, the sound Level Meter becomes a Type 0 instrument, in accordance with IEC 651 recommendations. Features of the Type 2231 Sound Level Meter include: ■ Fulfils IEC 804 Type 1, relevant sections of IEC 651 Type 11, and ANSI SI .4-1983 Type 1. ■ When used with Microphone Type 4133 and Extension Cable AO 0027, fulfills IEC 804 Type 0 and relevant sections of IEC 651 Type 0 I. WH 24 to 113dB(A)* measuring range (30 to 133dB(A)* with attenuator) in 7 overlapping sub-ranges. M 73 dB Pulse range; 70 dB RMS Linearity range. ■ RMS and Peak detection in parallel. ■ Internal memory has back-up battery power which prevents loss of application Software and data when the instrument is switched off.
About the 2238 Mediator Standards 2238 Mediator Integrating Sound Level Meter complies with the coming IEC 1672 Class 1 standard. This standard will supersede the IEC 651 and IEC 804 Type 1 standards. This implies that the Mediator also complies with current inter- National and National standards. The Mediator is categorized as a Group X sound Level Meter according to IEC 1672, i.e. a self-contained battery-operated instrument that requires no external connections to other apparatus to measure sound levels. Basic Configuration The Mediator comprises the following: ● 2238 Mediator Integrating Sound Level Meter ● Basic SLM Software BZ 7126 ● Microphone Preamplifier ZC 0030 ● Prepolarized free-field 1/2 ′′ Condenser Microphone Type 4188 ● 9-pole cable with 25-pole Adaptor AO 1386 (null-modem cable for serial interface) ● Shoulder Bag KE 0323 ● Protective Cover UA 1236 ● 4 × Alkaline Batteries QB 0013 1.2.1 How Mediator Works The Mediator can be configured to a wide range of require- ments with different Software packages or a combination of these packages. You can easily upgrade the Software via the serial RS – 232 Interface or it can be performed at a Brüel & Kjær service centre. The Frequency Analysis Soft- ware option requires Type 2238 – A – F (with filter set) or a hardware upgrade (installation of filter set 2238 MUF), that must be made at a Brüel & Kjær service centre. If the Medi- ator is ordered with Frequency Analysis Software BZ 7123, the filter set is part of the instrument. Refer to the block diagram in Fig.1.1 for an overview of how the Mediator works. The signal from the microphone is fed through the appropriate amplifiers, the desired filters (“A”, “C”, “L” or octave filters (if fitted)) and correction filters (“Sound Incidence”, “Windscreen”). The multiplexer switches two signals (either the same signal or with different weight- ings) through to the RMS and the RMS/Peak detectors and succeeding Time Weighting filters. At this point the signals are still in the analogue domain. The signals are now con- verted in the D/A-converter and all subsequent signal process- ing is in the digital domain. Finally the signals are fed through the D/A-converter and the buffered signals are out- put to the Aux 1 and Aux 2 connectors via the multiplexer. Detectors One of the main features of the Mediator is that it contains two detectors with independent frequency weighting func- tions. In the basic package, one is an RMS detector and the other a Peak detector. Linear and A- and C-weighting can be selected for both detectors. F (Fast), S (Slow) and I (Impulse) time weighting must be selected in the basic version. Both frequency and time weightings must be selected before a measurement is performed.