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.