B&K 2250 Light Manuel d'utilisateur télécharger pdf (Page 20)

Chapter 3

Conformance Testing

3.1 Introduction

This chapter contains the information needed to conduct conformance testing according to the specified

standards.

3.2 Mounting for Acoustical Tests

For acoustical tests, it is important that the test rig for mounting the microphone to be tested is

designed to minimise the influence of reflections to a level that is comparatively smaller than the test

parameter’s maximum Expanded Uncertainties of Measurement. This has to be demonstrated with a

good, known laboratory microphone.

Various ways in which the different microphone assemblies can be mounted to the test rig are:

• Microphone Type 4189 on Microphone Preamplifier ZC 0032 can be mounted in the ½″ Microphone

Holder UA 1317. The Microphone Holder can be mounted using the tripod mount thread. To mini-

mise the influence of reflections from the Microphone Holder, bend the holder part to an angle of 45°

± 15° from the straight position

• Outdoor Microphone Kit UA 1404 can be mounted using the tripod mount thread in the Mounting

Ring

3.3 Mounting for Mechanical Vibrations Tests

Only the microphone and preamplifier assembly contributes significantly to the sensitivity to mechani-

cal vibrations. Therefore, only this assembly has to be tested.

Microphone Type 4189 and Microphone Preamplifier ZC 0032 assembly is mounted on the shaker with

a suitable holder so that the vibration is applied in a direction perpendicular to the plane of the

microphone diaphragm.

3.4 Electrical Substitute for Microphones

To obtain a BNC type electrical input, replace the Type 4189 microphone with a WA0302-B, 15 pF,

fitted with a UA 0245 adaptor.

Electrical specifications obtained when introducing signals in this way are equal to the specifications

given in section 4.13.

All electrical inputs can be short-circuited when needed for test.

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B&K 2250 Light Manuel d'utilisateur Page 20