MODUK DEF STAN 59-41: PART 4 PDF

Introduction

Some equipments may be too large or high powered for testing in screened rooms and recourse must therefore be had to open site testing Open site testing shall not be authorized unless the Project manager is satisfied that no other procurement testing route is available. Open site testing of large or high powered individual items of equipment presents many problems in achieving a reasonable degree of quality control. The absence of a screened enclosure imposes the local electromagnetic environment upon the test item and also means that the Part 3 susceptibility tests at rf are excluded. It therefore follows that if the local electromagnetic environmental levels are high, compliance with limits cannot be demonstrated and immunity to radio frequency fields cannot be established.

There are however, methods by which these problems may be overcome, for instance, a large generating system can be split into:

(a) the main generator, manually excited;

(b) the electronic control circuits.

The equipment can then be tested separately.

The generator without its electronic control circuits will not be susceptible to ripple or radio frequency energy and the emission characteristics usually reduce to very low levels of energy at frequencies in the region of 10 MHz. Furthermore, a generator is unlikely to produce narrowband rf energy so that measurements of generated noise can be made even in the presence of local radio stations during an open site test. The electronic control circuitry can be tested in a screened enclosure as its size will be relatively small and the methods described in Part 3 of this Standard can be used. Most large equipments can be dealt with in a similar manner.