Maintenance can violate EMC integrity

 

In order to avoid accidental degrading of the EMC integrity during maintenance activities, maintenance/service engineers should be aware of any protection measures incorporated in the design of the equipment. This information should be contained in the maintenance documentation and should include precautions required during opening and closing of lids/panels with RF gaskets and the torque required to tighten bolts or screws correctly after the maintenance activity has been completed. Details on handling the harnesses, including details on minimum bend radii of cables harnesses, harness routing and segregation details should also be included.

 

When the cabinets or lids are opened during maintenance activities and circuit boards removed and replaced, they are susceptible to any ESD discharges caused by static build-up on the maintenance engineer, or his accessories.

 

In order to avoid this problem, with systems or equipment containing static sensitive devices the maintenance manual should include the following guidelines for the maintenance engineer to follow:

 

1.  The maintenance engineer should be provided with, as part of the maintenance tool kit, a static

protection kit containing:

 

•    Conductive wrist strap and lead.

•    Wrist strap tester or bond tester.

•    Antistatic work mat.

•    Assorted antistatic bags for components.

 

2.  The maintenance engineer should determine where the nearest grounding point to the place of work.

On a CPU, the nearest point would normally be the cabinet frame.

 

3.  The Engineer should fit the conductive wrist strap before commencing maintenance work and check it

is working correctly.

 

4.  The wrist strap lead should be connected to the grounding point on the cabinet frame and also attach

to the antistatic mat.

 

5.  The Engineer should wear the wrist strap at all times when opening and closing the cabinet and while handling packages.

 

6.  Ensure spare carrying cases or antistatic bags, applicable for the product, are available.

 

7.  Never touch the pins of connector or devices on the packages.

 

Ian Weatherilt, Senior Regulatory Consultant, Technology International. Tel: +1 804 421 9600 http://www.techintl.com/

 

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