Case Studies : Compliance Engineering
& Testing
You may not always know what it is you want for your business,
or even if it is possible. We find it important to highlight
certain case studies to show you just what can be done and
that we will always do our utmost to meet your requirements.
Case Study 1
CE + CE - Does not equal CE
A client came to us with a computer that had been constructed
from various off the shelf sub-assemblies. There was a specific
application for the PC and one of the design criteria was
to enclose all of the sub-assemblies including the LCD screen
panel into a metal housing. During the design process the
client had taken extreme care to ensure all of the sub-assemblies
had been tested and were CE compliant in their own right.
It was therefore only logical to him that as all sub-assemblies
were CE compliant that the final product would automatically
comply.
During the process of verifying the EMC compliance of the
computer it very quickly became apparent that there were significant
non-compliances. These included radiated emissions and susceptibility
to electrostatic discharge or ESD.
We identified that a number of metal panels had been used
to manufacture the cabinet housing and several of these had
been powder coated thus insulating the panel from the main
chassis. This was allowing some of the metal panels to re-radiate
RF emissions from within the computer rather than helping
to screen them. Removal of the coating from the contact areas
of the metal panels immediately resolved the radiated emissions
problem and at the same time overcame the ESD non-compliance.
This simple modification also addressed a potential protective
earthing safety issue.
Case Study 2
29p saves the day
Product EMC compliance often requires testing of immunity
to surges on the mains power feed and possibly other inter-connecting
cables. This involves injecting a very high energy pulse into
the mains supply of the product under test and this can be
as high as 2000 volts. With such a large amount of energy
being applied it can sometimes have catastrophic results,
occasionally these can be quite spectacular.
A client requested us to carry out EMC testing on some sensitive
scientific analysis equipment. One module alone cost in excess
of £50,000 to produce. As the final product was intended
to be used in a semi-hostile environment we explained that
surge testing would be necessary, However there were serious
reservations from the client about subjecting the unit to
such treatment.
We reviewed the schematic diagram for the main power supply
within the product and indeed concurred with the client's
concerns in carrying out such tests. We calculated that there
was more than a 60% chance that the product would have sustained
serious damage.
Our solution was to add a transient voltage suppressor or
varistor to a specific area of the power supply. The result
being that the equipment withstood all of the surge tests
and continued to function perfectly.
Simply taking a product in and testing it without consultation
can end up with severe consequences, both in terms of product
damage and time delays. By working closely with clients we
are able to address these issues whilst testing products and
provide practical advice.
Not bad value in terms of insurance - 29p to protect £50,000
of capital expenditure. |
