Tech Notes
Qualification / QPL
TSE TECH NOTE
1007-1PZ
A part is said to be qualified when it has passed all of the qualification tests of the specification. The owner of the specification will then list those qualified manufacturers for use by those who desire to buy a qualified part. In the case of MIL-PRF-15733, the general specification, Table X, lists all of the qualification tests, the test method, and the quantity to be tested. The detail requirements of a MIL-PRF-15733 part will be found in what is known as the 'Slash' Sheet (MIL-PRF-15733/24). The owner of the specification, in this case, the military, will then publish a list of all those qualified manufacturers by part number. This list is the 'QPL'.
A private corporation follows the same procedure to some extent. They write a specification containing electrical, mechanical and environmental requirements as well as qualification requirements. They are the owners of the specification and ultimately the owners of parts produced to that specification. As owners, qualification requirements are of their choosing. Here is where they may vary from the military. They may choose to require certain electrical and mechanical test in their specification and then perform environmental tests themselves. Once a manufacturer has completed the specification tests and the owner has completed the environmental tests, the owner will then list the qualified supplier(s) in his specification.
Qualification / QPL & TSE
TSE TECH NOTE
1007-2PZ
Texas Spectrum Electronics, Inc. designs and manufactures custom EMI Filters in accordance with the general requirements of MIL-PRF-15733. TSE does not manufacture any of the detail filter slash sheets of 15733, therefore is not on the QPL for that specification. TSE in it's more than 30 years of existence has manufactured many EMI Filters for military subcontractors and is listed as a qualified supplier on the subcontractor specification.
MIL-STD461 and EMI Filters
Filter manufacturers are often asked to provide a MIL-STD-461 filter. No one filter or filter line can be said to make all products meet MIL-STD-461. MIL-STD-461 is a sub-system and equipment EMI requirement, not a filter requirement. A filter may be designed which will bring the system within the specified limits of MS461, but the filter insertion loss design depends on the extent to which the system exceeds the MS461 limits. The only true method of determining the filter IL requirement for a given system is to run a MS461 test on the system (see figure below).
The solid line in the figure represents the MS461 CE102 requirement. The dashed line represents the result of a MS461 (MS462) test. Test results show that the system exceeds MS461 limits by 11DB at 0.1MHz, by 3DB at 0.5MHz, by 7DB at 3MHz and by 5DB at 10MHz. In general this means an EMI filter must now be designed, which will have an insertion loss of 11DB at 0.0MHz, of 3DB at 0.5MHz and so on for each frequency that the system exceeds MS461. Usually, a well designed EMI filter that meets the lower frequency insertion loss requirements will meet these upper frequency requirements.
The filter must meet the insertion loss with the source and load impedances of the system (see TSE Tech Notes XXX(?)of MIL-STD-220). The filter must also meet the current and voltage requirement (as well as other electrical requirements of the system), the mechanical requirements and the environmental requirements of the system.
TSE has designed and manufactured EMI filters to meet specific MIL-STD-461 requirements, however the particular filter design will not make all systems meet MIL-STD-461.