Systems Test

All systems are subject to a number of tests before shipping and there are fairly obvious stages of the production build where it would be of benefit to test a sub assembly, or Line Replaceable Unit (LRU).

All products go through a final test and the test procedure to do this is generated in engineering / design and includes a range of standard tests, such as safety testing, basic system tests as well as product specific tests. Generally, engineering work closely with the customer in defining these tests and where necessary, they are defined within the original contract review / quote stage.

Basic test includes safety testing; Elma-Mektron has both PAT testers and low resistance measuring equipment for this purpose. In addition, any new design will require some level of thermal testing, for this we have a Cambridge Accusense system for airflow and temperature testing. I/O wiring is also tested and this can be done by manual ‘wire-to-wire’ buzzing out while standard connectors and cableforms can be tested on our CableEye ATE.

Alternatively, as part of the design process, we can design some test tooling so that non-standard connectors such as circular connectors can be tested using the ATE equipment.

Thermal management is a key issue, and with most designs, the available space within the chassis is usually fully utilised. Ensuring the airflow requirements of boards and peripherals within the chassis are met requires some thermal testing of the chassis. Our Cambridge Accusense system has 24 airflow and 24 temperature channels, and probes can be placed on cards or peripherals prior to the system being turned on. Invariably, this leads to some form of tweaking to improve the thermal management. This usually includes adding baffling to direct or restrict the airflow and it’s surprising how much difference this can make. However, this also provides a method of documenting the airflow that can easily be made available to the customer.

A point to note however, is that boards do not provide a uniform profile, and hence impedance to airflow; for instance VME boards with PMC slots can restrict the air much more than a simple digital I/O card. Elma-Mektron have developed a load board that presents a fixed impedance, so populating a card frame with load cards and running the test will produce an airflow profile for the system. This may not be the profile that the customer’s cards produce, however, but it does provide an indication of the system’s performance.

If more extensive testing is required, for example including EMC testing for full qualification testing, then Elma-Mektron can help here also as we have our own pre-compliance EMC test chamber. Many customers have asked us to test the basic chassis prior to delivery, however, adding cards and particularly I/O cabling changes the thermal profile. Elma-Mektron are happy to support customers after the integration stage with the use of this pre-compliance facility. Clearly since the customer knows the parts he has integrated, and we know the chassis, then together we can find and fix any EMC problems prior to full compliance testing.