Creating a Reliable Test Interface for a Unit Under Test

Abstract

When creating a test platform, the primary focus is often on the selection of test and measurement instrumentation or the test programming environment. Although it is important to ensure that the selected instrumentation can provide the proper stimulus and measurement capabilities, it is also important to consider how you are going to cable and interface the test platform to the Unit Under Test (UUT). High accuracy measurement devices can be undone by a poorly performing interface. Here are some examples; • UUTs incorporating wireless communication will need a test platform to measure high frequency and low power signals. Selecting the wrong cable or not accounting for insertion loss on connectors can severely impact the accuracy of testing. • Measurement devices which are used to test a wide number of products can degrade their instrument's connectors from frequent changing of the test interface or cabling. This can be mitigated by using external test interfaces. In these applications it is important to consider the lifetime of the interconnect used and how easily it can be repaired on-site. Apart from manual bench top testing, automated test applications will involve some signal management, or switching. This adds a whole layer of potential factors that could limit the performance of any test solution if all factors are not taken into account. In all but the simplest test scenarios, test resources will need to be shared between multiple UUT points requiring some kind of switching system and interfacing. This interfacing between test instrumentation, switching system and the UUT could involve connector to connector and connector to UUT wiring. Also, there may be a test fixture interface that is either manually or automatically operated. This requires careful consideration as the cumulative effect of all these factors may significantly degrade the ability to test the UUT to the desired specifications. Another factor to consider is that the testing application may involve adverse environmental conditions. This paper will discuss aspects of test interfacing. While we cannot cover all possible methods in this short paper, we will look at considerations for selecting a test fixture interface, cables and connectors, mass interconnect and RF/Microwave applications. Please note that while we are using some Pickering products as examples, these recommendations apply to any test vendor or platform.