Understanding Star Switching: The Star Of The Switching Is Often Overlooked

By Walt Strickler, Giga-tronics Incorporated

Understanding the Impact of Switching

Switching is probably the most overlooked and undervalued part of a test system design. Great attention is spent selecting the measurement and stimulus instruments. But more often than not, the signal switching solution does not complement the instruments. It doesn't matter how accurate the instruments are if the signals pass through a poor switch to get to them. Engineers are familiar with test instruments because they have used them during their school years and at work in the lab and on the bench testing products or debugging new designs. So it's easy for them to select instruments for an automated test system. On the other hand, the engineers probably did not use switching in day-to-day testing and only consider switching a minor component in an automated test system.

Choosing a switching system can be difficult because engineers often have little experience in test "system" design. They are accustomed to moving test probes by hand, carefully connecting the probes and ground clips to the unit under test (UUT), and/or attaching cabling with the proper torque to ensure a quality connection. A good automated test system design should select the switching that best emulates what the engineer would have done when connecting instruments manually.