TUTORIALS 761

Automatic Test Equipment on a Budget


Abstract: The complexity of electronic-device testing varies widely, ranging from the simplest type—manual testing—to the most complex—large-scale automatic test equipment (ATE). In between simple manual testing and large-scale ATE lies the low-budget and medium-scale testing that is the focus of this application note. These types of test systems are usually dedicated to testing a specific component or circuit, under the control of a PC. A PC's parallel or serial port provides a convenient connection between the PC and small, cost-sensitive applications. The IEEE-488 bus can conveniently connect the PC to multiple test instruments, which can not be accomplished by a parallel or serial port. Although it increases the price of the test system, the capability it offers for connecting more than one instrument at a time to the PC justifies the extra cost. When designing the hardware for a test instrument, using the proper design technique from the beginning eliminates or minimizes difficult-to-solve problems that could occur as the design progresses. Separating digital and analog grounds, using optoisolators, identifying high-impedance nodes, spending time on component placement, accounting for voltage drops in power and ground traces, and other techniques all increase the chances of a successful design.