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The CONTEST 800 Backplane tester system measures path resistance between every pair of points on a unit under test. Resistance is measured by sourcing a known current to a single pin and then sequentially grounding every other pin on the unit one at a time. The path voltage drop is measured from the source and the path resistance is then calculated. Current is driven to each pin by a transistor “source” driver connected to a DC power supply through a known source resistor. Each pin is grounded in turn by a transistor “sink” driver that provides the switchable connection to ground. The fixed voltage drops across the source driver and sink driver transistors is measured and calibrated out of the final path resistance calculation.
Electrically, the CONTEST 800 is divided among numerous printed circuit boards. Each board capable of supporting 192 connection points. The interface to the unit under test is via two 96-pin DIN connectors. Within each board, the source and sink driver transistors are addressed in a serial fashion. The transistor source drivers are 32-bit serial in Bi-MOS drivers. The transistor sink drivers are 32-bit serial in Bi-MOS drivers. Each printed circuit board contains six of each driver chip connected serially on the board.
The basic CONTEST 800 contains Sink/Source Driver cards for a total of 768 supported points. This basic capability can be expanded to tens of thousands, by adding additional Sink/Source Driver cards.
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