Jeffrey E Collette

US Patent:

58119809, Sep 22, 1998

Filed:

Aug 21, 1995

Appl. No.:

8/517573

Inventors:

John Doyle - Franklin MA
Jeffrey Collette - Acton MA

Assignee:

GenRad, Inc. - Concord MA

International Classification:

G01R 3102

US Classification:

324758

Abstract:

The invention is a tester that uses a capacitive probe to test whether components that have multiple power and/or ground pins are correctly oriented relative to the signal-pin tracks on a circuit board. The tester connects, to the signal-pin track to which the pin under test is connected, a test-signal source that supplies to that pin a relatively high-voltage test signal. The tester actively guards the pin by applying to the remaining component pins, through the tester scanning system and its internal resistance, a signal that has the same voltage as that sensed by the capacitive probe. If the component is oriented such that one of the multiple power or ground pins is connected to the signal-pin track to which the test signal is applied, the test signal appears also at the other power or ground pins, since these pins are interconnected by a low impedance path through the component. The signals on these interconnected pins are capacitively coupled through the component lead frame to the capacitive probe, which senses a much higher voltage than it does when the test signal appears at a single signal pin. Accordingly, the tester determines if a power or ground pin is connected to the signal-pin track by comparing the voltage at the capacitive probe with a predetermined threshold.