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Versatile Capacitance Measurement Test Fixture for Modules

IP.com Disclosure Number: IPCOM000053079D
Original Publication Date: 1981-Aug-01
Included in the Prior Art Database: 2005-Feb-12
Document File: 3 page(s) / 81K

Publishing Venue

IBM

Related People

Meier, HE: AUTHOR [+2]

Abstract

The test fixture simulates card and board application conditions, and interfaces with a capacitance bridge in order to obtain precision measurements of maximum module circuit capacitance for each pin/line circuit on the module. All pins/lines not being measured must be electrically grounded.

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Versatile Capacitance Measurement Test Fixture for Modules

The test fixture simulates card and board application conditions, and interfaces with a capacitance bridge in order to obtain precision measurements of maximum module circuit capacitance for each pin/line circuit on the module. All pins/lines not being measured must be electrically grounded.

A copper plate containing a large recessed area and appropriate holes is assembled with a nylon tube, a spring-loaded contact, a plastic retainer, a steel wool pad, a copper-epoxy glass laminate which contains a grid of holes, a hole location template, long screw legs, miniature coaxial connectors, connector mounting board and bracket, and electric wiring. Eight screws secure the template and laminate to the copper plate. The laminate copper side compresses the steel wool into the copper plate recess. The tube in the approximate center of the recess insulates the plunger contact from the copper plate, the steel wool, and the laminate copper surface. The tube also provides mechanical support for the center of the laminate area. Two wires soldered to the bottom end of the plunger contact are routed to the miniature coaxial connectors. One wire, which is soldered nearest to the plunger contact at the bottom end of the contact, is also soldered to the miniature coax internal signal wire for the "high side" current connection. A second wire is soldered to the miniature coax internal signal wire for the "high side" voltage connection. The two "low side" miniature connector internal wire contacts have separate braided strap leads soldered on and routed in the shortest path to a common reference connection located under a screw head which is also used to help secure the retainer to the copper plate. All wires are insulated from each other. A "guard shield" foil mounted on the miniature connector board is isolated electrically from the copper plate. It serves as a common electrical bond for the four miniature connector bodies to maintain the guard shield integrity from the capacitance bridge. The coax wiring braid is the "guard shield" between the br...