Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – With rotor
Patent
1989-10-20
1991-05-21
Wieder, Kenneth
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
With rotor
324158D, 324158F, 324 731, 324 713, G01R 3128, G01R 3102
Patent
active
050178636
ABSTRACT:
A test arrangement for printed wiring boards or the like employs a scanned laser beam which impinges upon a photoemissive grid mounted close to the board under test. The laser beam causes the grid to locally emit electrons which are attracted toward the board due to an electric field between the grid and a conductive plane behind the board. The spacing between the grid and the workpiece is very small so the electron beam is very localized and travels a short distance; there is no need for deflecting the electron beam, because it is the laser beam which is scanned. The charge transferred from the grid to the part under test by electron flow is detected and correlated with the position of the beam to provide an indication of the status of the conductive pattern. Undesired shorts or open circuit conditions among the conductors on the board is determined by comparing the charge transfer as a function of beam position with the desired standard pattern produced by a fault-free board.
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Digital Equipment Corporation
Nguyen Vinh P.
Wieder Kenneth
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