Wayne Martin

US Patent:

52451399, Sep 14, 1993

Filed:

Feb 18, 1992

Appl. No.:

7/836663

Inventors:

Robert L. Protheroe - Lawrenceville GA
Wayne A. Martin - Cumberland OH
Joseph E. Brehm - Cambridge OH

Assignee:

NCR Corporation - Dayton OH

International Classification:

G08C 2100

US Classification:

178 18

Abstract:

An apparatus and method for digitizer sampled point validation which determines the contact resistance at a point of contact between the upper and lower layers of the digitizer and compares the contact resistance with a valid range of contact resistances to either accept or reject the sampled point. The apparatus includes an analog drive circuit for driving the digitizer with one of a plurality of drive sources, a switch control logic coupled to the drive circuit for determining which drive source is coupled to the digitizer, an analog-to-digital convertor coupled to the digitizer, and a microcontroller coupled between the analog-to-digital convertor and the switch control logic. The method of the present invention determines the contact resistance, compares the contact resistance with the valid range, and determines and stores the location of the point if the contact resistance is within the valid range.