Apparatus and method for digitizer point sampling and validation
US5225636A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 21, 1992 |
| Grant date | Jul 6, 1993 |
| Priority date | — |
| Expiry date | Feb 21, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F3/045
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
An apparatus and method for digitizer sampled point validation which compares charge and discharge voltages across a capacitive element within the digitizer or a filter coupled between the digitizer and an analog-to-digital convertor to accept or reject the point. The method of the present invention detects excessive contact resistance, typically caused by insufficient actuation force. The method alternately charges and discharges the digitizer sampling circuitry to positive and negative voltage rails prior to readings. The sampling circuitry includes the layer in use, and the wire connections, all of which provide resistance and capacitance affecting the time constants for charging and discharging. The sampling circuitry also includes the filter in use, when so installed. High contact resistance due to excessive contact resistance prevents adequate charging and discharging of the sampling circuitry to the position voltage of the point and results in unequal values for the two readings. A comparison of the two values shows conclusively whether contact resistance is too high, and therefore whether the sample is valid.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.