Browse Prior Art Database

Sensor Test Circuit

IP.com Disclosure Number: IPCOM000051722D
Original Publication Date: 1981-Mar-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 24K

Publishing Venue

IBM

Related People

Hamilton, CB: AUTHOR [+4]

Abstract

A circuit tests whether a failure sensor is operational by forcing a sensor failure detection.

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Sensor Test Circuit

A circuit tests whether a failure sensor is operational by forcing a sensor failure detection.

In a copier, insufficient toner concentration may be detected by sensing the reflectivity of the developer mix. The source of the sensor measurement may be the light provided by light-emitting diode (LED) 10 in the figure. The additional circuitry 11 is provided in parallel with the existing LED drive circuitry 12 and 13. When a diagnostic check is to be made, a signal asynchronous to the normal frequency of operation is provided at input 14 from a control, causing circuitry 11 to overdrive LED 10. The increased light intensity is sensed by an operational toner concentration sensor, but no sense signal will occur if the sensor has failed.

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