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Print Hammer Coil Temperature Measurement

IP.com Disclosure Number: IPCOM000077742D
Original Publication Date: 1972-Sep-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Wray, TE: AUTHOR

Abstract

The circuit shown accurately measures resistance increase of a hammer drive coil due to temperature rise and also corresponding flight time change directly, while a printer is in operation. A Wheatstone Bridge 10,consisting of resistors R1, R2, R3 and the resistive component of hammer drive coil L1, is initially balanced for a null condition with a measured cold resistance of drive coil L1 by adjusting resistor R3.

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Print Hammer Coil Temperature Measurement

The circuit shown accurately measures resistance increase of a hammer drive coil due to temperature rise and also corresponding flight time change directly, while a printer is in operation. A Wheatstone Bridge 10,consisting of resistors R1, R2, R3 and the resistive component of hammer drive coil L1, is initially balanced for a null condition with a measured cold resistance of drive coil L1 by adjusting resistor R3.

The printer is then operated resulting in a start pulse output of flight counter 16 being applied to the base of transistor T1, which activates hammer drive coil L1 causing hammer 12 to travel to impact sensor 14. Upon impact, impact sensor 14 generates a stop pulse which stops flight time counter 16 with an indication of the flight time of hammer 12 contained therein.

During the operation of the printer, the temperature rise of drive coil L1 is measured through the measurement of resistance change, as indicated at the output terminals of the Wheatstone Bridge arrangement 10. The coil temperature rise measured in degrees centigrade will be (for copper wire) Delta = R hot - R cold over R cold x K.

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