Arrangement for failsafe evaluation of a position encoder

US7705492B2 · kind B2 · utility

Assignee

• Pilz GmbH & Co. KG · DE

Inventors

• Juergen Pullmann · Großenhain, DE
• Thomas Nitsche · Eßlingen, DE
• Guenter Hornung · Echterdingen, DE
• Christoph Zinser · Wolfschlugen, DE

Key dates

• Filing date: Apr 4, 2008
• Grant date: Apr 27, 2010
• Expiry date: Oct 14, 2028

Classification

• Technology area (CPC G): Physics
• CPC primary: G01R27/08
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A safety switching device comprises a position encoder, such as a potentiometer, for user selection of an operational quantity, such as an operating mode. The position encoder has a first terminal, a second terminal, and a tap moveable through a plurality of positions. A total impedance is defined between the first terminal and the second terminal. A first partial impedance is defined between the first terminal and the tap, and a second partial impedance is defined between the tap and the second terminal. An arrangement for determining an instantaneous position of the tap comprises a first evaluation circuit designed to determine a first measurement value representative of the first partial impedance, and a second evaluation circuit designed to determine a second measurement value representative of the second partial impedance. At least one from the first and second evaluation circuits is designed to determine the instantaneous position of the tap by means of the first and second measurement values.