Siemens Aktiengesellschaft

Siemens Industry, Inc.

James F Archer

Robert Alan Weddle

To reduce the cost and/or space occupied by diagnostic circuitry in a module of a programmable logic controller with multiple outputs, a multiplexer connects the same diagnostic circuitry to the different outputs. The outputs are sequentially tested with the same circuitry. To limit stress on an output driver, an overload condition may be tested while the driver is off. A different source of power is applied to the output, and the results of the application are measured for shorting to ground.

Diagnostics for a programmable logic controller

Inductive commutation is detected for programmable logic controller (PLC) diagnosis. By detecting the inductive commutation, the need for any delay may be determined. Where the load is not inductive, the diagnostic may be performed with little or no delay.

Detection of inductive communication for programmable logic controller diagnosis

A circuit is provided that includes a power source and a sensor circuit electrically coupled by a switch to the power source. The circuit further includes an A/D converter electrically coupled to the sensor circuit and adapted to read a voltage difference across a resistive element to determine an impedance of the sensor circuit. A method is provided that includes closing a switch electrically coupling a power source to a sensor circuit and measuring a voltage difference across a resistive element at an A/D converter electrically coupled to the sensor circuit. The method further includes determining an impedance of the sensor circuit based on the voltage difference.

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Gray, TN, United States of America

James F Archer