Diagnostics for a programmable logic controller
AssigneeSiemens Industry, Inc.
InventorsRobert Alan Weddle, James F. Archer
Life of this patent
Estimating the term…
Abstract
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.
Claims27
A system for diagnostics in a programmable logic controller, the system comprising:
- a plurality of outputs of the programmable logic controller;
- a current source;
- a diagnostic detection circuit;
- and
- a multiplexer configured to connect the current source and the diagnostic detection circuit to the outputs in sequence.
A method for diagnostics in a programmable logic controller, the method comprising:
- multiplexing a diagnostic circuit to outputs of the programmable logic controller;
- measuring a diagnostic of the outputs with the same diagnostic circuit, the measuring being performed sequentially for the outputs based on the multiplexing.
A system for diagnostics in a programmable logic controller, the system comprising:
- an output of the programmable logic controller;
- a power source connected with the output;
- and
- a diagnostic circuit configured to compare a voltage at the output to a threshold while the output is in an off state with the power source connected, the comparison testing for a short-to-ground.
A method for diagnostics in a programmable logic controller, the method comprising:
- setting an output driver of an output of the programmable logic controller for a load to an off state;
- and
- testing for a short-to-ground at an output of the programmable logic controller for a load, the testing occurring without changing the output driver to an on state.
Dependencies are inferred from the claim text.