Glossary · Process instrumentation and analytical measurement
Short-circuit detection
Also known as: Short-circuit monitoring, Line short detection
German: Kurzschlusserkennung
In automation and instrumentation, short-circuit detection is a diagnostic function of an input, output or switching amplifier that recognizes an unintended low-resistance connection in the signal line and reports it as a fault instead of a valid signal.
- Process instrumentation
In one sentence
Short-circuit detection recognizes unintended low-resistance connections in signal lines and reports them as faults instead of valid values.
Example
A NAMUR switching amplifier detects a crushed sensor cable as a short circuit and sets its fault output, so the PLC does not read a false switching state.
How it applies
- Engineering: Detection depends on the signal type. NAMUR inputs and 4–20 mA inputs detect shorts by current levels; digital safety inputs often use test pulses to detect shorts to supply or between channels (cross-circuit detection).
- Safety: Short-circuit detection contributes to the Diagnostic coverage (DC) of a safety function. Whether it is sufficient depends on the architecture and the fault analysis; it is not a safety function on its own.
- Commissioning: Enable detection where required and test it, for example by simulating a short in a controlled way.
- Documentation: State which channels have short-circuit detection, how faults are signaled and what the operator or maintenance team should check.
Short-circuit detection vs. wire break detection
Short-circuit detection recognizes too low a resistance; Wire break detection recognizes an open circuit. Many inputs offer both, configured separately.