Compared to conventional concepts, monitoring signal circuits using interface modules with line fault transparency (LFT) saves you additional wiring effort. Conventional concepts require an output on the field device and an additional input at the DCS system. Line fault transparency offers another advantage: errors between the DCS system and interface modules are detected.
Switch amplifiers with LFT simultaneously transfer switching and error signals from the hazardous area to the control room via a single output. Possible line faults between the isolated barrier and the control system can be distinguished from switching signals.
A resistive switching output in the isolated barrier transfers line fault and short circuit error signals from the input to the output circuit along with the sensor signal. Many switch amplifiers from K-System and H-System are equipped with this type of resistive transistor output. These modules are especially designed for NAMUR sensors (EN 60947-5-6) and intrinsically safe applications up to SIL 2 or SIL3.
Line fault transparency permits: