When you enable IEPE signal conditioning, the FieldDAQ device monitors each channel for open sensor and shorted sensor conditions:
Open Circuit Detection—Indicates whether a sensor is connected. An open circuit is detected when the IEPE excitation current falls below 4 mA. When an open circuit is detected, the Open Current Loop status is set in NI-DAQmx and the Signal Input LED lights red.
Short Circuit Detection—Indicates if a sensor or wiring has shorted. A short circuit is detected when the voltage between AI+ and AI- drops below
180 mV. Refer to the FD-116xx Specifications for additional short circuit thresholds. When a short circuit is detected, the Overcurrent status is set in NI-DAQmx and the Signal Input LED lights red.