You can power a 3- or 4-wire external sensor with an output voltage range of 5 V to 24 V by connection through the sensor power (SP) and ground (GND) terminals on the FD-11601.

The output voltage level is configurable using a 10-bit resolution for maximum flexibility. Use NI software to configure a sensor to turn on prior to the start of an acquisition.

Figure 21. Powering a 4-Wire External Sensor


Figure 22. Powering a 3-Wire External Sensor


The FD-11601 goes into a current limited voltage fold-back mode to protect the sensor power excitation supply from short circuits or higher current than those listed in the FD-11601 Specifications . In this mode, the output voltage folds back to a lower value than the set voltage, the overcurrent status is set in NI-DAQmx, and the voltage input LED lights red. Removing the overload condition automatically triggers the output to return to the desired set voltage, the overcurrent status is cleared in NI-DAQmx, and the voltage input LED returns to normal conditions.

The FD-11601 also has an open circuit detection mode to indicate whether a sensor is connected. For any sensor power output voltage, an open circuit is detected when the minimum output current for sensor detection is not drawn, as listed in the FD-11601 Specifications . When an open circuit is detected, the Open Channel status is set in NI-DAQmx and the voltage input LED turns off.

If a connected sensor draws a total current below the maximum specifications values, the voltage input LED lights green.