When choosing a digital I/O module, we must answer the following three questions:
What characteristics of the digital signal output by the sensor can characterize the measurement results of the sensor? You can select a set of digital I/O modules from List 1.
Is the output of the sensor suction type or pump type? Table 1 also provides a set of NI digital I/O boards classified according to suction and pumping capabilities. If you are using a suction type output sensor, you need to choose a pumping type input I/O board, and vice versa.
What components are used to achieve sensor output? At this point, we may need to consider the sensor’s off state leakage current and on state minimum holding current. By comparing the specifications of the sensors in Table 2 with the specifications of the data capture devices, you can select the most suitable digital I/O device for your sensor.
In the selection process, in addition to considering voltage, the following two conditions must also be taken into account (sometimes we ignore them):
- The off state leakage current of the sensor is ≤ the low state maximum input current of the I/O board;
- The minimum holding current of the sensor is ≤ the maximum high input current of the I/O board
