Technical note explaining digital I/O concepts, input types, timing, voltage levels and sink/source output for data acquisition systems.
This technical note from ZHIYUAN Electronics provides an overview of digital I/O fundamentals used in data acquisition, covering basic concepts, terminology and the role of digital signals in measurement systems.
It details input types (dry, wet, source, sink, differential), timing parameters such as rise/fall time and settling time, duty cycle, voltage level definitions, and sink/source output characteristics, along with a disclaimer on copyright. This manual is written in Chinese.
| PCI/PCIe bandwidth | 0.2 - 3.2 GB/s |
|---|---|
| USB bandwidth | 60 MB/s |
| Typical digital I/O high‑level voltage (5 V CMOS) | 4.44 V VOH |
A dry node is a passive switch with two interchangeable states and no polarity, used for signals like limit switches or push buttons.
Rise time is the time a signal takes to go from 20 % to 80 % of its high voltage level.
A wet node commonly uses DC 0‑30 V, with DC 24 V being a standard level.
The output high voltage (VOH) must be greater than or equal to the input high voltage threshold (VIH).