I am using an Advantech PCIE-1805 data acquisition card to measure a 4–20 mA analog input.
The same hardware and input signal work correctly under Windows, where the measured current accurately follows the input from 4 mA to 20 mA.
However, under Linux, the measured value increases normally only up to 10 mA. For any input current greater than 10 mA (e.g., 12 mA, 16 mA, or 20 mA), the reported value remains fixed at 10 mA and does not increase further.
Observed behavior:
- 4 mA → 4 mA (Correct)
- 8 mA → 8 mA (Correct)
- 10 mA → 10 mA (Correct)
- 12 mA → 10 mA
- 16 mA → 10 mA
- 20 mA → 10 mA
Since the hardware functions correctly in Windows, I believe this is related to the Linux driver, DAQNavi API configuration, range selection, or scaling.
Has anyone experienced a similar issue with the PCIE-1805 or other Advantech DAQ cards under Linux? Are there any known limitations, driver bugs, or configuration settings (such as ValueRange, ChannelMode, or current input mode) that could cause the analog input to saturate at 10 mA?
Any suggestions or troubleshooting steps would be greatly appreciated.