The NI-9203 noise probelem is discussed in http://forums.ni.com/t5/Multifunction-DAQ/NI-9203-generates-noise-pulses-when-acquired/m-p/3546439
Attached document describes how noise measurements were perfromed with oscilloscope. 9203 emits peaks with the same frequency as acquisition rate. These spikes do affect 4-20mA measurents accuracy quite a bit. It should not be like that. Probably 20pF capacitance on each input inside the module shoud be increased to 200pF or 2nF. I am sure that NI R&D knows better how to improve 9203 🙂
Support reference#: 2703970
