I am a novice, using ni daqmx and ni number acquisition card for the first time. I am using a data acquisition card with a model of USB 6255. I have connected a noise sensor (with an output of 4-20mA) to the AI0 port. The hardware connection method is shown in the figure.
When I select Data Acquisition ->Current ->RSE mode on daqmx, the resistance value defaults. The data obtained from the AI0 port has always been 20 mA, which is the maximum value that will not change. But I can clearly see the current changes at the AI0 port when the noise is different using a multimeter, and I don't know where I have a problem.
Because I used a 24v switching power supply and measured a voltage of 20v at both ends of the AI0 port and the GND, I adopted a voltage dividing method to reduce the voltage to below 10v. I have noticed that the maximum settable voltage for DAQMX can only be 10V, but this still does not solve the problem.
There is no problem with the data acquisition card self-test. Because I am a novice, I do not know what problems I may have. I hope you can give me some guidance.