DAQ input does not fit with pressure measurement

[maxmusterphd]

Hi everyone,

I have a setup which uses a sinewave input to increase and decrease the pressure inside a cavity with a membrane. This seems to work so far, but when I log the sinewave next to the pressure measurement inside the cavity I get readings that are slightly off and get worse over time. I ploted both in a picture.

What would be your first guess? What might cause this shift?

blue: input signal

orange: measurement

kind regards,

[maxmusterphd]

we have two boxes so far: NI-USB-6229 and NI-9250. The later seems to add the delay and shift, while the first one works without a problem. Due to compatibility issues with 6229 and our pressure sensors, we will need to use the 9250 for pressure. Is this some known issue? Is 9250 just not capable or does it need some specific fine tuning?

[bstreiff]

My first guess is clock drift. Your USB-6229 and your NI 9250 (in which chassis or carrier?) are clocked from different oscillators and they're not synchronized, so even though they're configured to the same sample rate they drift with respect to each other.