Min sampling rate using SignaExpress 3.0, cDAQ9172 and NI9211

[MWJ]

Hi,

I'm using SignalExpress 3.0, cDAQ-9172 and NI 9211 Thermocouple modules. My question is what is the minimum sampling rate. I would like to take one sample every 5 minutes but I get an error when I do. I don;t kow if I am using the wrong format or if it cannot sample that slow.

Thanks,

Mark

[Brad_K]

Hi Mark,

What error are you getting? If you're getting error -200284: "Measurements: Some or all of the samples requested have not yet been acquired" then select the "Advanced Timing" tab in your DAQmx Acquire step and make sure that you have the timeout set to a large enough value (such as 301 seconds for an "N Samples" acquisition of 2 samples).

As for what the minimum sampling rate is, the chassis has a 32-bit counter which can divide down 20 MHz and 100 kHz timebases. Sample rates above 0.00466 S/s should use the 20 MHz timebase, and the 100 kHz timebase should support sample rates down to about 2.33e-5 S/s (1 sample every 11.9 hours). Sample rates slower than that are effectively possible using software timing.

Brad

Message Edited by Brad K on 08-14-2009 01:57 PM