Learnings and best practices from working with NI DAQmx hardware.

In rare cases, it can happen that when starting the “NI MAX” a popup like in the screenshot below is displayed.

The refereed knowledge base article says the following about the cause of this problem: “NI MAX Database corruptions are rare, but may be caused when a system reboots without being properly shut down due to a power loss or a system crash.”

1. Reset the MAX database. From the KB article: From within NI MAX, select Tools » Reset Configuration Data. Confirm the warning dialog with “Yes”.
2. Reconfigure all needed device (especially the device names) DAQmx tasks.
3. If MAX doesn't start anymore, refer to the MAX Database Corruption Removal Tool or reset manually.

The following errors can indicate a problem with the MAX database. Check the MAX if one of these errors occur.

• Error code -229771 “Internal Software Error occurred in MIG software. Please contact National Instruments Support.”
  (e.g. in DAQmx Create Scale (Linear).vi)
• Application hangs during “Discover hardware” (or MAX doesn't start anymore)

• 10 DAQmx functions

No device has a perfectly exact timing behaviour. Some are more precise, others less. The accuracy is usually given in the specs of a device in ppm.

The only way to have precise timing of all involved components (DAQ, OS, etc) is to use a system that allows for all components to be synched to a GPS timing source (eg PXI chassis with 6683H etc).

• The cDAQ-9189 specifies a timebase accuracy of 50 ppm of the sample rate

  • the time axis will drift ~50 ppm relative to ideal time if you free-run on the chassis oscillator
• Using drift ≈ elapsed_time × 50 ppm:

  • Assume 3 months ≈ 90 days = 7776000 s
  • Drift = 7776000 s × 50e-6 = ~390 s = ~6:30 minutes

We must expect up to ~6:30 minutes of timestamp drift over ~3 months.