Signal Express “Sample period too Short” Troubleshooting

[bryn41]

Hey guys,

I’m an undergrad at the moment working with my professor, so I’m not super familiar with the labVIEW and signal express software yet. But we are trying to solve an issue where we are unable to sample data at the rate we would like to.

We are using signal express to measure resistance and strain data of an object with a sample rate of ideally 3 Hz, but whenever we set the sample period to anything more than 2 Hz, we get a DAQ error only saying “sample period too short”. We are using the 1 sample on demand acquisition mode. I have been playing around with other acquisition modes but they just give an error as soon as the timeout time period ends (whatever it’s set to).

If anyone could provide a suggestion for an acquisition configuration that would allow for a greater sample rate, or some general information about what causes the “sample rate too high” error so we can further troubleshoot.

If there’s any more information I’d need to provide please ask. Any help or information would be appreciated.

[Bob_Schor]

Please provide more details on what you are trying to do.  Some comments and questions:

• SignalExpress has not been available from NI since 2015.  You should really be using LabVIEW itself, which easily interfaces to multiple Data Acquisition hardware and can facilitate acquiring data samples at a variety of acquisition timing and frequencies.
• What version of LabVIEW are you using?  Is it 32-bit LabVIEW or 64-bit LabVIEW?  [I strongly recommend 32-bit LabVIEW].
• What computer (PC, Mac) and what Operating System (should be 64-bit!) are you using?
• What are you using to connect to equipment ("resistor", "strain gauge")?
• Are you familiar with NI MAX, the Measurement and Automation Explorer?

A good "first step" in starting to learn about LabVIEW, MAX, and Data Acquisiition and Control is to plug your device(s) into your PC (I assume you are connecting with a USB cable, or maybe through Ethernet or even RS-232 or so other technology -- please advise us), and start MAX.  Expand "Devices and Interfaces" and makes sure your plugged-in devices show up there.  Click on one, and notice if "Test Panels" show up on the right.  If so, play around with them a little.  You can easily set up acquisition sequences or generation sequences (depends if your device receives or sends data).

For sampling, I recommend you set up sampling 100 points at 100 Hz, and set it for "Continuous".  When you run it, MAX will show you (in a scrolling window) what it is seeing, so you can "know" your device is working and you can get some measurements from it.  Now learn a bit more about DAQmx, the LabVIEW system for Data Acquisition and Control.  An excellent article can be found by doing a Web search for "Learn 10 Functions in NI-DAQmx and Handle 80 Percent of your Data Acquisition Applications" (I'm deliberately not pasting a link here to encourage you to not be afraid to "look it up" on the Web).  [Another reason is that when I stumbled upon this myself many years ago, I finally "got" DAQmx and have memorized the catchy title].

Bob Schor