What you should know
The platform options available from National Instruments cover a huge spectrum of capability, so chances are your application will be a good fit for one of the platforms; the challenge is more in figuring out which one is best for your scenario.
NI platforms tend to shine in scenarios where lots of data is being acquired from several channels of different types (e.g., vibration, temperature, pressure, strain, voltage, current, etc.). Does that sound like your scenario at some level?
Gotchas / where people sometimes go wrong
Trying to run a deterministic loop in Windows. Don’t do it. Generally, if you’re loop rate is over a few tens of hertz, you need something more deterministic (like RT or FPGA).
Selecting a PXI, only to use 1/20th of its capabilities, out of concern that a cRIO or cDAQ controller would not have done the trick. PXI is clearly the right choice when you need I/O more than around 64 analog channels or 256 digital channels and have aggregate data rates of more than around a few MBs per second. These numbers are only a “rule of thumb”; other factors such as data processing speed and communications latency need to be considered.
Selecting a cRIO or cDAQ controller with lower capabilities when not sure how much horse-power you need just to save cost. You’ll burn through the cost difference pretty quickly with the extra hours in re-design needed to squish the application into an under-powered controller.
Recommendation / What to do instead
1. Start with a PXI as a baseline, and then convince yourself that you either need to move to a cRIO or cDAQ or perhaps just a PC running LabVIEW.
- A lot of the decision will boil down to whether or not you need a real-time OS and/or an FPGA for determinism in your measurement and/or control.
- Secondarily, the decision will branch on the quantity and fidelity of your I/O needs, with a PC or PXI having modules with higher channel counts sometimes with better accuracy and performance than cRIO or cDAQ.
- If you are at all concerned about processor horsepower or I/O expansion capability, you should lean towards a PXI with a PC as an alternate (you have more I/O choices with PXI, since PCs have fewer slots these days).
- If you are at all concerned about deterministic behavior and OS reliability, you should stay away from a PC running Windows.
2. If you’re new to FPGAs, check out: FPGA Basics – A Look Under the Hood and then FPGA Gotchas.
3. Check out Which NI Platform is Most Appropriate for My Test Needs? for more details.
4. Unless you’re replicating 10 or more test systems, you can likely rule out the sbRIO and SOM; they likely won’t be worth the additional NRE involved, unless a small form factor is a critical requirement.