Data Acquisition Idea Exchange

Dear NI, please consider a future hardware feature addition:

Add a "Power Up Delay DIP Switch" to the back of the PXI Power Supply Shuttle.

It would allow end users to reliably sequence the powering-up of multi PXI chassis solutions. It could also be handy to sequence any other boot-order sensitive equipment in the rack or subsystem. This would also be a world-voltage solution since this capability already exists in the power shuttle. We are seeing the need for more input-voltage-agnostic solutions. I'm sure you are too.

It might offer time delay choices of 1,2,4,8,16 seconds, etc.

We run into this problem on every multi-chassis integration. We have solved it several ways in the past like: human procedure (error prone), sequencing power strips ($$$ and not world-voltage capable), custom time-delay relays ($$$).

Imagine never having your downstream chassis(s) disappear. Or worse yet, having them show up in MAX, but act strangely because of not enough delay time between boots.

Thanks for reading this, and consider tossing me a Kudos!

Hello

I don't know if there is already an "idea exchange" about this, it could be usefull that USB devices or adapter support USB 3.0.

A device isn't recognized through an USB 3.0 port.

Thanks !

Vincent O.

I have an application in which I have to digitize a pulse across a shunt resistor.  The common mode voltage can be up around 60VDC.  The digitizing cards I was able to find cannot perform a differential measurement without digitizing both sides of the resistor and then subtracting.  This method causes a lot of error due to the needed voltage ranges.  I have been able to digitize some of these pulses with the PXI-4072 DMM with great success.  However, I can control when those pulses occur and setup trigger lines as needed.  Other pulses I need to digitize will occur whenever the UUT decides to put it out.  What is really needed is a way to trigger the DMM on a measured voltage level.  Just for reference, Agilent's PXI DMMs can do this.  It seems such a shame I haven't found a way to do this with NI's DMM.  As a final thought, some pretrigger data would be needed to properly capture the pulse.  Though, pretrigger data would be nice in any hardware triggered acquisition.

In the case of a power failure on a cRIO or cDAQ having a C Series module which could provide back up power would be helpful.

We can use this to:

• Keep the system clock going on cRIOs that do not have an internal battery
• Take time stamp of the crash
• Grab the last known value of shared variables and store them for the reset
• Perform any shutdown operations that are nessecary

The NI DAQmx read is currently limited to 4 multithreaded tasks due to the fact that it is merely a wrapper for an underlying DLL call.  Significant jitter and performance degredation is experienced (#7339294) as the number of parallel reads is increaced beyond 4. As NI transitions to the PXI platform and away from SCXI and users begin acquiring data from large numbers of PXI devices, this thread limitation limits the flexibility and ultimately performance that can be had with such a versatile platform.

NI marketing pictures frequently show PXI chassis fully outfitted with various DAQ input cards, but this limitation limits the practical usability of running large numbers of PXI DAQ devices much more so than the bandwidth limitation of the bus. Also, this limitation is referenced nowhere in any documentation pertaining to PXI DSA, DAQ, or SC series hardware. 

DAQmx read should be fully thread safe.