Will LabView Base Package do the job?

[kalexeff]

I want to monitor two load cells and an encoder to determine the backlash in a rotary drive system.  In other words, I want to map the output of the two load cells (one measuring clockwise torque, the other measuring counterclockwise torque) against the position of the shaft.  When I reverse the drive, the amount of rotation I get before the load registers on the opposite load cell is the backlash.  Can I do this with the LabView Base Package?  Or, do I need a dedicated DAQ package?  I am afraid that the Base Package running on a PC with direct input from the sensors won't have enough bandwidth to give me an acurate measure of timing between the shaft rotation and the load cell changes.  Am I worried for nothing?  Please advise.

[Alex.T]

You sure can.

In terms of fundamental building blocks of LabVIEW, in base the only real important element you're missing is the Event Structure, which allows you to write code that doesn't need to perform software polling for user input, and instead accepts it asynchronously. Similarly, you'll be missing the functionality to package away and distribute your VIs as executable files (.exe) too; this is useful for people who need to use your application who don't have access to the IDE.

The operations you're talking about are all based in the NI-DAQmx driver (Free to download), which works in a fully featured manner regardless of the type of LabVIEW you're running. At the moment I'm running LabVIEW 2011 Base Edition and I have pretty much every driver installed and perfectly accessible from the environment, including things like NI-HSDIO and NI-SCOPE. I even have modules such as LabVIEW FPGA and LabVIEW Real Time working within the base package too.

When you say direct input from the sensors, what kind of hardware are you talking about? If it's not NI DAQ hardware I might have to follow up with a few ammendments to the above!

[Chris_Jones_NIUK]

Alex has pretty much covered it there. Just to add though, from LabVIEW 2012 onwards the event structure is included in LabVIEW base: http://digital.ni.com/public.nsf/allkb/86256A47004E16D286256B490060C5A1

[Alex.T]

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@Chris_J wrote:

Alex has pretty much covered it there. Just to add though, from LabVIEW 2012 onwards the event structure is included in LabVIEW base: http://digital.ni.com/public.nsf/allkb/86256A47004E16D286256B490060C5A1

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No way! Brilliant.

[kalexeff]

We have several test fixtures that use similar hardware (load cell amplifiers, limit switches, encoder, etc.) plugged directly into the PC running LabView.  Our engineer familiar with using LabView told me that LabView essentially "reads" the input from each sensor sequentially, one at a time (of course, depending on how the program is structured... but essentially one data point at a time).  With the PC clock not being very precise, and with other tasks interrupting the data stream, he said that I wouldn't get an accurate enough correlation between the load cell and the encoder.  He thought that I would need a stand-alone DAQ system (like NI CompactDAQ?), which would read multiple channels at the same time.  We don't use that on our other test fixtures because we aren't looking for that close timing.  When I looked into a NI CompactDAQ System, the cost quickly got up to $12K... compared to the Base Package of LabView at about $1K -- ouch!  Are you saying that I don't need the CompactDAQ System?  Can I do what I want to do with an add-on module (Data Logging & Supervisory Control) or a free driver (NI-DAQmx)?

[Alex.T]

Sounds like you might be using a PCI Card; these slot into your machine the same way a graphics card would.

Could you open up your PC and tell us what the model of the card is? You might be able to perform some hardware driven measurements that won't require any kind of intervention from your software, which will make your results a whole lot more reliable through hardware timed measurements. But we can only really be sure about that if we find out some more details about the acquisition hardware; then we can talk some more about the software side!

[kalexeff]

Sure.  I will have to dig into it a little deeper on this end.  It may take a couple of days.

[ajmartin]

Alex,

Couldn't he just go into Measurment and Automaation Expolrer and see what DAQ is installed with out opening the PC.

Also to the OP, you are plugged into a DAQ of some kind, if you dont see it, like Alex has said it is inside the PC.

Alan

[Alex.T]

Man, I'm getting rusty! I was was too rigidly thinking along the lines of it being third party equipment. You're totally right.