Load cell VI with NI-6009, LabVIEW

[NI_Joel]

I have recently switched jobs and am now a test engineer.  I am currently setting up a test where an objected is pressed with a stepper motor that has an inline load cell. 

Setup:

A LCFD-1KG Omega load cell with a DMD-465WB AC Powered Bridgesensor that sends a voltage to a NI-6009 Ai0 analog input. 

VI:

I am trying to use the labview built in example file, Bridge - Continuous Input.vi (attached image), but the NI-6009 is not supported. 

Questions:

Is there an example (I've done searching for an hour) VI out there? 

Is this the best solution in the future (ie is there another module that would be better and can save me time)?

If no to the first question, what is the best way to use the calibration page from Omega (attached) to ensure that I am getting a correct load measurement?

[SnowMule]

That AI reads voltage.  Can you open up test panels and see a voltage change as you apply force to the load cell?

You've got some data points from the mnaufacturer's datasheet for how the voltage correlates to force.

[NI_Joel]

I have opened Signal Express, for a quick check, and it does read a voltage. 

Do I now need to make a function to convert Volts to Kg and then check it against a known weight until it is calibrated? 

My other question is, if I were using a NI-9237 would the setup process shorten and be more acurate without having to check known loads?  I ask because I am conisdering a purchase if I can 'plug and go'.

[SnowMule]

You've got the data for 0.5kg and 1.0kg (as well as zero) in the table. 

It's a small signal, I'd suggest an op-amp circuit before the DAQ to amplify things a little.  It'll also help with the input loading since the 600x has pretty low impedance inputs. 

The 9237 is certainly an option, but you've got the cost of the module plus the cost of a cDAQ chassis... which is a lot more than a 741 and a handful of resistors costs.

Got a system in the lab making noise right now with a load cell and LVDT into a 6008, as well as a bunch of other I/O.  I know it's doable.

It's just time and money.

[NI_Joel]

Are you saying to put an op amp between the bridgesensor and the 6009?

What does the circuit look like that you are using with your op amp?

Would you consider a 9237 if you wanted quick setup to streamline testing?  Possibly used by 'less qualified' labVIEW users?

[Dennis_Knutson]

That bridge sensot appears to already have the amplifier.

Imo, if you needed 4 channels, instead of buying 4 separate bridge sensors, I'd get the 9237 which has all of that inside.

[SnowMule]

Small voltage of the load cell into the noninverting input, feedback resistors to get you a decent gain (0-5 or so), output of the opamp into the analog input of the 6008.  All I'm doing is amplifying the small signal from the load cell to a big signal (with healthy output impedance) into the DAQ. 

9237 is kind of an application-specific device, where the 600x is more of a one-size-fits-all.  I've got dozens of 6008's around here (3 on my desk right now ).

There's also a size/cost difference - I can buy a lot of 600x's for the cost of a 9237.  A dollar or two worth of ICs/passives, and maybe $100 to have a handful of PCBs printed gives me the same functionality.  Multiply that cost by a couple of test setups and it becomes a pretty big dollar difference.

You're paying for the simplicity of plug-and-play, vs. engineering/dev time to put some circuits together.  I'm a hardware nerd, so the signal conditioning comes easy for me.

On the software side, it's all pretty much the same whether you use the 600x or a cDAQ.

 

[NI_Joel]

"That bridge sensot appears to already have the amplifier.

Imo, if you needed 4 channels, instead of buying 4 separate bridge sensors, I'd get the 9237 which has all of that inside."

Dennis, you are correct it does excite the full bridge load cell and also amplify the signal which I connect to a 6009.  It also has a variable gain.  If I run into a situation where I need to use multichannel load cells, which I do have one soon, then I will probably purchase a 9237 and make the solution more simplified.  I have a test stand where I need DAQ on 6 load cells with 5-10V excitation and also need DAQ on the deflection.  A linear encoder may work but it needs to be rugged since it will be used in a mechanical test lab that takes samples to failure...any thoughts?

[NI_Joel]

 Snowmule,  I think I understand your setup now.  You are exciting the load cell externally and then using an op-amp to amplify the signal.  The Bridgesensor is doing these two functions for me.

[VrajMS]

Is the Query solved? I am trying to use the same VI and same DAQ device for reading a Quarter bidge Wheatstone network( with one leg Straing Guage). i understand that the device reads only voltage values, so what changes should I make in the example VI? I am a beginner Labview Programmer