Strain Gage Measurement

[Artiklab]

Dear All, 

I was hoping to possibly get a brief expert advice on the most appropriate signal conditioning hardware that I should buy for a simple pressure vessel strain gage test. 

The goal of the test is to verify stress values in numerical FEA Pressure Vessel model by phisical strain measurement, to comply with ASME section VIII-2 requirements. 

The plan is to use just one or two strain gage half bridges installed on the pressure vessel to measure strain when the vessel is pressureized. 

I was looking into two possible hardware options: 

1) Connecting Strain Gage Bridge directly to SCXI-1121 Signal Conditioner (SCXI-1121 inside SCXI Chassis), connected via chord to Laptop with LabView for data processing. 

Or, 

2) Connecting Strain Gage Bridge directly to NI USB-6210 M Series Multifunction DAQ, which then connect directly via USB chord to Laptop with LabView for data processing. 

Can someone please comment on which option would be most appropriate for such a test? 

If there is a different, better option I am not aware of out there, I would greatly appreaciate your advice. 

Many thanks and Regards, 

Artem

[David22JRA]

Hello Artiklab

Regarding with both devices is better that you use the USB because is a newest device if we compare with the SCXI and the USB is portable. Actually you can use the diagram that I am going to attach for the USB devie connection (see the diagram).

On the other hand another option is the NI-9237 C-Series module is another good option.

Regards

[Artiklab]

@ David22JRA, thank you for the responce and the schematic. I am assuming the schematic shows the NI USB-6210 M Series connected to a bridge. 

From the schematic it looks like the excitation voltage terminals are connected to an outside voltage source.

Doesn't the NI USB-6210 M Series provide an excitation voltage to the bridge like the SCXI-1121 does?

Also, can you please comment on the merits of running a simple test using the strain gage bridge, gain amplifier and Multimeter (ex.Fluke).

In your opinion will the results have an excessive error (more than 5%) that would deem it unpractical?

Thanks again, 

Artem 

[David22JRA]

Hi Artiklab

Actually you can use the Power Supply output that this device has. I believe the best way is that you use an external power supply. On the other hand the value of 5% depends of your application in some cases that is very high in other cases that is good.

Regards

[Artiklab]

Okay will have to wrap my head around it and see what makes more sense. 

Thanks alot David22JRA for advice. 

cheers, 

Artem

[Ian_Ren]

What is the expected voltage from the bridge? I am worried about connecting the bridge directly to a standard (and low cost 🙂 ) DAQ device like USB 6210. You may run into high noise issue. If possible, a dedicated DAQ device for strain gage measurement or via an external strain gage conditioner/amplifer may be more suited for your test.