how strain gauge can be using with PXI 6070E and BNC 2110?

[pjoule]

i have to do some measurement on strain and in my previous research, by refer to NI recommended, the strain can be implement using  SCXI  but unluckily i only have these three possible things:
1) PXI 6070E,
2)BNC 2110 connector block with its cable
3) full-bridge strain gauge.

how can i connect them to get the measurement?plz give me some idea.=(

[ceties]

 

Hi,

Just put the PXI card into appropriate chassis, connect it with appropriate cable with the BNC adapter and the output from your bridge module connect to one of the channels on the BNC adapter. The only question is your bridge realization but I suppose you use some commercial solution like this that gives you normalized voltage output. In case you built or you are going to build your own Wheatstone bridge realization you will need to amplify the output from the bridge because it gives voltage around mV. Than you just simply acquire the voltage. Some of the examples shipped with LabVIEW can be handy. Then of course you have to scale and compute the data according to what you are trying to measure (deformation, strain, force...)

Hope it helped

Message Edited by ceties on 03-08-2008 08:58 AM

[Mark_E]

Hi pjoule,

Not only will you need to amplify the output, you need excitation for the Wheatstone bridge. Ni.com/strain is a good starting place to learn about what is needed for strain measurements (“Strain Basics” in the upper left in blue) and also what hardware can be used. Not only can SCXI be used, but there are some newer technologies such as CompactDAQ (more portable) and PXI (newer than SCXI). These can be found by clicking on the “Choose the Right DAQ System” link, also from ni.com/strain.

[ceties]

Actually he can use the card itself to supply the bridge in case of need.

[pjoule]

thanks to all, it's guide me a lot.

but, i have little bit confius here, does it really that i no need to  put  the excitation regulator? how can i prove it?


Message Edited by pjoule on 03-11-2008 10:37 PM

[ceties]

Excitation regulator? What do you mean by this? I have never heard this term. You have to supply the bridge by voltage of course - if you meant this. If you use commecial solution than it has power suply. If you build your own you have to suply the bridge for which you could use the DAQ card's analog output. You just attach the analog output to the bridge and send there let's say 5V. The bridge will give you signal dependent on the value of the supply voltage (mV/V).

[Mark_E]

Hi pjoule,

I’m not sure if I entirely understand the question. It sounds like you’re asking about providing an excitation regulator, is that correct?

With our CompactDAQ (cDAQ) strain gauge module, the NI 9237, the excitation voltage is also the same voltage used for a reference to the ADC, so no matter how much the voltage fluctuates you will always get a consistent mV/V reading.

With you particular setup, you would need something to regulate the excitation voltage, because the DAQ card only reads voltage, not mV/V like the NI 9237, so if your excitation is higher or lower, you reading would also be higher or lower. Again, what you have isn’t specifically designed for strain gauge measurements, so you’ll need to be careful how you do your measurements.

I hope that helps.