Measure Voltage PXIe-4331

[Fran_itin]

I want to use the PXIe-4331 to measure the changes (very small) in voltage of one resistor. I want to use the built-in excitation source (2.5 V) to excite a wheatestone bridge (non standard); the wheatestone bridge will be balance via a potentiometer.

Once the bridge is balanced, I want to monitor the changes of the output of the bridge. Is it possible to configure the card for working  as I am describing? The bridge is going to look like a "quarter bridge" configuration (3 resistors are constant, and 1 is going to fluctuate), but the resistances are going to have non-standard values. I just want to understand the changes of the output, so I can correlate them to resistance. Best regards and many thanks in advance.

[Fran_itin]

Hello,

I want to use the PXIe-4331 to measure the changes (very small) of one resistor (it is an strange material which change its resistance in a random way; I want to monitor the changes to understand why this is happening). I want to use the built-in excitation source (2.5 V) to excite a wheatestone bridge (non standard); the wheatestone bridge will be balance via a potentiometer.

Once the bridge is balanced, I want to monitor the changes of the output of the bridge. Is it possible to configure the card for working  as I am describing? The bridge is going to look like a "quarter bridge" configuration (3 resistors are constant, and 1 is going to fluctuate), but the resistances are going to have non-standard values. I just want to understand the changes of the output, so I can correlate them to resistance. Best regards and many thanks in advance.

[Fran_itin]

Hello,

I want to use the PXIe-4331 to measure the changes (very small) of one resistor (it is an strange material which change its resistance in a random way; I want to monitor the changes to understand why this is happening). I want to use the built-in excitation source (2.5 V) to excite a wheatestone bridge (non standard); the wheatestone bridge will be balance via a potentiometer.

Once the bridge is balanced, I want to monitor the changes of the output of the bridge. Is it possible to configure the card for working  as I am describing? The bridge is going to look like a "quarter bridge" configuration (3 resistors are constant, and 1 is going to fluctuate), but the resistances are going to have non-standard values. I just want to understand the changes of the output, so I can correlate them to resistance. Best regards and many thanks in advance.

[GerdW]

No need to start 3 threads just for attaching your document!

And please attach your image directly instead of hiding it inside some weird Office document!

[johnsold · Accepted solution]

If you have non-standard values for the resistances, it is not clear how you would use the internal bridge completion circuits of the PXIe-4331. It appears that the full bridge configuration (which requires you to supply all the fixed resistors and the potentiometer) may be the better choice. Look at Chapter 2 of the User Manual.

The specifications are in terms of mV/V so you may need to do some calcualtions to get the actual resistances.

Lynn

[Fran_itin]

Hello, Lynn

Many thanks for your help. I am trying to use it as you are explaining:

1- Creating my own balanced wheatestone bridge

2- Using the internal stabilised excitation voltage of the card

3- Reading the output of the bridge (mV/V), and by multiplying by the excitation voltage get the mV.

4- Having 3 known resistor, work out the value of the fourth one.

Best regards and many thanks again.