Why full bridge resistance needed if sensitivity is known for load / pressure cell?

[captsteel]

Using SignalExpress 2015 and configuring a "Force (Bridge)" or "Pressure (Bridge)" Measurement Type for a PXIe-4331, the inputs include both Bridge Resistance and a button for Configuration Scale. 

In the Configuration Scale, I can specify end points for the Two-Point Linear option based on hardware documentation of mV/V sensitivity and the known capacity of the sensor. 

If the sensor is a full bridge configuration, why is the bridge resistance even requested?  Won't the differential of AI+ and AI- just be scaled by the sensitivity specified in the Configuration Scale?  Is the bridge resistance input just ignored by SignalExpress for a full bridge?

Thanks for any insights!

[Kodester]

Hi Captsteel,

The configuration scale is strictly to make a custom scaling for your own viewing and voltage interpretation (from voltage units to a physical unit).

There are internal resistors used for calibration inside your PXIe card, and it's possible that they need to know the resistance of the full-bridge set-up. Additionally, there are limitations to Excitation voltage based on your bridge resistance. You can see these limitations on page 2 of the specifications sheet (linked below).

PXIe-4331 Spec Sheet: http://www.ni.com/pdf/manuals/375487c.pdf