Further on in our voyage, we come to small circuit board.
The two voltage out points from the bridge circuit are fed to an amplifier that changes the very small voltage into a 0-5V signal or most commonly to a 4-20 mA signal. This signal is fed out the cable (sometimes along with a vent tube) which finishes our voyage.
The output of a Strain gauge is sometimes referred to as ratiometric to the supply voltage. The term ratiometric means that the output varies as a ratio of the the supply voltage. An example helps make all things things clear.
· Let us assume that With a 1/2 full scale pressure input the out put is x volts, if we double the supply voltage, the voltage output will now be 2X.
By varying the supply voltage we have a handy way to scale the output to what ever units we want. Changing the value of the reference element resistor gives us a way to offset the zero point. Between the two adjustments we can scale and offset the output to what ever we want. In real word practice the output voltage and currents are kept low to minimize thermal error so the output is usually followed with an amplifier stage.
Info From : MySensorBlog