I am designing a circuit where a microcontroller can measure the load forced upon a load cell with strain gauges, making a half bridge.
A traditional Wheatstone bridge looks like this:
Resistors R1 and R2 should be exactly the same value so a reference of VCC/2 is made. This reference is then compared to the voltage between the two strain gauges - which is also VCC/2 when they are resting.
But from prior experience I've seen that the to nodes rarely are exactly VCC/2, either because there are some tolerance on R1 and R2 or because the strain gauges are worn. My prior solution has been to add a variable resistor i series with R1 to be able to adjust/calibrate the reference voltage between R1 and R2.
Problem is that this solution is tedious, and pricey. So my question is if I could just use a DAC (the MCU already has one) to create the reference voltage of VCC/2 - or what ever matches the voltage between the strain gauges when they are resting:
Though I haven't been able to find this solution anywhere else (which is usually not a good sign). What pros and cons do you consider with my DAC solution?