I have a pressure sensor, the output of which is ratio metric to it's supply voltage, within a certain supply voltage window (approx 4.5 to 5.5 volts)
I wish to read that sensor into a sperate external device, which has its internal (precision) analogue Vref set at 4.096v ie i cannot power the sensor directly from this voltage as it is too low.
I am trying to avoid is having to have a precision voltage reference in the pressure sensor device,ie to keep the overal system ratiometric to the 4.096v refference in the external device
I can supply the pressure sensor with a seperate "Bulk" power feed (at around 11 to 12v) and i can break out the 4.096v Vref to the pressure sensor to act as a reference voltage.
It is not a particularly high precision device, i'd aim for around 1% accuracy or thereabouts
Options seem to be:
1)
use the 4.096v reference to generate a nominal 5v rail in the pressure sensor device, (that rail is now dependant upon the 4.096v reference), take the power for this rail from the 12v bulk supply - ie use an opamp with some 0.1% resistors to gain the 4.096vref up by 22%, then use a resistive divider with the same resistor values to drop the 0-5v output of the pressure sensor back down into the VREF range (ie divide by 22%)
2)
Use a non precision 5v LDO off the 12v bulk power, power the pressure sensors, somehow compare that 5v rail and the pressure sensor output to get a ratiometric value, then use the 4.096v supply to scale that output to that range. This has the advantage that it would work with pretty much any VREF voltage potentially making the pressure sensor device more useful in future (ie i could use it for 3.3v VREF projects etc). Not sure how this would be done tbh in terms of amplification etc
3)
Another way i haven't thought of.....
So, analogue guru's, whats the best way of doing this???