ADC with 2.5V as reference

Projects Programming
1

Dear all,
Im new in this world and was experimenting with strain gauges. since i have a compression and tension, there will be some voltages below and abov 0. can i adjust my adc so that for compression i get a value between 0 and 2.5V and for tension i get a value between 2.5V and 5V? how can this be done? thanks for your time.

2

Depends,

do you have a link of the datasheet of the strain gauges you are using?

3

Maybe not with adjusting the ADC but maybe yes with offsetting the input to go between 0-5V.

4

heres the link for the strain gauges datasheet: http://www.vishaypg.com/docs/11189/062uw.pdf

i have a full wheatstone bridge and compression and tension are highly defined. the problem is not with the strain gauges but how to define that the adc is from 0V to 5V but having 2.5V as reference so it can go below and above.

5

the problem is not with the strain gauges but how to define that the adc is from 0V to 5V but having 2.5V as reference so it can go below and above.

If you feed a 2.5V input to VRef, the ADC will report values from 0 to 1023, still, with measured values above 5.0 being clamped. This is not what you want.

Typically, the strain guage output would be fed to an op-amp with an offset of 2.5V, so that the range of values being measured still fell between 0 and 5V, with 2.5V being the relaxed condition, and lower voltages representing compression and higher values representing tension (or the other way around).

6

Typically, the strain guage output would be fed to an op-amp with an offset of 2.5V, so that the range of values being measured still fell between 0 and 5V, with 2.5V being the relaxed condition, and lower voltages representing compression and higher values representing tension (or the other way around).

so i can offset the voltage to 2.5V withouht the opamp and still get it as an aref? is that the correct way of understanding?

7

so i can offset the voltage to 2.5V withouht the opamp

How would you do that?

8

at the moment i have an offset of 12v so to minimise it i put a potentiometer and then an amplifier to maximise the signal. therefore instead of doing a zero reference when adjusting i will put it to 2.5V.