Virtual Ground Voltage Reference

[teroenza]

I'm building an Arduino voltage logger that includes an op-amp (OP27G) as a buffer on the input. Since I'd like to be able to measure voltages all the way down to zero, I want to power the amp with a bipolar supply. My initial thought was to build the rail-splitter below so I wouldn't have to come up with two discreet (plus and minus) supplies.
http://www.goldpt.com/virtual_ground_circuit.html

My question is, if I power the OP27 with the virtual ground circuit above, then the voltage logger won't function correctly unless the voltage I'm trying to measure is also referenced to that virtual ground? I was hoping to use the logger to record voltages from various sources.

 

[berkeman]

I've found floating grounds like that to be problematic. Have you looked at the LM324 family of opamps? Its input voltage range includes ground. I use an LM324 input opamp stage to shift the input signal up to some reference voltage first, and then process the signal from there...

 

[teroenza]

Thanks. The virtual ground circuit is a neat idea, but I'd like to avoid the complexity if possible.

 

[berkeman]

One important tip -- the LM324 is just for commercial temperature range (0C to 70C). The LM2902 is the similar part for the full Industrial temperature range (-40C to 85C). Please don't ask me how I know this...

https://classes.soe.ucsc.edu/cmpe118/Winter13/LectureNotes/MidTermDataSheets_2013.pdf

 

[teroenza]

Thanks. If temperatures exceed the commercial range for me, I'll have bigger problems than the amp :-)

 

[berkeman]

LOL

 

[dlgoff]

I've found floating grounds like that to be problematic.

I've never had anything to work correctly with an offset ground reference. Well, maybe a simple MOS circuit could work with one.