I am trying to work out how to create a -5V line to upto 8 instrument amp IC's. The outputs will be connected to a DAQ for logging by a laptop. The DAQ has ground,+2.5V and +5V powered by the laptop but no negative. The circuit used must provide a low ripple output or false readings will be given.

 

If it's low current, check an inverting charge pump like a 7660. Put in +5 and out comes -5.

 

I'm sure Beenthere means ICL7660, ICL7660A, ICL7660S.
They're made by Intersil. You can download a datasheet from their website.

http://www.intersil.com
This will get you to the particular datasheets:
http://www.intersil.com/products/partsearch.asp?txtprodnr=icl7660

 

Thank for the quick response, alread on the datasheet.

 

Oops, the "ICL" prefix is pretty significant.

 

Actually, they ARE made by other manufacturers with different prefixes. National has the LM7660. It's pretty much an industry standard part. I didn't bother doing a lot of searches. The ICL7660S looks pretty interesting, though.