Following on from previous messages, you might want to look at the following
items (discovered as a result of trawling around the Linear technology
website after looking at Dave's project)

For an input op amp, use an LT1990 (will withstand +/-250V on inputs, a bit
hard to blow up accidentally, has switchable gain of 1 or 10) or an LT1991
(has switchable gains through internal resistors which can be mixed and
matched to select gain, configurator spreadsheet also downloadable). Either
one could provide useful gain switching under software control with a bit of
thought.

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