Hello
Just another note about Optima versus Delta-S. We have had the Delta-S at 
Michigan for about six years and I have to conclude that it is a very 
robust machine that is fairly easy to work on. In the six years we had 
some trouble with the magnet current supply and the high voltage source. 
Both problems, with a little technical knowhow were relatively 
inexpensive to repair ($12 and $2.50!!). It took a little while to trace 
the problem though since both went down more or less simultaneously and 
the Delta-S has little display features to indicate the status of the 
electronic equipment (voltage stability, magnet current display, etc. - 
just like the new 252 sadly!). Since the software is also awkward, it 
does not help very much. The machine worked great for CO2 but has a very 
high H3-factor, which gets even worse with the software (correction may 
not be correctly applied). While this can be corrected for, if you are 
out of the calibration range of the standards, there may be trouble.
Other minor problems were transmitting valves (largely on the multiport 
which is based on a cracker-system and provides ample glass-shards) and a 
mechanical problem with the sample-side bellows - gear linkage broke but 
could be repaired with spares from the local hardware.
In short - good, robust machine for CO2, but not recommended for H2.
That is it for now,
Torsten Vennemann

Department of Geological Sciences
University of Michigan
Ann Arbor MI 48109.