After about 15 years as a professional mechanical engineer and lecturer in (mechanical) engineering design at UNSW, I'm now self-employed (full-time) as a consultant "expert witness".
The firm I am building is high-level: myself having a PhD is something of a USP.
Most Clients are from commercial legal firms but there is also a bit of work from Government departments including WorkCover and the Crown Solicitor's Office. Thus the target audience is mostly non-technical people - like solicitors, barristers and accountants.
My work usually involves looking at a failed machine - or at least photos of one - and then providing an opinion regarding what went wrong. The opinion is always first in the form of a report, then sometimes I testify in Court
I have some cliched ideas for a logo in mind, like a geartrain or nuts and bolts under a magnifying glass. Hopefully though you guys can do a bit better :-)
"Scalability" of the logo design isn't much of an issue: it will mostly just be used on letterheads, cards and e-mail signatures. If the graphic is catchy then any words could probably be dropped-off to just leave a "thumbnail".