I'd been thinking about getting a differential manometer to check duct static and filter pressure drop,
and then I found a used C75 combustion analyzer that I can pick up for about 1/3 of new. Would be fun to play with if it also does temperature and manometer readings.

Any particular shortcomings compared to a Testo for example?
Keep in mind that I don't need it to do real work, just for education and entertainment purposes.

found the UEI web site, and it looks like the C75 doesn't do differential pressure but the C125 and C155 do?