Yes, they do. I've worked on the AWOS III-PT. Unless they have done something custom it doesn't use separate sensors for temperature and humidity. It uses a combination 5190-F temperature/humidity sensor inside the 8190 MARS.
Interesting!
My local airport, KSAW, seems to run about 2-3 degrees low lately in dewpoint as compared to other airports/RAWS stations. Just checked the spec and max error is 3F between +30 and +90F. So, I guess they're within spec!
Do the AWOS IIIP/T capacitive sensors tend to drift noticeably and, if so, which direction is typical?
Also, any idea of the aspiration rate (m/s, cfm, whatever)?