Hum... ok, you've done your part...
http://www.omega.com/ppt/pptsc.asp?r...-DM&Nav=temj04
The accuracy is ~1%, or more specifically for this unit, about 5 degrees.
Need I say more?
It's just easier to stick a thermometer inside the loop. I picked up a Cole-Parmer mercury thermometer for ~$25-$30, and it'll measure a temp within the range of 19 deg C to 27 deg C, with an accuracy of +/- 0.1 deg C. Cheaper, better...
The core temp is, and always will be an issue.