Take a brass hose mender of the correct diameter and a couple of Omega's precision RTD's
http://www.omega.com/ppt/pptsc.asp?r...0KN&Nav=temc13 . Drill holes to fit to insert the RTDs into the hose mender in the middle and then insert the RTDs with Artic epoxy. After letting everything setup, solder wires to the RTD and then strain relieve the wires by potting with RTV in a 3/4" tubing sleeve as a form. After all is done you can calibrate your sensors to .1 or better using an ice bath and boiling water and then insert into any line in your system to get a pretty good reading at that point