Im designing a control system for an unusual central heating system and want to be able to measure the temperature of the water in the copper pipes in a couple of different places.

Im planning to use this clever little module Here

Would I be able to get a semi accurate reading if I fix the thermister onto the outside of the pipe using some form of conductive compound and insulate it very well?

Failing that, what other ways are there of getting a more accurate temp reading?

Obviously having the probe directly in the flow would be ideal, but making some form of housing thats not going to leak under pressure is too tricky...

get a standard domestic central heating system temperature probe with a screwed thread (or welded or soldered) and put in the line of the copper tube a suitable boss to attach the probe to

You might find the setup above described as a "pocket" where the probe goes inside the pipework, if your searching for one.

Standard industrial and marine engineering way is to use a pocket that protrudes into the pipe so probe is near the centre of the cross section area of the pipe.
To ensure good thermal conduction between the pipe pocket and the probe the pocket should be filled with a thermally conductive grease or fluid.


However with micro bore pipe work this is over the top simply clamp the thermistor to the pipe and wrap with lagging.

[Edited on 17/11/07 by britishtrident]

Its 28mm domestic heating pipe...

The "pocket" thing is a good idea..

I could use a copper pipe "T" with a copper "plug" soldered into place with a recess sized to take the thermister.... Gets it a bit closer to the water flow...

hmmm

[Edited on 17/11/07 by tegwin]

Being of the KISS school of engineering I'd go for one clamped to the pipe then well insulated. Copper is such a good conductor that any heat loss through the metal will be minimal and partic. on a small bore pipe centre to outside edge temp drop minute.
Cheers, Pewe
PS friend of mine had central heating installers back three times as system wasn't perfoming properly. They eventually discovered a metre of pipe under the floor unlagged. He's a Prof. of Thermodynamics!