best location of thermocouple for pid ????????????????

[wyattjames]

Okay here is the question :
what is the best location on a star for placement of the thermocouple?
My thoughts are mounting it on the tube but my concerns are that the base may get too hot till the tube reaches temp? currently I have it mounted on the base and warm up time is way too long atleast an hour and a half has to be a a better way quicker way thinking it is thermo position so where do you have yours mounted ?
I would like to thank everyone in advance for your input !

[Dave Bob]

I'm not sure what type of heated base you are using, you don't say but will assume its the magma one. Over an hour to come to temp is way to long. I have a homemade rig that uses a 200 watt cartridge heater and its up to temp in 15 minutes or less with the thermocouple placed on the base close to the sizer.
http://i821.photobucket.com/albums/zz136/RobertnotRoberts/IMG_1065.jpg
The base is 3 4x6x1/4" pieces of aluminum plate sandwiched together.

Dave

[Frozone]

Mounted on the tube will give more accurate early results, but after the lube is up to temp it won't make much difference.
Try using heatsink grease under the sizer to get better heat transfer between the plate and the sizer.

How long it takes to come to temp is dependent on heater wattage, thermal mass, and convection area.

A large AL plate is harder to Get/Keep at temp because it has more area exposed to the air.
I have 2 pieces of 3/4" Al plate, one that mounts the auto feeder on it (6" x7"), and one that only fits just the sizer (4"x3").
A 40 watt cartridge will work fine on the smaller one, but it can't put enough heat into the big one to get it past ~ 80º.
The big plate needs a 100W+ heater to work well.