Dear AMMRL Members:
I have a Doty PFG probe that is rated to 300 C. My VT controller is
a standard Chemagnetics solid-state VT controller. The problem is that
the Doty heater element is overheating and getting destroyed, the last
time after operating at only 165 C (we use nitrogen gas for temperatures
above 150 C). I have sent the probe back to Doty a couple of times for
repair and Doty can not find anything wrong when the newly repaired
heater circuit gets tested at Doty Scientific. I have taken the
precaution of inserting a pressure switch right a the input of the
heater element to stop current to the heater in case of a loss of
heater element VT gas. I have yet to observe the Chemagnetics VT
controller ouput any temperature higher than the set temperature. But
apparently, the Doty heater circuit and the Chemagnetics VT controller
are not compatible. Has anyone else experienced a similar problem? If
so, is there a solution other than buying Doty's VT controller? Thanks
for your help.
Steve Dec
Colorado School of Mines NMR Facility
sdec_at_mines.edu
Received on Tue Aug 06 2002 - 15:10:08 MST