Automation of DTA Instrumentation

Present-day DTA instruments are capable of automatic operation in that after the sample has been manually inserted the temperature rise is controlled by a temperature programmer which will turn off the instrument after a preselected temperature limit is attained. When the furnace has been cooled 

Wendlandt and Bradley (88, 89) have described an automated instrument which is capable of studying eight samples in a sequential manner. The samples are automatically introduced into the furnace, pyrolyzed to a preselected temperature limit, and then removed. After the furnace has cooied back to room temperature, the cycle is repeated. Operation of the sample-changing mechanism, furnace-temperature rise and cooling, recording, and so on is completely automatic. 

The powdered samples are contained in glass capillary tubes, D, of 1.6-1.8-mm id, which are placed in the circular sample holder plate, A. 

After the sample capillary tube is in position, the furnace platform, C is raised so that the tube is positioned into the aluminum heat transfer sleeve, located on the sample thermojunction. Movement of the furnace platform is controlled by a reversible electric motor connected to the platform by a screw drive. Upper and lower limits of travel are controlled by two microswitches. The furnace is insulated from the platform by a 0.25-in. layer of transite and, while in the heating position, by a Marinite sleeve, E. The rotation interval for sample changing is 15 sec, while it takes 50 sec to raise the furnace platform to the full upper limit. 

After the sample has been heated to the upper temperature limit, the furnace is lowered, the sample-holder plate rotates to a new position, and a cooling fan is activated to direct air on the hot furnace. Cooling time for the furnace, from 450°C to room temperature, takes about 20 min. After the furnace has been cooled to toom temperature, the above cycle is repeated with a new sample. 

---