Temperature Control

High Temperature Operation

The temperature controller has a limiter set on the control unit box that is accessible from the back of the console. The limit is set for 40 or 45 degrees C. It can be increased using the buttons on the control unit box, but you must then flow dry N2 gas thru the cooling line instead of compressed air. To do this, hook up a N2 tank thru the wall from the compressor room and move the VT tubing from the air compressor output to the tank outlet on the wall. Use a flow regulator and adjust the flow to about the same value as normally used with the air compressor. You may need to also adjust the regulator pressure. Monitor the tank to make sure you do not run out of gas during your measurement. I am not sure how long a new N2 tank will last, but should be more than 2 hours (maybe 6 hours or more?).

Low Temperature Operation

The wall drying unit must be activated for low temperature operation. Taken from the dryer’s manual:
  • make sure the inlet and outlet air-filter bowls are closed
  • turn on dryer’s electrical switch
  • slowly open inlet air valve
  • let run for 30 minutes to regenerate dryer material
  • close bypass air valve below dryer
  • slowly open outlet air valve
  • allow unit to run for several hours before turning on the chiller.

After the wall dryer has been on for a few hours, turn on both switches (compressor and controller) for the chiller, which is halfway between the magnet and the air supply (the VT air always flows thru this chiller, even when turned off). The controller has several set points (labeled SP) for different temperatures, as printed on the top of the controller. Select the SP that fits your needs. It should be at least 10 degrees C below your desired temperature.

Turning Off Chiller

First switch off the compressor. Leave the controller running for a few hours until the chiller temperature (displayed on the front of the controller) approaches room temperature. Then turn off the controller.

After turning off chiller as described above, deactivate the wall dryer:
  • close outlet air valve for dryer
  • open bypass air valve below dryer
  • close inlet air valve
  • turn off dryer electrical switch
  • slowly open outlet air-filter bowl to let dryer vent pressure
  • close outlet air-filter bowl

Setting Temperature within an Experiment

Setup tab -> temp page.
Set the temperature on this page. UNcheck "allow temp control with go" to prevent an inadvertent temperature change when you change experiments. Do NOT press reset. (Note: for this to work you must have set vttype=2, which should usually be the case)

Calibrate the temperature using the methanol standard sample. See the Probe manuals for directions.