Only the Gemini 200 in room 38 of building 65 has the capability variable temperature (VT) capability. The Unity 400 also has VT capability. The following precaution should be taken when working with high temperatures. The probe can not be used above 200°C. or below -150°C. Liquid nitrogen is not required to operate at temperatures below room temperature. Instructions are also found in Varian manuals for Gemini System Operations on page 215 and in Gemini Accessory Installation manual beginning on page 1. The following instruction are intended to be brief instructions for work above ambient temperatures. CAUTION: Remember the boiling point of the common solvents used for NMR are around 60° C, e.g. CDCl3. If your sample is in a sealed tube around the boiling point of the solvent the glass may shatter and contaminate the probe with solvent, your sample, and broken glass. If the sample is not in a sealed tube vapors from the solvent could cause damage. Plan your VT experiments carefully. Also think about how long you want to keep the sample at the test temperature, i.e. during lock and shim. 1. Turn on the variable temperature controller power by pushing the red button on the Gemini console. The VT unit should be left off when it is not being used. When the unit is turned on it will perform some diagnostic checks and say PASS and then indicate the room temperature. The normal temperature is about 20.9° C. The readout will show +020.9 or whatever the values is for current room temperature. If the reading is extremely high or low the reading is an indication of a broken thermocouple wire or poor connection, e.g. a reading of +209.9 2. Type CONFIG and set VTYPE to VXRSTYLE and exit the configuration screen. 3. Load=Y SU Load=N 4. Use VTC? to make certain the transition temperature is below room temperature, e.g 19°C. 5. Type DG to observe the temperature being set then type TEMP=25 or your selected value. 6. When you type GO or GA to begin acquisition you will hear a click in the magnet leg and the green status light will flash on and off and the temperature will begin to climb. We have NMR temperature calibration standards. 7. To shut down the system go to DG and type TEMP=N and even though it probably is not necessary go to CONFIG and set VTYPE to NONE. Depress the RED power switch on the console to turn of the VT unit and log off.
8. Repeat: Load=Y SU Load=N
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