Parr Instrument 6725 - Manual (Page 23)

6725
Semi-micro Calorimeter Instruction Manual
4-3
The default parameters of the 6772 Calorimetric Thermometer can be changed to
guarantee that the thermometer, when cold restarted, will always be in the desired
configuration before beginning a series of tests. Users who wish to permanently revise
their default settings may do so using the following procedure:
• Establish the operating parameters to be stored as the user default settings.
• Go to the Program Info and Control Menu, User/Factory Settings, User Setup ID, and
enter the desired User Setup ID.
• Select Save User Default Settings
To re-load the user default setting, go to the Program Info and Control Page,
User/Factory Settings, Re-load User Default Settings, and YES.
Performing an analysis
Tests can be run in a strictly manual fashion or automatically where the thermometer
sequences the calorimeter through the pre and post periods. The manual sequencing
approach is useful for applications where raw data is logged and subsequently analyzed,
off-line. In the automatic mode, the thermometer fully sequences the test and applies
real time corrections to the calorimeter temperature rise in order to correct for all
systemic heat leak effects. In either case the operator must determine the appropriate
temperature source for the jacket.
• Probe – This method uses an additional 1168E2 thermistor probe attached to the
jacket wall to measure the actual temperature of the surroundings (at the chosen
point) and the heat leak correction are based upon the actual differences
between the bucket and this external jacket temperature.
• Calculated – During the initial equilibrium period this method analyzes the actual
heat leak rate and calculates the apparent temperature of the surroundings which
would generate this rate and applies this calculated jacket temperature for the
determination.
• Fixed – In this method the operator determines what his jacket temperature will
be and enters it into the thermometer. All heat leak corrections are then based
upon this fixed jacket temperature.
For most applications the calculated method is recommended.
Detailed instructions for preparing the sample and charging the 1109 oxygen bomb are
given in the Operating Instructions for the 1109/1109A Semi-micro Oxygen Combustion
Bomb, manual 492M. Follow these instructions carefully, giving particular attention to
the precautions to be observed in charging and handling the bomb.
The bomb parts should be wetted and then dried in the manner used at the conclusion of
a test. This serves to wet all sealing parts as well as leaving the bomb with the same
amount of residual water which will exist in all subsequent testing.
The two operating modes, (manual or automatic) are outlined below: