Parr Instrument 6772 - Manual (Page 23)

6772
Calorimetric Thermometer Instruction Manual
4-3
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 1108 oxygen bomb are given
in the Operating Instructions for the 1108 Oxygen Combustion Bomb, manual 205M. 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:
Manual Test Sequencing
Some users may wish to construct their own thermogram and apply the classic graphical
corrections developed by Dickenson and others. In this case, the actual temperatures can
be logged to the memory of the thermometer and then analyzed at the end of the test.
These logged temperatures can be recalled to display on the thermometer, printed on an
attached printer or transferred to a computer using either the Ethernet Connection or a
Compact Flash Card. The Ethernet Connection can also be used to transfer temperatures to
a computer for plotting and analysis in real time.
First, select the appropriate jacket temperature source as described previously. Then
prepare the sample and charge the oxygen bomb as described in Operating Instructions No.
205M, the Filling Connection Section. Using multiple bombs and water buckets can increase
the throughput of the 1341 Calorimeter. With this arrangement, the calorimeter can operate
almost continuously since the operator will be able to empty a bomb and recharge it while a
run is in progress. The bomb and bucket for the next run will be ready to go into the
calorimeter as soon as it is opened. Each bomb and bucket combination will have to be
standardized separately and the proper energy equivalent for each set must be used when
calculating the heat of combustion.