Parr Instrument 6725 - Manual (Page 34)

6725
Semi-micro Calorimeter Instruction Manual
5-7
User Function Setup:
This key leads to sub menus that support the configuration of five factory/user definable
function keys. The function keys are accessible from the Diagnostics page.
Cold Restart:
This is essentially the same as cycling power on the unit. All valid test data will be
retained during this cold restart procedure.
Calibration Data and Controls Menu
Calibration Run Limit:
Displays the maximum number of runs that
will be included in determining the EE value
of a bomb and bucket combination and
accesses the sub-menu on which this limit is
set. Most test methods suggest 10 tests.
Tests in excess of the most recent ones
used are still available but are not used in
the calculation of the EE value. For example
if 11 standardization tests have been run, the
calorimeter will only use the most recent 10.
The 11
th is still stored in the memory and is
available for view or printing. Only runs that
are at final status will be used in this calculation.
EE Max Std Deviation:
Displays the maximum relative standard deviation in percent that will be
permitted for any EE value calculated by the Calorimetric Thermometer and
accesses the sub-menu on which this limit is set. If this value is exceeded, the
user will be warned to take corrective action before proceeding with testing. A
setting of zero disables this check.
Heat of Combustion of Standard:
Displays the heat of combustion in calories per gram for the material used to standardize
the Calorimetric Thermometer and accesses the sub-menu on which this value is set.
For benzoic acid, this value is 6318.4 calories per gram.
Bomb Service Interval:
Displays the maximum number of times a bomb may be fired before it is flagged as due
for service and accesses the sub-menu on which this limit is set. Parr recommends 500
firings for this service interval. (Parts may need to be replaced on a more frequent basis
depending upon the nature of the sample).
Control Chart Parameters:
A control chart is a graphical tool which can assist the user in determining whether or not
their process is in control. Many standard methods will dictate that a reference sample
be measured periodically and the results plotted on a graph. Limits for acceptable values
are defined and the process is assumed to be in control as long as the results stay within
these limits. Since results are expected to scatter with a normal distribution within
established limits, systematic trends or patterns in the data plots may also be an early
warning of problems.