Hach-Lange ORBISPHERE 410 User Manual - Manual (Page 42)

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View Menu
5.1 Selection of the view style
Numeric view
This is the default view. Display shows the numeric measurement value identified for the gas
measurement channel, a graphic showing measurement value evolution during the set time
frame, and sample temperature.
This display can be configured to suit individual conditions and convenience.
Diagnostic view
The diagnostic view contains useful information for troubleshooting purposes. The amount of information
displayed depends on the gas being measured and the channel configuration.
Statistic view
This feature offers statistical data that matches with Total Quality management tools. Statistics is a tool
to better analyze how a process behave. The 410 statistics window gives some useful information.
The statistics are calculated from the data in the measurement file. The values are updated each time a
new value is added to this file. Therefore the changes made in the configuration window are considered
only once a new value is added.
Cp process capability
Cp is an index used to assess the width of the process spread in comparison to the width of the
specification. It is calculated by dividing the allowable spread by the actual spread.
•
A Cp of one indicates that the width of the process and the width of the specification are the
same.
• A Cp of less than one indicates that the process spread is greater than the specification. This
means that some of the data lies outside the specification.
• A Cp of greater than one indicates that the process spread is less than the width of the
specification. Potentially this means that the process can fit inside the specification limits
CPk process variability
Cpk takes into account the center of the data relative to the specifications, as well as the variation in
the process.
•
A Cpk value of one indicates that the tail of the distribution and the specification are an equal
distance from the overall average.
• A Cpk of less than one means that some of the data is beyond the specification limit.
• A Cpk greater than one indicates that the data is within the specification.
• The larger the Cpk, the more central and within specification the data.
CPm process repeatability
Capability index that takes into account variation between the process average and the target. If the
process average and the target are the same value, Cpm will be the same as Cpk. If the average
drifts from the target, Cpm will be less than Cpk.
Skewness
negative
positive
Figure 27 Skewness
An asymmetric frequency distribution is skewed to the left if the lower tail
is longer than the upper tail, and skewed to the right if the upper tail is
longer than the lower tail. Distributions of positive-valued random
variables values are often skewed right.