Tools and Templates
These winzipped tools were written for internal use but are general enough
that CLAS makes them available to interested parties on the understanding
that they have been validated against published examples and commercial
software. NRC is not to be held liable in the unlikely event of loss from
incorrect results.
Uncertainty Budget Template
Excel template for preparing simple uncertainty budgets. The spreadsheet
includes a completed example for the calibration of a micrometer using
gauge blocks. DOWNLOAD
Calibration Control Charts
Control charts for analyzing quality control data obtained from period
checks of the measurement process. It is presumed that the user has a
rudimentary understanding of statistical process control (SPC). For information
on SPC, consult any of a large number of publications written on the subject.
CLAS provides a bibliography of representative
publications on SPC.
In general, control charts are used to detect variations in calibration
processes which are not random in nature and which, therefore, can be
assigned to a cause. The information is used to determine whether or not
the calibration process is working properly (i.e., in control). This is
analogous to the use of the Student's T-Test for deciding whether or not
a single observation comes from a distribution (i.e., process) with known
mean and unknown standard deviation.
Like any tool, control charts can be used in many different ways to provide
different types of information on the calibration processes. CLAS provides
sample spreadsheets for a number of different types of control charts.
It remains the responsibility of the user to select the most appropriate
type of chart for the given application and to interpret the results accordingly.
It is also the responsibility of the user to collect the measurements
over a sufficiently wide range of operating conditions to ensure a correct
characterization of the distribution and over a sufficiently long period
of time to ensure independence. In some cases, 25 measurements over several
months is sufficient.
Instructions
To use the spreadsheets, simply click on the Data tab and overwrite the
sample values of Date and Observations with your own data. The Upper and
Lower 2 warning limits (UWL &
LWL) and 3control limits (UCL &
LCL) and other appropriate statistics will be calculated automatically.
To view the control charts, click on the Charts tab.
- Spreadsheets (31 kbytes) for individual observation (no subgroups).
Download (Revised January 2001)
- Spreadsheets (165 kbytes) for Mean and Range charts with subgroups.
Download (Revised January 2001)
- Spreadsheets (165 kbytes) for Mean and Standard Deviation charts with
subgroups. Download Revised January 2001)
To unzip the spreadsheets, evaluation copies of Winzip software are available
for download at the following location: http://www.winzip.com/download.cgi.
|
