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Step 3: Evaluate Resolution
Objective:
Determine if the measurement system can detect and discriminate
between small changes in the measured characteristic.
NOTE: This process can be performed concurrently with the
previous process, Evaluation of Stability.
Process:
Choose a sample standard. If one is not available, then use a
production unit whose measurement falls into the middle of the
expected measurement range.
Measure the sample standard three to five times in as short a period
of time as possible to obtain one group of data.
Repeat the measurement process to obtain a minimum of 10, and
preferably 25 groups of data. Each of the repeated measurement
sets should be performed on a regular basis, such as hourly, daily,
or weekly.
Plot the data on a R control chart with its appropriate control limits.
Analysis:
If any of the following exist, then the resolution is inadequate:
There are only one, two, or three possible values for the range.
There are only four possible values for the range when the subgroup
size is greater than or equal to three (
n
3).
