Measurement Process Characterization
2.4. Gauge R & R studies
2.4.5. Analysis of bias
|Resolution||Resolution (MSA) is the ability of the measurement system to detect and faithfully indicate small changes in the characteristic of the measurement result.|
|Definition from (MSA) manual||The resolution of the instrument is δ if there is an equal probability that the indicated value of any artifact, which differs from a reference standard by less than δ, will be the same as the indicated value of the reference.|
|Good versus poor||
A small δ
implies good resolution -- the measurement system can discriminate between
artifacts that are close together in value.
A large δ implies poor resolution -- the measurement system can only discriminate between artifacts that are far apart in value.
|Warning||The number of digits displayed does not indicate the resolution of the instrument.|
|Manufacturer's statement of resolution||Resolution as stated in the manufacturer's specifications is usually a function of the least-significant digit (LSD) of the instrument and other factors such as timing mechanisms. This value should be checked in the laboratory under actual conditions of measurement.|
|Experimental determination of resolution||To make a determination in the laboratory, select several artifacts with known values over a range from close in value to far apart. Start with the two artifacts that are farthest apart and make measurements on each artifact. Then, measure the two artifacts with the second largest difference, and so forth, until two artifacts are found which repeatedly give the same result. The difference between the values of these two artifacts estimates the resolution.|
|Consequence of poor resolution||No useful information can be gained from a study on a gauge with poor resolution relative to measurement needs.|