Limit Setting
- Updated2022-11-09
- 1 minute(s) read
Limit Setting
There are two types of test limits: absolute limits and relative limits. Absolute limits apply to research and development design tests which require absolute values to evaluate the performance of DUTs. For manufacturing tests, both absolute and relative limits can be used.
Absolute Limits
Determine absolute limits based on DUT specifications or a golden sample.
Absolute limits apply to typical test items, such as frequency response, distortion, and sensitivity.
Using absolute limits is beneficial because you do not need to maintain the golden sample after the limits are determined. However, absolute limits are valid under certain conditions. If the environment or any test component changes, the existing absolute limits are no longer applicable.
Relative Limits
Determine relative limits based on one or a batch of golden samples that conform to engineering specifications and customer requirements.
For manufacturing tests, a batch of golden samples is required. Specifically, the average, standard deviation, and the Ppk are calculated for each test item. Then, a certain number, which varies depending on DUT performance, is added to and subtracted from the standard deviation to determine relative limits.
Using relative limits is beneficial because there is no need to consider changes in test environment, temperature, humidity, chamber, and jigs which have the same impacts on golden samples and DUTs. However, relative limits need to be updated from time to time as new samples always replace old samples whose performance drifts over time.
Refer to the NTi Audio website for more information on how to set limits and select between absolute and relative limits.