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Measurement capability is a critical aspect of ensuring product quality, therefore a measurement system must be assessed before being used on products. Understanding how to assess measurement capability becomes critical. The Type 1 Gauge study is typically the first step in a measurement system analysis program. Type 1 Gauge parameters are explained, and a worked example using electroless nickel immersion gold (ENIG) is provided.
What Does the Type 1 Gauge Study Do? There are two major types of measurement system variation:
1. Accuracy is variation between the measurement and a true or reference value
2. Precision is variation between repeated measurements
A Type 1 Gauge study involves repeated measurements of one sample by one gauge and by one operator. With this information, the
Type 1 Gauge study provides an assessment of the following:
1. Accuracy, assuming a reference value is available
2. Precision of repeated measurements
Without an accepted reference value, the Type 1 Gauge study only measures precision, and accuracy becomes unavailable. Bias is a quantitative term used to describe accuracy. Bias is the difference between the average of measurements made on the reference value and its true value.
A Type 1 Gauge study considers only the inherent variation of the gauge itself. A Type 1 Gauge study isolates the effects of accuracy and precision, and evaluates the capability of the gauge to make accurate measurements with acceptable variability. A Type 1 Gauge study does not assess operator-to-operator or gaugeto-gauge variation. A more complex gauge repeatability and reproducibility (R&R) study is indicated for a more comprehensive measurement system analysis.
To read this entire article, which appeared in the July 2016 issue of The PCB Magazine, click here.
