GW Instek GBM-3080, User Manual

Page: 70 / 184

GBM-3080/3300 User Manual
70
Saving data to USB flash drive
User can save recorded data to USB flash drive at any time after
statistics function is activated. The steps for saving data to USB
flash drive are the same as that described in data logging section.
Please refer to page 64 for details.
Process Capability Index
Process capability refers to the ability of meeting the processing
quality in process. It is to measure the minimum fluctuation in the
internal consistency, steady state in the process. When the process
is in steady state, the product has 99.73% of the quality
characteristic values scattered in the interval [μ-3σ, μ + 3σ] (where μ
is the overall mean of the product characteristic values and σ is the
overall standard deviation of the product characteristic values).
Almost all product characteristic values fall within the 6σ range, so
the process capability is usually expressed as 6σ. The smaller the
value, the better it is.
Cp, CpK > 1.33 means that process capacity is full
1.00 < Cp, CpK
≤
1.33 means that process capacity is appropriate
Cp, CpK ≤ 1.00 means that process capacity is not enough.
Process capability index and some related formulas:

Mean

Standard deviation population (σ
n
)

Standard deviation sample (s = σ
n-1
)

Process Capability Index (Deviation) Cp