FISCHER FISCHERSCOPE X-RAY 4000 Series, Operator'S Manual

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Measurement device monitoring for the Fischerscope X-RAY Pre-run for determining the control limits
110 FISCHERSCOPE
®
X-RAY
retain a once secured measurement application essentially without
changes than to overwrite it through re-calibration, often done for
no reason. Thus, please only follow the corrective measures
recommended by us.
14.10 Pre-run for determining the control limits
NOTE: Note : The equations and factors used here are all de-
scribed in the equation collection of the operator’s
manual for the Fischerscope XRAY. The control limits
can be calculated using the ”calculator” functions in
the control chart of WinFTM. Beyond that a spread-
sheet that contains the equations beneath for the cal-
culation of the control limits can be used for the pre-
run.
The pre-run consist of a minimum of m = 10 groups each with
n = 5 single readings, i.e., a total of 50 measurements. The
measurement application and the identity designations must be
documented.
The single readings for the pre-run should be carried out
successively using the setting parameters (measurement time,
measurement distance, collimator, etc.) typically used for the
measurement application and should be concluded within a short
period for the instrument to remain stable during this time.
Systematic changes during this period are then negligible. After
each group (not after each measurement!), the reference sample
should be taken from the instrument and re-positioned in order to
simulate as good as possible the subsequent procedure during the
check measurement. With instruments featuring a variable setting
of the measurement distance, such as the Fischerscope XRAY, the
measurement distance must be retained during the pre-run and the
subsequent check measurement because the standard deviation
correlates to the measurement distance. This distance can be
noted and viewed in the ”notepad” of the product that is used for
measurement device monitoring.
At first, the mean values x.
i
of the m groups 1 to 10 are used to
calculate the overall mean value x.. :
(2)
x.. = (1/m) ·

x.
i
= x_est
This overall mean value forms the estimated value x_est for the
mean value of the quality control chart.