10
Evaluation of the Test Results
Simplified Procedure for Evaluating the Reproducebility:
Calculate the following value from 6 weighing operations:
Max. value displayed - Min. value displayed
——————————-——————————-
2
and write down this average value on the Balance Test Record.
Evaluation: The value calculated in this way must be written the permissible tolerance for
the reproducebility (standard deviation) givenon the Service Specifications
Sheet. If this requirement is not met, calculate the standard deviation as
described in the section entitled “Calculating the Standard Deviation”.
Calculating the Standard Deviation
Calculate the standard deviation using a suitable calculator or according to
the following formula:
s
n
x
i
i
n
x
=
−
=
−
∑
1
1
1
2
*
()
Evaluation: The value calculated in this way must be within the permissible tolerance for
reproducebility (standard deviation) given on the Service Specifications
Sheet.
If the standard deviation calculated in this way is too high, carry out the
following tests:
– Are the requirements listed under “Place of Installation” and “Getting
Started” met?
– Recheck the permissible off-center load tolerances.
– Clean the weighing system and make sure that there is no friction
between the movable parts (Friction between movable parts causes
unstable weighing results).
Recke the reproducebility (standard deviation) as described in the section
“Checking the Reproducebility”.
x
i
= Individual weighed values
= Mean value of the individual
weighed values
n = Number of weighings
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