(2) The following computations and graphs are required:
(a) The value of each cell and the mean of the working group based
on the mean of the reference group (compute and graph).
(b) The value of each cell in the reference group based on the
mean of the reference group (compute and graph).
(c) Left-right component (compute only).
(3) Upon receipt of the calibration report from the USASL, the AACL
will construct graphs similar to table 3 and in accordance with (a) through
(c) below.
(a) Enter the calibration report value for each of the cells and
the mean of each group at the appropriate point on the graphs at time zero
and enter the date at the bottom of the graph.
(b) Enter the upper and lower control limits.
These limits will
be supplied by the USASL in the calibration report.
(c) At monthly intervals following calibration, compare
the
reference and working cells. Enter the computed data in the graphs.
(4) Surveillance plots are considered within control if plotted data
is within upper and lower control limits.
(5) Out-of-control conditions and actions will be determined in the
following manner:
(a) The average left-right component (residual EMF) is 0.03
microvolt for system used in the AACL.
Any computed left-right component
exceeding 0.30 microvolt indicates a requirement for determining system
errors (sources of thermal EMF, cell instability, potentiometer errors,
etc.).
In situations where left-right component computations exceed 0.30
microvolt and the sources of errors cannot be traced locally, guidance
should be requested from the USASL.
(b) Control limits on the surveillance charts signal out-of-
control conditions for the cell.
Individual out-of-control cells in the
working group should not be used as standards for calibration; however,
surveillance should continue.
In some cases, the condition will be
temporary and will return to an in-control condition. In the event of an
out-of-control working group mean, request guidance from the USASL.
The
reference group mean will track a straight line by definition. In the event
that as many as two reference group cells drift out-of-control, request
guidance from the USASL.
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