7. MAINTENANCE OF TRACEABILITY AND RECALIBRATION
Page 135
© 2005 - 2007 DH Instruments, a Fluke Company
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7
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M
M
A
A
I
I
N
N
T
T
E
E
N
N
A
A
N
N
C
C
E
E
O
O
F
F
T
T
R
R
A
A
C
C
E
E
A
A
B
B
I
I
L
L
I
I
T
T
Y
Y
A
A
N
N
D
D
R
R
E
E
C
C
A
A
L
L
I
I
B
B
R
R
A
A
T
T
I
I
O
O
N
N
7.1
PRINCIPLES OF ADCS-601-AF TRACEABILITY MAINTENANCE
The ADCS-601-AF system is designed to provide state of the art measurement uncertainty specifications
with a very high degree of confidence over time whle minimizing maintenance requirements.
The maintenance of traceability and associated recalibration of the ADCS-601-AF system requires
metrological maintenance procedures that are performed locally at regular intervals (see Section 7.2) and
the regular recalibration of certain system elements (see Section 7.3).
ADCS-601-AF is made up of two pressure standards, a PG7601 piston gauge for the majority of the
range and an FPG8601 force balanced piston gauge for the low end. The fact that ADCS-601-AF
includes two independent pressure standards is exploited to reduce recalibration requirements. The two
standards have ranges that overlap between 10 and 15 kPa (3 and 4.5 inHg).
The PG7601 measurement uncertainty is predominantly dependent upon the uncertainty in the effective
area of its piston-cylinder and the value of the masses that are loaded on the piston-cylinder (see Section
2.2.1). The FPG8601 measurement uncertainty is predominantly dependent upon the effective area of its
piston-cylinder, the value of its internal calibration mass and the linearity and repeatability of its force
balanced load cell (see Section 2.2.2).
In the air data range of 1 to 15 kPa (0.3 to 4.5 inHg) that is covered by the FPG8601 in the ADCS-601-AF
system, the typical pressure measurement uncertainty of the FPG8601 (see the most recent revision of
DHI Technical Note 2090TN05) is much lower than is required to maintain an adequate uncertainty ratio
with modern Air Data Test Sets (ADTS). For use in the ADCS-601-AF system, the FPG8601
measurement uncertainty specification is significantly expanded from its typical measurement uncertainty
to allow it to be validated within the ADCS-601-AF system and its calibration interval to be indefinite.
When the internal ADCS-601-AF validation procedures determine a possible out of tolerance condition of
the FPG8601 it is considered to have failed and to require repair.
7.2
LOCAL METROLOGY MAINTENANCE BETWEEN
RECALIBRATIONS
7.2.1
OVERVIEW
To assure that the ADCS-601-AF operates within pressure measurement uncertainty limits
between recalibrations, certain metrology maintenance functions are required. These are
summarized in Table 21, including cross-reference to manual sections detailing each procedure.
