DH Instruments PPC4, Руководство по эксплуатации и обслуживанию

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PPC4™ OPERATION AND MAINTENANCE MANUAL
© 2009 DH Instruments, a Fluke Company Page 56
Note
In dynamic mode, the pressure value returned from the PR and
PRR commands (see Section 6.5.4, PR and PR Commands) is
the measured pressure, not the target pressure. The control
uncertainty is based on the target pressure and may be
considered conservative when applied to the measured
pressure. The value of control uncertainty may be considered
pertinent, however, since the measured pressure can vary
within the hold limit while Ready.
Table 13. Default Values for PPC4 Uncertainty Components
UNCERTAINTY
Q-RPT CLASS
FULL SCALE STANDARD
F CLASS
STANDARD
S CLASS
PREMIUM
P CLASS
PRODUCT
READING
0.000% 0.010% 0.008%
SPAN
0.015% 0.003% 0.0024%
SCALE
30%, 10% for G15K, BG15K 100% 30%
HEAD
0.0 (cm or in) 0.0 (cm or in) 0.0 (cm or in)
ZERO
STABILTY
AUTOZ ON*
0.000% 0.000% 0.000%
AUTOZ OFF*
0.005% 0.005% 0.005%
*Does not apply to gauge type
3.2.29.5 Combining uncertainties
3.2.29.5.1 Measured Pressure Uncertainty
Measured pressure uncertainty is the combination of the product uncertainty and
the uncertainties in pressure head and zero stability.
2 2 2
3
2 2
2






×
+






× ×
+






× =
QRPT AutoZ std gas head prod
meas
S U g U U
U
ρ
where:
U
meas
: Measured pressure uncertainty.
U
prod
: Product uncertainty = Max [(U
read
x P
curr
), (U
span
x AutoRange Span)] (see
Figure 6).
P
curr
: Current measured pressure.
U
span
: Threshold uncertainty component. Allowable scaling is defined by
“ Scale ” which specifies the extent to which the uncertainty can be
downranged.
U
head
: Uncertainty of head height measurement in cm or inches.
ρ
gas
: Density of the test gas. In gauge mode replaced with (
ρ
gas
-
ρ
air
) , where
ρ
air
is standard air density, 1.2 kg/m
3
.
g
std
: Standard gravity 9.80665 m/s
2
.
U
Autoz
: Uncertainty associated with zero drift of the Q-RPT, specified with AutoZ
On and separately with AutoZ Off.
S
QRPT
: Q-RPT span.