66
9 Supplement
WIKA Operating Instructions - Process pressure transmitter CPT-2x
Time pe-
riod
Measuring cell ø 28 mm
Measuring cell ø 17.5 mm
All measuring ranges Measuring range
0 … +0.025 bar
(0 … +2.5 kPa)
All process fittings
Process fitting G½
(ISO 228-1)
One year
< 0.05 % x TD
< 0.1 % x TD
< 0.1 % x TD
< 0.25 % x TD
Five years
< 0.1 % x TD
< 0.2 % x TD
< 0.2 % x TD
< 0.5 % x TD
Ten years
< 0.2 % x TD
< 0.4 % x TD
< 0.4 % x TD
< 1 % x TD
Tab. 24: Determination of the long-term stability from the table, consideration for one year: F
stab
=
0.05 % x TD
4. Calculation of the total deviation - 4 … 20 mA signal
1. step: Basic deviation F
perf
F
perf
= √((F
T
)
2
+ (F
Kl
)
2
+ (F
a
)
2
)
F
T
= 0.79 %
F
Kl
= 0.2 %
F
a
= 0.15 %
F
perf
= √(0.79 %)
2
)
2
+ (0.2 %)
2
) + (0.15 %)
2
)
F
perf
= 0.83 %
2. step: Total deviation F
total
F
total
= F
perf
+ F
stab
F
stab
= (0.05 % x TD)
F
stab
= (0.05 % x 2.5)
F
stab
= 0.13 %
F
total
= 0.83 % + 0.13 % = 0.96 %
The total deviation of the measurement is hence 0.96 %.
Deviation in bar: 0.96 % of 4 bar = 0.038 bar
The example shows that the measurement error in practice can be considerably higher than the
basic deviation. Reasons are temperature influence and Turn down.
Содержание CPT-2 Series
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