VEGA VEGABAR 55 4 … 20 mA_HART - climate compensated User Manual
Page 46
46
8 Maintenance and fault rectification
VEGABAR 55 • 4 … 20 mA/HART - climate compensated
39441-EN-130321
F
perf
= √((F
T
)
2
+ (F
Kl
)
2
+ (F
a
)
2
)
With:
•
F
total
: Total deviation
•
F
perf
: Basic accuracy
•
F
stab
: Long-term drift
•
F
T
: Temperature coefficient (influence of medium or ambient
temperature)
•
F
Kl
: Deviation
•
F
a
: Error current output
Example
Pressure measurement in the pipeline 8 bar (800 KPa)
Ambient temperature 40 °C, product temperature 10 °C, hence within
the compensated range
VEGABAR 55 climate compensated, with measuring range 10 bar
Calculation of the set Turn Down: TD = 25 bar/8 bar, TD = 1.25
Basic accuracy digital output signal in percent:
F
perf
= √((F
T
)
2
+ (F
Kl
)
2
)
F
T
= (0.05 + 0.1 x TD)%
F
Kl
= 0.25 %
F
perf
= √((0.05 + 0.1 x 1.25)%)
2
+ (0.25 %)
2
)%
F
perf
= 0.31 %
Total deviation digital output signal in percent:
F
total
= F
perf
+ F
stab
F
stab
= (0.1 % x TD)/year
F
stab
= (0.1 % x 1.25)/year
F
stab
= 0.125 %
F
total
= 0.31 % + 0.125 % = 0.43 %
Total deviation digital output signal absolute:
F
total
= 0.43 % x 8 bar/100 % = 34.4 mbar
Basic accuracy analogue output signal in percent:
F
perf
= √((F
T
)
2
+ (F
Kl
)
2
+ (F
a
)
2
)
F
T
= (0.05 + 0.1 x TD)%
F
Kl
= 0.25 %
F
a
= 0.15 %
F
perf
= √((0.05 + 0.1 x 1.25)%)
2
+ (0.25 %)
2
+ (0.15%)
2
)
F
perf
= 0.34 %
Total deviation analogue output signal in percent:
F
total
= F
perf
+ F
stab
F
stab
= (0.1 % x TD)/year
F
stab
= (0.1 % x 1.25)/year
F
stab
= 0.125 %
F
total
= 0.34 % + 0.125 % = 0.47 %