Calculation Of Total Deviation (Similar To Din 16086) - Vega VEGABAR 66 Operating Instructions Manual

Total deviation
Example
VEGABAR 66 • 4 ... 20 mA/HART
8.3 Calculation of total deviation (similar to
DIN 16086)
The total deviation F
total
accuracy F and longterm stability F
perf
maximum practical deviation or utility error.
= F + F
F
total perf stab
2
= √((F + (F
F ) )
perf
T Kl
With analogue output, the error of the current output F
2
= √((F + (F
F ) )
perf
T Kl
With:
: Total deviation
F
l
total
: Basic accuracy
F
l
perf
: Long-term drift
F
l
stab
: Temperature coefficient (influence of medium or ambient
F
l
T
temperature)
F : Deviation
l
Kl
: Error current output
F
l
a
Level measurement 1500 mmWs
Product temperature 40 °C, reference temperature 20 °C
Selected: VEGABAR 66 with measuring range 0.2 bar
Calculation ΔT: ΔT = 40 °C - 20 °C = 20 K
Calculation of the set Turn Down:
TD = 200 mbar/147 mbar, TD = 1.4
Basic accuracy digital output signal in percent:
2
= √((F + (F
F ) )
perf
T Kl
= 0.05 %/10 K x TD
F
T
= 0.1 %
F
Kl
= √((0.05 %/10 K x 20 K x 1.4)
F
perf
= 0.17 %
F
perf
Total deviation digital output signal in percent:
= F + F
F
total perf stab
= 0.1 %/year x TD
F
stab
= 0.1 %/year x 1.4
F
stab
= 0.14 %
F
stab
= 0.17 % + 0.14 % = 0.31 %
F
total
Total deviation digital output signal absolute:
= 0.35 % x 147 mbar/100 % = 0.46 mbar = 4.7 mm
F
total
8 Maintenance and fault rectification
according to DIN 16086 is the sum of basic
. F
stab
2
)
2 2
(+ F ) )
a
2
)
2
+ (0.1 %)
is also called
total
is also added.
a
2
)
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