63
10 Supplement
VEGABAR 86 • Secondary Device for electronic differential pressure
48048-EN-220817
F
T
= 0.26 %
F
Kl
= 0.1 %
F
perf
= √(0.26 %)
2
+ (0.1 %)
2
)
F
perf
= 0.28 %
- 2. step: Total deviation F
total
F
total
= F
perf
+ F
stab
F
perf
= 0.28 % (result of step 1)
F
stab
= (0.05 % x TD)
F
stab
= (0.05 % x 2.5)
F
stab
= 0.13 %
F
total
= 0.28 % + 0.13 % = 0.41 %
5. Calculation of the total deviation of the measuring system
Both sensors are included in the calculation of the total deviation of the measuring system. With the
4 … 20 mA Primary Device the thermal error of the analogue output is also added:
F
total
= √(F
total-Primary
)
2
+ (F
total-Secondary
)
2
+ (F
a
)
2
0,3 %
-0,15 %
-40°C
-20°C
20°C
40°C
60°C
80°C
0,15 %
-0,3 %
Fig. 27: F
a
through thermal change current output, in this example = 0.1 %
F
total
= √(0.41 %)
2
+ (0.41 %)
2
+ (0.1 %)
2
)= 0.59 %
The total deviation of the measuring system is hence 0.59 %.
Deviation in mm: 0.59 % of 1,600 mm = 9 mm
The example shows that the measurement error in practice can be considerably higher than the
basic accuracy. Reasons are temperature influence and Turn down.
The thermal change of the current output is in this example is negligible.
10.4 Dimensions
The following dimensional drawings represent only an extract of the possible versions. Detailed
dimensional drawings can be downloaded at www.vega.com under "
Downloads
" and "
Drawings
".
