VEGA VEGAPULS 66 (≥ 2.0.0 - ≥ 4.0.0) Foundation Fieldbus - Manual (Page 60)

60
11 Supplement
VEGAPULS 66 • Foundation Fieldbus
36522-EN-121011
Installation reference conditions
Ʋ Min. distance to installations > 200 mm (7.874 in)
Ʋ Reflector Plane plate reflector
Ʋ False reflections Largest false echo 20 dB smaller than the useful echo
Deviation with liquids See following diagrams
1,0 m (3.28 ft)
20 mm (0.788 in)
8 mm (0.315 in)
- 8 mm (- 0.315 in)
- 20 mm (- 0.788 in)
0
1 2 3
Fig. 48: Deviation under reference conditions
1 Reference plane
2 Antenna edge
3 Recommended measuring range
Reproducibility ≤ ±1 mm
Deviation with bulk solids The values depend to a great extent on the application.
Binding specifications are thus not possible.
Variables influencing measurement accuracy
Temperature drift - Digital output
±3 mm/10 K relating to the max. measuring range or
max. 10 mm
Additional deviation through strong, high
frequency electromagnetic fields acc. to
EN 61326
< ±50 mm
Influence of the superimposed gas and pressure to the accuracy
The propagation speed of the radar impulses in gas or vapour above the medium is reduced by
high pressure. This effect depends on the superimposed gas or vapour and is especially large at
low temperatures.
The following table shows the resulting deviation for some typical gases and vapours. The specified
values refer to the distance. Positive values mean that the measured distance is too large, negative
values that the measured distance is too small.
Gas phase Temperature Pressure
1 bar
(14.5 psig)
10 bar
(145 psig)
50 bar
(725 psig)
100 bar
(1450 psig)
200 bar
(2900 psig)
Air 20 °C/68 °F 0.00 % 0.22 % 1.2 % 2.4 % 4.9 %
200 °C/392 °F -0.01 % 0.13 % 0.74 % 1.5 % 3.0 %
400 °C/752 °F -0.02 % 0.08 % 0.52 % 1.1 % 2.1 %