VEGA VEGAPULS 66 (≥ 2.0.0 - ≥ 4.0.0) standpipe ver. Profibus PA - Manual (Page 48)

48
11 Supplement
VEGAPULS 66 standpipe version • Profibus PA
36525-EN-121011
Deviation with liquids See following diagrams
2
0,5 m
(1.6 ft)
10 mm (0.394 in)
5 mm (0.197 in)
- 5 mm (- 0.197 in)
- 10 mm (- 0.394 in)
0
1 3
Fig. 28: Deviation under reference conditions
1 Reference plane
2 Distance vent hole from reference plane 47 mm (4.85 in)
3 Standpipe end
Reproducibility ≤ ±1 mm
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 %
Hydrogen 20 °C/68 °F -0.01 % 0.10 % 0.61 % 1.2 % 2.5 %
200 °C/392 °F -0.02 % 0.05 % 0.37 % 0.76 % 1.6 %
400 °C/752 °F -0.02 % 0.03 % 0.25 % 0.53 % 1.1 %