VEGA VEGAFLEX 81 Foundation Fieldbus - Manual (Page 81)

81
11 Supplement
VEGAFLEX 81 • Foundation Fieldbus
44218-EN-130910
0
-15 mm
(-0.591 " )
2 mm
(0.079 ")
-2 mm
(-0.079 ")
15 mm
(0.591 " )
0,3 m
(11.811 ")
0,15 m
(5.906 " )
0,15 m
(5.906 ")
20 mm
(0.787 " )
0,05 m
(1.969 ")
1 1
L
Fig. 59: Deviation VEGAFLEX 81 in cable version ø 4 mm (0.157 in), in oil
1 Dead band - no measurement possible in this area
L Probe length
Repeatability ≤ ±1 mm
Variables influencing measurement accuracy
Temperature drift - Digital output
±3 mm/10 K relating to the max. measuring range or
max. 10 mm (0.394 in)
Additional deviation through electromag-
netic interference acc. to EN 61326
< ±10 mm (< ±0.394 in)
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)
Air 20 °C/68 °F 0.00 % 0.22 % 1.2 %
200 °C/392 °F -0.01 % 0.13 % 0.74 %
400 °C/752 °F -0.02 % 0.08 % 0.52 %
Hydrogen 20 °C/68 °F -0.01 % 0.10 % 0.61 %
200 °C/392 °F -0.02 % 0.05 % 0.37 %
400 °C/752 °F -0.02 % 0.03 % 0.25 %