Vega VEGAFLEX 81 - Influence of the superimposed gas and pressure to the accuracy

73
10 Supplement
VEGAFLEX 81 • Modbus and Levelmaster protocol
42283-EN-140430
L
0
-2 mm (-0.079
")
2 mm (0.079")
10 mm (0.394")
5 mm (0.197")
-5 mm (-0.197")
0,15 m (5.906")
0,1 m (3.937
")
0,05 m
(1.97
")
0,1 m
(3.937
")
1 1
Fig.37:DeviationVEGAFLEX81incoaxversioninoil
1 Dead band - no measurement possible in this area
L Probe length
Repeatability ≤±1mm
Variablesinuencing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)
Inuence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eect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specied
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 %
Steam (saturated
steam)
100 °C/212 °F 0.26 % - -
180 °C/356 °F 0.17 % 2.1 % -
264 °C/507 °F 0.12 % 1.44 % 9.2 %
366 °C/691 °F 0.07 % 1.01 % 5.7 %