80
PBD-51041066
SITRANS LG270 - Operating Instructions
44295-EN-140321
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
10
bar
(145
psig)
50
bar
(725
psig)
100
bar
(1450
psig)
200
bar
(2900
psig)
400
bar
(5800
psig)
Air
20 °C/68 °F
0.22 %
1.2 %
2.4 %
4.9 %
9.5 %
200 °C/392 °F 0.13 %
0.74 %
1.5 %
3.0 %
6.0 %
400 °C/752 °F 0.08 %
0.52 %
1.1 %
2.1 %
4.2 %
Hydrogen
20 °C/68 °F
0.10 %
0.61 %
1.2 %
2.5 %
4.9 %
200 °C/392 °F 0.05 %
0.37 %
0.76 %
1.6 %
3.1 %
400 °C/752 °F 0.03 %
0.25 %
0.53 %
1.1 %
2.2 %
Steam (satu
-
rated steam)
100 °C/212 °F -
-
-
-
-
180 °C/356 °F 2.1 %
-
-
-
-
264 °C/507 °F 1.44 %
9.2 %
-
-
-
366 °C/691 °F 1.01 %
5.7 %
13.2 %
76.0 %
-
Characteristics and performance data
Measuring cycle time
< 500 ms
Step response time
4)
≤ 3 s
Max. filling/emptying speed
1 m/min
Ambient conditions
Ambient, storage and transport tempera-
ture
-40 … +80 °C (-40 … +176 °F)
Process conditions
For the process conditions, please also note the specifications on the type label. The lowest value
always applies.
The measurement error through the process conditions in the specified pressure and temperature
range is < 1 %.
Vessel pressure relating to the flange
nominal stage
see supplementary instructions manual "
Flanges ac-
cording to DIN-EN-ASME-JIS
"
Process pressure
-1 … +400 bar/-100 … +40000 kPa
(-14.5 … +5800 psig), depending on the process fitting
Process temperature
-196 … +280 °C (-321 … +536 °F)
4)
Time span after a sudden measuring distance change by max. 0.5 m in liquid applications, max 2 m with bulk
solids applications, until the output signal has taken for the first time 90 % of the final value (IEC 61298-2).