Siemens SITRANS LG270 Operating Instructions Manual page 80

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