Siemens SITRANS LUT400 Operating Instructions Manual page 221

In gasses other than air, the temperature variation may not correspond with the speed of
sound variation. In these cases, turn off the temperature sensor, select value Fixed
Temperature, and set a fixed temperature [see Fixed Temperature (2.12.1.4.) (Page 219)].
If Ultrasonic/Temperature Transducer, TS-3 Temperature Sensor, or Average of Sensors
value is selected, faults on the temperature sensors will be displayed if the sensor appears
open or short.
When a transducer temperature sensor fault occurs, Temperature Source can be set to
FIXED. This allows the device to continue measuring (and no cable fault will display), until
the transducer is replaced. Once replaced, set Temperature Source back to its original
setting.
Fixed Temperature (2.12.1.4.)
Use this feature if a temperature sensing device is not used.
Values
Enter the temperature (in °C) of the atmosphere within the transducer acoustic beam. If the
temperature varies with distance from the transducer, enter the average temperature.
Sound Velocity at 20 degrees C (2.12.1.5.)
This value is used to automatically calculate sound velocity.
Values
If the acoustic beam atmosphere sound velocity at 20°C (68 °F) is known, and the sound
velocity vs. temperature characteristics are similar to that of air (344.1 m/s), enter the sound
velocity. Units displayed in meters per second (m/s).
Auto Sound Velocity (2.12.1.6.)
Note
Auto Sound Velocity supports adjustments to distance value only.
Adjusts the speed of sound and changes the distance measurement calculations. Defined in
Units (2.1.1.) (Page 168).
Values
Condition for use of this feature:
● The acoustic beam atmosphere is other than air
● The acoustic beam atmosphere temperature is unknown
● The Reading accuracy is acceptable at higher material levels only.
SITRANS LUT400
Operating Instructions, 07/2019, A5E33329501-AC
Range: -100.0 to +150.0 °C
Default: +20.0 °C
Range: 125.000 to 20000.000 m/s
Default: 344.13 m/s
Range: 0.000 to 60.000
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