Siemens SITRANS L 7ML5400 Operating Instructions Manual page 223

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 223)].
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 172).
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.
For best results, calibrate with the level at a known value near Low Calibration Point.
SITRANS LUT400
Operating Instructions, 04/2021, A5E33329501-AG
Parameter reference (LUI)
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
9.2 Setup (2.)
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