Distance Calculation; Sound Velocity - Siemens sitrans LU10 Instruction Manual

ECHO PROCESSING DISPLAYS (Scope Displays, P810)
TVT Curve
Echo Profile
Near Blanking
(P800)

Distance Calculation

To calculate the "round trip" transducer to material level (object) distance, the
transmission medium
transmission to reception time period. This result is divided by 2 to calculate the "one way"
distance.
The Reading Value displayed is the result of performing any additional modification to the
calculated distance (Operation P001, Units P-005, Volume Conversion, P050 to P054,
Reading Value, P060 to P063.)

Sound Velocity

The sound velocity of the transmission medium is affected by the type, temperature, and
vapour pressure of the gas or vapour present. As preset, the SITRANS LU10 assumes the
vessel atmosphere is air at 20°C (68°F). Unless altered, the sound velocity used for the
distance calculation is 344.1 m/s (1129 ft/s).
Variable air temperature is automatically compensated when a Siemens Milltronics
ultrasonic / temperature transducer is used. If the transducer(s) are exposed to direct
sunlight, TS-3 temperature sensor(s) should be used.
Also, if the temperature varies between the transducer face and the object monitored, a
TS-3 temperature sensor, mounted near the material surface (solids) or submerged
(liquids), should be used in combination with the ultrasonic/temperature transducer. Then
when Temp Source, (P660) is set for "both", the transducer and TS-3 temperature
measurements are averaged.
If the air temperature within all vessels is identical, a single TS-3 temperature sensor may
be used to represent the temperature of all vessels if Temp Source (P660) is set to Temp
Sensor # 1.
Atmosphere composition other than air can pose a challenge for ultrasonic level
measurement. However, excellent results may be obtained if the atmosphere is
Page 80
Empty Distance (P006) +
Range Extension (P801)
msec x 100
(atmosphere) sound velocity (P653) is multiplied by the acoustic
Distance = Sound Velocity x Time
SITRANS LU10 – INSTRUCTION MANUAL
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