Siemens SITRANS LUT400 Operating Instructions Manual page 247

Symptom
Accuracy Varies
Reading erratic
A5E33329501 SITRANS LUT400 (HART) – OPERATING INSTRUCTIONS
Cause
Faulty temperature sensor
Vapours present in varying con-
centrations
Thermal gradients
Calibration required
Transducer mounting: wrong
location or incorrectly mounted
Unavoidable false echoes from
obstructions
Confidence too low
Multiple echoes
Noise in the application
Action
Verify operation;
Replace if required, or use fixed
temperature. See Temperature
Source (2.12.1.3.) on page 181.
Eliminate vapours or consider a
different technology. Contact your
Siemens representative.
Insulate vessel;
Consider external temperature
sensor.
If accuracy is better when level is
close to transducer, and worse
when level is far from transducer,
perform calibration [see Auto
Sound Velocity (2.12.1.6.) on page
182].
If accuracy is consistently incor-
rect, use Sensor Offset (2.2.3.) on
page 141 or perform calibration
[see Auto Sensor Offset (2.2.6.)
on page 142].
Ensure beam has a clear path to
material surface;
Verify transducer is not too tight;
Use an isolation coupling.
Use Auto False Echo Suppression.
See Auto False Echo Suppres-
sion (2.12.3.1.) on page 184.
Check Noise, Echo Strength, Con-
fidence. See Echo Quality (3.2.9.)
on page 204.
Check LOE Timer is not set too
short. See LOE Timer (2.4.2.) on
page 144.
Check mounting location;
Verify material is not entering
Near Range zone. See Near
Range (2.2.4.) on page 141.
Verify source and minimize. See
"Noise Problems" on page 242.
Page 239