Siemens SITRANS LUT400 - Determine the Noise Source; Acoustical Noise; Non-Transducer Noise Sources

SITRANS LUT400
Operating Instructions, 07/2019, A5E33329501-AC
277
11.5.1 Determine the Noise Source
Disconnect the transducer from the SITRANS LUT400. If the measured noise is below 5 dB,
then continue here. If the measured noise is above 5 dB go to Non-Transducer Noise
Sources below.
1. Connect only the shield wire of the transducer to the SITRANS LUT400. If the measured
noise is below 5 dB, continue with the next step. If the noise is above 5 dB, go to
Common Wiring Problems below.
2. Connect the white and black transducer wires to the SITRANS LUT400. Record the
average noise.
3. Remove the positive wire of the transducer. Record the average noise.
4. Re-connect the positive wire and remove the negative wire. Record the average noise.
Using the table below, determine the appropriate next step. The terms higher, lower and
unchanged refer to the noise recorded in the previous steps.
These are guidelines only. If the suggested solution does not solve the problem, try the other
options also.
-removed
+removed
Go to:
noise
higher
higher
Reducing Electrical Noise (Page 278)
unchanged
Common Wiring Problems (Page 278)
lower
Reducing Acoustical Noise (Page 278)
unchanged
higher
Reducing Electrical Noise (Page 278)
unchanged Contact Siemens representative.
lower
Reducing Acoustical Noise (Page 278)
lower
higher
Common Wiring Problems (Page 278)
unchanged
Common Wiring Problems (Page 278)
lower
Reducing Acoustical Noise (Page 278)
11.5.1.1 Acoustical Noise
To confirm that the problem is acoustical, place several layers of cardboard over the face of
the transducer. If the noise is reduced, the noise is definitely acoustical.
11.5.2 Non-Transducer Noise Sources
Remove all input and output cables from the SITRANS LUT400 individually while monitoring
the noise. If removing a cable reduces the noise, that cable may be picking up noise from
adjacent electrical equipment. Check that low voltage cables are not being run adjacent to
high voltage cables or near to electrical noise generators such as variable speed drives.
Filtering cables is an option but is not recommended unless all other options have been
exhausted.
The SITRANS LUT400 is designed to work near heavy industrial equipment such as variable
speed drives. Even so, it should not be located near high voltage wires or switch gear.