Determine The Noise Source; Acoustical Noise; Non-Transducer Noise Sources - Siemens SITRANS LUT400 Operating Instructions Manual

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.
noise
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.
SITRANS LUT400
Operating Instructions, 07/2019, A5E33329501-AC
-removed +removed
higher higher
unchanged
lower
unchanged higher
unchanged
lower
lower higher
unchanged
lower
Go to:
Reducing Electrical Noise (Page 278)
Common Wiring Problems (Page 278)
Reducing Acoustical Noise (Page 278)
Reducing Electrical Noise (Page 278)
Contact Siemens representative.
Reducing Acoustical Noise (Page 278)
Common Wiring Problems (Page 278)
Common Wiring Problems (Page 278)
Reducing Acoustical Noise (Page 278)
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