Siemens SITRANS LG240, Operating Instructions Manual

Page: 59 / 88

59 PBD-51041038 SITRANS LG240 - Operating Instructions
44286-EN-171021
A PC with the software PACTware and the suitable DTM or the soft-
ware PDM with a suitable DD offer further comprehensive diagnostics
options. In many cases, the reasons can be determined in this way
and faults can be rectified.
Connect a multimeter in the suitable measuring range according to
the wiring plan. The following table describes possible errors in the
current signal and helps to eliminate them:
Error Cause Rectification
4 … 20 mA signal not sta-
ble
•
Fluctuations of the
measured variable
•
Set damping appropriate to the instrument via the
display and adjustment module or PACTware/DTM
4 … 20 mA signal missing
•
Electrical connection
faulty
•
Check connection according to chapter " Connection
steps " and if necessary, correct according to chapter
" Wiring plan "
•
Voltage supply missing
•
Check cables for breaks; repair if necessary
•
Operating voltage too
low or load resistance
too high
•
Check, adapt if necessary
Current signal greater than
22 mA or less than 3.6 mA
•
Electronics module in the
sensor defective
•
Exchange the instrument or send it in for repair
The below tables show typical examples for application-relevant
measurement errors. There are two measurement errors:
•
Constant level
•
Filling
•
Emptying
The images in column " Error pattern " show the real level as a broken
line and the level displayed by the sensor as a continuous line.
1
2
Level
time
0
Fig. 27: The broken line 1 shows the real level, the continuous line 2 shows the
level displayed by the sensor
Note:
•
Wherever the sensor displays a constant value, the reason could
also be the fault setting of the current output to " Hold value "
•
If the level indication is too low, the reason could be a line resist-
ance that is too high
Check the 4 … 20 mA
signal
Treatment of measure-
ment errors