ABB LMT100 Operation Instructions Manual page 58

58
Troubleshooting using waveform display
Error
The presence of dashed lines in place
the process variable value
Small amplitude of the signal
The float is moving along the probe
as well as the signal but the level
does not change
L M T S E R I E S | M A G N E TO S T R I C T I V E L E V E L T R A N S M I T T E R | O I/ L M T 1 0 0/ 2 0 0 - E N R E V. B
Possible Cause
Indicates that a valid level cannot be detected
Degradation of the signal amplitude could be an
indication of other underlying problems like
weakling of the magnetic flux of the float or
sensor deterioration issues
Artifacts could be created as result of magnetic
materials or components in the proximity of the
probe
Suggested Action
• Navigate to the waveform screen to verify the presence of a
signal with amplitude equal or close to 2V unless the probe
length exceeds 20 feet.
• Verify that the float is not damaged
• Make sure the blanking value does not exceed the signal to be
detected
• Make sure the threshold is not set too high
If the signal is present but the amplitude does not cross the
threshold line verify that:
• The float is present and not damaged
• The strength of the magnetic field of the float is correct
The sensor has deteriorated or been damaged navigate to the
pulse width parameter to change it to a larger value
• This temporary remedy might give enough time to perform a
deeper evaluation of the instrument and replace defective
components
Check for artifacts with amplitude larger than the threshold
value located on the left side of the signal
• Adjust the blanking to bypass the artifacts seen in the
waveform screen