L ST4 0 0 |
U LT R A S O N I C L E V EL T R A N SM I T T ER
| O I/L S T4 0 0 - EN R E V. E
27
9 Fault finding
There are three categories of possible faults: the malfunction
of the instrument, loss of echo, and wrong reading. The biggest
problem is to identify the malfunction. If the instrument is not
working satisfactorily then remove the transmitter and
transducer to the workshop. Connect the power and the
transducer directly, not using any extension cable. Aim the
transducer to a wall about 4.95 ft / 1.5 m away, making sure
that it is perpendicular to the wall. Now reset the instrument by
the Factory Reset prompt. The Instrument should now read
Distance 4.95 ft / 1.50 m. If it does not read the above then
there is a malfunction with the instrument and it should be
returned for repair. If the above works and it still does not work
in the field then there are many possible problems. A list of
possible problems follow.
If the above works and it still does not work in the field then
there are many possible problems, which is listed below.
Loss of echo .
• Check all transducer cable connections and that the joints
are soldered together.
• Check the specification of the transducers as agitated
surfaces and solids do not reflect as powerful a signal as
flat surfaces.
• Aim the transducer straight down if used on liquids and
perpendicular if used on solids.
• Check if the transducer face is dirty.
Wrong reading, always reading close to Transducer
• Check to see if the isolation kit has been used correctly
and is only hand tight.
• Do not reduce blanking distance below 1.63 ft / 0.5 m
unless consultation has been made with ABB.
• Electrical noise can cause this error. Remove noise.
Wrong reading, anywhere in weir/channel
• Check to see if there is a reflection from the wall. Please
Note! A piece of wire across a tank can cause a big enough
echo to be accepted.
• Are the parameters correct? Reset to factory default and
check that LST400 reads correctly. If the factory settings
are OK then your parameters need to be changed. Re-
check these parameters with a tape measure.
Wrong reading, erratic .
• Reduce Rate of Change. Not many levels move faster than
3.28 foot/minute / 1 meter/minute.
• Make sure the application is set up correctly. On liquid
applications it is very important that the liquid application
is selected. Solid applications are only used for objects or
substances being measured, which are in a solid form.
Wrong reading, slow
• Increase Rate of Change.
