SECTION 5
F) The display shows 'LOSS OF ECHO':-
1. Check the transducer wiring and connections to the instrument. Note that
different connections are used if a temperature compensated transducer is
connected. See Figure 3, Page 3.
If the transducer cable has been extended as per Page 8, disconnect and
remove the transducer and connect it direct to the Miniflex LR. If the unit now
operates, recheck the extension cable connections and routing, avoiding power
cables. Re-install the transducer checking that its aim is perpendicular to the
target surface.
2. Check whether the neon light on the bottom PCB nearest terminal 1 is
flashing. If it is proceed to number 3, if it is not then:-
a: Disconnect the transducer: If the neon now lights then there is a short
circuit in the cabling.
b: If the neon does not light the transmission fuse may have blown.
Check F1 T80mA fuse on the bottom PCB.
c: If the unit still shows 'LOSS OF ECHO' check that you can hear the
transducer "clicking" when close to the ear.
d: If the transducer does not click proceed to 5.
3. Is there a target within the empty distance specified in Pr.2.0? This is
particularly important if temperature variations are experienced and no
compensation is applied.
4. Is the vessel empty with a conical, parabolic, sloping or spherical bottom?
This commonly causes loss of echo if the transducer cannot be mounted
over the centre of the vessel. When the vessel becomes empty the pulse from
the transducer hits the sloping sides of the bottom section and the signal is not
reflected back to the transducer. Under this condition the display will indicate
'LOSS OF ECHO' but the failsafe designation will operate until product
returns and the system will automatically recover and track level. If the
transducer cannot be mounted centrally, the problem may be overcome by the
installation of a target plate.
5. Connect a known good transducer to the instrument and check the operation.
If the known transducer gives a good signal check the instrument’s gain by
pressing the ' ' key. The number displayed ranges from 0.1 – 100, the lower
the number the greater the signal strength.
If the gain figure is 50 - 100 check the surface level for foam or other
materials which may float in and out of the beam and cause poor echoes.
Ref: MINIFLEX LR MANUAL Rev. 0 44
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